SPECIAL PUBLICATION 18-94 

IMPROVING SAFETY AT SMALL UNDERGROUND MINES 

Proceedings: Bureau of Mines Technology Transfer Seminar 

Compiled by Robert H. Peters 

United States Department of the Interior 

Bureau of Mines 

1994 
U.S. Department of the Interior 

Mission Statement 

As the Nation's principal con2ervation agency, the Department of 

the Interior has responsibility for most of our nationally-owned 

public lands and natural resources. This includes fostering 

sound use of our land and water resources; protecting our fish, 

wildlife, and biological diversity; preserving the environmental 

and cultural values of our national parks and historical places; and 

providing for the enjoyment of life through outdoor recreation. 

The Department assesses our energy and mineral resources and 

works to ensure that their development is in the best interests of 

all our people by encouraging stewardship and citizen participation in their care. The Department also has a major responsibility 

for American Indian reservation communities and for people who 

live in island territories under U.S. administration. 
Special Publication 18-94 

Improving Safety at Small Underground Mines 

Compiled by Robert H. Peters 

UNITED STATES DEPARTMENT OF THE INTERIOR 

Bruce Babbitt, Secretary 

BUREAU OF MINES 
CONTENTS 

Page 

Abstract ........................................................................... 1 

Introduction ........................................................................ 2 

Statistical Profile of Accidents at Small Underground Coal Mines, by Robert H . Peters and Barbara Fotta . . 5 

Pillar Design and Strategies for Retreat Mining, By Frank E . Chase and Christopher Mark .............. 15 

Shiftwork: A Guide for Schedule Design, By James C . Duchon .................................. 24 

Nature and Cost of Low Back Pain, by Sean Gallagher and Christopher A . Hamrick .................. 37 

A Scientific Look at Back Belts, by Sean Gallagher and Christopher A . Hamrick ..................... 44 

Job Design: An Effective Strategy for Reducing Back Injuries, by Christopher A . Hamrick and Sean 

Gallagher ........................................................................ 48 

Developing and Maintaining Safety Programs for Improved Worker Performance: Don't Forget the Basics, 

by Michael J . Klishis and Ronald C . Althouse ............................................. 55 

Emergency Response Planning for Small Mines: Who Needs It?, by Launa Mallett, Michael J . Brnich, Jr., 

and Charles Vaught ................................................................ 71 

Experimental Training To Reduce Variability in the Interpretation and Application of Machine Guarding 

Requirements, by Lynn L . Rethi and William J . Wiehagen .................................... 102 

Ergonomic and Statistical Assessment of Safety in Deep-Cut Mining, by Lisa J . Steiner, Fred C . Turin, and 

Christopher A . Hamrick ............................................................. 124 

Crewstation Analysis Programs-An Easy To Use Personal Computer-Based Lighting and Visibility Analysis 

Software Package for Underground Mining Equipment, by Richard L . Unger ...................... 133 

Impact of Maintainability Design on Injury Rates and Maintenance Costs for Underground Mining 

Equipment, hy Richard T .. 1-Jnger and Kirk Conwap ......................................... 140 

Inexpensive, Easy To Construct Materials-Handling Devices for Underground Mines, by Richard L . Unger 

andKirkConway .................................................................. 168 
UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT 

cd/m2 candela per square meter kg/h kilogram per hour 

cm centimeter lb pound 

d/wk day per week Ix lux 

day per year 

footcandle 

foot lambert 

foot 

hour 

hour per day 

hour per year 

inch 

kilogram 

m 

min 

min/d 

mm Hg 

MPa 

psi 

st 

st/yr 

t/h 

meter 

minute 

minute per day 

millimeter of mercury 

megapascal 

pound (force) per square inch 

short ton 

short ton per year 

ton (metric) per hour 

.,i-ence to specific products does not imply endorsement by the U.S. Bureau of Mines. 
IMPROVING SAFETY AT SMALL UNDERGROUND MINES 

Proceedings: Bureau of Mines Technology Transfer Seminar 

Compiled by Robert H. peters' 

ABSTRACT 

This U.S. Bureau of Mines report identifies the types of serious accidents that occur most frequently 

at small underground coal mines and describes the strategies that could help prevent these accidents. 

A wide variety of methods for improving safety are suggested, including improvements in the design of 

equipment, work procedures, work schedules, safety programs, and emergency response plans, as well 

as techniques for diagnosing the potential hazards associated with new technologies and work procedures. Some of the papers in this volume focus on preventing specific types of mining accidents--ones 

associated with materials handling (primarily back injuries), equipment maintenance, improper machine 

guarding, and ground failure during retreat mining. AIthough the recommendations in this volume are 

heavily influenced by research performed at underground coal mines in the Appalachian coalfields, most 

of the papers contain advice that is equally pertinent to almost any type of mine. 

'~esearch psychologist, Pittsburgh Research Center, U.S. Bureau of Mines, Pittsburgh, PA. 
BACKGROUND 

The vast majority of underground coal mines in the 

United States are relatively small operations. Of the 1,345 

U.S. underground coal mines in operation durhg 1992, 

about one-half (638) employed 20 or fewer people and 

about one-third (454) employed between 20 and 50 people. 

The median number of employees was 22. Mines of fewer 

than 50 employees accounted for 26% of total underground coal production and 28% of the total number of 

hours worked in underground mines. 

Unfortunately, small mines seem to account for far 

more than their share of total fatalities. Although small 

mines (50 or fewer employees) accounted for only about 

28% of the total work force, they accounted for 66% of 

the fatalities that occurred in 1992. These statistics are not 

too different from other recent years. During the period 

1989-91, 58% of the fatalities occurred at mines of fewer 

than 50 employees. 

To assist small mine operators with improving safety, 

the U.S. Bureau of Mines (USBM) is conducting a series 

of technology transfer seminars at multiple locations within 

the four States that contain most of the small underground 

coal mines in the United States-Kentucky, West Virginia, 

Virginia, and Pennsylvania. This report was prepared to 

summarize the information presented at these seminars. 

It contains 13 papers on various issues related to safety at 

small underground coal mines. These papers describe a 

wide variety of approaches to improve mine safety: modifications to the design of mining equipment, work proceBack injuries are the most frequent type of nonfatal 

injuries at small underground mines. These injuries are a 

major problem for both employers and employees. Back 

injuries are responsible for a great deal of suffering and 

account for from 30% to 40% of worker compensation 

costs at underground coal mines. Miners working in thinseam mines must handle materials and perform other 

duties while iri unusual and somewhat awkward postures, 

resulting in stress to the lower back. Four of the papers 

in this volume address various aspects of miners' back 

injuries and how to prevent them (2-4, 7). 

The major causes of fatalities and serious injuries at 

underground coal mines are basically the same regardless 

of the size of the mine. The recommendations contained 

in this volume are generally just as applicable to large 

mines as they are to small mines. However, because of 

greater limitations on work force and capital, the alternatives for solving certain types of safety problems may be 

more limited for small mines than for larger operations. 

The authors of this volume have been encouraged to concentrate on proposing solutions that would be feasible for 

implementation at most small mining companies. However, large mlning operations may be able to solve certain 

types of safety problems via strategies that would not be 

feasible for most small mining operations (e.g., major 

changes in equipment or mining techniques). 

Several hypotheses have been proposed to try to account for why fatality rates are so much higher at small 

mines (5, 9). However, there is almost no research evidence available indicating whether or not any of them are 

dures, and work schedules; development of effective safety valid. Data need to be collected and analyzed to evaluate 

programs and emergency response plans; and techniques the impact of various factors on safety at small mines. 

for diagnosing the potential hazards associated with new The National Academy of Sciences (5) researchers anatechnologies and work procedures. Some of the papers lyzed data on a variety of factors that sounded like plaufocus on preventing specific types of mining accidents, such sible explanations for the difference between fatality rates 

as back injuries and roof falls. 

Ground control is a particularly important problem at 

small mines. Roof falls are the most frequent cause of 

fatalities at small underground coal mines, accounting for 

over one-half (56%) of all fatal accidents. The Peters and 

Fotta (6)2 analysis of accident statistics indicates that, in 

comparison to large mines (over 50 employees), the rate 

of groundfall fatalities is 10 times higher at mines with 20 

or fewer employees. This volume contains only one paper 

on this topic (1). However, the USBM conducted several 

seminars on preventing groundfall accidents at small mines 

during 1992-93. The eight papers prepared for those 

seminars are published in a proceedings volume-USBM 

Information Circular (IC) 9332 (8). 

2~talic numbers in parentheses refer to items in the list of references 

at the end of this introduction. 

at small mines versus large mines, but found that none of 

them were capable of accounting for the large differences 

that exist. It is clear that small mines differ from large 

mines in several respects (e.g., seam height and longevity 

of operation), but it remains to be determined whether 

these differences are of any significance in explaining why 

small mines have higher fatality rates. 

During the 1980's, there was a substantial decline in the 

number of underground coal mines and in the number of 

jobs for miners in the United States. The number of 

mines in the United States declined by 32% and the 

number of hours employees worked in underground coal 

mines declined by 40%. These dramatic changes have no 

doubt influenced mine safety in various ways. In some 

respects, these changes may have improved miners' safety 

and, in other respects, they may have worsened it. There 

is currently very little in the way of theory or data on 
which to base any predictions or arguments. However, 

future safety researchers and economists may wish to 

explore how mine closures and the threat of job loss 

impact safety and whether the impact varies across mine 

size. 

PLANS FOR FUTURE RESEARCH 

The USBM plans to conduct further analyses of 

existing data to try to determine if there are characteristics of mines or miners that tend to vary with mine 

size and whether any of these factors are significantly 

related to variations in fatality rates. Very little information is available concerning what small mine operators 

are currently doing to ensure their employees' safety. It is 

very difficult to determine what types of changes are 

needed without having a better picture of what small mine 

operators are currently doing and what kinds of constraints 

and opportunities for improving safety exist at these operations. Therefore, the USBM plans to conduct structured interviews with underground coal miners, mine 

owners, and mine inspectors to find out more about the 

approaches small mine operators are currently using to 

prevent accidents and what the people who work at small 

mines perceive as the obstacles to maintain a safe workplace. Once this information has been collected, it will be 

summarized and published, and the USBM will assist, if 

possible, with implementing any recommendations. 

REFERENCES 

1. Chase, F. E., and C. Mark. Pillar Design and Strategies for 

Retreat Mining. Paper in this proceedings. 

2. Gallagher, S., and C. A. Hamrick. Nature and Cost of Low Back 

Pain. Paper in this proceedings. 

3- - .A Scientific Look at Back Belts. Paper in this proceedings. 

4. Hamrick, C. A., and S. Gallagher. Job Design: An Effective 

Strategy for Reducing Back Injuries. Paper in this proceedings. 

5. National Academy of Sciences. Fatalities in Small Underground 

Coal Mines (contract J0100145). BuMines OFR 124-83, 1983, 20 pp. 

6. Peters, R H., and B. Fotta. Statistical Profile of Accidents at 

Small Underground Coal Mines. Paper in this proceedings. 

STATISTICAL PROFILE OF ACCIDENTS AT SMALL 

UNDERGROUND COAL MINES 

By Robert H. peters' and Barbara ~otta* 

ABSTRACT 

The U.S. Bureau of Mines prepared this paper to provide statistical information on accidents, production, and 

employment at small U.S. underground coal mines. Mines 

are categorized according to size as follows: fewer than 

20 employees, 20 to 50 employees, 50 to 100 employees, 

and more than 100 employees. For each size category, 

statistics are presented showing the following: (1) the 

number of mines and the States in which they are located; 

(2) changes in employment, production, and rates of fatal 

and permanently disabling accidents between two periods 

(1978-80 and 1989-91); and (3) rates of coal production 

and rates of various types of serious accidents. The fiv 

States with the largest number of small underground coi 2 

mines are Kentucky, West Virginia, Virginia, Pennsylvanr; 

and Tennessee. Statistics are presented to show how val 

ous sizes of mines in these 5 States compare with st 

another in terms of safety and productivity. Statistics 

also presented showing how miners who are injured wh- : 

working at mines of various sizes compare in terms of a:: 

and experience. Several propositions about why srn, 

mines have higher fatality rates are reviewed. 

INTRODUCTION 

The National Academy of Sciences (NAS) published 

studies (5-6)3 in 1982 and 1983 examining the relationship 

between the size of underground coal mines and the rate 

of fatal accidents. It found that during the period 1978-80, 

the fatality rate for mines with 50 or fewer employees 

(0.14) was about 3 times that of mines with over 250 employees (0.05), and almost twice that of mines with 51 to 

250 employees (0.08). The researchers note: 

This strong correlation between mine size and fatality rates was evident in all the data from the 

[U.S.] Mine Safety and Health Administration 

(MSHA) we examined dating back to 1969. 

Furthermore, the association was not explainable by 

'Research psychologist. 

'Research methodologist. 

Pittsburgh Research Center, U.S. Bureau of Mines, Pittsburgh, PA. 

3~talic numbers in parentheses refer to items in the list of references 

at the end of this paper. 

company ownership, union status, seam thickness, :,: 

any of the other factors we examined. 

More recent data from MSHA indicate that the -2.: 

crepancy between fatality rates at small versus large nn..: ,, 

has grown even more extreme since the NAS study ,, . performed. Tisdale (8) writes: 

In 1992, small underground coal mines, with 

fewer than 20 employees, had a fatal incidence rate 

of about 6 times that of larger mines, and those with 

more than 20 but fewer than 50 eniployees had a 

rate about 4 times that of larger mines. 

The NAS researchers analyzed data on accidents 

underground coal mines during the late 1970's to try A. 

establish which of several factors might be responsible ft 

the fact that fatality rates are so much higher at sS!! 

mines. Their findings are reviewed briefly as fullon. 
Exposure to Face Areas of the Mine.--One potential 

explanation of the association between mine size and 

fatality rates is that in large mines there are proportionally 

more workers away from the working face and therefore 

at reduced risk for a fatality. If this were true, then 

smaller mines would have larger fatality rates even though 

the risks for miners at the working face were the same as 

in larger mines. The NAS researchers allowed for this 

possibility in their analyses (6, pp. 91-93), but found that, 

at best, it could explain only a part of the strong association between minc size and fatality ratcs. 

Seam 77zick11ess.-The NAS researchers investigated the 

impact that seam height might have on explaining the 

differences between fatality rates at slnall versus large 

mincs. They note that, in general, smaller mines have 

thinner coal seams than larger mines. However, they were 

unable to find any clear relationship between scam thickness and the fatality rate in small mines. In contrast, 

within each thickness category the fatality rate tends to 

decline with increasing mine size. Therefore, the authors 

concluded that the association between minc size and 

fatality rate is not due to differences between small and 

large mines with respect to seam thickness. However, 

about 78% of mines with 20 or fewer employees and 59% 

of mines with 21 to 50 employees failed to report seam 

heights for the period being studied (1975-80). Such a 

large amount of missing data precluded doing a thorough 

analysis of seam height relative to mine size. Unfortunately, it is impossiblc to determine thc extent to which 

this lack of data may have influenced the results that were 

reported. 

Dirratio~z ofAcfive 0l~erulion.-The NAS (.5) rcscarchers 

shortly after a mine first opens and thereafter declinesi.e., the risk of fatalities decreases over time. Although 

this notion appears plausible, the NAS researchers could 

not find sufficient evidence from their data to support it. 

The NAS findings strongly suggest that various factors 

that sounded like plausible explanations for the difference 

between fatality rates at small versus large mines are 

actually NOT capable of accounting for the large differences that exist. Unfortunately, researchers have yet to 

establish what the factors are that can account for the 

large disparity. The NAS (5) researchers speculate that 

the following factors may have been at least partly 

responsible for the disparity: 

On the basis of our examination of fatality 

reports, discussions with operators of small underground coal mines, and the experience of the Committee's three mining engineers and geologist with 

small mine operations, we believe the following 

factors exacerbate the safety problem in small mines: 

1) The mining equipment in small mines is of 

lower quality, sometimes secondhand, and less well 

maintained. 

2) The physical condition of employees in small 

mines is less favorable to safety--small operators 

sometimes employ workers that large companies will 

not accept. 

3) The financial resources available to operators 

of small mines are limited. Hence many of these 

operators are not able to support the more extensive 

safety programs employed by some major coal companies (using safety engineers and technicians). 

note that there are striking differences bctwccn small and Statistics on ratcs of fatalities and permanently dis- large mines with respect to the length of time thcy remain abling injuries strongly suggest that small mine operators open. They note that smaller mines operalc for shorter face some unique obstacles to maintaining their employ- periods of time and more intermittently than larger mincs, ees, The U.S. Bureau of Mines (USBM) prepared which tend to operate more or less continuously. The paper to update the NAS accident statistics, majority (57%) of small mines in their sample were active (2) identify changes that have occurred since 1980, and 

for 18 months or less during 1975-807 compared with only (3) enumerate the ~ro~ositions that have been set forth to \ I * L 4% of larger mines. try to account for the differences in the safety performance 

The NAS rt~earchers hypothesized that Part of the dif- of small versus large mines. The information this paper 

ference between fatality rates at small versus large mines may be useful in arriving at causal explanations 

may reflect a "learning curve" phenomenon. The reasoning and successful interventions aimed at improving miners' 

behind this notion is that the risk of a fatality is greatest safety-especially at small underground coal mines. 

METHODS 

The data presented here are drawn Gom MSHA's information, MSHA requires mines to submit a form 

database of mining production, employment, and accidents (7000-1) that describes each "reportable" accident. Also, 

for the entire population of U.S. underground coal mincs. each working mine must submit quarterly information 

MSHA gathers these data in accordance with Part 30 of about their operations, including production, employeethe U.S. Code of Federal Regulations. To collect this hours. and mine characteristics on another standard form 
(7000-2). The USBM has access to computerized copies 

of this information for all mine operators from 1975 

through 1991. The USBM does not have access to computerized data about independent contractors. Independent contractor employees have become a more sidcant 

part of the mining work force in the past decade. They 

may perform a wide variety of support functions for mine 

operators, such as hauling coal or constructing various 

facilities on mine property. Consequently, the numbers 

presented here will be slightly smaller than analyses that 

include independent contractors. Also, reporting requirements for contractors are somewhat different from those 

for operators, so the data are not readily comparable. 

The analyses presented here primarily cover the years 

1989 through 1991. At this writing, the 1991 data are the 

most recent available in the USBM's copy of the MSHA 

database. A limitation of the MSHA data is that not all 

of the information on the reporting forms is complete for 

all the mines in the database. For instance, information 

on employment, production, and other variables is sometimes missing. A total of 2,187 mines met the selection 

criteria of reporting nonzero underground production, or 

reporting a fatality during at least 1 of the 3 years studied. 

(That is, mines that reported zero coal production were 

included in the analyses only if a fatality had occurred at 

that location.) 

The injury data analyses will focus on three types of 

injuries: (1) fatalities (MSHA "Degree of Injury" code I), 

(2) permanently disabling injuries (MSHA "Degree of 

Injury" code 2), and (3) lost-time injuries that caused the 

employee to miss more than 20 days of work (referred to 

as serious injuries). 

Throughout the tables of statistics presented in this 

paper, mines have been stratified according to their size. 

Mines were usually put into one of the following four sue 

categories based on the average number of employees at 

that operation: 1 to 20,21 to 50,51 to 100, and more than 

100. Both the number of employees and the number of 

employee-hours included people who worked (1) underground, (2) at the surface of underground mines (except 

ofice workers), and (3) in preparation plants at underground mines. The sue of each mine was usually determined by averaging the annual number of employees 

reported by the mine for 1989,1990, and 1991. However, 

there were a couple of exceptions to this procedure: (1) 

All data pertaining to office workers were excluded from 

the analyses because these workers are not normally 

exposed to the types of hazards that other mine employees 

face; (2) mines where a fatality had occurred were placed 

into the mine size category that corresponded to the average number of employees the mine reported for the year 

of the fatality as opposed to using the 3-year average. This 

was done to accurately characterize what mines were like 

at the time the fatal accident occurred and also to be consistent with MSHA's statistics for the number of fatalities 

occurring in mines of a particular size category. 

The NAS researchers considered mines of 50 or fewer 

employees to be "small" mines. This paper follows the 

same convention--the term "small mines" always refers to 

mines of 50 or fewer employees. However, close to half 

of U.S. underground coal mines employ 20 or fewer 

people. Because so many mines are in this category, statistics are always reported for each of two separate categories of small mines: mines of 20 or fewer employees 

and mines that employ between 20 and 50. Throughout 

this paper, mines that employ 20 or fewer people are 

always referred to as "very small" mines, and mines that 

employ more than 50 people are considered to be "large" 

mines. 

The findings are organized into 10 tables of statistics. 

Each table is discussed below, beginning with a look at the 

number of mines in each size category that are located in 

each State. 

well. Of the 1,217 mines in this size category, 507 (41.7%) 

are located in Kentucky, 298 (24.5%) in West Virginia, 206 

in Virginia, 120 in Pennsylvania, and 53 in Tennessee. 

UNDERGROUND COAL PRODUCTION 

LOCATION OF MINES 

Table 1 breaks down the total number of underground 

coal mines that reported any coal production during 1989- 

91 by State and mine size. Over half of the underground 

coal mines in operation during this time period were 

concentrated in the States of Kentucky and West Virginia, 

with 38.6% and 28.4% of the total number of mines, 

respectively. Virginia accounted for 15.4% of the mines, 

followed by Pennsylvania with 8.3%. Similarly, the majority of very small mines are concentrated in these States as 

The total amount of coal produced from underground 

mines during 1989-91 is broken down by State and mine 

size in table 2. West Virginia mines produced 29.1% of 

the underground coal mined in the United States, followed 

by Kentucky mines with 24.4%. Other major producers of 

underground coal include Illinois (10.5%), Pennsylvania 

(10.1%), and Virginia (8.9%). Most of this production 

(60.3%) was from mines employing over 100 employees. 

Very small mines accounted for 8.5% of total underground 

coal production, and mines employing from 21 to 50 
employees accounted for 20.2%. Of the coal produced 

by very small mines, 40% came from Kentucky, 30% from 

West Virginia, 20% from Virginia, 3.8% from Pennsylvania, and 2.7% from Tennessee. 

Table 1 .-Number of underground coal mines stratified 

by State and mine size (number 

of employees) in 1989-91 

Number of employees 

State 1 to 21 to 51 to Over % of 

20 50 100 100 Total U.S. 

total 

Alabama ..... Colorado ..... Illinois ....... Kentucky ..... Ohio ........ Pennsylvania . . Tennessee .... Utah , ........ Virginia ...... West Virginia . . Other' ....... 

U.S. total ... % of U.S. 

total ..... 

17 0.8 

17 0.8 

31 1.4 

844 38.6 

19 0.9 

182 8.3 

80 3.7 

22 1.0 

337 15.4 

622 28.4 

16 0.7 

2,187 NAp 

55.6 31.2 5.7 7.4 NAp 100 

NAp Not applicable. 

'Arkansas, Indiana, lowa, Maryland, Montana, New Mexico, 

Oklahoma, and Wyoming. 

Table 2.-Total underground coal production' stratified by 

State and mine size (number of 

employees) in 1989-91 

Number of employees 

State 1 to 21 to 51 to Over % of 

20 50 100 100 Total U.S. 

total 

CHANGES IN PRODUCTION, EMPLOYMENT, 

AND INJURY RATES DURING THE 1980's 

Table 3 presents eight different measures of the U.S. 

underground coal mining industry stratified by mine size. 

To be able to see how the industry changed during the 

1980's, statistics are presented that reflect two different 

periods: 1978-80 and 1989-91. Also included in the table 

is the percentage of change over the intervening 8-year 

span for each of the mine characteristics listed. 

1978-80 Statistics 

Several trends relating to mine size are evident for the 

period 1978-80. As mine size increases, the number of 

mines within each size category decreases and the number 

of employee-hours and the amount of production increases. The productivity rate, however, decreases with 

increasing mine size from 1.69 t/h at very small mines to 

0.98 t/h at mines with 50 or more employees. Both the 

fatality rate and the permanent disability rate decrease 

with increasing mine size. However, the decrease in permanent disability rates (from 0.205 to 0.165 injuries per 

200,000 h) is of a much lower magnitude than the decrease 

in fatality rates (from 0.245 to 0.062). 

1989-91 Statistics 

Trends similar to those observed for 1978-80 are evident for this period as well with one notable exception. 

The productivity rate is now highest for mines with 21 to 

50 employees (2.69 t/h), followed by a productivity rate of 

2.46 t/h for mines with 50 or more employees. It is the 

very small mines that now have the lowest productivity 

rate, 2.27 t/h. 

Alabama ..... 0.06 0.01 0.33 43.44 43.83 4.0 

Colorado ..... 0.76 2.03 4.44 17.70 24.92 '2.3 

Illinois ....... 0.06 1.88 4.04 109.75 115.70 10.5 

Kentucky ..... 37.30 79.89 41.71 108.98 267.88 24.4 

Ohio ........ 0.93 1.71 0.23 29.75 32.61 3.0 

Pennsylvania . . 3.57 9.24 13.09 85.26 111.16 10.1 

Tennessee .... 2.56 4.37 2.62 1.54 11.09 1.0 

Utah ........ 1.62 0.69 10.24 45.60 58.16 5.3 

Virginia ...... 18.34 30.51 15.49 33.82 98.16 8.9 

West Virginia . . 27.98 90.85 24.57 176.35 319.74 29.1 

Other2 ....... 0.16 0.78 4.40 10.23 15.58 1.4 

U.S.tota1 ... 93.37 221.94 121.14 662.38 1,098.83 NAp 

% of U.S. 

total ..... 8.5 20.2 11.0 60.3 NAp 100.0 

NAp Not applicable. 

'~roduction is in millions of metric tons. To convert to short 

tons, multiply by 1.10232. 

2Arkansas, Indiana, lowa, Maryland, Montana, New Mexico, 

Oklahoma, and Wyoming. 

1978-80 Versus 1989-91 Statistics 

The last three columns in table 3 summarize the data 

aggregated across mine size for the two time periods and 

show the percentage of change from one time period to 

the next. 

Productivi&.-The most significant change is 2 136% increase in overall productivity. This reflects a 42% increase 

in overall production and a 40% decrease in the overall 

number of employee-hours. Looking across mine size 

categories, the increase in production rate becomes more 

dramatic with increasing mine size, such that for mines 

with more than 50 employees the production rate has 

increased by 152%. 

Number of Mines andAmount of Production.-The total 

number of mines in operation decreased by 32%. The 
largest decrease (51%) was sustained by mines with 50 or 

more employees. Although the number of very small 

mines decreased by 39%, this category still constitutes over 

half (56%) of the total number of mines in operation. 

Conversely, the number of mines with 21 to 50 employees 

has increased by 8% from 631 mines in 1978-80 to 683 

mines in operation during 1989-91. Similarly, this mine 

size category, in contrast to the larger and smaller mine 

sizes, shows a substantial increase in total production and 

number of employee-hours. Production at mines with 21 

to 50 employees has increased 155% compared with an 

increase of only 21% and 29% for very small and large 

mines, respectively. 

Fatalitie,, arld Disabli~lg Irzjl~ries.-During the 1980's, the 

overall fatality rate decreased by 26%. The percentage of 

decrease in fatality rates becomes more pronounced with 

increasing mine size. For mines with more than 50 

employees, the fatality rate has been decreased by almost 

half (43%). For very small mines, the fatality rate has 

ACCIDENT TYPES 

Fatal Accidents4 

Table 4 breaks down the total number of accidents that 

resulted in one or more fa~alities during the period 1987- 

91 by type of accident and mine size. Because fatalities 

are a relatively rare event, a 5-year span was used for this 

table rather than a 3-year span. Increasing the number of 

incidents under consideration helps to mifiimize the impact of annual fluctuations. Overall, ground fall accidents 

constituted close to half (46.7%) of the total number of 

fatal accidents occurring over this 5-year period. The majority (72%) of the 85 fatal ground fall accidents occurred 

in mines with 50 or fewer employees. [See Randolph (7) 

for an analysis of how ground fall accident rates vary according to mine size and various other factors. For some 

ideas about how to prevent ror~f la11 accidents at small 

mines, see USBM Information Circular 9332 (lo).] 

decreased bv 29%. Converselv. the ~ermanent disabilitv J J, 41t is important to note that the accident statistics in tables 4 and 5 rate increased for a11 three mine size categories the do not fatalities erperienced by independent contractors. If in- 1980's. The increases ranged Irom lor the dependent contractor fatalities were included, the trends might appear 

mines to 30% for mines in the 21- to 5~-employee cate- different. For example, powered haulage accidents are one of the most - - 

gory. Overall, the increase was 20%. This increase is common causes of fatalities to independent contractors, but ground falls 

somewhat unexpected, and the reasons for it are not clear. are 

Table 3.-Number of operations, employee hours, production, and rates of fatalities and permanently disabling injuries 

during two 3-year periods stratified by mine size (number of employees) 

Number of emplovees 

1 to 20 21 to 50 Over 50 Total or overall rate 

1978- 1989- % 1978- 1989- % 1978- 1989- % 1978- 1989- % 

80 91 change 80 91 change 80 91 change 80 91 change 

Number of 

operations . . . . . . . . ~rnplo~ee-hours1 . .. . Production2 . . . . . . . . Productivit? . . . . . . . . Fatalities . . . . . . . . . . Fatality rate4 . . . . . . . . Permanent 

disabilities5 . . . . . . . Permanent disability 

rate4 . . . . . . . . . . . . 

l~mployee-hours are in millions of hours. 

2~roduction is in millions of metric tons. To convert to short tons, multiply by 1.10232. 

3~umber of metric tons per employee-hour. 

4~er 200,000 employee-hours of exposure. 

51ncludes all total and partial permanently disabling injuries except inguinal hernias that are repaired and losses of teeth or the tips of 

toes and fingers. 
Table 4.-Number of accidents resulting in one or more 

fatalities at an underground coal mine stratified 

by type of accident and mine size (number 

of employees) in 1987-91 

Number of employees 

Accident type 1 to 21 to 51 to Over Total % of 

20 50 1 100 total 

Ground fall ........ 33 28 6 18 85 46.7 

Powered haulage ... 7 11 5 14 37 20.3 

Machinery ........ 1 7 4 11 23 12.6 

Electrical ......... 5 3 3 6 17 9.3 

Explosives ........ 3 1 1 0 5 2.7 

Other ............ 5 4 0 6 15 8.2 

Total .......... 54 54 19 55 182 NAp 

%oftotal ..... 29.7 29.7 10.4 30.2 NAp 100 

NAp Not applicable. 

The next most frequent type of fatal mining accidents 

are those associated with powered haulage equipment. 

MSHA7s accident classification scheme considers powered 

haulage accidents fr: Le those that are "... caused by the 

motion of the haulage unit, e.g., motors and rail cars, conveyors, shuttle cars, haulage trucks, front-end loaders, etc. 

Also includes any accidents caused by a moving part of the 

haulage unit." Fatal powered haulage accidents are almost 

evenly split between mines with over 50 employees versus 

mines with 50 or fewer employees. Further statistics on 

powered haulage accidents may be found in the Holmes 

Safety Association Bulletin (4). 

Of the 182 zccidents causing 1 or more fatalities, 54 occurred at mines with 1 to 20 employees, another 54 occurred at mines with 21 to 50 employees, 19 occurred at 

mines with 51 to 100 employees, and 55 occurred at mines 

employing over 100 people. Thus, a sizeable number of 

fatal accidents have occurred at both large and small 

underground coal mines. 

It is interesting to note that the NAS (5) researchers 

found that the distribution of types of accidents causing 

fatalities did NOT vary much across mine size. They conclude thatThis indicates that the larger fatality rate in small 

mines is not the result of an increase in a specific 

type of accident (e.g., roof falls). Rather, the data 

indicated that smaller mines are more likely than 

larger mines to have fatalities from each of the 

major types of accidents. This would suggest that 

the problem in small mines is not isolated to a specific work activity (such as roof bolting), but is present in all aspects of the mining effort. 

Based on analysis of more recent data, this conclusion 

no longer appears true. Table 5 shows rates of fatal accidents stratified by accident type and mine size during 

1987-91. In comparing the rate of various types of accidents at mines of 20 or fewer employees versus mines of 

50 and over, one sees that the rate of fatalities is greater 

at very small mines for each major accident type (except 

machinery). This is in line with what the NAS researchers 

found. However, looking down the last column of table 5, 

one sees that the magnitude of the difference between 

rates of various types of fatal accidents at very small versus 

large mines varies quite a bit from one type of accident to 

the next. In particular, the rate of fatal ground fall accidents is 10.7 times greater at very small mines than it is 

at mines with over 50 employees. The corresponding 

ratios for fatal powered haulage, machinery, and electrical 

accidents are 2.9, 0.5, and 4.4, respectively. Thus, there is 

a much bigger disparity between fatal ground fall accident 

rates at very small versus large mines than there is for 

rates of other types of fatal accidents. 

Table 5.4ates1 of fatal accidents stratified by accident type 

and mine size (number of employees) in 1987-91 

Accident type Mine size 

1 to 20 21 to 50 Over 50 Fhtio2 

Ground fall ......... 0.0965 0.0418 0.0089 10.8 

Electrical .......... 0.0146 0.0045 0.0033 4.4 

Machinery ......... 0.0029 0.0104 0.0056 0.5 

Powered haulage .... 0.0205 0.0164 0.0071 2.9 

'per 200,000 employee-hours of exposure. 

2Ratio of rate for 1 to 20 employees to rate of over 50 employees. 

Serious Injuries 

Table 6 breaks down the total number of serious injuries during 1989-91 by type of accident and mine size. 

In this table, serious injuries are considered to be any 

nonfatal injury that caused a permanent disability or that 

resulted in more than 20 days of lost work. The last two 

columns in table 6 list the numbers and rates of the various types of accidents that were reported by all the mines 

over this 3-year period. Overall, "handling material" accidents occurred at the highest rate (1.97), accounting for 

36.4% of all serious injuries. The next highest rate was for 

"slip or fall" accidents (0.89), which accounted for 16.4% 

of all serious injuries. Together, these two accident types 

accounted for over half of the serious injuries reported 

over this 3-year period. For some ideas about how to prevent handling material accidents in coal mines, see Unger 

(9), Gallagher (2), Conway (I), and Hamrick (3). 

A few trends are evident when looking at variations 

in the rate of specific types of accidents across mine size 

categories. It appears that rates of serious handling material accidents increase as mines get bigger. The rate of 

handling material accidents ranges from 1.42 at very small 

mines to 2.05 for mines with over 100 employees. Whereas handling material accidents account for 28% of all 

serious injuries at very small mines, they account for 38% 

of all serious injuries at mines of over 100 employees. 

Similarly, the trend is for serious injuries caused by slips 

or falls to occur at a higher rate as mine size increases. 

At mines of over 100 employees, the rate is over twice as 

high as at very small mines (1.11 versus 0.47). 
Table 6.-Number and rates1 of serious injuries2 stratified by accldent type and mlne slze (number of employees) In 1989-91 

Number of employees 

Accident type 

Handling material ........... Slip or fall ................ Machinery ................ Powered haulage ........... 

Ground fall ................ Hand tool ................. Stepping or kneeling ........ Striking or bumping ......... Electrical ................ 

Other2 .................. 

. - 

1 to20 21 to 50 51 to 100 Over 100 Overall 

lnjuries Rate lnjuries Rate lnjuries Rate Injuries Rate Total rate 

292 1.42 805 1.95 478 2.03 2,787 2.05 4,362 1.97 

96 0.47 230 0.56 140 0.60 1,502 1.11 1,968 0.89 

21 1 1.02 422 1.02 207 0.88 782 0.58 1,622 0.73 

227 1.10 427 1.04 178 0.76 746 0.55 1,578 0.71 

97 0.47 220 0.53 92 0.39 493 0.36 902 0.41 

51 0.25 91 0.22 64 0.27 462 0.34 668 0.30 

20 0.10 49 0.12 28 0.12 153 0.11 250 0.1 1 

7 0.03 10 0.02 5 0.02 132 0.10 154 0.07 

9 0.04 30 0.07 14 0.06 43 0.03 96 0.04 

29 0.14 53 0.13 38 0.16 271 0.20 391 0.18 

Total ........... 1,039 5.04 2,337 5.67 1,244 5.29 7,371 5.42 11,991 5.42 

'per 200,000 employee-hours of exposure. 

2~erious injuries include those classified as permanently disabling and those that caused the employee to miss more than 20 days of 

work. 

Machinery accidents are the third most common type of 

accident resulting in serious injuries. They account for 

13.5% of the total and occur at a rate of 0.73. Powered 

haulage accidents, with a rate of 0.71, account for 13.2% 

of the serious injuries reported by underground coal 

mines. In contrast to the previously noted trends across 

mine size categories, the trend is for serious powered 

haulage and machinery accidents to occur at successively 

lower rates as mine size increases. From the smallest to 

the largest mine size category, the rates for both categories 

of accidents decrease by about half. 

Other differences relative to mine size include a slight 

decrease in the rate of serious ground fall accidents with 

increasing mine size (from 0.47 to 0.36), and a slight 

increase in the rate of serious hand tool accidents with 

increasing mine size (from 0.25 to 0.34). 

FATALIlT AND INJURY RATES 

FOR SELECTED STATES 

Table 7 displays rates of fatalities, permanent disabilities, and serious injuries (injur~es resulting in more 

than 20 lost workdays), stra1ifit;d by State and mine sue 

for 1989-91. The tablc is limited to only those States with 

at least 50 very small underground mines. The "overall" 

rates listed at the bottom of the table, however, include 

fatalities and injuries in underground coal mines from all 

States. Data are not given for Tcnnessee mines in the two 

largest size categories because of the extremely small 

number of large mines in Tennessee. 

Fatality Rates.-As noted previously, looking across mine 

size categories, the overall fatality rate is highest for mines 

with 20 or fewer employees, then drops suddenly by almost 

half for mines with 21 to 50 employees, and drops by half 

again for mines with more than 50 employees. For the 

most part, this trend of decreasing fatality rates with increasing mine size is evident within each of the five States. 

The major exception to this overall pattern occurs in 

Virginia where the fatality rate for mines with 21 to 50 

employees is slightly higher than that for the smaller 

mines. The last column in table 7 shows the overall fatality rates for each of the five States. They range from 0.015 

for Pennsylvania to 0.114 for Kentucky. Of the five States, 

West Virginia and Kentucky have the highest fatality rates 

for very small mines, 0.223 and 0.180, respectively. It is 

interesting that these also happen to be the two States with 

the largest number of small mines. 

Permanent Disability Rates.-The trends observed in 

fatality rates relative to mine size are not as clear and pronounced in the permanent disability rates. For example, 

although the overall fatality rate for very small mines 

(0.175) is five times as great as the fatality rate for very 

large mines (0.033), the overall permanent disability rate 

for very small mines (0.228) is only 1.2 times as great as 

that for the largest mines (0.183). Mines in the 51- to 100- 

employee category actually have the highest overall rate of 

permanent disabilities (0.238). 

Serious Injury Rates.-Again, the clear trend that was 

observed in fatality rates relative to mine sue is not present in the overall serious injury rates. The overall serious 

injury rates for very small mines (4.82) is actually less than 

that for the largest mines (5.24). 

Other Trendr.-Looking down the last column at the 

overall rates across States, one sees that the three measures of safety for Pennsylvania mines lead to conflicting 

conclusions. Although Pennsylvania had the lowest fatality 

rate among the five States, it had the second highest permanent disability rate (0.236) and the highest serious injury rate (6.81). 

Looking across mine size categories within States, a 

few trends are apparent. In Pennsylvania, both the permanent disability and serious injury rates increase with increasing mine sue, a twofold to threefold increase from 

the smallest to the largest mine size category. Conversely, 
in Virginia, the serious injury rate decreases with increasing mine size, from 6.43 to 5.03, a 22% decrease from the 

smallest to the largest mine sizes. 

Table 7.-FIates1 of fatalities, permanent disabilities, 

and serious injuries2 stratified by State and mine 

size (number of employees) in 1989-91 

Number of employees 

State and rate 1 to 21 to 51 to Over Overall 

20 50 100 100 rate 

Kentucky: 

Fatality .......... 0.180 0.100 0.094 0.105 0.114 

Permanent disability 0.252 0.288 0.216 0.1 77 0.227 

Serious injury . . . . . . 4.36 5.36 4.97 4.50 4.79 

Pennsylvania: 

Fatality .......... 0.156 0.000 0.000 0.010 0.015 

Permanent disability 0.078 0.1 55 0.199 0.259 0.236 

Serious injury . . . . . . 3.05 4.82 6.46 7.30 6.81 

Tennessee: 

Fatality . . . . . . . . . . 0.1 12 0.073 Neg. Neg. 0.058 

Permanent disability 0.224 0.366 Neg. Neg. 0.259 

Serious injury . . . . . . 4.60 4.46 Neg. Neg. 3.97 

Virginia: 

Fatality .......... 0.122 0.166 0.050 0.013 0.084 

Permanent disability 0.171 0.1 81 0.250 0.139 0.177 

Serious injury . . . . . . 6.43 5.89 5.85 5.03 5.68 

West Virginia: 

Fatality .......... 0.223 0.066 0.021 0.015 0.047 

Permanent disability 0.241 0.173 0.338 0.146 0.1 76 

Serious injury. . . . . . 4.88 5.65 5.04 4.66 4.96 

Total: 

Fatality . . . . . . . . . . 0.175 0.097 0.047 0.033 0.060 

Permanent disability 0.228 0.221 0.238 0.1 83 0.200 

Serious injury. . . . . . 4.82 5.45 5.05 5.24 5.22 

Neg. Negligible. Data are not reported because the number 

of mining operations in this category was extremely small. 

'per 200,000 employee-hours of exposure. 

21njuries, other than those classified as permanently disabling, 

which caused the employee to miss more than 20 days of work. 

EMPLOYEE-HOURS AND PRODUCTIVITY 

Table 8 displays total employee-hours and productivity 

during 1989-91 for each of the five States where the majority of small mines are located, broken down by mine 

size. Across the five States, productivity ranges from 

1.60 t/h for Tennessee to 2.69 t/h for West Virginia. 

Across the different categories of mine size, productivity 

ranges from 2.27 t/h for very small mines to 2.69 t/h for 

mines with 21 to 50 employees. 

CHARACTERISTICS OF SERIOUSLY 

INJURED MINERS 

Table 9 displays the mean age of seriously injured 

miners during 1989-91, as well as the number of years 

of experience they had (1) working at their current mine, 

(2) working in their current job classification, and 

(3) working as a coal miner. The overall means as well as 

the means for four mine size categories are presented. 

The means for each of the four victim characteristics 

steadily increases as mine size increases. The mean for 

"experience at mine" displays the most dramatic increase, 

from 1.95 for very small mines to 11.0 for mines with over 

100 employees. This may largely reflect the fact that most 

small mines do not remain open for nearly as long as large 

mines. It may also reflect a tendency for younger, less 

experienced miners to be hired by small mines rather than 

large mines, and that when larger mines have had to lay 

off workers during the 1980's, it was the younger miners 

who lost their jobs. 

Table 8.-Total employee hours' and productivityZ stratified 

by State and by mine size (number 

of employees) in 1989-91 

-- 

Number of employees 

State and variable 1 to 21 to 51 to Over Total or 

20 50 100 100 overall 

rate 

Kentucky: 

Employee-hours 16.646 29.876 14.835 41.926 103.282 

Productivity . . . 2.24 2.68 2.81 2.60 2.59 

Pennsylvania: 

Employee-hours 2.557 3.860 6.041 39.344 51.803 

Productivity . . . 1.40 2.39 2.17 2.17 2.15 

Tennessee: 

Employee-hours 1.782 2.734 1.254 1.177 6.946 

Productivity . . . 1.43 1.60 Neg. Neg. 1.60 

Virginia: 

Employee-hours 8.21 1 13.274 8.006 15.826 45.317 

Productivity ... 2.23 2.30 1.93 2.14 2.17 

West Virginia: 

Employee-hours 10.787 30.1 13 9.479 68.61 7 1 18.996 

Productivity . . . 2.59 3.02 2.59 2.56 2.69 

Total or overall rate: 

Employee-hours 41.203 82.383 47.025 271.820 442.431 

Productivity . . . 2.27 2.69 2.58 2.44 2.49 

Neg. Negligible. Data are not reported because the number 

of mining operations in this category was extremely small. 

 ours are in millions. 

2~umber of metric tons per employee-hour. 

Table 9.-Mean age and experience of seriously injured1 

miners stratified by mine size (number 

of employees) in 1989-91 

Number of employees 

Victim characteristic 1 to 21 to 51 to Over Overall 

20 50 100 100 

Age ............... 32.3 34.0 36.7 40.3 38.0 

Experience at mine . . . 1.95 2.6 5.3 11.0 8.0 

Experienceinjob ..... 5.6 5.8 6.0 6.7 6.1 

Total mining experience 12.1 13.0 13.4 14.9 14.2 

'serious injuries include those classified as permanently disabling and those that caused the employee to miss more than 

20 days of work. 
It is interesting to note that the age distribution of 

miners at various sizes of mines appears to have changed 

since the NAS (6) study was conducted. The NAS researchers reported finding no age differences relative to 

mine size. However, the present data show a difference of 

8 years between the average age of injured miners at small 

mines (32.3) versus large mines (40.3). (A note of caution: 

One must keep in mind that the ages of injured miners 

may not necessarily correspond to the ages of all miners 

in the work force.) 

MINE-LEVEL DESCRIPTIVE STATISTICS 

Data on mining accidents, employment, and production 

can be aggregated or grouped at various levels of analysis. 

Throughout the tables of statistics discussed thus far, the 

data have NOT been based on mine-level analyses. The 

data from all mines that fell within a specified size category were aggregated or pooled together in the calculation 

of statistics. For instance, accident rates have been calculated by adding together all the accidents that occurred 

throughout all the mines in a particular size category, 

dividing this number by the sum of all the employee-hours 

worked throughout those same mines and then multiplying 

by 200,000. 

However, in table 10 the statistics are based on data 

aggregated at the mine level of analysis. In this procedure, 

the first step is to calculate an accident rate for each mine. 

The mean accident rate for mines in a particular size 

category is then computed by finding the average of the 

rates for each of the mines in that size category. An 

important feature of using the mine level of analysis is 

that each mine is treated as a single data point and given 

the same weight as any other mine. An advantage of this 

procedure is that it allows one to see the variation that 

exists among the mines in a particular size category. Table 10 presents mine-level descriptive statistics for productivity, seam height, and rate of serious and fatal accidents 

during 1989-91. 

Productivity.-Statistics arc: reported for all underground 

coal mines as well as for each of four mine size categories. 

The differences in the figurcs for mean mine-level productivity bctwecn different mine size categories correspond 

fairly closely to what was reported in table 3. The smallest 

mines have the lowest mean productivity rate (2.07), and 

mines in the 21- to 50-employee category have the highest 

productivity (2.66). 

Seam Heig1lt.-As was reported in the NAS (5) study, 

there is still a clear trend toward larger mines operating 

in higher coal seams. The overall median seam height is 

109 cm (33 in). The median for the category of very small 

mines is 102 cm (40 in). As mine size increases, the 

median seam height steadily increases, such that mines 

with over 100 employees have a median seam height of 

168 cm (66 in). 

Rate of Fatalities and Serious Injuries.-Looking at the 

mean and median rate of fatalities and serious injuries 

across mine size categories, there appear to be no clear 

trends. However, the standard deviations (std dev) show 

a decreasing trend with increasing mine size. The difference between the largest mines (std dev = 3.16) and 

the smallest mines (std dev = 17.10) is particularly dramatic and is further reflected in the differences between 

the medians for these two categories. The median of 0.00 

for mines with 20 or fewer employees indicates that at 

least 50% of the mines in this size category reported zero 

serious injuries or fatalities for the period 1989-91 even 

though the average number of such incidents reported for 

these small mines is almost 6. 

In contrast, for mines with more than 100 employees, at 

least 50% of these mines reported almost 5 fatalities or 

serious injuries and the average number reported is 5.71. 

With regard to this particular characteristic, smaller mines 

look very different from one another relative to the homogeneity exhibited by larger mines. 

Table 10.-Mine-level descrlptive statistics for productivity, 

seam height, and rate of fatalities and serlous 

lnjurlesl stratified by mine slze (number 

of employees) In 1989-91 

Mine characteristic Number of employees 

and rate 1 to 21 to 51 to Over Overall 

20 50 100 100 

~roductivity:~ 

Median ........... 1.92 2.46 2.54 2.30 2.15 

Mean ............. 2.07 2.66 2.60 2.49 2.31 

Stddev ........... 1.34 1.24 1.05 1.07 1.31 

Seam height:3 

Median ........... 102 117 135 168 109 

(40) (46) (53) (66) (43) 

Mean ............. 112 127 145 180 124 

(44) (50) (57) (71) (49) 

Std dev . . . . . . . . . . . 43 46 46 53 51 

(17) (18) (18) (21) (20) 

Rate of fatalities and 

serious injuries:' 

Median ........... 0.00 4.82 4.69 4.92 3.21 

Mean ............. 5.57 6.20 5.25 5.71 5.76 

Std dev . . . . . . . . . . . 17.10 6.30 3.24 3.16 13.28 

Std dev Standard deviation. 

'serious injuries include those classified as permanently disabling and those that caused the employee to miss more than 

20 days of work. 

2~umber of metric tons per employee-hour. 

3~entimeters (numbers in parentheses are in inches). The U.S. 

mining industry refers to seam height in terms of inches. 

4~er 200,000 employee-hours of exposure. 
SUMMARY AND CONCLUSIONS 

It was found that fatality rates decline substantially 

as mine size increases. The fatality rate is 0.175 deaths 

pcr 200,000 h for mines with 20 or fewer employees. The 

rate drops by almost half for mines with 21 to 50 employees, and drops by half again for mines with more than 

50 employees. Likewise, rates of permanently disabling 

ilijuries declice as mine size increases. However, there is 

no clear-cut trend in the relationship of mine size to the 

rate of other types of serious accidents-ones that cause 

the employee to miss more than 20 days of work. The 

rate of serious accidcnts is lowest for mines that employ 

1 to 20 employees, highest among mlnes that employ 21 to 

50 people, and intermediate for mines that employ more 

than 50 people. 

Fatality rates are currently substantially lower than they 

were in the late 1970's. Although fatality rates decreased 

during the 1980's for each mine size category, the percentage of decrease was lowest among the smallest size 

mines and highest among the largest size mines. In looking at the differences between rates of various types of 

fatal accidents at small versus large mines, it appears that 

ground fall accidents are a particularly important problem 

for small mines. The rate of fatal ground fall accidents is 

over 10 times greater at mines with 20 or fewer employees 

than it is at mines with over 50 employees. 

Several trends become evident when looking at differences in the rates of specific categories of serious accidents 

across mine size categories (see table 6). In particular, the 

rates of accidents classified as "handling materials" and 

"slips or falls" increase with increasing mine size. Conversely, rates for accidents classified as "machinery" and 

"powered haulage" decrease with increasing mine size. 

REFERENCES 

1. Convay, E. J., and R L. Unger. Material Handling Devices for 

Underground Mines. BuMines I@ 9212, 1989,48 pp. 

2. Gallagher, S., T. G. Bobick, and R L. Unger. Reducing Back 

Injuries in Low-Coal Mines: Redesign of Materials-Handling Tasks. 

BuMines IC 9235, 1990, 33 pp. 

3. Hamrick, C. A,, and S. Gallagher. Job Design: An Effective 

Strategy for Reducing Back Injuries. Paper in this proceedings. 

4. Holmes Safety Association Bulletin. Statistical Profile of Powered 

Haulage Accidents in the Mining Industry. Aug. 1993, pp. 16-17. 

5. National Academy of Sciences. Fatalities in Small Underground 

Coal Mines (contract JOJ0100145). BuMines OFR 124-83, 1983, 20 pp. 

6. National Research Cou~cil (NAS). Toward Safer Underground 

Coal Mines. 1982, 190 pp. 

7. Randolph, Ei F. A Statistical Profile of Groundfall Injuries. 

Paper in Preventing Coal Mine Groundfall Accidents: How To Identify 

and Respond to Geologic Hazards and Prevent Unsafe Worker 

Behavior. BuMines IC 9332, 1992, pp. 79-89. 

8. Tisdale, J. Meeting the Challenge of Serious Safety Problems at 

Small Coal Mines. Paper in Proceedings of the 24th Annual Institute on 

Coal Mine Safety Health and Research (Sept. 1, 1993). VA Polytech. 

Inst., Blacksburg, VA, pp. 115-126. 

9. Unger, R L. Mechanization of Materials Handling Tasks. Paper 

in Back Injuries. BuMines IC 8948, 1983, pp. 102-110. 

10. U.S. Bureau of Mines. Preventing Coal Mine Groundfall Accidents: How To Identify and Respond to Geologic Hazards and Prevent Unsafe Worker Behavior. IC 9332, 1992, 89 pp. 
PILLAR DESIGN AND STRATEGIES FOR RETREAT MINING 

By Frank E. chase' and Christopher ark* 

ABSTRACT 

One of the keys to miner safety and an efficient re- Mines is in the process of field testing and refining a "user 

covery of the reserves is to design sufficiently sized pro- friendly" computer program called Analysis of Retreat 

duction pillars that will prevent pillar squeezes, excessive Mining Pillar Stability (AKMPS) to estimate abutment 

pillar spalling, severe floor heave, roof falls, and pillar pressures developed during pillaring. Analyses of 68 pillar 

bumps. Currently, few mine operators design sections that design case histories using the ARMPS program indicate 

will be retreat mined using empirical formulas or numer- that it can be successfully employed to predict pillar line 

ical models that estimate abutment pressures generated stability during retreat mining operations. 

by adjacent mined-out workings. The U.S. Bureau of 

INTRODUCTION 

Use of remote-control miners, extended-cut waivers 

up to 12 m (40 ft), and mobile roof supports have enabled 

room-and-pillar retreat mining (also referred to as pillaring, robbing, and second mining) to be competitive with 

longwall mining. While longwall mining can claim an admirable safety record (12); the same cannot be said of 

retreat mining. During the period between 1989 and 1993, 

29% of the roof fall fatalities occurred on retreat mining 

sections. One of the most hazardous underground operations during retreat or any other type of mining is the 

removal of the push-out stump. Over a recent 10 year 

period, 10% of the fatalities resulting from roof or rib falls 

occurred during the removal of the push-out stump (11). 

Roof fall accidents are not the only problem associated 

with retreat mining. Each year, considerable amounts of 

coal are lost because of squeezes, heave, pillar line roof 

falls, and pi!lar bumps. Yet few empirical formulas or numerical models are available that can estimate abutment 

pressures that develop when gob areas are created during pillar extraction. As part of its goal to reduce injuries 

and fatalities. the U.S. Bureau of Mines (USBM) is field 

testing and refining a method called Analysis of Retreat 

Mining Pillar Stability (ARMPS) to aid in the design of 

pillar retreat sections. This payer presents the findings 

thus far. 

ARMPS METHOD 

The ARMPS formula is based on the Analysis of Long- longwall pillar design (8-9). The ALPS method was origwall Pillar Stability (ALPS) method that is widely used for inally developed from measurements of abutment loads in 

five longwalls and later validated by back analysis of more 

than 100 longwall mining case histbries. To be useful for 

'~eolo~ist. 

%lining engineer. pillar retreat mining, the ALPS method had to be modified 

Pittshlrgh Research Center, U.S. Bureauof Mines, Pi ttshrgh, PA. fOT the different ... extraction geometries that are created 

3~ta~ic mtms in pmtheses refer to itm in tfie list of refew during pillar extraction. 

at the end of this paper. 
The goal of the ARMPS method is to help ensure that more representative of conditions than an SF calculated 

the pillars developed for eventual extraction (production for individual pillars. 

pillars) are of adequate size for all anticipated loading The load-bearing capacity of thc AMZ is calculated as 

conditions. The most severe loadings usually develop on the sum of the load-bearing capacities of the pillars within 

the extraction front (or pillar line), particularly whcre it. The strength of an individual pillar (SP) is dctcrmined 

older gob areas from previously extracted panels are using the Bieniawski forinula (3): 

nearby. The ARMPS method determines a stability factor 

(SF) as- SP = S1 [0.63 t (0.36 w/h)], (2) 

SF = LBC/LT, (1) where S1 = in situ coal strength [assumed value 

= 6.2 MPa (900 psi)], 

where LBC = estimated load-bearing capacity of pillars within active mining zonc (AMZ) w = pills wiclt11, 

and LT = estimated load applied to pillars within and h = pillar height. 

AMZ. 

Longwall studies have indicat~cihat 6.2 MPa (900 psi) 

The AMZ is defined as being the width of the extraction is normally the appropriate value for S, for use in this 

front and three pillars deep (fig. 1). formula (8), and this value was used in all the case history 

Studies of longwall gate entries have indicated that analyses discussed. Current indications are that both coal 

three rows of pillars typically behave as a single system strength and floor strength may be more important during 

and that an SF calculated for the system as a whole is pillar retreat than they are in longwall operations. 

I-- GL -I AMZ -I 

KEY 

AMZ Active mining zone H Depth of cover 

6 Abutment angle LA Abutment load 

EFW Extraction front width LD Development load 

GL Mined-out area 

Figure 1 .-Schematic of active mining zone. 
The loading applied to the AMZ (fig. 1) is the sum of- 

* Development loading present before pillar retreat 

and 

Abutment loads created by load transfers from adjacent gobbed-out areas. 

The development load (LD) is estimated using the tributary area formulaLD = (H) (7) (AT), 

where H = depth of cover, 

7 = unit weight of overburden, 

The abutment angle value is dependent upon the caving 

conditions in the mined-out area. Three possible caving 

conditions have been found to occur. If good caving has 

developed in the gob areas and few stumps have been left, 

then the abutment angle is assumed to be the same as that 

used for longwall mining, or 21". At the other extreme, if 

few stumps have been left, but caving has not occurred in 

the gob, then B = 90". A third case arises when caving 

has not occurred and significant remnant pillars (fenders 

or stumps) have been left in the gob. In the later case, it 

is assumed that the remnant pillars have yielded and their 

strength is assumed to be 50% of that calculated from 

equation 2. Then B is adjusted so that the remnant pillars 

carry only the load they are capable of and the remainder 

is transferred. 

and AT = total area of AMZ. In its current form, the program can analyze four 

loading configurations, as illustrated in figure 2. The 

Abutment loads (LA'S) are determined using either equa- simplest-loading condition 1-is development loading only. 

tion 4 or equation 5, depending on the length of the Loading condition 2 occurs where a panel is being fully 

mined-out area (GL): retreated and no other mined-out areas are nearby. The 

total applied load is the sum of the development loads 

When GL 22 (H tan B), and the front abutment load. Loading condition 3 occurs 

where the AMZ is surrounded on two sides by mined-out 

LA = H~ (tan B) (712) (EFW), (4) areas and the pillars are subjected to development, side 

abutment, and front abutment loads. When the pillar line and when GL < 2 (H tan B), is surrounded by gob on three sides (sometimes referred 

to as bottleneckgg), an additional kde-abutment load 

[(H)(GL) - a2 ] results and loading condition 4 is produced. LA = 2 8 tan B (7) (5) Unfortunately, the irregular mining geometries that 

sometimes occur in practice can be difficult to categorize 

where B = abutment angle into one of these four loading conditions. Efforts are currently underway to expand the number of available loading 

and EFW = extraction front width. configurations with numerical modeling. 

VERIFICATION OF ARMPS METHOD 

Design criteria have been established for the ARMPS 3. Severe sloughage. 

method through back analysis of 68 case historics of pil- 4. Exccssivc heave. 

lar design from 10 different States. The case histories 5. Numerous roof falls. 

were obtained from mine visits and from the literature. 6. Coal pillar bump. 

Case histories cover an extensive range of geographic locations, roof rock cavability characteristics, extraction Case history loading conditions were categorized as 

methods, and loading conditions. In addition, overburden being successful abutment loading, unsuccessful abutment 

thicknesses ranged from 53 to 591 m (175 to 1,938 ft), loading, and unsuccessful development loading. Figure 3 

coalbed heights ranged from 0.9 to 3.4 m (2.8 to 11 ft), clearly suggests that many failures, but few successes, have 

and pillar width-to-height ratios varied from 1.0 to 11.1. resulted when designs with ARMPS SF'S of less than 0.75 

Each case history was categorized as being either suc- were employed. Between SF'S of 0.75 and 1.50, there 

cessful or unsuccessful. Unsuccessful cases (table 1) were seems to be a "middle ground," where both successful and 

deemed as being such because one or more of the follow- unsuccessful cases arefound. Based on figure 3, failure 

ing unfavorable conditions occurred: is unlikely when an ARMPS SF of 1.5 is employed. 

Bieniawski also recommends an SF of 1.5 for short-term 

1. Squeezes. pillars subjected to development loads only (3). 

2. Massive pillar failure and resultant airblast. 
Loading condition 1 Loading condition 2 

Loading condition 3 Loading condition 4 

Figure 2.-Retreat mining loading configurations. 
Table 1.-4RMPS values for unsuccessful pillar design case histories 

Location Coalbed Source Loading 

condition1 

ARMPS stability factor 

1.27 

1.11 

Comments 

Pillar squeeze caused panel to be abandoned. 

Squeeze conditions caused 20 pillars 21 by 

21 m (70 by 70 ft) to be lost. 

Arblast generated by sudden collapse of 204 

Alabama ... Blue Creek ....... .. do. ........... Mine visit ....... .. do. .......... 

Colorado ... Cameo "B ....... Abel (1) ........ by 402-m (670 by 1,320 ft) of 3 by 24 m (10- 

by 80-ft) fenders. 

Roof falls, 56 cm (22 in) of floor heave, and 

severe sloughage. 

Inability to break roof caused excessive pillar 

spalling and heave. 

Coal pillar bump fatally injured roof bolter 

operator. 

Squeeze conditions caused 14 rows of pillars 

to be lost. Most of main entries were closed 

entirely. 

Extensive pillar line heave, sloughage, and roof 

falls caused 9 rows of pillar to be lost. 

Squeeze conditions caused 10 rows of pillar to 

be lost. Numerous roof falls and continuous 

miner was buried. 

Severe pillar line weighting. Scores of fenders 

were lost after pillar splits. 

Squeeze conditions caused numerous pillars to 

be lost. 

152 m (500 ft) of pillars were lost in 3 days. 

Large-scale squeeze 1,600 ft outby pillar line. 

Squeeze conditions essentially closed 671 m 

(2,200 ft) of main entries. 

Section and barrier pillar abandoned because 

of squeeze conditions. 

Section abandoned because of violent coal 

pillar bump. 

Excessive roof slaking and subsequent bump 

due to idle pillar line. 

Numerous coal pillar bumps. 274- by 396-m 

(W by 1,300-ft) area of pillars was abandoned because of squeeze. 

Continuous miner was buried for 2 weeks. 

Crushed out cribs due to 0.9 to 1.2 m (3 to 

4 ft) of heave. 

Coal pillar bump during pillar split fractured 

roof bolter operator's leg. 

Squeeze that occurred in partially pillared 

workings caused 2 rows of 12- by 15-m (40- 

by 50-ft) pillars with SF of 1.37 to be lost. 

Arblast generated by approximately 100 fenders collapsing blew out 26 cinder-block stoppings and fan-house weak wall. 1 miner was 

injured. 

10 rows of 12- by 12-m (40- by 40-ft) pillars 

were lost because of squeeze conditions. 

Dangerous pillar sloughage caused scores of 

pillar to be lost. Barrier pillar was also lost. 

Arblast generated by massive pillar failure 

blew out 38 stoppings. 

Massive pillar failure, pillar squeeze, and 

severe spalling. 

Do. 

After losing several rows of pillars because of 

squeeze conditions, section was abandoned 

for fear of losing bleeders. 

Illinois ..... Herrin No. 6 ...... 

Kentucky ... Coalburg ........ 

Harlan .......... 

.. do. ........... 

Chugh (6) ...... 

Unrug (16) ...... 

Mine visit ....... 

.. do. .......... 

Hazard No. 4 ..... 

.. do. ........... 

.. do. .......... 

.. do. .......... 

Wallins .......... 

Ohio ...... Pittsburgh ....... 

Pennsylvania .. do. ........... 

Tennessee .. Beech Grove ..... 

.. do. ........... 

Utah ...... Gilson .......... 

.. do. ........... 

Virginia .... Pocahontas No. 3 .. 

.. do. .......... 

Artler (2) ........ 

Mishra (10) ...... 

Mine visit ....... 

.. do.. ......... 

.. do. .......... 

.. do.. ......... 

Campoli (4) ..... 

West Virginia Beckley ......... Mine visit ....... 

.. do. ........... 

Coal burg ........ 

.. do. .......... 

.. do. .......... 

.. do. ....... .. do. ........ 

.. do. ........... .. do. .......... 

.. do. .......... 

Dorothy ... .. do. ...... 

Lewiston ........ Tang (15) ....... 

.. do. ........... No. 2 Gas ....... .. do. .......... Mine visit ....... 

See footnotes at end of table. 
Table 1.-ARMPS values for unsuccessful pillar design case histories--Continued 

Location Coalbed Source Loading ARMPS sta- Comments 

condition' bility factor 

West Virginia .. ..... (cont.) Pocahontas No. 4 Campoli (4) 3 0.32 Crushed pillars and floor heave. .... .. do. ........... Mine visit ....... 1 1.03 Airblast generated by failure of 11 7 pillars. 

Sewell .......... Peng (13) ....... 3 1.45 Section abandoned because of concern that 

floor heave [0.6 to 0.8 m (2 to 2.5 ft)] might 

prevent equipment retrieval. 

Stockton ........ Mine visit ....... 1 .74 Airblast generated by 140 fenders collapsing 

blew out 32 stoppings and fan-house weak 

wall. 

..do ............ ..do ........... 1 .72 Airblast generated by 90 fenders collapsing 

blew out 40 stoppings. 

..do ............ ..do ........... 1 1.29 Airblast generated by 72 fenders [6 by 12 m 

(20 by 40 ft)] and 50 pillars [9 by 9 m (30 by 

30 ft)] blew out 70 stoppings. 

..do ............ ..do ........... 2 1.17 Squeeze conditions caused 22 pillars [12 by 

14 m (40 by 45 ft)] to be lost. 

NI ........ Lower Kittanning .. Tang (14) ....... 1 (‘7 A massive failure of pillars occurred when pillars to left of chain pillar "A were split. 

Severe entry roof falls occurred. 

NI ........ Taggart ........... do. .......... 1 1.14 Massive pillar failure 15 crosscuts outby pillar 

line. - - 

Do. Same as above. 

NI Not indicated. 

'~oading condition 1 = development loading; 2 = development and front abutment loading; 3 = development, front abutment, and 

side abutment loading; 4 = development, front abutment, and loading from two side abutments. 

2~butment angle = 90". 

3~illars measuring 4.6 by 12 m (15 by 40 ft) had an SF of 0.45. 

4~illars measuring 6 by 6 m (20 by 20 ft) had an SF of 1.32; pillars measuring 3.8 by 13.7 m (12.5 by 45 ft) had an SF of 1.08. 

Successful abutment 

Unsuccessful abutment 

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 

ARMPS STABILITY FACTOR 

Figure 3.-ARMPS stability factors for case histories. 
ADDITIONAL FACTORS INFLUENCING PILLAR LINE STABILITY 

Abutment loads are not the only factor that should be 

considered in pillar design for retreat mining. Pillar line 

conditions are also markedly affected by multiple-seam 

interactions, the rate of pillar line advancement, and roof 

rock cavability characteristics. In the case of multipleseam interactions, the best case scenario is to begin with 

the uppermost seam and to extract it as cleanly as possible. Any barrier, production, or remnants of production 

pillars (miners refer to these as stumps or sprags) left in 

the upper seam gob can transfer loads to pillars in the 

lower seam. However, this is dependent on the thickness 

and the geology of the interburden and the depth of cover 

(5, 7). The load transfer is more intense if the pillars 

and/or stumps left in the upper seam gob are underdesigned. In one mine visited in southern West Virginia 

that had extremely competent roof, the only unintentiocal 

fall that ever occurred on the pillar line or in the mine 

happened directly beneath a barrier pillar. Ic room-acdpillar retreat mining, the mains, barrier pillars, and panels 

that are to be retreated should be superimposed for optimum ground conditions. 

In virtually every mine visited, operators indicated that 

the rate of pillar line advancement played a crucial role in 

overall pillar line conditions. When the pillar line moved 

slowly or remained idle over the weekend or during a 

miner's vacation, normally stable pillars began to take 

weight, as evidenced by sloughage, heave, and even 

squeeze conditions. Mine operators also remarked that 

timely pillar line advancement was even more critical when 

the coalbed thickened because high ribs taking weight 

caused large rib rolls, which are dangerous to the mine 

operator and helper. 

The caving characteristics of the roof also affect pillar 

line stability. The Pittsburgh Seam has gained the reputation of having very weak roof where the Pittsburgh Sandstone Member is absent. During pillar retreat, the roof 

usually breaks directly inby the breaker posts, providing 

excellent pillar line conditions. 

The other extreme roof condition, fairly common in 

portions of southern West Virginia and areas of eastern 

Kentucky, occurs where massive sandstones or siltstones 

[I2 m (40 ft) and thicker] are directly above the coalbed. 

Such roof conditions have been associated with sudden, 

widespread pillar collapses that, in turn, can cause damaging airblasts (fig. 4). Evidence indicates that massive 

and competent roof rock units are able to bridge relatively 

wide spans, particularly when they are aided by the support provided by the regularly spaced remnants of production pillars. When the extraction area is still small, the 

remnant pillars are not subjected to the full overburden 

load because of the stiffness of the roof. A pressure arch 

is created, with most of the weight being carried by 

barriers surrounding the extracted area. Eventually, the 

bridging capability of the main roof can be exceeded, 

either by overextending the extraction area or by the 

weakening of the roof and/or remnant pillars over time. 

Once the pressure arch breaks down, the structural characteristics of the system are such that sudden, massive pillar failures can occur (17). For example, at one of the 

mines visited during this study, production pillars measuring 12 by 12 m (40 by 40 ft) were split down the middle, 

leaving 3- by 12-m (10- by 40-ft) fenders in the gob. 

Shortly after one panel was completed, an area measuring 

152 by 152 m (500 by 500 ft) and containing approximately 

100 fecders ccllapsed suddenly. The resulting airblast 

damaged the fan-house weak wall and 26 stoppings, and 

closed the mine for days. Fortunately, because of the 

location of the blast, only one miner was injured. 

Underground observations and analysis suggest that two 

alternative strategies may be successful in preventing airblasts under competent roof conditions. One approach is 

to limit the partial pillaring conducted in a panel with the 

intention of designing for long-term stability. This can be 

accomplished either by increasing the size of the remnant 

pillars or by periodically leaving rows of unsplit pillars as 

barriers between smaller areas of split pillars. The latter 

was successfully employed in a southern West Virginia 

mine that experienced two moderate-to-severe blasts. The 

second strategy is to go to full pillar extraction. By removing the support provided by the fenders, the bridging 

capacity of the roof should be substantially reduced. If the 

roof does not break during full pillar extraction, caving can 

be induced through explosives (16). 

In another mine visited, pillar splitting was responsible 

for three significant airblasts. Wanting to arrest the situation, the "Virginia three-cut method" was employed (fig. 5). 

The sequence in which the lifts are extracted are numbered as shown in figure 5. In the collapsed areas where 

12 x 12 m (40 x 40 ft) pillars were split, the extraction 

percentage was 78% as opposed to 74% using the 3 cut 

method. However, the 3 cut method leaves non-uniformly 

spaced stumps that have an irregular geometry in the gob. 

According to the mine operator, these stumps routinely 

yielded and crushed out. Since the 3 cut method has been 

used in this mine, no airblasts have been recorded, 

Finally, it appears that massive pillar collapses may be 

more likely where the floor and roof are strong. Where 

the floor is weak, the pillars should be more prone to 

punch, resulting in a pillar line squeeze. 
-- 

Figure 4.--Concrete stopping damaged by airblast. 

0 Scale 40ft 

Figure 5.-Virginia three-cut pillar extraction method. A, First pillar mined; B, second pillar mined. (Numbers 

indicate sequence in which lifts are extracted.) 
CONCLUSIONS 

Information gathered during this investigation lends 

credence to the following conclusions: 

1. Properly sized production pillars that are designed 

considering the front and/or side abutment pressures 

generated by gob creation can result in better miner safety 

and more efficient recovery of reserves. 

2. Case histories analyzed using the ARMPS method 

examined an extensive range of geographic locations, 

depths of cover, width-to-height ratios, roof rock cavability 

characteristics, floor conditions, and extraction methods 

that are representative of the population as a whole. It 

appears that production pillars with an ARMPS SF of 1.50 

or greater have a high probability of being extracted 

without a problem. 

3. Multiple-seam interactions can have detrimental 

effects on pillar line stability. The effect is dependent 

upon the sequence in which the seams are mined, the 

thickness and geology of the interburden, overburden, and 

the presence of production pillars or stumps left in the 

gob. 

4. Normally stable pillar line conditions often deteriorate if the pillar line moves slowly or remains idle for an 

extended amount of time. This deterioration can manifest 

itself in the form of excessive sloughage, heave, and 

squeezes. 

5. Airblasts or squeezes have occurred in mines that 

have competent and massive roof rock units that will not 

cave. If partial pillaring is to be conducted under competent roof that will not cave, the long-term stability of the 

gobbed-out area should be considered. This can be ac- - 

complished either by increasing the size of the production 

pillar remnants or by leaving rows of unsplit pillars as 

barriers between smaller areas of split pillars. 

1. Abel, J. F. Soft Rock Pillars. Int. J. Min. and Geol. Eng., v. 6, 

1988, pp. 241-245. 

2. Artler, L. R Pillar Design-Continuous Miner Butt Section and 

Longwall Development Sections. Paper in Proceedings, Fourth Conference on Ground Control in Mining. WV Univ., Morgantown, WV, 

1985, pp. 160-16s. 

3. Bieniawski, Z T. Strata Control in Mineral Engineering. Wiley, 

1987,212 pp. 

4. Campoli, A. A., C. A. Kertis, and C A. Goode. Coal Mine 

Bumps: Five Case Studies in the Eastern United States. BuMines 

IC 9149,1987, 34 pp. 

5. Chekan, G. J., and R J. Matetic. Loading Characteristics of Pillars in MultipleSeam Mining Operations. BuMines RI 9173, 1988, 

19 PP. 

6. Chugh, Y. P., K V. K Prasad, and R Missavage. A Case Study 

of Geotechnical Studies for an Improved Room-and-Pillar Retreat 

Mining System in Illinois. Paper in Proceedings of the 27th U.S. Symposium on Rock Mechanics. Univ. AL, Tuscaloosa, AL, 1986, pp. 390-397. 

7. Haycocks, C., B. L. Ehgartner, M. Kannis, and E. Topuz. Pillar 

Load Transfer Mechanisms in MultipleSeam Mining. Soc. Min. Eng. 

AIME preprint 82-69, 1982, 6 pp. 

8. Mark, C. Analysis of Longwall Pillar Stability (ALPS): An Up 

date. Paper in Proceedings of the Workshop on Coal Pillar Mechanics 

and Design, BuMints IC 9315,1992, pp. 238-249. 

9. - .Pillar Design Methods for Longwall Mining. BuMines IC 

9247,1990,53 pp. 

10. Mishra, G., and R L. Grayson. An Engineering Analysis of 

"Squeeze" Failure of Pillars in the Pittsburgh Coalbed. Paper in 

Proceedii~gs, Rrst Conference on Ground Control in Mining. WV 

Univ., Morgantown, WV, 1981, pp. 144-153. 

11. Montague, P. G. Pillar Recovery. Paper in Proceedings of 

the American Mining Congress (Chicago, IL). Am. Min. Congr., 

Washington, DC, 1988, pp. 531-548. 

12. Pappas, D. M. Roof and Rib Fall Accident and Cost Statistics: 

An In-Depth Study. BuMines IC 9lS1, 1987, U) pp. 

13. Peng, S. S., and P. Tsang. Mechanism and Control of Floor 

Heave-Development of a Model for Floor Stability Analysis. Paper in 

Proceedings of the Ninth Annual Workshop, Generic Mineral Technology Center, Mine Systems Design and Ground Control (Lexington, 

ICY, Nw. 10-12,1991). VA Polytech. Inst. and State Univ., Blacksburg, 

VA, 1991, pp. 21-25. 

14. Tang, D. H., and S. S. Peng. Mine Pillar Stability Analysis Using 

FEM Methods-% Case Studies. Paper in Proceedings, Ninth International Conference on Ground Control in Mining. WV Univ., Morgantown, WV, 1990, pp. 88-98. 

15. Tang, D. H., S. S. Peng, and C T. Holland. Massive Pillar 

Failure-Two Case Studies. Paper in Proceedings, Conference on 

Ground Control in Mining. WV Univ., Morgantown, WV, 1985, 

pp. 117-126. 

16. Unrug, K F., J. Tussey, and R Moore. Pillar Extraction With 

Application of Mobile Roof Support Eastern Kentucky. Soc. Min. Eng. 

AIME preprint 91-101,1991,8 pp. 

17. Zipf, R K, Jr. Analysis of Stable and Unstable Pillar Failure 

Using a Local Mine Stiffness Method. Paper in Proceedings of the 

Workshop on Coal Pillar Mechanics and Design. BuMines IC 9315, 

1992, pp. 128-143. 
SHIFTWORK: A GUIDE FOR SCHEDULE DESIGN 

By James C. ~uchon' 

ABSTRACT 

Based upon the perturbed performance, increased or 

more serious accidents, lowered production, higher absenteeism, health problems, familial problems, low morale, 

and job dissatisfaction due to working nights and shiftwork, the U.S. Bureau of Mines has analyzed shiftwork 

schedule design at mining operations. The purpose of this 

paper is to discuss in practical terms what mining companies can do if they are considering changes in their 

shiftwork practices. It is not the intent of this paper to 

persuade management or any workers that they should 

change their shiftwork schedule. 

This paper discusses various design considerations or 

dimensions that may vary. These dimensions are (1) fmed 

versus rotating schedules, (2) speed of rotation, (3) direction of rotation, (4) length of shift, and (5) starting 

time of shift. Also, extended workdays and other management considerations, such as training and evaluation, are 

discussed. 

INTRODUCTION 

In the ~ning industry, the proportion of employees 

working shiftwork is increasing. Data from the U.S. Bureau of Labor Statistics indicate that in 1991, 28.4 pct of 

all mine employees worked evening, night, or rotating 

shifts, as compared with 21.9 pct in 1985. Further, the 

percentage of miners working shifts other than straight 

days is considerably larger than the combined average of 

all U.S. industries (17.8 pct). 

There are several practical reasons why shiftwork in 

mining is prevalent, including (1) the increased demand for 

goods and services combined with limited overhead; (2) 

the need to maximize costly equipment for quick capital 

recovery; (3) the need to take advantage of lower utility 

costs at offpeak-hour utility rates; and (4) the need to keep 

equipment running continuously because of high startup 

costs. 

It has been demonstrated in published studies that 

workers in various industrial groups, such as mining, power, chemical, nursing, factory, and oil refineries, have displayed perturbed performance, increased or more serious 

accidents, lowered production, higher absenteeism, health 

problems, familial problems, low morale, and job dissatisfaction due to working nights and shiftwork (1-10).2 An 

excellent review of these effects can be found in a recent 

document completed by the U.S. Congress, Office of Technology Assessment (1). It is easy to understand, therefore, 

why there is a growing interest among all industries, including mining, to examine shiftwork interventions. 

A discussion of alternative work schedules provided other reasons why there is a recent trend in the United States 

toward new and better schedules (11). For instance, an 

increase in relative affluence creates a climate where many 

of life's privileges and comforts have become necessities. 

Employees are examining alternative schedules consistent 

with this. Also, cultural changes, changes in employment 

rates, an aging work force, labor force participation, and 

a shift to service work all contribute toward this move to 

seek alternative schedules. 

'~ngineerin~ research psychologist, U.S. Bureau of Mines, Twin 2~talic numbers in parentheses refer to items in the list of references 

Cities Research Center, Minneapolis, MN. at the end of this paper. 
For thcsc rcasons the U.S. Burcau of Mines (USBM) pcrsuadc management or any workers that they should 

has been involved in rcsearch on various shiftwork issucs change their shiftwork schedule. In many cases, currcnt 

to enhance the safcty of the minc worker. The purposc of work scheduling practices arc used succcssfully. Changes 

this paper is to discuss in practical terms what mining in such situations may, in fact, worsen their situation in 

companies can do if they are considering changes in their spitc of all good intentions. 

shiftwork practices. It is not the intcnt of this paper to 

ERGONOMIC CONSIDERATIONS OF SCHEDULE DESIGN 

The perfect shift docs not exist. Figure 1 illustrates 

that thcre are three ergonomic considerations for any 

schedule that are associated with various causes and effects, such as production, abscntecism, accident rates, 

worker fatigue, and morale. These coilsiderations include 

biocompatibility, socioco~npatibility, and job compatibility. 

A comprehensive assessment of any schcduic, thcrel'ore, 

must consider cach of these co~nponcnts. While each of 

these consideratioils arc iilterrelatcci, they will for the sake 

of simplicity be discusscd and trcatcd indepcndcntly. 

Biocompatibility refers to how a schedule conforms 

or does not conforin to human physiolobry that may afGcct performance. It is well known that humans have innate "biological clocks" that control certain physiological 

%unctions. Circadian rhythms are thosc functions that 

have an approximately 24-h cycle, such as the excretion 

sf human growth hormone and cortisol potassium, variation of body temperature, and sleep-wake cyclc. The 

sleep-wake cycle refers to the body's natural tendency to 

maintain wakcCulncss during the daylight hours and slccp 

during the night, Therc arc two observable conscqucnces 

that can occbr as d icsult of Jisuptiilg [lit: sleep-wake 

cyclc. First, remaining awakc at night results in fatigue or 

a fccling of being tired. This fatigue occurs cven when 

"enough" sleep is taken prior to the night shift. Fatigue 

occurs at night I~eca~i~,~ of ;l piiy4ioiogicai push [or sleep 

manifested by sleepiiic~s, perform:lncc: dclicicncies, lowered body temperature :~nd hcart rntc, and other sign5 

a~sociatcd with a need for sleep. When body temperature 

is used as an indicator of alerincss, the trough of this cycle 

tends to occur at approximately 3:00 a.m. for an individual 

who is not adjusting to a diffcicnt sclictlule or time ;lo~lc. 

A second situation related to circadian rhythms is refcrrcd to as ciccupation:ll jct l'lg. Just as our bodies adjust 

to different time 7ones during [ravel, so loo must our 

bodics adjust to rotalions from day or evenin2 shifts to 

night shifts. Faligue, malaise, diqturbcd sleep, and general 

flu-like syml~toms occur as a result of circadian rhythm 

Blocompatlblllty 

Productlon 

Absenteeism 

Morale 

Job Compatlbllity Soclocompatlbllity 

ERGONOMIC CONSIDERATIONS EFFECTS 

Figure 1.-Ergonomic considerations and effects of shiftwork schedules, 
desynchronization and physiological adjustment to the new 

shift (time zone). Such a biological adjustment to new 

time zones may take from 3 to 10 days, whereas adjustment to a night shift may take longer or may never occur 

because of conflicting day-night cycles, i.e., working during 

the night and sleeping during the daylight hours, as well as 

conflicting social and family cues on workdays and off 

days. 

Sociocompatibility refers to a compatibility between 

work schedule design and social-family life schedules. 

This design consideration is perhaps the most critical aspect from the perspective of the shift worker. The 

norm in our society is an 8-to-5, Monday-through-Friday 

schedule. Deviation from this could potentially create 

social conflict. For many workers, the most disliked shift 

in this respect is the evening shift. Working between 

3:00 p.m. and 11:OO p.m. precludes a satisfactory familysocial life. Working weekends, an unavoidable consequence of continuous operations, is a major source of social incompatibility. 

Job compatibility refers to how a schedule conforms 

with or competes with job or organizational demands. For 

instance, certain companies or industries require training 

days to be built into a schedule. Some underground mining companies have blasting periods that should be considered in a schedule. Such things as need for weekend 

work, need for equal personnel across the 24-h day, commuting times for employees, union regulations, exposure 

to harmful environmental agents, etc. should be considered 

in the choice of schedule design. Any schedule that involves evening, night, or rotating shifts will create problems for some people. 

MANAGEMENT-LABOR DIFFERENCES 

The focus of "important" schedule considerations can 

be different depending upon one's perspective. Figure 2 

illustrates the concerns management and labor typically consider critical in a "good" schedule. Traditionally, 

management tends to emphasize issues of job compatibility, while labor tends to emphasize issues of sociocomgatibility. This is not to say that management ignores the 

welfare of its employees or that employees do not consider 

the job considerations that are necessary for company survival. In fact, insight into each position is ultimately 

necessary for a successful and workable schedule. Until 

recently, biocompatibility issues in schedule designs were 

often ignored. However, research in the past 10 years has 

evaluated human sleep, biological rhythms, nutrition, etc. 

in relation to shiftwork schedules and has offered important considerations that should be of value to all parties. 

Figure 2.--Critical schedule concerns. 
RECOMMENDATIONS 

While there are virtually unlimited schedule designs, 

there are limited dimensions of the schedule that can vary. 

These dimensions are (1) night and evening shift, (2) futed 

versus rotating shifts, (3) slow or fast rotation schedules, 

(4) forward or backward rotation, (5) early or late shift 

start times, and (6) length of shift. The following is a discussion of each of these. 

NIGHT AND EVENING SHIFT 

As mentioned earlier, working night shifts has been 

associated with a variety of health and performance measures. It is the night shift that is incompatible to our body's 

natural rhythms. The night shift is also disliked by many 

workers because of social factors. There are situations, 

however, where individuals prefer working nights because 

of certain benefits, such as pay differentials and less pressure or less supervision at work. Working nights also 

allows for more parental involvement in child care and the 

associated cost savings. 

Considering only the criteria of adequate sleep, the 

evening shift is for most people the perfect shift. Virtually 

all studies have indicated that the evening shift is associated with the greatest sleep length when compared with 

the day or night shift. Nevertheless, it is the eyening shift 

that is the least preferred by workers. Clearly, this dislike 

for the shift is due to issues of sociocompatibility. 

Recommendations: 

1. Before anything else, an employer should consider 

the possibility of decreasing use of night shifts. 

2. The use of overtime should be avoided for workers on night shifts. Many workers nap prior to the shift 

and begin sleep immediately following the night shift. 

Therefore, any overtime may eat into the worker's total 

sleep length, which is already shortened. 

3. When night shifts are used, several special precautionary measures should be taken. These area. Longer or more frequent mandatory rest breaks 

when work is between midnight and 6:00 a.m. 

b. Physically or mentally difficult assignments 

should be left for the day or evening shifts. 

c. Ample opportunity for a hot and healthful 

variety of foods via machine or food cart should be 

made available to these "offshift" workers. 

d. Lunch breaks should occur at a consistent time 

of the night shift, i.e., meals should be eaten at approximately the same time each night. 

FIXED VERSUS ROTATING SHIFTS 

Fixed or permanent shifts are more common in 

Monday-through-Friday, 24-h operations. In these 5-day 

operations, three crews each working day, evening, or 

night shifts can cover a 24-h operation with either permanent or rotating shifts. However, in continuous operations, utilizing 8-h shifts, where each job totals 168 h per 

week (24 h/d times 7 d/wk), a minimum of four crews is 

needed to cover all three shifts. Therefore, at least some 

shift rotation is typically required. The question then 

becomes, Should the use of permanent shifts be minimized 

or maximized when possible? Table 1 shows one of the 

most commonly used schedules in continuous operations. 

This schedule maximizes rotating shifts by requiring all 

workers to rotate on a weekly basis. In contrast, table 2 

shows a schedule that utilizes three futed crews (1, 2, and 

3) and one rotating or "grasshopper" shift (crew 4). 

Table 1 .-Schedule consisting of four-crew, 8-h, 7-day backward rotating 

"Southern Swing" pattern 

Crew-week Mon. Tues. Wed. Thurs. Fri. Sat. Sun. 

1 ....... - - E E E E E 

2 ....... E E - M M M M 

3 ....... M M M - - G G 

4 ....... G G G G G - - 

E Evening shift. 

G Night shift. 

M Morning shift. 

NOTE.-Dashes indicate off days. 
Table 2.-Schedule consisting of 6-day-on and 2-day-off pattern, 

repeating every 8 days 

Crew Mon. Tues. Wed. Thurs. Fri. Sat. Sun. 

E Evening shift. 

G Night shift. 

M Morning shift. 

'~ixed. 

2~rasshopper shift, rotating every 2 days. 

NOTE.-Dashes indicate off days. 

One argument in favor of using fured shifts, such as 

permanent days, evenings, and nights, is to allow workers 

on the night shift to "adjust." However, research has 

consistently shown that night workers never completely 

adapt to that shift. Nearly all night permanent shift 

workers revert to a "normal" day schedule on their days 

off. They are, therefore, constantly rotating their worksleep cycles in spite of having a fured shift. Several studies 

have indicated that permanent night workers, as do 

rotating shift workers, tend to sleep several hours less 

before the night shift than any other shift. Working 

consecutive night shifts, therefore, may result in a cumulative "sleep debt." A summary of the pros and cons of fured 

versus permanent shifts is as follows: 

Advaiz tnges of Fixed Shifts: 

1. Often allows workers to choose.the e.vening or night 

shifts. These shifts are actually more sociocompatible for 

some workers. 

2. Allows a large percentage of employees to avoid the 

night shift altogether. 

3. Less disorienting since rotation among the other 

shifts is not required. 

Advaiztages of Rotatitzg Shifts: 

I. A "fair" schedule. No preferences given to individuals for the favored shifts. 

2. Minimizes the exposure to the night and evening 

shift to any particular group of employees by "spreading 

out" the exposure among all employees. 

3. If rotations are fast (see next section) then there 

may be less physiological disruption of circadian rhythms, 

i.e., occupational jet lag would not be an issue. 

1. The primary consideration should be the possibility 

of the reduction of the work force on the night shift. 

2. Unless the night shift and the evening can be filled 

by workers voluntarily choosing to work permanent shifts, 

rotating shifts are recommended. 

SLOW OR FAST ROTATION SCHEDULES 

Rotating shifts can differ with respect to how quickly 

workers rotate from one shift to another, or the number 

of contiguous days on each shift. In U.S. mining operations, rotations tend to be as short as 1 week and as long 

as 2 or more weeks on the same shift. It is not typical to 

find "rapid" rotations of 1 or 2 days, as is found in some 

service industries or as is typical in the European community. The rapid rotation will be discussed below. 

There are reasonable hypotheses for suggesting either 

the 1 week, or the slower rotation cycles of 2 or more 

weeks. On the one hand, it can be argued that it is more 

advantageous to work shorter stretches of nights to avoid 

a cumulative sleep deprivation that may occur with too 

many contiguous night shifts (12). On the other hand, it 

can be argued that a slower rotation has the advantage of 

letting workers adjust to night shifts, thereby lessening the 

negative effects of night work (13). 

The USBM conducted a study to determine whether or 

not there is an advantage to working the second week of 

a 2-week cycle, as would be indicated by reports of more 

positive health, mood, and sleep items on the second week 

as compared with the first week (14). Forty-two workers 

at a surface mine in the Midwest filled out the work, food, 

and sleep diary for 4 to 6 weeks. They rotated every 

2 weeks, going from days to nights to evenings with all 
weekends off. The dependent measures were defined as 

(1) health, the daily frequency of reported symptoms; (2) 

mood, based on a self-evaluation of four descriptorsalert, sleepy, grouchy, and relaxed; (3) total sleep length; 

and (4) sleep quality. Results indicated that on the second 

week of the night shift, workers reported significant improvements in all four mood descriptors for the second 

half of their shift. Also, sleep quality as measured by 

awakenings during sleep improved on the second week of 

the night shift. None of the variables showed a worsening 

on the second week of nights. These results do not support a "cumulative trauma" effect for the schedule studied in this paper. On the basis of this study, it could be 

recommended that 2-wcek cyclcs arc supcrior to I-week 

cycles. 

However, a truly last rotation schedule, rarely used 

in U.S. industries, is common in European countries. Table 3 shows a typical fast rotating schedule. Experts agree 

that there are several advantages to fast rotating shifts 

(15-17). First, individuals do not have time enough on any 

shift to adjust his or her circadian 'rhythms, thereby avoiding the physiological dyschrony associated with working 

stretches of night shifts. Second, working only two or 

three consecutive nights does not allow a sleep debt to 

occur, which is associated with working several consecutive 

nights. Third, short stretches of nights allow for more 

regular social contacts. 

Reconzmendations: 

I. On a rotating schedule, it is recommended that 

schedules have 2 weeks of a particular shift (with days off), 

as compared with I week. Table 4 shows an example of 

a schedule for an eight-worker continuous operation, utilizing 2-week rotations. 

2. A fast rotation, such as the one shown in table 3, 

may be considered as an alternative for those groups of 

workers wanting to avoid long stretches of night shifts. 

Table 3.-Rapid rotation schedule often used in European work systems1 

Crew-week Mon. Tues. Wed. Thurs. Fri. Sat. Sun. 

1 ....... M M E E G G G 

2 ....... - - M M E E E 

3 ...... G G - - M M M 

4 ....... E E G G - - - 

E Evening shift. 

G Night shift. 

M Morning shift. 

 h his schedule requires four crews working a repeating 2-2-3 pattern. For instance, 

crew 1 works 2 days, two evenings, three nights, 2 off days, two day shifts, two evening 

shifts, etc. 

NOTE.-Dashes indicate off days. 

Table 4.-Crewless schedule consisting of 2 contingent weeks of nights1 

Employee-week Mon. Tues. Wed. Thurs. Fri. Sat. Sun. 

1 ........... - M M M M M M 

2 ........... M - - M M M M 

3 ........... M M M - - M M 

4 ........... E E E E E - - 5 ........... - G G G G 6 6 

6 ........... 6 - - G G G G 

7 ........... G G G - - E E 

8 ........... E E E E E - - 

E Evening shift. 

G Night shift. 

M Morning shift. 

 h his schedule requires eight shift workers covering two positions around the clock. The 

shift workers are placed at 4-week intervals in an 8-week cycle. 

NOTE.-Dashes indicate off days. 

Source: Circadian Technologies, Inc. 
FORWARD OR BACKWARD ROTATION 

One popular suggestion offered by shiftwork expcrts is 

to prescribe schedules that rotate in a forward direction. 

Rotating from a day to evening to night shift (table 5) is 

preferred over rotating from a day to night to evening shift 

(table 1). Unfortunately, there are virtually no published 

studies that have systematically reversed ONLY the 

direction of the shift rotation in a mining or industrial 

setting that would show the benefit of such an intervention. 

There are, however, a few studies that have made shift 

changes, which have ii~cluded direction of rotation as one 

part of the total change. For instance, the most widely 

cited study is the intervention study at Great Salt Lake 

Minerals (10). In this study, the group that changed to a 

forward direction AND went from a weekly to a 21-day 

rotation schedule improved on measures of health, production, and turnover. 

There are two viewpoints as to why thcre may be benefits using a forward rotating schedule: 

Premise 1: First, Knauth and Rutenfranz (16) state that 

for a discontinuous three-shift system with a five-shift, twodays-off pattern: (1) a forward rotation produces a 72-hoff period between a day and evening shift, a 72-h-off 

period between an evening and night shift, and a 48-h-off 

period between a night and day shift, and (2) a backward 

rotation produces a 56-h-off period between a night and 

evening shift, a 56-h-off period between an evening and 

day shift, and an 80-h-off period between a day and night 

shift. The shortcr the off period, the less time for rest and 

recovery. Therefore, they conclude that since a forward 

rotation produces only one short, between-shift interval 

and a backward rotation produces two short, between-shift 

intervals, the forward rotation is recommended. 

Premise 2: A second and more popular reason for prescribing the forward rotation relates to circadian rhythms 

that are disrupted during phase advances or delays. Since 

humans have circadian rhythms that are over 25 h, it is 

easier to phase delay than to phase advance. Phase advances merely refer to adjustment of our circadian rhythms 

to earlier clock times. Phase delay refers to adjustment to 

later clock times. Research has shown that transmeridian 

air travelers have a much easier time adjusting to westward travel ("phase delay" or forward rotation) as opposed 

to eastward travel ("phase advance" or backward rotation) 

(18-20). Based on this research, many authors have recommended that shift rotation schedules take advantage of 

this finding by constructing schedules with forward rotations to hasten adjustment to each new shift (10, 16, 21- 

22). Unfortunately, no single study has compared the patterns of adjustment or completeness of adjustment for a 

group of shift workers who have rotated in each direction 

with all other factors being equal. In fact, no study has 

demonstrated complete circadian adjustment for shift 

workers rotating in either direction. 

The USBM challenged these viewpoints using an analysis based upon sleep times taken from survey data and attempted to evaluate the argument that forward rotations 

are BETTER than backward rotations. The primary concern in rotating shiftwork is rotating onto and off of the 

night shift. Therefore, each between-shift interval prior to 

or subsequent to a night shift was scrutinized. This paper 

is based on sleep timing only. Other factors that could 

influence adjustment, such as eating and social behaviors, 

internal biological functions, and rhythms should not be 

ignored. 

Night shifts are typically considered either the first or 

third shift, depending upon the placement within the overall schedule. For instance, in a Monday-through-Friday 

workweek, a night shift is the first shift if it begins at or 

about Sunday night and ends Monday morning. However, 

a night shift is considered the third shift if it begins late 

Monday night and ends early Tuesday morning. 

Table 5.-Schedule cons~sting of four-crew, 8-h, 7-day forward rotating pattern 

Crew-week Mon. Tues. Wed. Thurs. Fri. Sat. Sun. 

E Evening shift. 

G Night shift. 

M Morning shift. 

NOTE.-Dashes ~ndicate off days. 
It was shown that when nights are the third shift, the 

recovery interval after the night shift on both the forward 

and backward rotations are "short" intervals (figs. 3-4). 

However, the forward rotation contains only one full 

night's sleep and two shortened sleep times. Further, the 

day shift follows this, which could itself contribute to sleep 

deprivation. On the backward rotation, the recovery interval after a night shift contains two full night's sleep, following a shortened day sleep. The next afternoon series 

could actually help in recovery since these shifts are 

associated with the longest sleep lengths of any shift. 

When nights are the first in the series, the recovery 

intervals after a night shift are relatively long for both 

forward and backward shifts. However, the backward rotation contains a potential for three full night's sleep, 

as opposed to only two full night's sleep for the forward 

rotation. 

Therefore, when primary importance is placed upon 

recovery from night shifts, if nights are the third in the 

series, the backward rotation is the most desirable. 

The amount of slcep and time off prior to working a 

series of night shifts was also inspected (figs. 3-4). Ideally, 

individuals who are well rested will have a better chance 

of adjusting and coping with their night shifts. Where 

nights are the third in the series, both the forward and 

backward rotations have a long between-shift interval prior 

to the night shift, 72- and 80-h, respectively. Both allow 

three separate sleep periods to recover from the night 

shift. 

Where nights are the first in the series, both thp, 

forward and backward rotations have a "short" betweenshift interval, 48-h and 56-h, respectively. The day-to-night 

shift change on the backward schedule and the evening-tonight shift change on the forward schedule have only two 

nighttime sleep periods. 

Therefore, when analyzing sleep behaviors prior to 

night shifts, having nights as the third shift for both forward and backward shifts are more desirable than having 

nights as the first shift. 

Perhaps the more popular reason for promulgating thc 

forward rotation is its apparent consistency with the idea 

that it is biologically quicker to adjust when rotating in the 

forward direction than in the backward direction. Forward 

rotations have been compared with east to west travel, 

where sleep-wake cycles are phase delayed; i.e., sleep 

occurs later than what has been typical for an individual. 

Just looking at work start times, it appears that workers 

are phasing in a forward direction; i.e., day to evening to 

nights. However, when looking at the sleep-wake cycles of 

actual workers, they are not consistently rotating forward. 

8a.m. 4 p.m. Mid. 8 a.m. 4 p.m. Mid. 8 a.m. 4 p.m. Mid. 8 o.m. 4 p.m. Mid. 8 a.m. 4 p.m. 

Day to 

afternoon 185j m lssi II 

72 h off 

Afternoon to ni9ht pq F] -- - 

I 72 h off ~-{ 

Night to day 

KEY 

Work times 

TI Sleep times 

Figure 3.-Forward rotation with night as third shift. (Mid. = midnight) 
hased upon typical sleep times, the number of phase ad- EARLY OR LATE SHIFT START TIMES 

vances and phase delays are exactly equal for forward and 

backward rotating shift workers. Adjustment, therefore, Various factors can influence a preferred start and end 

'should be the same for both conditions. time. In the realm of job-compatibility, certain factors 

should be considered. For instance, daily blasting schedR ecomnzendafiotzs: ules are often coordinated with shift start times for underground mines, since evacuation of the mine is necessary. 

1. Where the speed of rotation is relatively slow (i.e., ~ociocom~atibilit~ issues involve such concerns as driving 

1 week or more), the preferred direction of rotation is through rush hour and being home at particular times to 

llinked to the amount of time off between changes. The coincide with meal times or child care. Biocompatibility 

amount of time off is related to the position of the night issues include such concerns as sleep quality and sleep 

shift, first versus third. An analysis of time off and typical 

sleep periods indicates that the backward rotation wlth 

nights as the first shift may be more conducive for 

recovery from a stretch of nights. However, a backward 

rotation with nights as the third shirt offers the best 

opportunity for sleep in preparation and recovery from the 

night shift. In general, it is suggested that there should be 

at least 56 h bctween the last of a series of night shifts and 

the next of a series of shifts. 

length, as well as individual differences such as morning 

and evening types. Morning types or larks are those individuals who tend to prefer to go lo bed early and wake up 

early. Evening types or owls are those individuals who 

prefer to go to bed late and wake up late. This factor may 

be an important consideration as the work force ages. 

Older workers are associated with being morning types. 

In general, research has shown that when working a day 

shift, sleep length decreases with earlier work start times. 

2. For fast rotations, as shown in table 3, forward Also, sleep taken between night shifts are of shorter durarotations are recomn~ended. tion the later the work times start and end. Therefore, to 

I 8o.m. 4 p.m. Mid. 8 a.m. 4 p.m. Mid. 8 a.m. 4 p.m. Mid. 8 a.m. 4 p.m. Mid. 8 a.m. 4 p.m. I 

Day to night 185 wl rl 

I 

rn 

80 h off ~-1 

Night to afternoon 

Afternoon to day 

1 56 h off--4 

KEY 

i-1 Sleep times 

Figure 4.-Backward rotation with night as third shift. (Mid. = midnight) 
maximize sleep length before the morning shift, the shift 

should not start too early. However, to maximize sleep 

length after a night shift, the shift should not end too late. 

Knauth and Rutenfranz (16) discussed studies of start 

times in various industries. In a coal mine, an experimental change on the day shift from a 6:00 a.m. to a 7:00 a.m. 

start time was associated with a 23.8 pct accident rate 

decrease. Similar findings of later start times being 

associated with fewer accidents or error rates have been 

found with bus drivers and train drivers. The study also 

suggested that earlier start times on,a "late shift," between 

1:OO p.m. and 4:00 p.m., was associated with more frequent 

accidents. 

1. On a one-shift system (i.e., a day shift), a 7:00 a.m. 

to 9:00 a.m. start time is suggested. 

2. For 24-h operations, it is suggested that a 7:00 a.m., 

230 min start time be employed. A latcr start time will 

hamper the ability of night shift workers to get adequate 

sleep. 

3. Ideally, a flexible start timc should be uscd if 

possible. This allows for individual preferences and 

differences. 

LENGTH OF SHIFT 

There is very little doubt that "extended workdays," 

regular shifts of 10 or 12 h, maintaining an approxinlately 

40-h week, is a very popular alternative among the work 

force because of the significant increase in days off, including weekends, especially when compared with traditional rotation schedules of working seven straight shifts or 

having only one weekend off every 4 to G weeks. 

While the popularity of extended workdays has been on 

the increase, there are some serious concerns by managcment, workers, unions and various governmental policymakers that working 10- or 12-h days may create an addcd 

risk of accidents and health problems (23). Unfortunately, 

there is very little objective information available regarding 

the nature and degree of safety and health risks associated 

with the application of extended workday schedules (1, 24- 

25). As a consequence, when it comes to questions of designing and managing extended workdays, decisionmaking 

by management must now proceed on limited information. 

Health and safety issues are not important considerations for the implementation of 12-h shifts in relatively 

safe workplaces such as white collar settings. However, in 

labor-intensive and environmentally stressful conditions as 

in mining, where accidents and health are major concerns, 

or where safety is a public concern as in the nuclear power 

industry, the application of Boilg workdays must be carefully analyzed. Since all indications are that the application of extended workday schedules by U.S. industries will 

become increasingly widespread over the decade, it is imperative that a careful and comprehensive evaluation of 

safety and health risks associated with such schedules be 

initiated. In a report requested by the House Committees 

on Appropriations; Energy and Commerce; Science, Space, 

and Technology; Veterans Affairs, and the Senate Subcommittee on Science, Technology, and Space of the Office of 

Tcchnology Assessment, it was stated that there is "... a 

compelling need for inore studies of the interactions between work schedules and safety in the workplace" (I, 

p. 18). 

The change from an 8-h rotating shift to a 12-h rotating 

shift implies scvcral critical schedule differences (26). 

Below are thc crucial similarities and differences between 

8-h rotating shifts and 12-h rotating shifts. These are the 

factors that could make a difference in workers' tolerance 

to their schedules: 

1. Length of the workday.-An extended workday is 

typically considered a 10- or 12-h workday, while still 

maintaining an approximately 40-h workweek. Table 6 

shows an example of "2-3-2 every other weekend off' 

extended workday scheduleO3 

%is schedule is the continuous pattern of the days on-days off 

sequence; i.e., two shifts on, followed by 3 days off, followed by two 

shifts on, foliuweJ by two shirts oCC, etc. 

Table 6.-Schedule consisting of two-three-two,' every other weekend off, 

12-h shift pattern 

Crew-week Mon. Tues. Wed. Thurs. Fri. Sat. Sun. 

1 ....... - D D - - D D 

2 ....... D - - D D - - 

3 ....... - N N - - N N 

4 ....... N - - N N - - 

D 12-h day shift. 

N 12-h night shift. 

 his schedule is the continuous pattern of the days on-days off sequence; i.e., two 

shifts on, followed by 3 days off, followed by two shifts on, followed by two shifts off, etc. 

NOTE.-Dashes indicate off days 
2. Amount of time off between workdays.-Extended 

workdays typically have less off-time between shifts. This 

would have implications for physical recovery from fatigue 

and potentially less time for sleep. 

3. Length of the workweek.-Extended workweeks typically have shorter workweeks at the expense of longer 

workdays. This could have implications for adaptation of 

circadian rhythms or less cumulative fatigue across a 

workweek (27). 

4. Amount of time off, i.e., length of "weekends."- 

Extended workdays usually allow more days off. This 

would have implications for recovery from fatigue or sleep 

deficit. 

5. Speed of rotation.-U.S. shift workers usually rotate 

slowly, 1 week or more on any one shift. Exzended workdays usually require faster rotations, 2 to 4 consecutive 

days, which would have implications for adaptation to circadian rhythms. 

6. Time of day.-Both 8-h schedules and 12-h schedules can involve around-the-clock operations. Therefore, 

working the night shift will still be an issue in extended 

workdays. 

The USBM conducted a study designed to examine the 

safety and health implications of extended workdays at 

an underground copper, lead, and zinc mining operation 

(28). Measures were taken before and after a change 

from the old 7-days-on, 2-days-off, 8-h continuous schedule 

to the new 4-days-on, 4-days-off, 12-h continuous scheduIe. 

These measures included (1) behavioral performance 

measures to analyze perceptual-motor changes, (2) continuous heart-rate monitoring and aerobic capacity to 

measure physical fatigue, (3) pulmonary-respiratory measures to examine air coiltaminant exposure, and (4) a variety of self-report questionnaires to measure perceived 

adaplion and satisfaction will1 the new schedule. A control 

group consisting of 5-days-on, 2-days-off day shift workers 

at the same mine was also included. 

Survey results indicated an overwhelming support for 

extended workdays at the underground copper, lead, and 

zinc mine (25). However. self-reported mood scales and 

the Stanford Sleepiness Scale indicated that workers on the 

12-h night shift expericnced more sleepiness and lowered 

energy-alertness levels altcr the eighth hour into their 

shift. The 12-h shifts did not seem to be associated with 

a decrease in most measures of performance across the 

shift. Only on one measure of physical endurance task 

(tapping lapses) was there a decrease in performance 

across the shift for the 12-h night shift. Most of the physiological and pulmonary data indicated few differences 

between the 8- and 12-h shifts. 

In this study, because of the remote location of the 

mine, the workers on 12-h shifts were expected to lodge at 

the minesite during their 4-day shift week. This undoubtedly had a beneficial effect on the sleep and rest between 

shifts. This was confirmed by the diary data that indicated 

improved sleep quality and no lessening of sleep length, as 

compared with the workers' 8-h schedule. 

Based upon the overall acceptance of the new schedule 

by the workers and lack of evidence to suggest serious performance decrements, it was recommended that the mine 

retain the 12-h schedule, with certain precautionary measures to ensure the safety of the workers. Such measures 

included maintenance of the on-site lodging for 12-h workers, continuous observation and evaluation of group and 

individual adjustment, and customizing work tasks and 

work breaks to accommodate longer work hours. 

In an area fraught with inconsistencies, there are several valid comments that can be safely made: (1) workers 

tend to embrace the use of extended workdays; (2) in spite 

of item 1 above, some studies in some industries have 

shown performance and/or safety decrements associated 

with extended workdays; and (3) more research on extended workdays is needed, especially for companies and industries considering the use of extended workdays where 

safety is of major importance. These conclusions underscore the need for caution by companies using or considering the use of extended workdays. Based upon this review, 

it is recommended that the use of extended workdays be 

accompanied by special efforts to create safe working 

conditions. Also, since no a priori predictions from prior 

research can be made with certainty about the probable 

consequences of introducing 10- or 12-11 shifts into a mining company, evaluation of each miner should be made on 

a periodic basis. 

Recommendations: 

The use of extended workdays is recommended provided that certain precautions are considered. These are1. Extended workdays should not be considered where 

the frequency of accidents or near-miss accidents are at 

unacceptable levels. The use of extended workdays should 

not be expected to reduce the likelihood of accidents. 

2. Extended workdays should not be considered for 

jobs that require extremely high physical workloads. For 

example, the American Industrial Hygiene Association 

recommends a workload not to exceed one-third VO,,, 

(maximum aerobic capacity) for an 8-h workshift. While 

similar recommendations have not been made for extended workdays, this standard should be strictly enforced. 

3. Job sharing and cross training should be considered 

where extended workdays are used. Since vigilance, boredom, and mental or physical fatigue can lead to errors, 

changing job tasks may alleviate these stressors. 
4. Workers should not be expected to work overtime evaluate schedules before and after changes are made 

on extended workdays. Working on scheduled days off is (29). Also, long-term monitoring of health, accident, and 

not recommended. production effects should be considered. 

5. If extended workdays are used, regular evaluation 6. Hybrid schedules that utilize both 8- and 12-h shifts 

and assessment should be undertaken. For instance, should be considered. Table 7 is an example of a schedule 

survey methods have been developed by the USBM to utilizing both 8- and 12-h shifts. 

Table 7.-Hybrid schedule consisting of both 8- and 12-h shifts 

Crew-week Mon. Tues. Wed. Thurs. Fri. Sat. Sun. 

E Evening shift. 

G Night shift; third shift of the day, running from 11 p.m. to 7.a.m. 

GI2 Shifts from 7 p.m. to 7 a.m. 

M Morning shift. 

MI2 Shifts from 7 a.m. to 7 p.m. 

NOTE.-Dashes indicate off days. 

Source: Circadian Technologies, Inc. 

MANAGEMENT CONSIDERATIONS 

Changing a schedule: Equally important to the new 

schedule itself is how the process of choosing a schedule 

is carried out. There is not a single method that has been 

shown to be the best. A prescription for failure is for any 

one manager to take it upon himself or herself to decide 

upon a schedule and i~nplement itwithout consulting thosc 

workers who would be affected by the change. This method, although seemingly efficient, sets up the potential for 

suspicion and inaccurate assumptions that could lead to 

possible rejection of the schedule, regardless of how good 

it is. 

The following steps are recommended as one way that 

has proven effective: 

3. Determine operational requirements. 

4. Design alternative work schedules that consider the 

information from steps 2 and 3. 

5. Evaluate alternative work schedules. This evaluation 

is based upon the opinions of the shiftwork committee, 

experts in the field, and/or other workers. 

6. Choose three alternatives for a vote. 

7. Make the shiftwork change. 

8. Evaluate the change 6 months, 1 year, and every 

year thereafter. If the presurvey was used for evaluation, 

a postsurvey can be used as a basis of comparison. Inform 

the work force of the results of the evaluation. 

9. Decide to keep or reject the schedule. 

I. Construct a company-wide shiftwork committcc. Traitlittg atzd followzly: Offer training to the shift 

2. Evaluate work problems and worker needs. Social workers in ways to cope with shiftwork. Involve family 

requirements of a schedulc can be determined at [his timc. members in this training. 

Focus groups or surLfcys can bc: used at this slep. 

SUMMARY 

For thc vast majority of the work force, any schedule reported upon. The literature is full of studies and reports 

that involves hours outside [he parameters of a "normal" of actual work settings that have changed schedules with 

schedule (i.e., 9 to 5), will involve sacrifice and physical positive outcomes. Shiftwork practice is an ergonomic 

and psychological distress. There seems to be, however, consideration, where the fit between the worker and 

schedules that are better than others. This paper presents workplace may have serious consequences caused by job, 

various aspects of schedules that have been studied and sociological, and biological compatibility. 
REFERENCES 

1. U.S. Office of Technology Assessment (Congr.). Biological 

Rhythms: Implications for the Worker. U.S. GPO, Sept. 1991, 249 pp. 

2. Andlauer, P. Shift Work. Ch. in Encyclopedia of Occupational 

Health and Safety, Volume 11. Int. Labour Off., Gcneva, Switzerland, 

1972, pp. 2023-2027. 

3. Carpentier, J., and P. Cazamian. Night Work: Its Effects on the 

Health and Welfare of the Worker. Int. Labour Off., Geneva, Switzerland, 1977, 85 pp. 

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F. Aghazadeh. Elsevier, 1988, pp. 151-160. 
NATURE AND COST OF LOW BACK PAIN 

By Sean ~alla~her' and Christopher A. am rick^ 

ABSTRACT 

Low back pain (LBP) represents a huge expense to the current state of knowledge regarding LBP-the causes, risk 

mining industry and to society as a whole. Any effort to factors for LBP, effectiveness of treatments, recovery from 

control the problems associated with LBP requires an back pain, and methods that can be used to help control 

understanding of the nature of LBP. This review paper the problem. 

was written by the U.S. Bureau of Mines to describe the 

INTRODUCTION 

Low back pain (LBP) is very common in Western countries and is a major cause of worker disability, limitation 

of activity, and economic loss. Many studies have indicated that up to 80% of the general population are affected by LBP at some time during their lives (26, 35).3 

Furthermore, it is estimated that approximately one in seven Americans are currently experiencing LBP (25). The 

cost of back injuries in the United States in 1989 was variously estimated to be anywhere from $27 to $56 billion 

(38). These costs have undoubtedly risen by a substantial 

amount since that time. 

Few need to be reminded of the magnitude of the back 

pain problem in the mining industry. Back injuries 

consistently rank as the leading cause of lost workdays, 

account for up to 40% of worker compensation payments, 

and cost the industry tens of millions of dollars every year 

(20). In underground coal mines alone, back injuries cost 

the industry in excess of $30 million in 1991. The average 

cost of a back injury that year was over $8,000.4 As part 

of its mission to enhance the safety and efficiency of 

mining, this review paper was written by the U.S. Bureau 

of Mines to describe the current state of knowledge 

regarding LBP-the causes, risk factors for LBP, effectiveness of treatments, recovery from back pain, and methods 

that can be used to help control the problem. 

CAUSE OF LBB 

While a great deal of knowledge has been accumulated individual ages. It is thought that the changes that occur 

regarding LBP in the past couple of decades, doctors and as one gets older may lower the resistance of the spine to 

scientists still cannot explain the exact mechanisms causing heavy workloads. Consequently, heavy loads on the spine 

pain in the majority of patients with LBP. Many experts trigger the onset of low back symptoms (26-27, 34, 41). 

believe that LBP is caused by changes in the spine as an 

'~esearch physiologist. 4~npublished data prepared by C. A. Hamrick in 1994; available 

2~ndustrial engineer. upon request from S. Gallagher, BuMines, Pittsburgh, PA. 

Pittsburgh Research Center, U.S. Bureau of Mines, Pittsburgh, PA. 

3~talic numbers in parentheses refer to items in the list of references 

at the end of this paper. 
TYPICAL LBP HISTORY 

LBP typically begins fairly early in life (usually in one's (radiating back pain) are more frequent, and there is often 

twenties). Back pain during this period is typified by a residual pain between attacks. Improvement is frequently 

mild and diffuse pain of relatively short duration, which is seen in the fifties. This period is characterized by less 

followed by a return to full activity. In one's thirties, there severe pain, which appears to be arthritic in nature (mornare often more frequent attacks of LBP, which are relieved ing stiffness) and is largely relieved by activity during the 

by rest and followed by relatively pain-frcc periods. Back day. The sixtics often bring substantial relief from pain for 

pain typically peaks in the forties; episodes of sciatica the LBP patient (41). 

BACK INJURY RlSK FACTORS 

Effective control of LBP requires an understanding of 

activities that increase the risk of an injury. Some of the 

major factors associated with increased risk of back pain 

follow: 

Manual materials handling (especially lifting). 

Twisting of the trunk. 

Bending the trunk forward. 

Bending the trunk to the side. 

Excessive reaching. 

Falls. 

Prolonged sitting. 

Sedentary jobs. 

Highly physical jobs. 

Exposure to whole-body vibration. 

Cigarette smoking. 

Obesity. 

Extreme tallness. 

As can be seen, a wide variety of activities arc associated 

with back injuries (from prolonged sitting to heavy lifting). 

The following sections give some additional detail with 

regard to these risk factors. 

SPECIFIC RISK FACTORS FOR LBP 

Manual Materials Handling.-According to a study performed by Bigos (7), manual handling tasks are associated 

with almost two-thirds of all low back compensation 

claims. Lifting is a particular concern, being associated 

with 49% of low back compensation cases (43). Studies 

have shown that lifting is especially hazardous if the object 

workers have to lift is excessive, i.e., greater than 15.9 kg 

(35 lb) in weight (13, 30, 42). Perhaps more important 

than the actual weight of an object is the moment that is 

imposed on the low back. Figure 1 illustrates this point by 

posing the question: Which is more stressful on the low 

back, 15 kg (33 Ib) of feathers or 15 kg (33 Ib) of lead? In 

this example, 15 kg (33 lb) of feathers actually makes the 

load experienced by the spine greater. This is because the 

15 kg (33 lb) of feathers must be packaged in a bulky 

container, which causes the worker to hold the object further away from his or her body (creating a larger moment). This increases low back stress. Fifteen kilograms 

(thirty three pounds) of lead, on the other hand, makes for 

a compact load that can be carried quite close to the body, 

which will decrease the stress on the low back. Many 

othcr aspects of manually lifting a load have been shown 

to be potential hazards to the musculoskeletal system. 

These include horizontal and vertical location of the load, 

shape and size of the load, lifting frequency, load stability, 

couplings, duration of lifting, workplace geometry, asymmetric lifting, environmental issues, etc. (21). 

Figure 1.-Fifteen kilograms (thirty-three pounds) of feathers 

result in Increased loading on the spine compared with 15 kg 

(33 Ib) of lead. The Yead (being compact) can be held much 

closer to the body, which decreases the horizontal distance (H) 

from the low back to the center of gravity of the object The 

result is a decreased load on the low back. (Adapted from "UAWFord Job Improvement Guide," copyright 1988, Regents of the 

University of Michigan. Used by permission.) 
Body Motions.- Twisting of the trunk is associated with 

a significant proportion of low back compensation cases 

(approximately 18%). Bending the trunk forward is also 

associated with such cases, but to a somewhat lesser degree (12% of cases)? More recent studies have also 

shown that the more quickly one twists the trunk or bends 

the trunk to the side, the higher the back injury risk (32). 

Other studies have demonstrated that excessive reaching 

(for example, reaching over obstacles or handling bulky 

objects) is associated with higher back injury rates (3, 48). 

Falls are responsible for only about 10% of compensation 

cases (9, but these cases lend to be somewhat more severe and costly (7, 47). 

Environmental Factors.-Workers who are required to 

sit for prolonged periods of time have a higher risk of 

back pain (31). 'l'his may be due in part to the lac1 [hat 

the spine is almost fully bent forward in a relaxed sitting 

posture (4). It appears that jobs with low physical demands (sedentary jobs) and jobs possessing high physical 

demands both have somewhat higher incidences of LBP 

(36). A moderate amount of physical work is related to 

lowest back injury rates. Exposure to whole-body vibration (such as that experienced by shuttle car drivers) has 

also been implicated as a risk factor (9, 19). Another environmental factor that has received a great deal of attention recently is that of job satisfaction. Several studies 

have recently reported that an employee's satisfaction with 

his or her job, working environment, and/or first line 

supervisor is related to LBP (6, 45). One reason for this 

relationship may be that workers who enjoy their jobs are 

willing to work through minor bouts of back pain, while 

persons who do not like their job will use the same type 

of pain as a chance to get away from an undesirable 

situation. 

Personal Factors.-A recent study has demonstrated that 

smokers have an increased risk of LBP (17). In fact, this 

study showed a dose-response relationship between 

cigarette smoking and LBP. What this means is that the 

more a person smokes, the greater is his or her risk of 

LBP. The reasons for a smoker's increased LBP risk are 

probably due to two factors: (1) Smokers develop a deep 

cough, which places increased stress on the low back, and 

(2) smoking decreases blood circulation to the spine, which 

prevents essential nutrients from being delivered, causing 

tissues to be increasingly vulnerable to injury. Other personal risk factors involve body size. Back pain appears to 

be about twice as common in the 20% most obese (17). 

Furthermore, exceptionally tall individuals seem to have a 

higher incidence of LBP (3). Certain types of LBP (especially those cases involving intervertebral disk problems) 

seem to have a genetic component, as well (39). 

MULTIPLE RISK FACTORS 

Although the exact relationship is not known, it is believed that the various personal and task risk factors listed 

above interact with one another (21). That is, several risk 

factors may be present at the same time, which may increase the chances of a worker experiencing a back injury 

(14). Thus, in a general sense, the greater the number of 

risk factors an individual has, the greater the likelihood 

will be that an individual will experience an episode of 

EBP. 

As an example, let's look at a truck driver, whom we'll 

call Charlie. In his everyday job, Charlie may be exposed 

to a large number of back injury risk factors. As a truck 

driver, Charlie typically has to remain seated for prolonged 

periods of time and is exposed to whole-body vibration 

when driving. Charlie is a two-pack a day smoker and is 

also very obese, both of which Iliay increase the likelihood 

of experiencing LBP. Furthermore, Charlie has to do 

heavy lifting to unload his truck. In the unloading process, 

Charlie is forced to bend and twist to get some of the 

loads off of the truck. One can easily see that Charlie has 

a large number of risk factors that increase the likelihood 

that he will experience an injury to his lower back. 

S~rivate communication from Stover W. Snook, Liberty Mutual 

Insurance Co., Aug. 1989. 

Contrast Charlie's situation with that of Frank. Frank 

works in an office. While he sits at his desk a fair amount 

of the time, he's often called upon to do other jobs that 

require him to be up and around the office. Frank is rarely required to do any heavy lifting, but is called upon to do 

light lifting every so often. Frank is a nonsmoker and 

takes pride in keeping himself in shape. Compared to 

Charlie, it should be fairly obvious that Frank has fewer 

risk factors for LBP and would be less likely to experience 

an injury. The authors want to make it clear that it is 

possible that Frank might experience a back injury, while 

Charlie may remain injury-free. However, the probability 

is that we would expect Charlie to be the one to most likeBy experience bouts of LBP and disability. 

Looking at these two cases brings up another point. 

Let's suppose that both Charlie and Frank are experiencing a moderate amount of back pain. Frank may well be 

able to go to work and tolerate his LBP and still be able 

to do his job effectively. However, the same amount of 

back pain might be disabling for Charlie, because the pain 

may well prevent him from being able to perform the tasks 

that are required in his job. So not only does Charlie's job 

increase the chances that he will experience a back injury, 

it also increases the chances that his back pain will result 

in lost time. 
TREATMENT OF LBP 

CHOICE AND EFFECTIVENESS OF TREATMENT 

The majority of individuals who experience EBP cope 

with their pain without seeking any sort of medical treatment. While a large number of therapies have been attempted to combat LBP, most studies have demonstrated 

relatively little difference in the effectiveness of various 

therapies (49). One therapy that clearly fares worse than 

others is extended bed rest (49). It is clear that a few days 

of bed rest may be necessary during episodes of acute 

LBP; however, it is important that the patient be mobilized 

as soon as possible. 

MANIPULATION 

One difference that was noted in a large, carefully controlled study was that patients who received "chiropractictype" rotational manipulation of the spine reported more 

immediate relief than that of the control group. However, 

over the long run there was no difference in pain relief 

between those receiving spine manipulation and those who 

did not (24). 

EXERCISE 

There is some support for the use of exercises to decrease the degree of incapacity and increase the mobility 

of the spine that typically accompanies LBP. Furthermore, 

endurance training of the back muscles appears to have 

some benefits in patients with postural LBP. Finally, exercise appears to have a significant effect in decreasing 

stress, improving the patient's attitude, and allowing better 

RETURN TO WORK 

sleep; exercise may provide a positive alternative to prolonged use of medication in the chronic LBP patient. 

BACK SCHOOLS 

Back schools appear to reduce sick leave, improve work 

status, decrease pain intensity or duration, and increase the 

activity level of patients. The "self-care" approach taught 

at back schools generally consists of enhanced knowledge 

of the anatomy and physiology of the back, better body 

mechanics and work techniques, and improved muscle 

strength and flexibility. Back schools have been used for 

patients with chronic pain, short-term (acute) pain, and as 

a preventive technique for industrial workers. Of the three 

groups, back schools appear to provide most help to 

patients with acute pah6 

SURGERY 

Surgery is only helpful in a very small segment (1% to 

2%) of back pain cases. Successful surgery is reliant upon 

careful selection of the patient. The successful surgical 

patient must have unrelenting sciatica (back pain that 

radiates down the leg), and even then, only 5% to 10% of 

such patients should be candidates for surgery. The 

unfortunate fact is that surgery often only provides shortterm benefits to the patient. Comparisons of surgical and 

nonsurgical patients indicate that surgical patients do 

somewhat better after 1 year, but after 4 years have 

passed, surgical and nonsurgical groups fare about the 

same (18). 

RECOVERY FROM LBP 

A study of compensation cases in 22 States for 1982 indicated that the average duration of a lost time back injury 

was 14 scheduled workdays (48). However, data from the 

U.S. Mine Safety and Health Administration records of 

mining accidents in 1990 indicated that the average 

days lost for a back injury was more than three times as 

long as that mentioned in the previous study (an avcrage 

of 43 days lost)! Table 1 illustrates the percentage of 

compensation cases returning to work, by time (44). This 

table illustrates that almost two-thirds of patients returned 

to work within 2 weeks and four out of five returned within 6 weeks. However, after 6 weeks, the return to work 

was much slower. Seven percent of compensation cases 

lasted longer than 1 year. 

Table 1.-Low back compensation cases 

returning to work, by time (44) 

Workers returning, % 

42 

62 

79 

87 

89 

93 

PROBABILITY OF RETURNING TO WORK 

Data show quite clearly that there is a limited time to 

get workers back on the job once they have experienced a 

'see footnote 5. 
back injury. Table 2 illustrates the probability of a worker 

returning to active employment after various durations of 

being off work, based on data collected in two different 

studies (33, 40). This table shows that if a worker is off 6 

months with a back injury, the chances are even that he or 

she will return to productive employment. If the worker 

is off for 1 year, there is only a one in four chance that the 

worker will return to work. But if the worker is off for 

2 years, the chances are very slim that the worker will ever 

return to the active work force. 

Table 2.-Probability of worker returning to work 

for low back compensation cases, percent 

DETERRENTS TO RETURNING TO WORK 

There are several factors that may act as barriers to the 

worker returning to work. Malingering by the worker is 

sometimes observed, but studies generally find that malingering is less prevalent than is generally believed. More 

likely deterrent factors associated with workers are psychological disability (anxiety and depression associated 

with chronic pain) (5) or illness behavior (a magnified or 

abnormal response to illness) (50-51). Management may 

also prevent an early return to work through policies that 

it may put in place. Often management does not provide 

followup or encouragement for the injured worker. Providing modified, alternative, or part-time work to an injuredemployee may help facilitate his or her early return 

McGill (33) Rosen (40) (16). Other deterrents to a quick return to work may inOff work over 6 months . . . 50 35-55 clude specific contract rules, extended treatment by the 

Off work over 1 year . . . . . . 25 1 0-25 medical practitioner (IS), or situations where legal pro- Off work over 2 years . . . . . Nil 2- 3 ceedings result. 

CONTROL OF LBP 

There are three traditional approaches to the control of unnecessary bending and twisting. Appropriate packaging 

back pain that will be considered here. These are (in of objects (to ensure that object weights match worker 

order of effectiveness) job design (ergonomics), worker capabilities) will also reduce exposure to excessive loads. 

selection and job placement, and education and training. In addition, proper seat design (providing an adjustable 

These will be discussed briefly below; however, a more seat with good lumbar support and vibration damping) can 

extended treatment of job design is given in a companion reduce the stress on the low back (28, 46). 

paper in this proceedings (23). Management is sometimes .reluctant to redesign jobs 

because of the costs involved. However, many companies 

JOB DESIGN (ERGONOMICS) have learned that devoting capital to job redesign is indeed 

a sound business in~estment.~ Reduced compensation 

Ergonomics is a science that strives to improve job de- costs and increases in worker productivity will return the 

sign so that job or task demands do not exceed the physi- cost of the initial investment over time. Determining the 

cal capabilities of the worker. This approach has become payback period will help persuade management of thc cost 

quite popular in general industry over the past couple of effectiveness of redesigning jobs. 

decades, and a scattering of ergonomic committees have 

been created in the mining industry over the past several WORKER SELECTION AND JOB PLACEMENT 

years (37). Studies have indicated that the proper design 

of jobs can reduce up to one-third of all low back compen- Medical Examination 

sacion by reducing the onset of painful episodes, allowing 

the worker to stay on the job longer and permitting the 

worker to return to the job more quickly (43). 

The job design approach begins with the evaluation of 

existing jobs to identify risk factors that may lead to back 

injury. As identified previously, back injury risk factors 

may include manual handling tasks; body movements such 

as bending, twisting, and reaching; excessive loads; prolonged sitting; prolonged work in static postures; and exposure to whole-body vibration. Job redesign consists of 

reducing the risk factors associated with the job. For 

example, exposure to excessive Ioads may be reduced by 

providing the worker with mechanical aids. Improving 

the layout of the workplace may also help to reduce 

It has been estimated that a maximum of 1 in 12 young 

(first hire age) workers susceptible to low back problems 

may be identified by performing a careful examination and 

obtaining a thorough medical history (41). The effectiveness of this approach for older workers may be somewhat 

higher (41). However, it should be pointed out that there 

is no guarantee that the workers screened out through this 

process will ever experience a bout of LBP. Use of X-rays 

in the examination process has been controversial, with the 

majority of physicians recommending that routine preplacement X-rays not be used (2). 

'see footnote 5. 
Strength and Fitness Testing may be to concentrate training efforts on workers with a 

history of LBP, rather than attempting to train the entire 

Studies have indicated that the chance of a musculo- work force. 

skeletal injury is up to three times higher when the lifting - - - - 

requirements of a job approach or exceed a worker's isometric lifting capacity (12, 29). However, it is important 

to note that if strength testing is used to place workers in 

jobs, there is a risk of possible legal problems involving 

discriminatory hiring practices. To prevent such accusations, it is crucial that the strength tests used to select 

workers match the job demands as closely as possible. 

In recent years, a large number of sophisticated 

strength testing devices have appeared on the market. 

However, thus far, there are no data regarding the effectiveness of these devices in reducing LBP. 

EDUCATION AND TRAINING 

Training in Safe Lifting 

Teaching workers the proper method of lifting would 

appear to be a useful way to prevent back problems. 

However, the studies examining the effectiveness of this 

approach have failed to demonstrate that training has any 

effect on LBP (8, 15, 43, 52). There may be several reasons why these studies have shown no effect. For one 

thing, the quality of training in industry is typically lacking. 

Presentations are generally poor, the content of programs 

uneven, and there is usually no followup associated with 

training programs. Furthermore, workers tend not to 

Strength and Fitness Training 

Some research appears to support the notion that improving worker fitness decreases the chances of worker 

compensation claims (10). Table 3 shows the results of a 

study examining the fitness of 1,652 Los Angeles firefighters. The firefighters were divided into three fitness categories based on strength, flexibility, heart rate and blood 

pressure, and physical work capacity. This study demonstrated that the most fit workers had fewer back-related 

compensation claims, the least fit had the highest number 

of claims, and those in between had a moderate number 

of claims. In a separate study (11), compensation costs 

were compared between workers with the greatest and 

least flexibility, strength, and physical work capacity. This 

study showed that workers with the greatest flexibility, 

strength, and work capacity had much lower compensation 

costs compared to those with the least flexibility, strength, 

and work capacity. The authors concluded that physical 

fitness and conditioning may have some preventive effect 

with regard to back disorders. 

Table 3.-Low back compensation claims for 1.0s Angeles 

firefighters, by level of fitness (10) 

comply with safe lifting rkcommendations, unless a Fro- Most Middle Least 

gram of performance feedback is provided (I). Safe lifting fit fit fit 

is not a way lift, more energy to per- Number of firefighters . , . . . . . . . . 266 1,127 259 

form, and is generally harder to do (22)- Uninjured work- LOW back compensation claims . . % . . 0.77 3.19 7.14 

ers are particularly hard to motivate. A better approach 

SUMMARY 

The economic costs of LBP are overshadowed only by injury does occur, there is a limited amount of time to get 

the pain and disability experienced by the sufferer. De- the worker back on the job. The longer the worker is off 

spite significant advances in knowledge of the low back, the job, the greater the chances are that the worker will 

the exact causes of LBP remain largely unknown. We do not return. Three main approaches have been used to 

know that there are several risk factors that increase the control LBP: job design (ergonomics), worker selection 

chances of experiencing LBP. These include lifting, bend- and job placement, and education and training. Of these, 

ing and twisting of the trunk, prolonged sitting, expo- job design appears to offer the greatest ability to reduce 

sure to whole-body vibration, and smoking. The best the occurrence of LBP; however, most effective back injury . . 

methods for controlling EBP in the workplace is to reduce control efforts use a combination of the approaches listed 

the worker's exposure to these risk factors. If a back above. 

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A SClENTlFlC LOOK AT BACK BELTS 

By Sean ~alla~her' and Christopher A. amr rick^ 

ABSTRACT 

In recent years there has been a tremendous increase of these have been based on sound scientific evidence. In 

in the use of back belts by companies attempting to con- fact, there is contradictory information on the value of 

trol back injury costs. Many claims have been made re- back belts. The U.S. Bureau of Mines reviewed literature 

garding the effectiveness of back belts; howcvcr, not many relating to the effectiveness of back belts in the workplace. 

A tremendous increase in the use of back belts by companies attempting to control back injury costs has been 

seen in recent pears. Numerous belt designs are being 

made available to industry, based on the premise that they 

reduce the risk of low back pain. Many claims have been 

made regarding the effectiveness of back belts; however, 

not many of these have been based on sound scientific 

evidence. In fact, there is contradictory information on the 

value of back belts. Some studies have supported the use 

of belts, while others havc suggested that workers would 

be better advised to refrain from their use. As part of its 

program to enhance safety for the underground mine 

worker, the U.S. Bureau of Mines (USBM) has reviewed 

evidence relating to the effectiveness of back belts and 

provided some suggestions relating to the use of back belts 

in the workplace. This paper is largely based on a review 

of back belt literature by the noted spinal biomechanist 

S. M. McGill (ll).3 

There are several potential benefits and drawbacks 

associated with wearing back bclts that should be considered before a responsible policy call be established. Let 

us first examine the hypothesized benefits associated with 

back belt usage and the related scientific evidence. 

POTENTIAL BENEFITS OF BACK BELTS 

The following list details the major benefits that might 4. Provide a safety margin by increasing an individual's 

be provided by back belts: tolerance to heavy loads. 

5. Decrease back injury incidence when used in indusI. Decrease the load experienced by the low back. trial settings. 

2. Help to "stiffen" the spine to make it stronger. 

3. Restrict spine mobility and prevent hazardous The following sections will address the scientific evidence 

movements. related to these hypothesized benefits. 

'~esearch physiologist. 

2~ndustrial engineer. 31talic numbers in parentheses refer to items in the list of references 

Pittsburgh Research Center, U.S. Bureau of Mines, Pittsburgh, PA. at the end of this paper. 
Do back belts decrease the load experienced by the low 

back? 

One of our best methods for establishing the answer to 

this qucstion is to examine muscle activity. If back belts 

decrease the load on the low back, we would expect to see 

a decrease in thi: electrical activity of the powerful back 

muscles. However, studies have convincingly shown that 

there is no difference in bxck n~uscle activity when wearing 

a belt compared with not wearing one (8, 13). Thus, back 

belts do not appear to lessen the load experienced by 

muscles of the lumbar spine (low back). 

Some have hypothesized that back belts help to reduce 

the load on the low 'back by increasing intra-abdominal 

pressure (IAP). Indeed, lifting while wcaring a belt does 

appear to increase IAP (5, 9). Years ago, higher IAP was 

thought to be beneficial by adding supporting forccs to the 

low back (3, 14). However, recent data have caused this 

theory to be reevaluated (12, 16). It now appears that 

increased IAP has little, if any, efSect that would decrease 

the load on the spine. 

Do back belts help to stifl'en tlie spine (niake it stronger)? 

While it is generally believed that increased L4P does 

not reduce the spinal load, the pcxsibility exists that higher 

IAR may assist thc low back by increasing the st;rfncss of 

the spine, Unfortunately, this is a difficult claim to test 

scientifically. Curreill thinking is that even if higher IAP 

does provide some additiondl stiffness, tllc advantage 

gained is probably fairly small (13, 19). Thus, at the 

present time, most back in~ury experts fcel that the justification for wearing belts based on increased IAP is probably not warranted. 

Do back belts restrict spine mobility and hazardous 

movements? 

There is evidence to suggest that certain types of belts 

restrict the amount of side-to-side bending and trunk twisting that a worker can perform (19). This may be in part 

responsible for the reporlccl perception of incrcased stability of the trunk by wedsers. However, belts currently 

available do not appear lo restrict forward bending of the 

lumbar spine. This appears to be an important exception, 

because of the fact that [he strength of the spine and its 

ability to tolerate loads arc considerably lower when the 

worker is in a forward bent position (1). Furthermore, 

this posture is associated with increased risk of back injury 

(IS). Therefore, while the reduction in side bending and 

twisting is viewed as generally positive, the fact that current belts do not restrict forward bending means that back 

belts still allow individuals to subject their spines to hazardous postures. 

Do back belts improve an individual's load tolerance? 

One possible benefit of back bclts is that they might 

provide a "safcty margin" by increasing the tolerance of 

individuals to heavy loads. Flowever, data from recent 

studies have indicated that wearing a back belt does not 

increase an individual's ability to sustain additional loads 

in forward bending, side bending, or twisting (lY). Thus, 

it does not appear that belts provide an additional safety 

margin by increasing a worker's tolerance to heavy loads. 

Does use of back belts in industry decrease the incidence 

of back injuries? 

Several recent studics have been performed that attempted to determine whether belts actilally do reduce the 

incidence of injury (2, 6, 18, 20). Ul~fortunately, the 

studies performed thus far have bcen ol widcly varying 

quality. Only t\vo back belt studies have bcen performed 

that use the method that provide:, 11ie hishest quality data 

(i.e., prospective studics udng rnalched control groups). 

These studies were performed by Reddell (IS) and Walsh 

(20) 

The Walsh (20) study is thc one pointcd to most frequently by back belt proponents as cvidence of the effectiveness of back bclts. Thc investigators studied 81 workers in an industrial warehousr setting. Results of this 

study did, in fact, demonstrate a reduction in lost-time 

back injuries due to use of back belts, but careful scru-. 

tiny of the data inclicates that the benefit was found only 

among workers who had experienced previous back injuries. No benefit was obscrved for previously uninjured 

cniployees. 

The second of these studics examined the effectiveness 

of back bclts, in which 642 airline baggage hanct'ers were 

observed (18). These researchers found no differences in 

back injury incidence rates between groups using back 

belts and those not using belts. However, these researchers did discover a disturbing trcnd. Workers who started 

the study wearing back bclts and dropped out (discontinued use of the belts) had a higher incidence of back 

injury than any other group. The researchers in this study 

concluded that back belt use may cause some physical dependency, leaving the back at increased risk when the device is withdrawn. 

It is important to noie that neither of the studies (18, 

20) demonstrated that bclt use haci any benefits for uninjured workers. However, it is noteworthy that belts did 

seem to help workers who had experienced prior back injuries. This indicates that belts may have some usefulness 

in the workplace under certain circumstances. 
POTENTIAL DRAWBACKS OF BACK BELTS 

The following arguments are typical of back belt does not appear to increase an individual's load tolerance. 

detractors: However, studies have indicated that workers are willing 

to lift up to 20% more weight when wearing a belt (10). 

1. Back belts may lead to weakened back muscles Thus, it appears that workers who use belts appear willing 

(muscle atrophy). to place higher strain on the back and, in fact, are willing 

2. Back belt use causes workers to develop a "false to work at a higher percentage of their maximum load 

sense of security." tolerance. Therefore, workers who wear belts may be 

3. Increased IAP observed during back use may working with a decreased safety margin with regard to the 

result in adverse physiological changes. low back. 

Let us examine the cviilencc with regard to these issues. Do back belts result in adverse physiological changes? 

Do back belts cause back museles to become weaker 

(atrophy)? 

Several studiec hare rxamincd this issue, and all of 

these studies seem to agrcc that back belts do not lead to 

a decrease in muscle strength, at lcast over the short term. 

This is consistent -; iri~ the observation that back muscle 

activity is not decreased with belt use, as mentioned above. 

However, a recent Swedish study suggested that while back 

belt use does not result in loss of strength, muscular 

endurance may be decreased with prolonged belt use (6). 

Back belts do seem to cause certain unwanted physiological changes to occur. The most significant of these is 

the increase in blood pressure that has been observed 

when lifting using a belt. Blood pressure has been shown 

to be elevated almost 15 mm Hg when lifting with a belt 

(7). Any individuals with a history of heart problems or 

those with significant cardiovascular risk factors should 

consult a physician prior to donning a back belt. An increase in blood pressure by 15 mm Hg may lead to serious 

health problems among those with a history of cardiovascular problems. 

Do back belts create a false sense of security? 

There is some evidence that belts may lead to a false 

sense of security in workers. As noted above, lifting belts 

SUMMARY AND RECOMMENDATIONS 

The foregoing information indicates a somewhat mixed 

bag of evidence-some in support of back belts and some 

in opposition. Evidence supporting use of back belts includes some restriction in end-range motion of twisting 

and side bending, clinical evidence of a decrease in losttime back injuries among those with prior back injuries, 

and a suggestion of increased trunk stiffness that may be 

of some benefit. Evidence in opposition of back belt use 

includes an increased risk of injury upon discontinuing belt 

use, increased blood pressure, and a false sense of security 

that may lead workers to overstrain their backs. 

This review of the literature indicates that the following 

approach to use of back belts should be followed (11): 

1. Back belts should be treated as a prescription item 

and should be provided only to individuals having had a 

previous back injury. These workers should be weaned 

froin the belts as soon as it is appropriate. 

2. Back belts should not be universally distributed to 

all workers at a worksite, gia'en the lack of demonstrated 

effectiveness among uninjured workefs and a potential 

increased risk of injury after discontinuation of use. 

3. Individuals considered for a back belt prescription 

should be screened for cardiovascular risk because of the 

increased blood pressure associated with belt use. 

4. Individuals using back belts should be required to 

participate in a mandatory exercise program and should 

continue in the program after being weaned from the belt 

during the period of increased back injury risk. 

5. Workers using back belts should be exposed to a 

mandatory education program to ensure that the back 

belts are used properly. 

6. A full ergonomic assessment of the workplace 

should be performed to reduce any physical hazards that 

may increase the incidence of back injuries. 

The evidence presented in this paper suggests that back 

belts have a rather limited role to play in controlling the 

costs and incidence of back injuries. Reliance on back 

belts as a sole method of combatting this problem clearly 
does not provide an effective solution. Effective back the USBMInformation Circular 9235 (4). Employers who 

injury control programs tend to emphasize job redesign, are interested in keeping the cost of back injuries down 

where the worker's job is changed to reduce the amount are encouraged to focus on job design as a primary 

of manual lifting that has to be done (or the lifting that method of injury control, and if back belts are to be used, 

must be done is made easier) (77). Methods of job re- careful consideration should be given to the factors 

design applicable to the mining industry are contained in discussed above. 

REFERENCES 

1. Adams, M. A., and W. @. Hutton. Mechanics of the Intervertebral 

Disk. Ch. in The Biology of the Intervertebral Disc, ed. by P. Ghosh. 

CRC Press, 1988, v. 2, pp. 39-72. 

2. Asundi, P., J. L. Purswell, and D. Bowen. Evaluation of Back 

Belts in the Prevention of Manual Material IIandling Injuries. Presented at Low Back Injury Symp., Columbus, 011, Apr. 14-15, 1993; 

available from S. Gallagher, BuMines, Pitlsburgh, PA. 

3. Bartelink, D. L. The Role of Abdominal Pressure in Relieving 

the Pressure on Lumbar lntervertebral Discs. J. Bone Jt. Surg., 1957, 

V. 39B, pp. 718-725. 

4. Gallagher, S., T. G. Bobick, and R. L. Ungcr. Reducing Back 

Injuries in Low-Coal M~nes: Redesign of Materials-Ifandling Tasks. 

BuMines IC 9235, 1990, 33 pp. 

5. Harman, E. A., R. M. Rosenstein, P. N. Frykman, and G. A. 

Nigro. Effects oE a Belt on Intra-Abdominal Pressure During Weight 

lifting. Med. and Sci. Sports and Exercise, v. 21, No. 2, 1989, 

pp. 186-190. 

6. Holmstrom, E., and U. Moritz. Effects of Lumbar Belts on Trunk 

Muscle Strength and Endurance: A Follow-up Study of Construction 

Workers. J. Spinal Disorders, v. S, No. 3, 1992, pp. 260-266. 

7. Hunter, G. R., J. McGuirk, N. Mitrano, P. Pearman, 13. Thomas, 

and R Arrington. The Effects of a Weight Training Belt or. Blood 

Pressure During Exercise. J. Appl. Sport Sci. Res., v. 3, No. 1, 1989, 

pp. 13-18. 

8. Krag, M. El., K. B. Byme, L. G. Gilbertson, and L. D. 1Iaugh. 

Failure of Intra-Abdominal Pressure '1.0 Iceduce Erector Spinae Loads 

During Liftrng 'Tasks. Pres. at the N. Am. Congr. on Biomech., 

Montreal, Canada, 1986, pp. 87-88; available from S. Gallagher, 

BuMines, Pittsburgh, PA. 

9. Lander, J. E., R. L. Simonton, and J. K F. Giacobbe. ?he Effectiveness of Weight-Belts During the Squat Exercise. Med. and Sci. 

Sports and Exercise, v. 22, No. 1, 1990, pp. 117-124. 

10. McCoy, M. A., J. J. Congleton, W. I,. Johnston, and B. J. Jiang. 

The Role of Lifting Belts in Manual Lifting. Int. J. Ind. Ergon., v. 2, 

NO. 4, 1988, pp. 259-266. 

11. McGill, S. M. Biomechanics and Lifting Belts. Pres. at Low Back 

Injury Symp., Columbus, 011, Apr. 14-15. 1993; available from S. Gallagher, i3uMines, Pittsbui-gh, PA. 

12. McGill, S. M., and I<. W. Norman. Reassessment of the Role of 

Inlra-Abdominal Pressure in Spinal Compression. Ergonomics, v. 30, 

No. 11, 1987, pp. 1.565-1588. 

13. McGill, S. M., R. W. Norman, and h4. '1'. Sharralt. 'Ilc Effects of 

an Abdominal Belt on Trunk Muscle Acti\tity and Intra-Abdominal Pressure During Squat Lifts. Ergonomics, v. 33, No. 2, 1990, pp. 147-160. 

14. Morris, J. M., D. B. Lucas, and B. Bresler. Role of the Trunk in 

Stability of the Spine. J. Bone Jt. Surg., v. 43A, 1961, pp. 327-351. 

15. Mundt, D. J., J. L. Kelsey, A. I,. Golden, 11. Pastides, A. T. Berg, 

J. Sklar, T. Iaosea, and M M. I'anjabi. An Epidemiologic Study of NonOccupational Lifting as a Risk Factor for IIcrniated Lumbar Intervertebra1 Disc. Spine, v. 18, No. 5, 1993, pp. 595-602. 

16. Nachemson, A,, G. B. J. Andersson, and A. B. Schullz. Valsalva 

Manoever Biomechanics: i3ffects on Lumbar Trunk Loads of Elevated 

Intra-Abdominal Prcssure. Spine, v. 11, No. 5, 1986, pp. 476-479. 

17. O'Green, J. E., R. 11. Peters, and A. B. Cecala. AEP Fuel Supply's Ergonomic Approach to Reducing Back Injuries. Pres. at the 23rd 

Annu. Inst. Min. IIcalth, Saf. and Rcs., Blacksburg, VA, 1992, pp. 187- 

196; available from S. Gallagher, DuMines, Pittsburgh, PA. 

18. Reddell, C. K., 9. J. Congleton, R. 1). Ilutchingson, and J. F. 

Montgomery. An Evaluation of a Weightlifting Belt and Back Injury 

Prevention Training Class for Airline Raggagc I landlcrs. Appl. Ergon., 

V. 23, NO. 5, 1992, pp. 319-329. 

19. Seguin, J., and S. M. McGill. The Effects of Abdominal Belts on 

Passive Stifrness of the Trunk About Three Axes. Pres. at Hum. Factors 

Assoc. Canada 25th Annu. Conf., Ilamilton, Ontario, Canada, 1992, 

pp. 67-72; available from S. Gallagher, IluMines, Pittsburgh, PA. 

20. Walsh, N. E., and R. K. Schwartz. The Influence of Prophylactic 

Orthoses on Abdominal Strength and Y.ow Back Injury in the Workplace. Am. J. Phys. Med. & Rehab., v. 69, No. 5, 1990, pp. 245-250. 
48 

JOB DESIGN: AN EFFECTIVE STRATEGY FOR REDUCING BACK INJURIES 

By Christopher A. am rick' and Sean ~alla~her~ 

ABSTRACT 

The U.S. Bureau of Mines conducted research to reduce musculoskeletal injuries. Occupationally related musculoskeletal injuries pose a significant problem to the mining industry. Ergonomics can help to reduce the costs 

associated with these injuries. Mines can institute committees to solve ergonomic problems. These committees 

should include representatives from management, the labor force, and the medical department. Various analysis 

techniques, such as job safety analysis, task analyses, 

materials-handling flowcharts, and preliminary hazards 

analysis can be used to identify ergonomic problems in and 

around a mine. 

Once hazards have been identified, then solutions can 

is to redesign the job by eliminating the hazard, removing 

the worker from exposure, or mechanizing the task. If 

these strategies are infeasible, then the job should be 

designed so that it can be performed within the workers' 

capabilities. After any ergonomic solution is implemented, 

a followup analysis should be performed to ensure the effectiveness of the change and to guard against the introduction of any new ergonomic or safety hazards. Physical 

fitness programs and training can be used to suppfement 

job redesign. By effectively instituting sound ergonomic 

implementation strategies, the costs associated with musculoskeletal disorders can be reduced. 

be formulated and implemented. The preferred strategy 

The U.S. Bureau of Mines (USBM) has undertaken rcsearch to reduce musculoskeletal injuries as part of its 

mission to improve the health and safety of the Nation's 

miners. Given the unique hazards in mining such as 

cramped work spaces, rocky and uneven walking surfaces, 

walking surfaces covered with water, hot and cold temperatures, low levels of lighting, and rough terrain over 

which heavy vehicles operate (12),3 one would expect that 

musculoskeletal injuries are a ma~or portion of all injuries 

in mining. According to an analysis of all underground 

coal mining accidents from the 1991 U.S. Mine Safety and 

Health Administration (MSHA) accident database, 34% 

were classified as sprains or strains, 21% occurred to the 

'Industrial engineer. 

'Research physiologist. 

Pittsburgh Research Center, U.S. Bureau of Mines, Pittsburgh, PA. 

3~talic numbers in parentheses refer to items in the list of references 

at the end of this paper. 

back, 24% were due to "overexertion," and 24% involved 

the handling of materials. 

In addition to the pain and human suffering created by 

these injuries, they result in a significant amount of lost 

time and, hence, lost productivity and contribute to high 

health care and compensation costs. In fact, Plummer, 

(14) reported that back injuries alone account for close to 

20% of all payroll dollars. According to an informal 

USBM analysis, in 1991 the average coal mining back injury cost over $8,400 and the total cost to society for coal 

mining back injuries was over $30 million. 

Many musculoskeletal injuries are a result of cumulative 

trauma, or wear and tear that occurs over a relatively long 

period of time (8). One science that deals with the reduction of such injuries is ergonomics, the study of how human beings relate to their work environment. By using ergonomics, the occurrence of musculoskeletal disorders in 

the workplace can be reduced. One approach that has 
been successfully used by the general industry, and the period after the establishment of ergonomics committees 

mining industry as well, to combat musculoskeletal injuries at the mine sites studied. These ergonomics committees 

is to establish an ergonomics committee. O'Green (13) can form the basis of a successful ergonomics program. 

reported a 41% reduction in back injuries over a 4-year 

ERGONOMICS COMMllTEES 

The implementation of a successful ergonomics program into the workplace usually requires a multidisciplinary approach. A number of individuals from throughout 

the mining company should participate. A team approach 

should be used whcrc a committee is established to provide a forum for the exchange of ideas and the execution 

of strategies to solve ergonomic problems. 

Effective committees should include management, labor, engineering, maintenance, personnel, and front-line 

employees; furthermore, support from each of these 

groups must be secured. In addition, the mine medical 

personnel and the safety specialist or corporate ergonomist 

should take part. Educating those involved is of utmost 

importance. According to Pope (16), it is crucial that all 

personnel be informed about "methods, goals, risk factors, 

and the possibility of prevention." Small mine operators 

may not have access to all of these personnel, but the 

committee should be comprised of as many of the above 

as is feasible. 

Including representatives from the front-line work force 

is a key element to the success of an ergonomics 

committee. Imada (10) outlines three reasons workers 

should be included in the ergonomic problem-solving 

process. He states that the workers are already aware of 

ergonomic principles and ergonomics simply provides 

labels for ideas already in use. Second, he reports that the 

likelihood of successful implementation of ergonomics is 

increased if the worker has some ownership in the ideas. 

Finally, Imada asserts that by the end-user implementing 

the technology, he or she "will be able to modify it to solve 

future problems," thus providing long-term benefits. 

Often times, the mine management must be sold on the 

idea of using ergonomic intervention strategies. A particularly good argument for the use of these strategies can be 

made through a cost-benefit analysis (15). When performing such an analysis, one must include both direct and indirect (or hidden) costs. Direct costs include such items 

as medical expenses, worker compensation, and liability 

costs. Indirect costs often outweigh direct costs and include such items as lost productivity, cost of rehiring and 

retraining a new employee, and loss of employee morale 

(5). 

IDENTIFYING PROBLEMS 

After the infrastructure is in place and support is secured, the next task is to identify ergonomic problems 

through various analysis techniques. These analyses can 

vary in sophistication from informal conversations with 

employees to more formal techniques, such as job safety 

analyses. An excellent place to start identifying ergonoinic 

problems is by examining the company salety records. By 

making a table of incidence rates by job classification, 

activity at the time of the occurrence, type of injury, etc., 

one can identify particular jobs or activities that contribute 

to the most musculoskeletal injuries. One must keep in 

mind, however, that musculoskeletal injuries are often a 

result of cumulative trauma; so assigning a single cause to 

a particular claim may be erroncous in many cases. 

After the records are examined, the committee can then 

rank the jobs and the activities that need to be examined. 

Prime candidates for job redesign are those jobs that have 

a particularly high frequency of injury or those activities 

that result in particularly severe trauma. The jobs should 

be ranked by the committee and the jobs with the most 

severe ergonomic problems should bc analyzed first. 

Task analyses can then be performed so that ergonomic 

hazards associated with a particular job or task are identified. These analyses usually involve describing in detail \, 

each motion or action required to execute a task. By 

closely examining each motion or action, the ergonomic 

stressors or the risk factors associated with a job can then 

be identified. Andersson (1) outlines the following work 

attributes as risk factors for low-back pain: heavy physical 

work, static (not moving) work postures, frequent bending 

and twisting, lifting and forceful movements, repetitive 

work, and vibration. 

One particular type of task analysis, job safety analysis, 

has recently received much attention in the mining industry 

and is ideally suited for identifying and correcting ergonomic hazards. MSHA (20) has developed a set of guidelines that detail the job safety analysis process for the 

mining industry. The guidelines detail four basic steps 

involved with a job safety analysis: (1) Select the job to be 

analyzed, (2) separate the job into its basic steps, (3) identify the hazards associated with each step, and (4) control 

each hazard. By using this method, accidents can be 
prevented by foreseeing and abolishing accidents before 

they happen. 

Since many ergonomic hazards in mining result from 

manual materials handling, Gallagher (6) suggests that the 

materials supply-handling system be examined in addition 

to the jobs. A flowchart can be developed that represents 

the movement of supplies from the delivery at the mine to 

the supply item's end use. By closely examining the flowchart, unnecessary manual materials handling can be identified and eliminated, thus reducing the miners' exposure 

to lifting hazards. Figure 1 presents an example of flowcharts for handling concrete blocks at two different mines. 

There is much manual handling of the materials in mine 

A, while the blocks are handled mechanically until their 

end use in mine B. 

Daling (3-4) has outlined safety analysis techniques that 

are useful for the mining industry, based upon certain criteria that the techniques must meet. The methods should 

not be too complex and should apply to most mining situations. Furthermore, the methods should be able to generate checklists and be cost effective. One of the hazard 

identification analyses identified as suitable for the mining 

industry that could be used to identify ergonomic hazards 

is the preliminary hazards analysis. 

According to Hammer (9), the preliminary hazards 

analysis is broad in scope and performs the following 

functions: (1) identifies possible hazards, (2) looks for 

ways to eliminate the hazard, and (3) if the hazard cannot 

be eliminated, investigates the best way to control it. A 

form is often developed where the hazard, contributing 

events, estimated probability, and means of control are 

listed. Hammer suggests a procedure of "signing off' on 

the form once the proper controls are taken so that these 

controls are sure to be carried out. Furthermore, Daling 

(4) warns of the dangers of the analyst simply filling out 

the form and caution that the analyst pay attention to subtle items and minute details. 

The mine worker should not be overlooked as a valuable resource when identifying ergonomic stressors. Asking the miner to explain conditions that contribute to 

ergonomic hazards can often provide enlightening information, since the miner probably knows the job requirements 

and methods better than anyone. The miner may have already changed the workplace to lessen an existing problem 

that could result in an ergonomic stressor. 

One effective means of getting information about possible ergonomic deficiencies from miners is with the critical incidence technique. This method collects data based 

on "hazards, near-misses, and unsafe conditions and practices from operationally experienced personnel" (9). The 

miner is asked about events that have happened to him or 

her or that he or she has seen first hand, similar to an 

accident investigation. If the critical incident technique is 

used to identify ergonomic problems, the work force must 

be informed about ergonomic principles. Once the ergonomic hazards have been identified, then solutions must be 

developed to eliminate or reduce the risk of these hazards. 

surface storage to supply ca; supply car I A I 

TYPICAL MOVEMENT OF CONCRETE BLOCKS IN MlNE A -4 b--J 

: End 

use 

KEY 

Manual transfer 

- Surface 

0 Manual transport 

0 Mechanical transfer 

or transport 

Underground . 

Banded unlts Unit dragged off Unlt unloaded 

loaded on supply supply car w~th cham In crosscut w~th 

car with forklift ~nto scoop bucket pusher plate 

- 

- - Stacked on 

TYPICAL MOVEMENT OF CONCRETE BLOCKS IN MlNE B 

Removed from Loaded manually Pos~tloned for 

removal from 

shuttle car 

Unloaded w~th 

pusher of scoop plate 

Pos~t~oned for Transported from Supply car POsltloned a%2a;;;d onto face veh~cle 

removal from surface storage removal from 

Stacked ~n crosscut 

Figure 1.-Flowchart of concrete block transportation at two mines. 
DEVELOPING SOLUTIONS 

Gallagher (6) presents a model for solving materialshandling problems (fig. 2); this model can be used to get 

rid of other ergonomic stressors as well. The ergonomic 

problem-solving strategies in the model include redesigning 

the job, using worker selection procedures, and training 

the work force in proper work methods. 

The preferred solution to any ergonomic problem is to 

eliminate the hazard or remove the miner from any exposure. Proper planning can eliminate the need to perform 

a task at all. Gallagher (6, p. 25) provides an example in 

which an underground coal mine cut the number of manual lifts required to deliver a supply car of materials from 

800 to 400 by keeping the supplies on the supply car during storage. This solution requires the purchase of an 

additional supply car, but can result in great savings by 

reducing the direct and indirect costs associated with 

occupational low-back pain. 

If the hazard cannot be eliminated, the miner can be 

removed from any exposure to the hazard. For example, 

if a continuous miner operator is being exposed to dangerous levels of whole-body vibration while seated in a 

machine cab, the task could be redesigned so that the 

miner operates the machine from outside the cab using a 

remote control. The miner would then be removed from 

the vibration exposure. 

The next strategy that should be considered to redesign 

the job, providing the previous strategies cannot be used, 

is to mechanize the task. One requirement for any piece 

of mechanized equipment is that it be rugged enough to 

withstand the harsh mining environment. Conway (2) has 

provided plans for six mechanical-assist devices that can be 

used to eliminate lifting associated with some underground 

mining tasks. These devices can be easily fabricated in 

most mine shops and include such items as a timber car, 

a scoop-mounted lift boom, and a container-work station 

vehicle. If the above strategies cannot be carried out, 

then the job must be designed so that it can be performed 

within the miners' capabilities. For example, it may not be 

possible to entirely eliminate a miner's exposure to wholebody vibration. However, the vibration levels should be 

lessened so that they are within existing standards. Furthermore, manual materials-handling tasks can be designed 

to fit the miners' capabilities. 

The National Institute for Occupational Safety and 

Health (NIOSH) (11) provides guidelines for manual lifting that can prove useful for many situations in mining. 

Lifting capacity can be significantly lower, however, if the 

task is being performed in low coal, where the miner must 

work in constrained postures (7). One way that tasks can 

be designed to fit within a worker's capacity is to reduce 

the weight of the object being lifted. For example, 

Gallagher (7) reports that rock dust packaged in 18-kg 

(40-lb) bags is a more appropriate size than 23-kg (50-lb) 

bags, given the reduced lifting capacity in restricted 

postures. 

After any ergonomic solution is carried out, it is crucial 

that a followup analysis be performed. This followup is 

done to ensure that all ergonomic problems in the original 

job design are resolved and to guard against the introduction of any new ergonomic or safety hazards. 

According to Snook (19), worker selection and training 

techniques alone are not an effective control for low-back 

injuries and the ergonomic redesign of jobs and workstations is the preferred approach. However, it is often "impractical, if not impossible, to design a job in such a manner that no training was required" (17). Thus, training 

should be an integral part of an effective ergonomics program. Furthermore, ergonomics training should be given 

to those workers who are serving on the ergonomics committee, as expressed earlier. Training should include an 

introduction to biomechanics (including safe lifting), anthropometry, and work physiology. In addition, ergonomic 

stressors common to mining, such as thermal stress, vibration, noise, and lighting, should be discussed. Annual 

refresher training could provide an excellent forum for 

such instruction. 

Another strategy that supplements job redesign strategies to reduce occupationally related musculoskeletal 

injuries is the implementation of an exercise program. 

Exercise leads to improved strength and cardiovascular 

fitness that can, in turn, lead to a reduction in the costs 

associated with musculoskeletal injuries. However, one 

must be care-ful when implementing such a program: 

Gallagher (6, p. 28), advises that "the worker should 

consult with a physician prior to participation in any 

exercise program." 

Examine supply - Identify materials-, 

handling system handling problems 

Figure 2.-Model for redesigning materials-handling tasks. 

Consider 

alternat~ve 

+ 

Can task be 

Can the lifting 

Evaluate 

changes 

1 

Ip 

yes task be redesigned 

to f~t worker 

lifting capacity? 

stmtegies 

4 NO 

Use worker 

selection and 

trainina ~rocedures 
CONTROL OF COSTS ONCE BACK INJURY HAS OCCURRED 

The previous sections have detailed methods that can 

be useful in preventing low-back injuries. However, it is 

important for management to realize that some back injuries probably will occur, despite eflorts to prevent them. 

When back injuries do occur, the policy that management 

puts in place to deal with the injury may have a significant 

role in determining the duration of the disability and the 

costs incurred by the company. 

As discussed by Snook (la), management often does 

not respond properly whcn workers experience a back injury. The injured worker may be accused of malingering 

either by direct accusation or through innuendo. This, in 

turn, causes the workers to look for ways to get back at 

management. As such adversary situations develop, the 

costs of the injury may significantly increase for both the 

worker and management. However, as discussed by Snook 

(la), studies have indicated that enlightencd management 

can often reduce and perhaps even prevent the disability 

associated with low-back pain through a program that includes positive acceptance of low-back pain, early intervention, good cominunicatio~l and followup, and early 

return-to-work programs. 

POSITIVE ACCEPTANCE OF LOW-BACK PAIN 

BY MANAGEMENT 

The most appropriate response by a supervisor to a 

back injury experienced by one of his or her workers is to 

show concern for the needs of the employee, and to avoid 

making rash judgments and setting up adversary relationships because of the injury. Such judgments are usually 

incorrect and may serve to make the situation worse than 

it should be. Instead, managemcnt should be trained to 

realize that a certain number of back injurics are likcly to 

occur and should be taught to rcspond in an appropriate 

manner when they do occur. The supervisor should encourage the worker to seek immediate medical treatment 

and (if possible) adapt the workplace or modify the task so 

that the employee can continue to work on the job. One 

company that instituted a policy of positive acceptance of 

low-back pain immediately and dramatically reduced its 

worker compensation costs. Over a 3-year period, costs 

were reduced from over $200,000 per year to about 

$20,000 per year (18). 

EARLY INTERVENTION 

One key feature of the program described above was 

the fact that all workers complaining about low-back pain 

were immediately referred to the company clinic for 

treatment--even those with minor complaints. Treatment 

was given during work time by the company nurse. This 

treatment consisted of heat applications and nonprescription analgesic-anti-inflammatory drugs, such as aspirin. 

During the treatment sessions, worker education was initiated on a one-to-one basis. The education program consisted of basic spinal anatomy and physiology, the expected 

results from the treatment regimen, proper posture, and 

suitable exercises. Light-duty work and rest periods were 

provided by managemcnt to the injured employee. If the 

initial in-house treatment was ineffective, the worker was 

referred to the company physician for further medical 

treatment. The physicians were familiarized with the physical demands of the jobs at the company to place injured 

workers in appropriate job positions. 

Because this company encouraged the reporting of all 

episodes of low-back pain (even minor cases), it is not 

surprising that the number of cases reported actually 

increased. However, the amount of lost time due to lowback pain was significantly reduced. This indicates that 

the workers were able to stay on the job and did not rely 

on outside practitioners for treatment, thus reducing the 

company's cost because of low-back pain. 

FOLLOWUP AND COMMUNICATION 

When workers do become temporarily disabled, it is important that management establishes and maintains good 

communications with the worker and appropriate medical 

personnel. Supervisors should be instructed to followup 

every disability case with a telephone call or visit before 

2 days of lost time have elapsed. The purpose of the call 

is to let the worker know that the company is concerned 

and to inform the supervisor of the status of the worker's 

rccovery. 

One company recently instituted a program that 

increased the communication between the worker, employer, practitioner, and insurer (18). When a workercompensation claim was received, the employer made immediate contact with the worker and insurer and followed 

up with calls at regular 10-day intervals to make certain 

that the claim was progressing smoothly. The possibility 

of retraining was explored for extended claims, and a liaison was established between management and the insurer 

if a gradual return to work was indicated. The focus of all 

communications was that every action taken was in the 

best interest of the worker. This program significantly reduced the proportion of long-term worker's compensation 

claims and also significantly reversed a trend of increasing 

accident rates (18). 
EARLY RETURN-TO-WORK PROGRAMS 

The data from several studies have shown that the longer a worker is off from work because of a back injury, the 

less likely the worker will be able to return to productive 

employment. These studies underscore the importance of 

providing modified, alternative, or part-time work to the 

injured employee to facilitate a quick return to the job. 

Unfortunately, management will often extend the period of 

disability by requiring workers to be fully recovered before 

returning to work. This policy can often be more costly 

than providing modified, alternative, or part-time employment to the injured employee. Because there appears to 

be a limited amount of time to act before losing control of 

the disability and the claim, efficient management should 

do everything in its power to encourage the worker's timely return to work. Data indicate that an early return to 

work is in the best interests of everyone: the worker, the 

company, and the union. In this regard, it may benefit 

both the company and the union to ensure that work rules 

in the current contract do not interfere with early returnto-work programs. 

SUMMARY 

Occupationally related musculoskeletal injuries pose a 

significant problem to the mining industry, and ergonomics 

can help to reduce the costs associated with these injuries. 

Mines can start committees to solve ergonomic problems. 

These committees should include representatives from 

management, the labor force, and the medical department. 

Various analysis techniques? such as job safety analysis, 

task analyses, materials-handling flowcharts, and preliminary hazards anaIysis can be used to identify ergonomic 

problems in and around a mine. 

Once hazards have been identified, then solutions can 

be formulated and realized. The preferred strategy is to 

redesign the job by getting rid of the hazard, removing the 

worker from exposure, or mechanizing the task. If these 

strategies are infeasible, thcn the job should be designed 

so that it can be performed within the workers' capabilities. After any ergonomic solution is implemented, a 

followup analysis should be performed to ensure the effectiveness of the change and to guard against the introduction of any new ergonomic or safety hazards. Physical fitness programs and training can be used to supplement job 

redesign. By effectively instituting sound ergonomic implementation strategies, a healthier work force can be 

maintained and the costs associated with musculoskeletal 

disorders can be reduced, thereby reducing health care and 

compensation costs. 

REFERENCES 

1. Andersson, G. B. Epidemiologic Aspects on Low-Back Pain in 

Industry. Spine, v. 6, No. 1, 1981, pp. 53-60. 

2. Conway, E. J., and R. I,. Unger. Material Handling Devices fcr 

Underground Mines (contract J0225005, Battelle, Pacific Northwest 

Lab.). BuMines IC 9212, 1989, 48 pp. 

3. Daling, P. M., and C. A. Geffen. Evaluation of Safety Assessment 

Methods for the Mining Industry. Volume 1. BuMines OFR 195(1)-83, 

1983, 123 pp; NTIS PB 84-126440. 

4. . Evaluation of Safety Assessment Methods for the Mining 

Industry. Volume 11. User's Manual of Safety Assessment Methods for 

Mine Safety Officials (contract J0225005, Battelle, Northwest Lab.). 

BuMines OFR 195(2)-83, 1983, 96 pp; NTIS PB 84-126457. 

5. Fettig, A. Selling Safety in the 90's. Growth Unlimited, Inc., Battle Creek, MI, 1990, p. 25. 

6. Gallagher, S., T. G. Robick, and R. L. Unger. Reducing Back Injuries in Low-Coal Mines: Redesign of Materials-IIandling Tasks. 

BuMines IC 9235, 1990, 33 pp. 

7. Gallagher, S., and C. A. Hamrick. Acceptable Workloads for 

Three Common Mining Materials. Ergonomics, v. 35, No. 9, 1992, 

pp. 1013-1031. 

8. Goel, V. K., and J. N. Weinstein. Time-Dependent niomechanical 

Response of the Spine. Ch. in Biomechanics of the Spine: Clinical and 

Surgical Perspective, ed. by V. K. Goel and J. N. Weinstein. CRC Press, 

Inc., Boca Raton, FL, 1'990, p. 158. 

9. Hammer, W. Occupational Safety Management and Engineering. 

Prentice-Hall, Inc., Englewood Cliffs, NJ, 4th ed., 1989, pp. 216-218,552- 

554. 

10. Imada, A. S. The Rationale and Tools of Participatory Ergonomics. Ch. in Participatory Ergonomics, ed. by K Noro and A. Imada. 

Taylor and Francis, New York, 1991, pp. 3049. 

11. National Institute for Occupational Safety and Health. A Work 

Practices Guide for Manual Lifting, Tech. Rcp. 81-122, U.S. Dcp. Health 

and IIum. Serv. (NIOSH), Cincinnati, 013, 1981, 183 pp. 

12. National Occupational IIealth and Safety Commission. National 

Standard for Manuaf Handling and National Code of Practice for Manual I-Iandling, Mining Industry Supplement. Austral. Gov. Publ. Serv., 

Canberra, Australia, 1990, 13 pp. 

13. O'Green, J. E., R I-I. Peters, and A. B. Cecala. AEP Fuel Supply's Ergonomic Approach To Reducing Back Injuries. Paper in Proceedings, Twenty-Third Annual Institute on Mining Health, Safety, and 

Research. VA Polytech. Inst. and State Univ., Blacksburg, VA, 1992, 

pp. 187-195. 

14. Plummer, R. W., T. J. Stobbe, and J. M. Peay. Cost Analysis of 

Back Injuries in Underground Coal Mining. Annals of the American 

Conference of Governmental Industrial Hygienists, Vol. 14, International 

Conference on the IIealth of Miners, ed. by R. W. Wheeler. ACGIH, 

Cincinnati, 011, 1986, pp. 469474. 

15. Pope, M. II. Modification of Work Organization. Ergonomics, 

v. 30, No. 2, 1987, pp. 449455. 

16. Pope, M. II., G. R. J. Andersson, J. W. Frymoyer, and D. B. Chaffin. Occupation21 Low Back Pain: Assessment, Treatment, and Prevention. Mosby-Year Rook, Inc., St. Louis, MO, 1991, p. 215. 

17. Sanders, M. S., and J. M. Peay. Human Factors in Mining. 

BuMines IC 9182, 1988, 153 pp. 
18. Snook, S. H. The Control of Low Back Disability The Role of 20. U.S. Mine Safety and Health Administration (Dep. Labor). The 

Management. Ch. in Manual Materials Handling: Understanding and Job Safety Analpis Process: A Practical Approach, Participants Guide. 

Preventing Back Trauma. Am. Ind. Hyg. Assoc., Akron, OH, 1989, MSHA IG 83, 1990, 14 pp. 

pp. 97-101. 

19. Snook, S. H., R A. Campanelli, and J. W. Hart. A Study of Three 

Preventive Approaches to Low Back Injury. J. Occup. Med., v. 20, 

No. 7, 1978, pp. 478-481. 
DEVELOPING AND MAINTAINING SAFETY PROGRAMS FOR IMPROVED 

WORKER PERFORMANCE: DON'T FORGET THE BASICS 

By Michael J. ~lishis' and Ronald C. ~lthouse* 

ABSTRACT 

While mines are safer today than they were in the past, 

miners are still being injured, maimed, and killed, and the 

incident and severity rates for the mining industry are still 

higher than those for most other industries. What's more, 

fatality rates are higher in the Nation's smaller mines and 

highest in the smallest mines. What can be done to improve safety in small mines? 

One key to improved safety is worker performance. To 

be effective, companies need proactive safety interventions 

involving training, changes in policies or procedures, 

and/or modifications to equipment that address minespecific needs and eliminate situations where the miner's 

actions unnecessarily expose him or her to hazards. 

While outside resources such as governmental agencies, 

academic institutions, and equipment manufacturers can 

provide assistance to mine operators, it is up to individual 

mines and companies to develop effective safety programs. 

This paper reviews the basics of developing safety interventions aimed at improving worker performance and 

describes approaches for maintaining program effectiveness. This information is based on research conducted at 

West Virginia Uni~ersity.~ Emphasis is given to identifying 

performance discrepancies (hazardous behaviors) by observations (safety sampling), accident data analysis, and input 

from workers and supervisors. 

INTRODUCTION 

Recent decades have seen safety regulations, improved 

mining techniques, safer mining equipment, and mandated 

safety training. Efforts by governmental agencies, equipment manufacturers, management, labor, and university researchers have resulted in these safer approaches, procedures, and equipment. While mines are safer today than 

they were in the past, miners are still being injured, 

maimed, and killed, and the incident and severity rates for 

the mining industry are still higher than those for most 

'~ssistant professor, Safety and Environmental Management. 

2~rofessor and chair, Sociology and Anthropology. 

West Virginia University, Morgantown, WV. 

other industries What's more, fatality rates are higher in the Nation's smaller mines and highest in the smallest mines (3). 

Worker performance is the key to improved safety. 

Unfortunately, small mine operators with minimal resources and safety and training personnel often feel they 

lack the time, work force, and skills to develop and 

 his research was funded by the U.S. Bureau of Mines under 

Cooperative Agreements (3167023 and (3178052, J. M. Peay, Technical 

Project Officer, Pittsburgh Research Center, Pittsburgh, PA. 

4~talic numbers in parentheses refer to items in the list of references 

at the end of this paper. 
implement effective safety programs. To be effective, Company records. 

companies need proactive safety interventions involving Observation of employees. 

training, changes in policy or procedures, and/or modifi- Ideas from workers and supervisors. 

cations to equipment. These innovations and changes 

must address specific mine needs and eliminate situations If safety interventions do not consider information where the miner's actions unnecessarily expose him or her from all of these sources, they may be based on faulty to hazards. assumptions and fail to identify an organization's under- While outside resources such as governmental agencies, lying safety problcms or the most effcctive ways to elim- academic institutions, and equipment manufacturers can inate those problems. Mine managers, safety officers, and provide assistance to operators, it is up to individual mines trainers often do not get this information. This may be a and companies to develop and maintain effective safety 

programs. The effectiveness of any program begins with result of inadequate planning, inappropriate information, 

the information that forms the basis of that program. The lack of time, or outdated and inadequate methods of obprimary sources of information for a safety program are- taining and maintaining data. 

DATA COLLECTION AND RECORDKEEPING 

Obviously, company records should be the easiest data 

to obtain. Company records of value include reportable 

accident reports, nonreportable accident information, citations, and the mines' roof control plan. Information on 

equipment modifications or changes, and even maintenance and production data, also may indicate a safety 

problem. 

To be useful, however, such records must be easy to 

obtain and in a format that is complete and detailed. 

Often, this is not the case. For example, while companies 

maintain records of reportable accidents, these records are 

often inadequate and may be functionally unusable. A 

cabinet full of accident forms is ineffective as a safety tool 

since it is difficult to analyze the data to determine problem areas and, if only reportable accident data are maintained, information about many other real or potential 

hazards may be missed. 

Many managers, safety officers, and trainers now have 

access to easily maintained, computerized accident databases. These databases may be maintained on a personal 

computer (PC) or a company minicomputer or mainframe. 

A PC can be purchased at a very modest price, and there 

are many approaches to keeping accident, violation, maintenance, and production data. They may be off-the-shclf 

materials such as William's "FingerTips," or The Pennsylvania State University's (PSU's) "Management Incident 

Reporting System," or they may be developed specifically 

for your company. In addition, there are many commersummarizing accident data. Once accident information is 

summarized, it is possible to get an idea about the types of 

injuries that are occurring, the equipment or job classifications involved, sections or shifts that have a high number 

of accidents, etc. 

However, simply maintaining accident information is 

not enough. Many accident reports do not include enough 

information about the circumstances surrounding the accident to permit managers and/or safety officers to make 

judgments about methods of preventing future occurrences 

of such accidents. Consider the following information 

taken from an actual report of a bolting-related accident: 

Example A: 

Job Title: Roof Bolter Helper. Work at: 

Object: Roof Bolter Galis Body Parts: Leg 

Description of Accident: Bolting roof and strained his leg. 

This description, and others like "hit by rock while bolting," do not provide any clue to the actions of the miner at 

the time he or she was injured or if any subsequent training, equipment modifications, policy changes, or personnel 

actions might be appropriate. 

The next description provides details about the action 

of the bolter operator at the time of the accident. This is 

the first step in gaining enough information to determine 

if some safety intervention is appropriate. 

cialspread sheets and database programs that can be B: 

easily adapted for accident and violation recordkeeping. 

If it is impossible to obtain the resources needed to ~,b ritle: shuttle car opr. work at: operating machine 

establish and maintain a computerized database, some Object: ~oof Bolter. Body Parts: Finger 

minimal data summarizing can be accomplished with the Description of Accident: Preparing to push resin bolt into hole 

use of simple forms. ~h~ appendix includes several with machine; as he aligned bolt head & bolt wrench, glove got 

sample forms that might be useful for collecting and caught on bolt, wrapped around bolt, pulled finger. 
SAFETY OBSERVATIONS OR BEHAVIOR SAMPLING 

Observations of workers performing their normal work 

routine is a second key to the implementation of safety 

programs. Called behavior sampling or safety sampling, 

these observations permit a connection between the accident and the situation and hazards leading to the 

accident. 

The performance discrepancies noted during observations may be quite different from those assumed from a 

mere analysis of accident data. For example, a large 

number of back injuries might lead one to believe that 

training workers on proper lifting procedures is in order. 

However, on-site observations may reveal that in ordcr to 

complete certain tasks, miners must twist their bodies 

whiie in awkward postures or overextend their reach; 

therefore, lifting training would not reduce the hazards 

that led to these accidents. 

Another example of the importance of observations 

concerns injuries from falling roof material. In roof bolting, the most frequently occurring accidents involve 

injuries to the hands, arms, and shoulders caused by falls 

of roof material. Observations of bolters show that they 

often have their hands on the drill steel or drill pod-boom 

while drilling. This unnecessarily exposed them to falling 

roof material at a time when they are disturbing and fracturing the top, a situation that is likely to cause falling 

rocks and/or coal. 

Observations can easily be made by managers, safety 

personnel, and/or supervisors, but there must be some systematic approach to conducting observations to ensure that 

the data are easy to collect and meaningful. If time permits, the observer could spend half a shift watching the 

bolting operators at work, but this is not necessary. A face 

boss could gather similar information by spending 5 min/d 

at some point wheil he or she was on the section. A Roof 

Bolting Observation Sheet (see figure 1) was developed to 

help when observations of bolter operators are conducted. 

This checklist allowed the observer to record behavior for 

the most common actions performed by bolter operators. 

CONDENSING AND ANALYZING DATA 

Observations must be put in some condensed form to 

be useful. For example, the Roof Bolting Observation 

Sheet enabled the authors to make a simple tally of safe 

and exposed behaviors to determine where problems exist. 

Table 1 is a simple tally complcted from observation 

sheets collected at a multiple section mine. It was easy to 

calculate the percentage of operator actions that resulted 

in hazard exposure (i.e., unsafe acts). It was also possible 

to determine the number of operators who consistently 

performed in a manner that left them exposed to hazards. 

After collecting the observational data, they must be 

reviewed and analyzed in light of accident data to determine specific problems. The next task is to determine the 

best approach for correcting those problems. In many 

companies, the tendency is to institute a training program 

that will instruct the miners on how to work in a safer 

manner. Depending on the nature of the hazard exposure, 

this may or may not be the most effective approach. 

Table 1.-Summary tally of bolter operator observations 

Bolting work task Number of Unsafe acts % unsafe Problem 

observations bolters' 

Hands on rotating steel ........................ 160 29 18 3 

Hands on mast (drilling) ........................ 158 94 59 7 

Removing steels ............................ 159 31 19 4 

Pinch points steels ............................ 77 1 1 0 

Align bolt wrench ............................. 75 4 4 0 

Hands on bolt wrench ......................... 76 25 33 5 

Hands on mast (inserting bolts) .................. 73 36 49 6 -- - - - - - -- - - - 

 u umber of bolters observed = 12. 
ROOF BOLTING OBSERVATION SHEET 

(Single Boom Bolter - 20-foot cut) 

Row 2 Row 3 Row 4 

Exposed 

Observer: 

Date: 

Row 5 

Crew I: - Cut I: 

Comments on unsafe acts andior 

exceptional performance 

Hand on MastIDrill Head 

Exposed 

Removing Steel from Hole 

Exposed SafeE££3 mm E!EEIRffl 

Drilling 

(W. finisher) Avoid Pinch Points 

Exposed 

Exposed 

Hand on Mast/ Drill Head 

Exposed 

Removing Steel(s) from Hole 

Exposed 

Boltinq Aligning Bolt & Wrench 

Exposed ""m mm mm 

Hand on Bolt while lnserting (raisinglspinning) 

Exposed SafeE££3 mm mm 

Hand on Mast while Inserting Bolt 

Exposed 

Bolt Spin Times (fully grouted bolts only) Manufacturer's recommended time: 

Time in [TI ml ml 

seconds 

Bolt torqued Torque range: 

Yesrrm rrrnm rrmm 

Other Observations: circle observations (use the back of this sheet for additional comments) 

not done Methane Checks not done I Supply'ng done properly y 1 n 1 

Bslkdim not seen 

a) Jams bolt into ground (like bow! 

b) Bends over tire 

c) Bends elsewhere on bolter 

a) On ground 

b) On bolter 

c) Against rib 

Dust Box Emotied not done Canooy no canopy 

a) After bolting place 

b) When filled 

c) Due to no suction 

Figure 1 .-Roof Bolting Observation Sheet. 

BOI~ pattern followed y 1 n 

I a) Done incorrectly 

(no extension rod, etc) I b) Done correctly 

a) Inadequate size 

b) Bolter stay under Personal protection worn Y 1 n 

Scaling done properly y 1 n 

a) Not properly positioned 

b) Not pressurized to roof 

c) Stab jacks not set 

Test Hole (if needed) 

Tramming properly yin 
ANALYZING PERFORMANCE PROBLEMS AND THE DECISION-MAKING FLOWCHART 

Performance problems, whether relatcd to safety or worker's failure to perform the task correctly because he 

productivity, arise from many different sources and, in or she doesn't know how to do the job? If the worker has 

turn, have differing solutions. A hlit7tan perfon7tance dis- just been assigned to a new job, or must use a piece of 

crepaltcy (i.e., a worker action or behavior that isn't performed in a desired manner) must be examined in light of 

potential solutions. All too often, managers decide that 

the only ways to correct a performance discrepancy is to 

train or terminate workers when neither of these is the 

most appropriate action. 

In the book Ylnalyzing Pefomtance Problet7ts or 'You 

Really Ougltta Wanna"' (2)' a proccdure is discussed for 

analyzing performance problems and selecting appropriate 

solutions. Possible actions are suggested, such as formal 

training, practice, feedback, removing obstacles, arranging 

consequences, changing the job, and transferring or terminating personnel. To assist the manager, trainer, or safety 

officer in determining which solution is best, they developed a decisionmaking flowchart. This flowchart was expanded by Klishiss and modified to reflect the "three E's" 

of safety: engineering, education, and enforcement. The 

modified version of the flowchart is shown in figure 2. 

This version describes possible solutions under four basic 

categories: education (training), enginecring (ergonomics), 

enforcement (policies-procedures), and personnel actions. 

To use the flowchart, you begin by identifying the problem, labeled on the chart as a 'pefon?7urtce discrepancy." 

Once a performance discrepancy is idcntified, decide if the 

problem is important. Just because a worker doesn't perform in the appropriate manner does not mean that it is 

really a problem. Often, workers will develop their own 

patterns and routines for performing a task. These "idiosyncratic behaviors" may be a5 good as, if not better than, 

those in the operating or training manuals. If the bel~avior 

of the worker is safe, efficient, and productive, it is probably not a problem and should be ignored. To use a 

sports analogy, if a batter has the wrong batting stance, 

doesn't keep his eye on the ball, "puts his foot in the 

bucket," etc., but manages lo bat .300 with power and 

doesn't strike out, does his form really matter? Getting 

the job done is the important thing. 

equipment that operates in a manner very differently from 

the old equipment, training is the best solution. 

On the other hand, perhaps the skill deficiency is a 

result of disuse of the skill. For instance, a miner who 

used to be a bolting machine operator months or years 

ago, but has been working as a continuous miner operator 

or as a shuttle car operator, is reassigned as a roof bolter. 

The worker's skills are "rusty" and he or she doesn't perform in the manncr expcctcd. In this case, it is practice, 

not training that is needed to get him or her "up to snuff." 

Sometimes a worker may be performing in an unacceptable manner and not realize it. No one has told the worker that he or she is performing in an unsafe or unproductive manner. The worker is doing what he or she thinks 

is right and will continue to do so until someone gives him 

or her appropriate feedback about his or her performance. 

Many of our skills or approaches will change over time, 

and perhaps we pick up an unfortunate habit or maneuver 

that isn't safe, event though it gets the job done and seems 

okay to us. If we aren't told we are performing a task incorrectly, we can't be expected to correct our errors. 

Perhaps the problem is not a skill deficiency; perhaps 

the task, as it is planned or designed, is not appropriate. 

That is, no matter how carefully the worker performs the 

task, there is unnecessary exposure to a hazard or inefficient production. Then the solution is an engineering one. 

Perhaps the problem is not a skill deficiency; perhaps 

there are obstacles that prevent the task from being performed correctly. If a bolter operator doesn't have a 

torque wrench, or the methanometer is inoperative or 

missing the extension rod, the operator cannot perform the 

work safely. If there have been requests for a new torque 

wrench or mcthanometer, and none is forthcoming, it is 

not the operator's fault. In this situation, it is up to the 

manager, supervisor, or safety officer to ensure that the 

obstacle to performing a task correctly (lack of appropriate 

or functioning equipment) is removed (the miner is given 

However, if the worker's performance is unsafe or re- needed equipment). 

sults in inefficiencies that hurt production, then this is a At other times, the problem may be a case of "inapproperformance problem that should be corrected. The next priate consequences." Consider the situation where the 

step is to determine the cause of the discrepancy. Deter- worker's performance on a specific task may not matter, 

mine if the problem is a skill deficiency. That is, is the thus the task doesn't get performed. For example, if it is 

part of the bolter operators' job to rock dust the workplace after bolting it, but the supervisor ignores this task 

'OFR 113193. Coal Mine Injury Analysis: LZ Model for Reduction an inspector is around, or has general inside laborThrough Training. Vol. III-Accident Risk During the Roof Bolting 

Cycle: Analysis of Problems and Potential Solutions, by M. J. Klishis, ers dust it on the next shift, why would the bolter operaR C. Althouse, T. J. Stobbe, R. W. Plurnrner. R. L. Grayson, L. A. tors perform the task? It matter to them if they 

Payne, and G. M. Lies. do it or not. In this case, it is up to the supervisor to 
performance 

Figure 2.-Decisionmaking flowchart. [Adapted from Mager and Pipe (2)] 

"consequate" the behavior, perhaps by "getting on" the 

bolters if they fail to rock dust. 

There are other types of inappropriate consequences. 

The most common situation involves a task that is "punishing" to perform correctly. Bolting a potted-out place 

where the automatic temporary roof support (ATRS) 

won't reach is a good example of this situation. If the 

ATRS won't reach, the roof still has to be bolted. The 

proper procedure in this situation would be to set jacks, 

build a ramp, add a crib block to the top of the ATRS, or 

use the ATRS extenders to gain the height necessary to 

get the ATRS to support the roof. Unfortunately, each of 

these choices requires considerable work, and most bolter 

operators admit that rather than go to all of this effort, 

including slowing down work on the production section, 

they will simply ignore the problem and bolt while under 

unsupported top. In this case, only a strongly enforced 

company policy that demands that the task be performed 

safely will counteract the aversive effects of performing it 

correctly. 

In other cases, the task may not be appropriate. That 

is? no matter how the worker tries, the task can't be performed safely. In these situations, the problem is an ergonomic one and the solution is an engineering one. To get 

the desired performance, the equipment will have to be redesigned, the environment changed, or the job redesigned 

before the worker can perform safely. For example, if the 

bolter operator can't stay under the drill canopy because 

it is too small, the canopy will have to be enlarged. If the 

bolter operator usually cannot reach the top to insert the 

glue and bolt and has to climb on top of the drill pod to 

get the necessary height, the bolting machine is obviously 
too small for the seam and only a more appropriate model 

will really solve the problem. However, an interim step 

may be to add a "step-up" device to the machine to permit 

the bolter operator to climb up on the drill pod in a safer 

manner. 

Another example might be an environmental problem. 

If an operation is plagued with bad ribs and bolter operators are getting injured by rib rolls, then rib bolting may 

be one solution, purchasing a walk-through bolting machine another, or perhaps both solutions are needed. 

The final alternative is a personnel action. If, after 

addressing the situation with the recommendations suggested above, the worker is still incapable of performing 

the task correctly, he or she should be transferred to a 

different job where it is possible to perform in an 

appropriate manner. If the employee is capable of performing [he task, but simply not willing to perform it correctly, a transfer may also be in order. In either case, if 

the employee won't perform or is incapable of performing 

tasks correctly, termination should be considered, but only 

as a last option. Terminations are always a hassle, but 

may need to be considered if the safety of the employee 

and other workers is at stake. 

After going through the flowchart and looking at the 

various possibilities, there may be more than one solution 

to the problem. At this point, the best solution is selected and implemented. The best solution is determined by 

the nature of the problem, the time and resources 

available to correct the problem, and legal or contractual 

responsibilities. 

COMMUNICATION AND EMPLOYEE FEEDBACK 

Good interactive communication and employee feedback are also essential in identifying, designing, and 

implementing any type of safety innovation. The workers 

are an important resource and their knowPedge can be critical in identifying potential problem areas that have an 

impact on safety and efficiency, Today we hear much 

about total quality management and quality circles. Thcse 

techniques are effective because they rely on employees 

for input and direction. Workers have many ideas on Plow 

to improve safety and productivity. Often an individual 

employee will have developed a "gizmo" or procedure to 

make work easier, faster, and/or safer; unfortunately, 

these ideas usually don't go beyond the worker or a crew 

in the mine. 

Involving the workers themselves in the process will 

allow you access to these ideas, techniques, and modi5cations. Of course it is best to review these suggestions with experts who are knowledgeable about the 

process or equipment such as Federal or Stale agents, 

equipment manufacturers, representatives from educational institutions, or the U.S. Bureau of Mines (USBM) 

from the standpoint of safety and efficiency, bur usually 

these suggestions are very valuable and can be easily 

implemented. 

Another benefit gained by involving the miners themselves is that they are usually more receptive to changes in 

their jobs or work routines when they are involved in planning and/or designing those changes. The changes then 

become "their" changes rather than changes mandated by 

management. 

When a change is implemented, it is also important 

to be sure that the "message" gets through to the employees. Effective communication requires reaching all the 

employees and informing them not only of the change, but 

the reason for that change. If not, they may not understand why a change was made and may ignore or even 

subvert the intervention. For example, one operation 

decided to weld a small piece of pipe to the bolting 

machine. This pipe was supposed to serve as an "aid" 

when bending bolts. The change was agreed upon at a 

meeting that included the safety director and the union 

safety committee chairperson. Unfortunately, all of the 

bolter operators were not informed of the reason for this 

"modification." As a result, one operator had the pipe 

removed. Another oper-ator determined that the pipe was 

mountcd at the wrong angle, but instead of having the 

angle corrected, he or she also had the pipe cut off. As a 

result of the failure of management to communicate with 

the work force and of a worker to communicate with 

management, the well-designed intervention was a failure. 

Improved communication also means the transfer of 

ideas between sections of the same mine and/or other 

mines in the same company. In working with "umbrella" 

companies with several small mines, researchers have observed safety improvements installed in one mine but not 

in other mines of the same company. They have even observed improvements in one section of a mine but not in 

another. 

Communication also means keeping employees informed about what is happening in the mine. What kind 

of information does the face boss and/or the workers get 

when they start a shift? Are they told about safety-related 

probiems or bad conditions? Have any changes or innovations designed as a safety intervention be initiated? If so, 

what are they and why were they made? 
PROBLEMS FACED WHEN BUILDING AND MAINTAINING A SAFETY PROGRAM 

Small operations, even "umbrella" operations that 

service several single unit mines, usually do not have 

enough data on accidents to make well-informed choices 

on safety and training interventions. Fortunately, accidents 

are a rare occurrence in any operation, but this results in 

a database that consists of a few, highly scattered incidences. It is difficult, if not impossible, to draw conclusions from such limited information. 

To have enough information to make decisions, small 

operations need a database and hazard inventory built on 

a large accident pool. An example of one such database 

is the roof bolting accident database developed by researchers at West Virginia University's (WVU's) Mining 

Extension Servi~e.~ This database and the resulting hazards inventory served as a guideline for making observations and taking actions to improve bolting safety at 

several small operations. 

Another problem safety personnel at smaller operations 

face is the need to make safety sampling observations with 

limited time and resources. Ideally, observations should 

be made by face bosses, but problems abound. There never seems to be any time to train face bosses to make observations, and if they are trained, they have so many demands on their time that they don't feel that they have 

time to make observations. 

Supervisors required to make observations face another 

dilemma. They don't want to look bad or have their section or people look bad, so they are hesitant of making 

"accurate" (truthful) observation reports for fear of actions 

against them and/or job loss. 

Although supervisors are the best persons to make safety observations, we cannot forget the safety manager. It is 

important that safety officers go underground, learn what 

is really happening in the mine, and identify potential 

problem areas. 

TRAINING AS A SAFETY INNOVATION 

Another problem faced by operators of small mines is 

making effective use of mandated health and safety training. Too often, training is done for compliance, not for 

safety. Training done by well-meaning, knowledgeable entrepreneurs who have little knowledge of the operation's 

specific safety problems serve to comply with the law but 

do little to meet the "true" safety training needs of the 

operation. When these entrepreneurs are finished training, the operator has a 5000-23 form with the correct 

boxes checked, but the safety level of the operation is at 

best maintained at an ongoing level, not improved. If 

training is to be an effective approach to improving safety, 

the trainer must treat training as an opportunity for improvement, not just as an activity needed to comply with 

governmental regulations. 

To be effective, training must be tailored to identified, 

specific company or mine needs. Canned or generic programs may include good information and many valid 

points, but do they really meet the needs of your organization? Training should also go beyond mandated 

requirements. If a problem exists with a certain piece of 

equipment or job classification, take the time to give appropriate training on that area. It is easy to cut training 

to the bare minimum, but in the long run this is not cost 

effective. 

Finally, management must not view safety as a "oneshot" deal. Once there has been a successful implementation of a safety intervention, the job is not over. Management must consider safety as a continuous process that 

requires constant attention and effective communications 

to maintain quality and safety on all working sections. 

Effective training involves the entire organization in an 

attempt to keep the workers safe and productive. 

Management must demonstrate its support for the 

training effort. This means taking interest in the training 

program, meeting with workers during annual refresher 

training sessions, and encouraging them to work in a safe 

manner. It means demanding that supervisors work in a 

safe manner and that they ensure that work crews and individual miners are also working safely. 

OTHER INITIATIVES 

While mine operators have the primary responsibility operators is needed from Federal and State agencies, 

for maintaining a safe workplace, it is difficult for them to technical schools, junior colleges, and major mining 

"go it alone." Safety and training assistance for small institutions with "outreach" services (WVU, PSU, etc.). In 

1980, a report by John Short & ~ssociates (4) suggested 

%Vork cited in footnote 5. that the most effective approach to work force 
development and training in the nining industry would be 

a national mining extension service. Perhaps it is time to 

reexamine that idea and strengthen the service to small 

operators. In this light, WVU's Mining Extension Service 

has recently stepped up and expanded its service to small 

rr,ine operators in West Virginia. 

The USBM has long been involved in research that has 

been a tremendous assistance to the mining industry. To 

be most effective, the USBM should continue to place an 

increased emphasis on human factors and training for 

small mine operators while maintaining its traditional research orientation for equipment and mining techniques. 

The intcrcliange of information is one key to successful 

safety and training programs. All governmental agencies 

should encourage and support local, regional, and national 

meetings of safcty and training personnel, such as the 

Holmes Saie!y Association, S!ate grants meetings, training 

resnurccs applied to mining, and the National Mine Instructors Conference. 

Of course the U.S. Mine Safety and Health Administration (MSHA) has an important function and can be a key 

agency in the improvement of safety in small mines. It 

should continue its efforts to develop easy access of Safety 

and Health Technical Center (SHTC) data for all operators (such as data on diskettes and user-friendly programs), but it can also provide much needed data to the 

small operator and academic researchers by conducting 

Gncr grained, more useful analyses of accidents in the 

SHTC database. These analyses should be similar to the 

"microanalysis" conducted at WW? 

What does this have to do with small mine operators? 

Simply put, while government agencies and educational institutions strive to provide the assistance and services 

needed most by the mining industry, small mine operators 

need to make their needs and wishes known to these agencies and encourage the support and funding of programs 

that are beneficial and practical. 

CONCLUSIONS 

T~P, safety program basics suggcstcd here involve identifying situations and conditions under which miners arc 

injured and using that information to develop interventions 

for critical areas in the job task. The key steps in this 

process are the analysis of accident and injury data, observations of employees performing tasks, communications 

between workers and supervisors, and development of 

appropriate training. 

Although govcrnmcntal agencies can provide assistance 

to operators in the form of research, especially in the area 

of human factors, and assistance in the interchange of 

ideas, it is up to the operator to place the appropriate 

emphasis on safety and training at his or her operation. 

This means management's involvement in the effort and 

viewing safety and training as an ongoing, ever-changing, 

integrated process. 

REFERENCES 

1. Jenkins, E. E., S. M. Kisner, and D. E. Fosbroke. Fatal Injuries 4. Siedcnstrang, D., D. Ellin~wood, and J. Short, Manpower and 

to Workers in thc Unitcd States, 1980-1989: A Decade of Surveillance: Training Model for the Mining Industry (contract 303.57109, John Short 

National I'rofilc. GI'O, DIltlS Publ. NIOSII 93-108, 1993, 337 pp. 8: ASSOC., Inc.). RuMincs OFR 92-81, 1980, 219 pp.; NTIS PB 

2. Mager, R. F., and P. Pipe. Analyring Performance Problems 81-222325. 

or 'You Really Oughta Wanna.' Lake Publ. Co., Belmont, CA, 1981, 

143 pp. 

3. Peters; R. IT., and D. Fotta. Statistical Profile of Accidents at cited in 5. 

Small Underground Coal Mines. Paper in this proceedings. 
APPENDIX.-ACCIDENT DATA COLLECTION AND SUMMARY FORMS 

When building a safety program that will permit the dcvelopment and implementation of safely interventions, one 

resource is company data such as accident and injury information. Other company records of value include citations of the roof control plan, informallon on equipment 

modifications or changcs, and even maintenance and production data. To be useful, however, such records must 

be easily obtainable and in a format that is complete and 

appropriately detailed, which means establishing a comprehensive and useful database. 

The focus of any safety program begins with accident 

and injury data. Unfortunately, these accidcnt records are 

often inadequate or unusable. While accident information 

is required by regulatory agcncics (MSI-TA and State mining departments) and for insurance purposes (Worker's 

Compensation), it is often main1aint:d as a number of reports in a filing cabinet. These repurls may not be an 

effective safcty tool since (1) [hey a! c designed to meet the 

needs of outside agencies, not comp,iny safety ant1 training 

personnel, and (2) it is diffical~ to ~inclIy7c. data that arc in 

raw report form. 

The first step in establishing an cffcctivc database begins with the collection of accideni data that are useful ts 

a safety program. Whil~ thc inlorn~atinrl required by government agencies may hr oI soii~c. uw, rherlx are many 

"nonreportable" accidents that s1it:uld be considcred, In 

addition, the most important inforrxation in an accident 

report is thc description of the bnruarlon or circumstances 

that surround the accident: lVhrlr \v'ts file worker tieing 

just before and when he or s11c got injured; how dicl 11e or 

she get in[(> ihc situation; if th~lrt, \,b1:i< :In\! warning b~\lore 

the incidcnt nccurrcd, ho,.,~ did t1;e worker r~.act: and what 

can be done LO prevent such an in( iclcnt in tlic futurc! 

To get this inlormalion you need an accident Form that 

specifies the leporting of incidcnts in enough Qctail and 

a company pol~cy rcquirlng the rzporting of all incidents 

wherc a wnrkcr ic inji~r.c,d. Tliic rcrl~iir.c\ grltirig a report 

from the victim and/or the \*ictiln s supervisor, as well as 

a followup visit, especially in the case of nonfatal days lost 

(NFDL's), to discuss the accident with the victim, the supervlsor. and any witnesses. The two-gage mine accident 

form with its accompanying supplemental third page for 

evaluation by a safety officer is an example of such a 

method of collecting accident information (see figure A-1). 

You may find it useful for your operation 

The key to this form is the narrative description of the 

accident (second page) and the accident assessment (third 

pagc). Gctting detailed information on the incident rather 

than simplistic descriptions such as "hit by rock" will give 

you an idea of the kind of problems that rnay exist and a 

starting point for observations. 

The second step in maintaining accidcnt data is 

consolidation into a useful summary that permits safety officials and mine management to maintain a "handle" on accidents. Such a form may be similar to the mine's production reports. There are two forms in this package that 

may bc useful. The first, called the Accident Summary 

Shcct (fig. A-2), is designed to keep a running tally of 

acciden~s. The second, called the Lost Time Accident 

Summary Sheel (fig. A-3), serves as a simple way to summarlze accidents on a monthly and yearly basis. 

Once the mine's accident data has been summarized, 

the mine operator can look for trends or problem areas. 

Remember, it is necessary to couple the analysis of accident data with a review of the narrative descriptions of 

the accidents and on-site observations to be able to pinpoint both the problem and its cause, as wcll as to identify 

potential corrective actions. 

Don't forget the olher company data. Citations for 

safety violations from Federal and State inspectors or 

writcups from company compliance officers can help to 

pinpoint problem areas. As with accident information, 

there has to be some organization of the information. A 

simple listing made on a form such as the Violation Summary Sheet (fig. A-4) might be helpful in identifying repeated violations that can be a sign of a problem. 
Mine Accident Form 

Name: Date of Accident: 

Witness: Time of Accident: 

Mine: Date Reported: 

Age: Sex: M / F 

Days Lost From Work: Was there time lost from work (or) time lost and restricted work? Y / N 

Total lost days from work (if any) 

Occupational Information 

Regular Job Title: - 

Job/Activity When Injured: -- 

Total Years Mining Experience: Years at Present Mine: 

Years at Present Job title: 

Accident Information 

Location of Accident in the Mine: (Circle all appropriate choices) 

Underpound / Surface 

1. Face 4. Mantrip / transportation 

2. Intersection 5. Underground shop or office 

3. Haulage way 6. Belt area 

7. Other 

Source of Injury: 

What Object/Material caused the injury, i.e., drill steel, falling roof, electrical cable, crib ... etc.) 

Body Parts Injured and Type of Injury (list as many as applicable!: 

Part Inlured of b-cture. etc.1 

- 

Figure A-1 .-Mine Accident Form. 
Description of Accident 

Instructions: 

Please give a detailed description of the accident. The purpose of this 

form is to help in the development of safety and training materials to 

make it safer to work in this mine. The more information you give 

the more useful it will be to you and your fellow workers. 

Thank you. 

Figure A-1 .-Mine Accident Form--Continued. 
Accident Form Supplement 

(To be completed by safety officer) 

Name: Date of Accident: 

Mine: Date Reported: 

Is there safetyltraining material that is related to this accident on hand? Y 1 N 

If YES, is the material current? Y 1 N 

Has the injured received safetyltraining material related to this accident in the last year? Y 1 N 

Personal observations from accident site: 

Comments from supervisor1witnesses: 

Provide an assessment of the accident including what actions can be taken to prevent the 

reoccurence of this type of accident: 

Figure A-1.-Mine Accident Form--Continued. 
ACCIDENT SUMMARY SHEET 

TOTALS (per accident type): 

Date 

HANDLING MATERIALS HAND TOOLS FALL of FACE or RIB 

HAULAGE ROOF FALLS FALLING or SLIPPING OBJECTS 

MACHINERY STEPPING or KNEELING on OBJECTS OTHERS 

SLIPS and FALLS ELECTRICITY 

Figure A-2.-Accident Summary Sheet. 

Regular 

Job Classification 

Job at Time 

of Accident 

- 

. - 

Accident Type Details of Accident 

-- 
LOST TIME ACCIDENT SUMMARY SHEET 

TOTAL INJURIES 

SHOULDER 

FINGERS 

ABDOMEN 

F3OGHU WAY 

SAFE WAY 

TOTAL INCIDENT RATES 

E TOTAL 

Figure A-3.-Lost Time Accident Summary Sheet. 
VIOLATION SUMMARY SHEET 

DATE SUBJECT OF STATEIFEDERAL 

VIOLATION REGULATION DESCRIPTION 

I 

Figure A-4.-Violation Summary Sheet. 
EMERGENCY RESPONSE PLANNING FOR SMALL MINES: WHO NEEDS IT? 

By Launa ~allett,' Michael J. Brnich, Jr., and Charles vaughtl 

ABSTRACT 

This paper discusses emergency response planning with past mine emergency situations are used to highlight the 

a special emphasis on small minesites. It addresses the discussion. The paper is intended to stimulate the thinking 

importance of an emergency response plan and offers of both small mine operators and those safety professome tips for developing a useful document. The content sionals who work with individuals from small mines. It is 

of the paper is based on U.S. Bureau of Mines research not meant to be the final word on emergency response 

focusing on mine emergency response. Examples from plans. 

INTRODUCTION 

Emergencies disrupt organizational routine. By their 

very nature, they create confusion and uncertainty. The 

expertise needed to respond effectively may not be common in an organization. One reason is that emergencies, 

being rare events, demand certain skills that are not 

developed during normal operations. If no one on site has 

those skills, the natural confusion and uncertainty will be 

compounded: 

. . . the two owners . . . got there basically about 

the same time. . . I said, "Hey, . . . we've had a rock 

fall. We got one guy that's not accounted for. What 

do we need to do here?" . . . These guys have been 

in business 20 plus years each, and they had never 

had nothing like this happen before . . . 

when the unforeseen emergency occurs? Chaos is likely to 

be the result. 

One of the major factors determining how quickly a 

situation may be brought under control is the amount of 

emergency response planning that has been done previously by mine management. Emergency response planning 

in larger organizations is often done as a matter of course 

by the safety or training specialist at the mine or by a 

special team at the corporate office. Small mine personnel 

do not have these luxuries and must therefore put forth a 

special effort to prepare themselves for the worst, even 

while hoping the worst never happens. Because small 

mines usually have fewer immediate assets to draw upon, 

this planning becomes especially critical. 

The insights about planning contained in this paper 

come from information that was obtained during U.S. 

The two small mine owners mentioned above had put Bureau of Mines (USBM) research that has been conducted over the past 4 years. The work is part of an over- together a management team that possessed the necessary all USBM effort to improve the efficiency and effective- expertise. They had an experienced safety director who 

ness of emergency response activities and thereby protect assisted Ihem through a lengthy recovery Is potential victims and response The authors 

there someone at every minesite has that re- have reviewed literature that addresses all types of emersponsibility, experience, and ability? If not, what happens gency response. They have also conducted in-depth interviews with 28 individuals who have extensive eGerience 

managing large-scale mine emergencies and 10 people who l~esearch sociologist. 

 inin in^ engineer. played key roles in responding to a major mine fire. This 

Pittsburgh Research Center, U.S. Bureau of Mines, Pittsburgh, PA. paper is based on preliminary analyses of these data. 
SOME DEFINING FACTORS OF A SMALL MINE 

For the purposes of this paper, a small mine is defined 

by a number of characteristics that are relevant to emergency rcsponse planning and activities. First, a small mine 

has limited resources, most of which go to production 

activities. There is little funding or personnel available for 

emergency response plan research, preparation, and training. The person who is responsible for safety at the mine 

may also perform a number of other tasks during a workday. This individual therefore has limited time and little 

(if any) money allocated to planning for a futurc event that 

may or may not happen. Second, the work force is small 

enough that management knows each employee and workers all know each other. If an injury or fatality takes 

place, responders know the victim and often also know 

that person's family. This increases the amount of stress 

on everyone during a response. A third characteristic of 

a small mine is local control. In other words, management 

personnel who conduct daily operations at the minesite 

will also be accountable for response efforts. There may 

not be experts from a corporate office who can be called 

or flown in to assist with decisionmaking. Even when they 

have a vast knowledge of mining, key decisionmakers at a 

small mine may have little or no experience with situations 

they will face during an emergency. All these factors present the operators of small mines with special concerns 

regarding mine emergency response. 

WHY PLAN FOR EMERGENCIES? 

According to the U.S. Mine Safety and Health Administration (MSHA) statistics for the 3-year period 1989-1991, 

there were 76 miners killed, 138 permanently disabled, and 

thousands more seriously injured at mines employing 50 

or fewer workers. When an incident occurs at a site, thcre 

will be an effort to rescue any trapped victims, get medical 

assistance, clean up the affected area, corrcct all hazards, 

and return the mine to production as soon as possible. If 

each of these activities must be planned as it is conducted, 

valuable time will be lost and responders who are under 

stress because of the event may not be able to make the 

best possiblt: decisions. If ernergcncy rcsponse planning is 

done before an event happens, it will be less difficult and 

take less time to return the mine to normal operation. 

A compelling argument for preplanning comes from 3 

situation created when miners survive the initial impact of 

an event and need immediate rescue. Take, for example, 

a roof fall that occurred in Pennsylvania (4).3 Two miners 

were attempting to pry down loose top a couple of feet 

inby permanent supports when the roof came down on 

them. One worker was covered completcly and the other 

was pinned from his knees down. Crew members removed 

the rock from these two victims. A miner who was an 

emergency medical technician (EMT) administered first 

aid at the scene and sent both victims outside to arriving 

ambulances. Initial reports stated that both individuals 

suffered broken legs. While this was true and one worker 

eventually recovered completely, the other worker's right 

leg had to be amputated. 

Frequently, self-protection is not the first thing that 

rescuers think about when someone is,in trouble. The 

State report on this accident docs not mention any safety 

precautions that the rescuers took while trying to remove 

the victims. It does not tell whether or not the rescuers 

had been trained to protect themselves in such a situation. 

It also docs not mention the added stress on two of the 

rescuers; one was the brother of a victim and the other 

was a cousin. The cousin was the section EMT and was 

therefore called on to assess both victims' injuries and 

treat them. The State Bureau of Deep Mine Safety was 

not officially notified of the accident. While this violation 

may not be as important as the life and safety of two 

miners, it is an important response detail that was not 

dealt wilh when the event occurred. In this case, rock 

removal was relatively easy and the victims were soon on 

their way to a hospital. But, if the roof fall had been 

larger and the response longer, would the rescuers have 

been ready? Would the right telephone calls have been 

made eventually? Would the victims have time to wait for 

someone to decide what should be done? These questions 

cannot be answered for this event, but they should be 

considered at all mines before a serious injury occurs. 

WHAT DOES THE LAW SAY? 

A violation was written in the incident cited above their agency of the event. While it is not possible here 

because State investigators determined that mine manage- to go through all State regulations pertaining to coal mine 

ment had not complied with regulations and informed emergencies, thcre are Federal regulations that can be ., reviewed (6). Both underground and surface mine opera3~ta~ic numbers in parentheses refer to items in the list of references tors are required by Federal law to be prepared to manat the end of this paper. age and respond to mine emergencies when they occur. 
Underground coal mines are covered under regulations 

in 30 CFR 49, 50, and 75 while surface coal mines and 

surface areas of underground coal mines are governed by 

regulations in 30 CFR 50 and 77. 

Regulations under 30 CFR 49 (section 49.9) require all 

underground mine operators to have a mine emergency 

notification plan. Within this plan, operators must outline 

procedures that are to be followed for notifying mine 

rescue teams when their services are required. Copics 

of the plan must be posted for workers' information and 

made available to the mincrs' representative where applicable. Section 50.2 (h) of 30 CFR 50 stipulates the requirements for notifying MSHA of all accidents. Operators of underground mines must also make arrangements 

for emergency medical assistance and transportation of 

injured persons, as specified in 30 CFR 75 (section 1713- 

1). In addition to making these arrangements, the operator must post at appropriate ioca~ions the names, titlcs, 

addresses, and telephone numbers of all persons or services that are currently undcr such arrangements to provide medical assistance and transportation. 

Section 383 of 30 CFR 75 rcquires that underground 

mine operators conduct practicc drills to familiarize their 

miners with emergency escape procedures. At lcast once 

every 90 days, each miner, including thosc with work locations between working scctions and main escapeways, is 

requircd to participatc in a practice drill. During the drill, 

each miner is rcquired to travel either the primary or 

alternate cscapeway from his or her working section to the 

point where the split of air ventilating the section intersects with a main aircoursc or 608 m (2,000 ft) outby the 

section's loading point, whichever distance is greatcr. All 

other miners arc to participatc in cscapcway drills by 

traveling at least 608 m (2,000 ft) in cithcr the primary or 

alternate escapeway from his or her work location toward 

the nearest escapc facility or drift opening. 

Besides the 90-day drills, at least two miners from cach 

production section who work on that scction and the 

supervisor must participatc in practice drills and travcl 

through the primary or alternate cscapeways to the surface, mechanical escape facilities, or to an underground 

entrance lo a shaft or slope to the surface at least once 

every 6 weeks. In addition, at lcast two miners and a supervisor on cach maintenance shift shall participate in 

escapeway drills by traveling through the primary or altcrnate escapeways to the surfacc, mechanical escape facilities, or to an underground entrance to a shaft or slope to 

the surface at lcast once every G weeks. In all cases, each 

escapeway drill cannot be conducted in the same escapcway as the immediately preceding drill. For the 6-week 

drills, operators are required to systematically rotate 

personnel to ensure that all miners participate. The practice escapeway drills required undcr section 383 of 30 CFR 

75 may be used to satisfy the evacuation specifications of 

fire drills that are requi~cd by section 1101-23 of 30 CFR 

75. Either before or during practice drills, miners must be 

informed of the following: the route of escape and any 

changes to these routes; the location of fire doors, check 

curtains, or smoke-retarding doors; and the plans for 

diverting smoke away from mine escapeways. 

The remaining regulations that address emergency 

response for underground mine operators are related 

specifically to fires. An operator is required to adopt a 

program for instructing all mincrs in the use of firefighting equipment and in proccdurcs for evacuating their 

mine (30 CFK 75, scction 1101-23). This program, which 

is submitted to thc MSHA district manager for approval, 

must include a specific fire-fighting and evacuation plan 

designed to familiarize mincrs at an operation with procedures for (1) cvacuation of workers not ncedcd for firefighting activities, (2) rapid marshalling and deployment of 

ileccssarjr personfie!, fire-fighting eqaipment, and rescue 

apparatus to the fire scene, and (3) opcration of firefighting equipment at the mine. 

Under the provisions of section 1101-23 of 30 CFR 75, 

mine opcrators must cnsure that at lcast two workers per 

scction on each production shift are proficient in the use 

of all fire-fighting equipment available in that section. 

Those workers are also to know thc location of this apparatus in their section. Operators of attended equipment, 

such as continuous mincrs and shuttlc cars, must be proficicnt in using the machine's fire-suppression system. On 

maintenance shifts, the shift forcman and at lcast one 

miner for every five working on that shift must be proficient in the usc of firc-fighting cquipmcnt available in the 

mine. In addition, they arc rcquircd to know the location 

of this cquipmcnt. 

Section 1101-23 of 30 CFR 75 also compcls operators 

to ensure that all mincrs employcd undcrground participate in firc drills. Thcsc drills, which must takc place at 

intervals of not more than 90 days, arc to sinlulatc thosc 

actions rcquircd by thc MSHA-approvcd firc-fighting and 

evacuation plan. Mine operators also have to keep a 

record of all firc drills hcld at thc minc. Finally, mine 

opcrators must provide annual instructiun, based on the 

approvcd plan, to all miners aild to newly employed 

miners within 6 months cf thcir date of employment. 

Surfacc coal mines and surface areas of undcrground 

mines arc govcrncd by minc cmergcncy rcsponse rcgulations found in 30 CFR 77. Whilc the stipulations of these 

regulations are similar to those for underground mines, 

thcy arc considerably lcss stringent and subject to greater 

interpretation. Surfacc operations arc requircd to make 

arrangements for cmcrgcncy medical assistance and transportation of persons injured at the minc, as specified in 

section 1702 of 30 CFR 77. Tn addition to making thcse 

arrangemcnts, an operator must post at appropriate locations the namcs, titlcs, addresses, and tzlcphonc numbers 
of all persons or seavices that are currently under 

such arrangements to provide medical assistance and 

transportation. 

There are also regulations specific to fire emergencies. 

Under 30 CFR 77, section 1100, operators are to provide 

fire-fighting facilities and equipment based upon the 

potential fire hazards at each structure or other facility at 

their mine. Operators must instruct persons working at 

these facilities and retrain them annually in the use of 

available fire-fighting facilities and equipment. Surface 

mines and surface areas of underground mines must have 

escape and evacuation plans. Section 1101 of 30 CFR 77 

specifies that operators are required to establish and keep 

up to date a specific escape and evacuation plan that is 

to be followed in the event of a fire. In addition, this plan 

has to include the designation and proper maintenance 

of adequate means for exit from all areas where miners 

or others are required to work or travel. This includes 

buildings, equipment, and all areas where persons normally 

congregate during the work shift. In addition, all employees must receive instruction on the escape and evacuation 

plans, fire alarm signals, and applicable procedures to be 

followed in case of a fire. 

Therefore, in terms of general emergency response 

planning, all mine operators are required by law to do the 

following: 

1. Make arrangements for emergency medical assistance and transportation. 

2. Post information about medical assistance providers 

at appropriate locations. 

3. Develop evacuation and escape plans. 

4. Train miners in evacuation and escape. (Underground mines must also conduct drills.) 

5. Develop an emergency plan for notification of mine 

rescue teams (underground only). 

6. Post emergency plan (underground only). 

The minimal mine emergency response planning currently mandated by Federal law consists of addressing those 

regulations that cite details for fire emergency planning 

(discussed above) and the items listed here. 

IS MORE NEEDED THAN WHAT IS REQUIRED BY LAW? 

All rules and regulations only specify what is acceptable at a minimum. Policies attempt to ensure compliance 

under real-world conditions. Strictly adhering tc what is 

legally required in the way of mine emergency planning 

may offer enough protection for small-scale accidents or 

situations in which an evacuation can be accomplished easily. When something more serious occurs, however, minimal planning will provide only for minimal activities 

related to mine evacuation, obtaining medical attention 

for any injured workers, and calling for assistance from a 

mine rescue team. There are no requirements to plan for 

a well-coordinated response that can protect personnel and 

return the mine to routine production in an efficient 

manner. 

There is a wide range of possible emergencies that can 

be encountered at a minesite. Many mining companies 

have not developed formal plans for dealing with these 

potential events. Instead, they have relied upon the skills 

of upper level mine managers and others in analyzing and 

responding to emergencies as they have arisen. In some 

cases, these informal procedures have worked well and 

many events have been managed successfully without the 

use of a formal emergency plan. At the same time, however, managing a mine emergency without a formal plan 

can pose great risks and result in poor handling of the 

event. There may be mine emergencies that exceed the 

technical capabilities of initial responders. In some events, 

the best technical people can become involved in front-line 

rescue or exploratory work when they could be better 

utilized on the surface. A disaster may incapacitate or kill 

key management officials. In other cases, the emergency 

can be of such magnitude that successful management requires sizable outlays for personnel, materials, technical 

advisors, and services of external organizations. One way 

to be prepared is to develop an emergency response plan. 

An emergency response plan is an all-encompassing 

document. It covers many aspects of response, including 

the following: (1) evacuating the mine, (2) setting up site 

security, (3) dealing with the media, (4) providing information to family members, (5) determining where cars 

should be parked to lessen traffic problems, and (6) scheduling shifts for workers, including decisionmakers. There 

are many other aspects of response that should be considered. However, the resulting plan should not be an 

encyclopedia that is too long and complex to understand. 

Instead, the plan should be a living document that is kept 

up to date, is tested and refined during practica, and is 

useful if it is ever needed. Selected details of what goes 

into a plan will be discussed in the section "What's Included in an Emergency Response Plan?" The first step 

in planning, however, is to decide that simple adherence to 

the laws regarding emergency response will not offer as 

much protection to a mine and the people who work there 

as is possible. Next, one must be willing to allocate 

resources to go that extra step toward being prepared for 

a large-scale mine emergency. 
HOW IS AN EMERGENCY RESPONSE PLAN DEVELOPED? 

When asked whether or not they have a mine emergency response plan, operators often point to a page of 

instructions hanging by a phone, or to a notebook or 

manual on a shelf. These documents may, in fact, be the 

written form of a good plan. But, for the plan to be successfully carried out, it must be more than a document 

that someone is to refer to when an event occurs. Having 

a workable plan starts with how it is developed. According 

to Auf der Heide (I), "The process of planning is more 

important than the written document that results." 

A plan should be developed by the individuals who will 

be involved if it should have to be implemented. In his 

book "Disaster Response: Principles of Preparation and 

Coordination," Auf der Heide (I) provides several reasons 

for this. He states that developers will have a better 

understanding of the plan. They will also know their roles 

in it. Additionally, personal networking will take place 

between key responders. The education about emergency 

response combined with personal relationships people 

form while writing a plan will prepare them individually 

for the things they must do if an event occurs. An example of this was given by a safety director who led the 

planning process for his mine. When a large-scale response was needed, he did not think to refer to the document created. He led the activities based on the education 

and thinking he had done while creating their responsc 

plan: 

Sitting down ah, I guess, laying out a format at 

one time. I did lay out a format for some ah, mines 

that I was working for, you know, of what to do in 

case of an emergency; who to call, and what to do 

. . .As a matter of fact, I'd even made one for this 

mine, but at that time everything was happening, I 

didn't even think about it, you know. I had it 

hanging on the wall. Ah, it was there for everybody 

to ah, in case of an emergency, to go to. Had the 

list of all the emergency phone numbers, who to call, 

who to call first, what information to find out before 

you call, and so on. And um, it just, like I said, at 

that time it just, it just went blank that I had that. 

But I designed it any way, and I prepared it. So it 

was still in my mind, you know. What I should do. 

This responder had learned the plan as it was written and 

was prepared to carry out the protocols that he had helped 

develop. At the very least, having individuals with this 

kind of knowledge and experience at a response will save 

time and cut down on details being forgotten. 

During planning, as mentioned above, connections 

should be made with organizations ar~d people who will be 

needed if a large-scale emergency occurs. This includes 

medical assistance and transportation organizations, mine 

rescue teams, local law enforcement personnel, equipment 

suppliers, government regulatory agencies, neighboring 

mines, and others according to local situations. Asking 

these people to meet during a nonemergency period is also 

an important aspect of the planning process: According to 

Auf der Heide (I), "A number of researchers have observed that predisaster contacts among representatives 

of emergency organizations result in smoother operations 

in subsequent disasters. . .Furthermore, in the process . . . participants become familiar with the roles of other 

individuals and organizations involved in the disaster 

response." 

Agreements for sharing resources between neighboring 

mines during an emergency may be made in the planning 

process. As one safety dircctor, reflecting on an experience at his mine, relates: 

You're going to have to have urn, accesses to get 

equipment. . . Such equipment as extra scoop, or 

mantrips ah, due to your battery power being exhausted, and not having time to recharge, due to it 

being traveled in and out. 

. . .call . . . someone [at a local mine] up and say, 

"Hey,. . . in case of emergency, if I need a . . . This 

inight never happen, but um, if I was to need you to 

bring me supplies, or borrow your truck or something . . . Just, you know, for my sake, can I feel 

comfortable calling you and say I can borrow your 

truck, or that you'll go to the store for me." . . . I'd 

have it like that. 

Setting up these relationships prior to an event will save 

time if such resources are ever needed. Of course, the 

bctter these agreements are worked out beforehand, the 

more effective they will be. 

Proper planning will result in experienced personnel 

and a more easily coordinated response. In terms of coordinating the various individuals and agencies who are 

involved in a response, having a smaller mine in a more 

rural area might be a plus. There may be fewer organizations and individuals to coordinate, and it is likely that the 

people who respond will already know each other. This 

will cut down on the possibilities for miscommunications 

and could shorten the time that it takes for responders to 

know who is playing what role. 
WHAT'S INCLUDED IN AN EMERGENCY RESPONSE PLAN? 

Adequate mine emergency response plans need to be 

suitable for use in managing any situation that could arise 

at a mine. These range from easily foreseen predicaments, 

such as fires, explosions, inundations, or roof fall entrapments, to even the least probable event, such as a hazardous chemical spill near an intake. If a mine emergency 

plan is well prepared it can cover the worst foreseeable 

situation. And, if it is designed to utilize all available resources to achieve predefined objectives, then it is likely 

that the basic plan can be adapted to cover a wide range 

of possible emergency situations. The scope of this paper 

does not permit the presentation of detailed descriptions 

of all of the elements of a mine emergency plan. This section, however, provides insight regarding some of the 

major components that comprise a basic mine emergency 

response plan. The ideas presented were taken from the 

interviews discussed above and from related literature 

(51 7). 

Plan Objectives.-A mine emergency plan must contain 

clearly defined objectives for each portion. If objectives 

are considered carefully and defined as an integral part of 

planning, then all individuals engaged in developing the 

plan, training in its use, or implementing it in an emergency will be better prepared to respond. Quite often, 

major events are handled initially by individuals who have 

little or no experience in dealing with a mine emergency. 

Determining the objectives and stating them within the 

plan helps personnel with less knowledge and experience 

deal with the emergency. 

Initial Response to the En1ergency.-As soon as possible 

after the onset of an emergency, certain tasks should be 

done. These items should be listed explicitly in the plan. 

Some things that the mine operator needs to consider 

having on this list follow: 

1. Determine if miners are trapped or missing and if 

they have been communicated with. 

2. Ascertain the exact nature of the emergency and its 

location in or about the mine. 

3. Notify mine rescue teams if necessary. 

4. Notify emergency medical services, hospitals, rescue 

squads, fire department, or other outside services if they 

are needed. 

5. Notify Federal and State regulatory agencies. 

6. Initiate fire-fighting or rescue-and-recovery 

operations. 

7. Determine if all mine fans are still operating. 

Conlmand Center and Otlzer Facilities .-Workplaces 

should be available for use by a number of individuals on 

the surface. These include company personnel, officials 

from State and Federal agencies, miners' representatives, 

and others who will be involved in directing a response 

to the emergency. An area needs to be set aside to serve 

as the command center. Space may also be required for 

meetings and briefings, servicing mine rescue equipment, 

first aid administration, a temporary morgue, and other 

functions. 

Definition of Roles and Respotisibilities .-Each person 

who will be participating in handling an emergency, from 

rank-and-file workers to the mine manager or superintendent, needs to know exactly what his or her responsibilities are during this event. Roles should be so well 

defined that any qualified person can be assigned any position and know what the associated duties are. This may 

he accomplished by developing task cards-pocket-size 

cards that clearly define the duties and responsibilities for 

each position. The cards can be distributed to responders, 

who will carry and refer to them at any particular moment 

during a situation. This will ensure that they have properly attended to all assigned duties. 

Rotation of Conznznttding Persotztze1.-Depending on the 

nature of a mine emergency, company officials may be 

required to be at the scene for several days. In one reported case, a mine superintendent worked 37 h straight 

at a mine fire before leaving the command center (8). Research has shown that lack of adequate rest severely 

inhibits a person's ability to make quality decisions. Poor 

decisions in a mine emergency can jeopardize the lives of 

responders at the scene and/or severely hamper efforts 

to deal with the event. Company officials need to make 

arrangements for rotation of command personnel at the 

emergency site to ensure that those individuals who will be 

required to make critical decisions are well rested. 

Activities Lo@ng.-At least until additional personnel 

arrive at a scene, the company should assign someone on 

the surface to maintain a log of all rescue and recovery 

activities. This log should be detailed and include all 

major activities that have occurred since the onset of the 

emergency. 

Fan Operation.-When required, the mine operator 

should have all surface fans examined to determine their 

condition. The operator should assign a person to each 

operating surface fan to ensure its continued operation. 

Propetty Entrance Restn'ction-Secliritj~.-The operator 

should, as part of planning, establish a policy restricting 

entrance to authorized personnel in the event of a mine 

emergency. Only those required to handle the situation 

should be permitted on mine property. Guards should be 

assigned at each mine entrance. Often, local law enforcement agencies will provide officers to fill this job. 
( Mine Maps.-Up-to-date mine maps will usually be 

needed for use by mine rescue teams, company officials, 

and others. A sufficient number of current mine maps or 

Iprints should be secured and made ready for distribution. 

Supplies and Equ@ment.-Depending on the nature of 

a particular mine emergency, supplies such as crib blocks, 

timbers, brattice curtain, concrctc blocks, water line, rock 

dust, and other articles may be needed in quantity very 

quicGy. In the event of a mine fire or explosion, materials 

such as ready-mix concrete, steel plates, wood, and stone 

or gravel may be required for sealing the mine. Liquid 

carbon dioxide may be needed in an attempt to smother a 

fire. Provision should be made with suppliers and other 

mining opzrations to provide these items on short notice 

when needed. Machinery such as scoop tractors, auxiliary 

fans, foam generators, power centers, pumps, front-end 

loaders, bulldozers, drill rigs, and other equipment and 

tools may have to be brought on site quickly. Arrangements should be made in advance with company purchasing agents and suppliers of this equipment to ensure 

quick delivery to the minesite of these and all other 

neccssary items. 

Interacting With the Media.-Any major mine emergency 

will draw attention very quickly. In a matter of hours, 

media representatives will be at the scene to obtain current information about the situation. It is important to 

determine beforehand how the media is to be dealt with 

and who will interact with them to ensure dissemination of 

accurate information. One group of small mine owners 

are looking to their operators association for support in 

this area (2). During a response, mine management keeps 

the operators association staff updated and tells all media 

representatives to go to that staff for information. The 

association staff then prepares press releases and handles 

all inquiries from the media. Whether the media is to be 

handled by mine personnel or by some designated representative should be decided and communicated before an 

event occurs. 

Needs of Personnel on the Scene.-If a number of responders are required on the scene of a mine emergency 

for a long period of time, arrangements should be made to 

provide these individuals with sleeping quarters, food, and 

other essentials. Agreements can be made in advance with 

area motels to provide lodging. Local restaurants and 

grocery stores can be commissioned to provide food as 

needed. 

Needs of Relatives and Friends.-When an emergency 

occurs, relatives and friends of miners working at the operation may arrive on site seeking informatioil about loved 

ones. Mine officials should prepare to deal with relatives 

and friends by providing them with the latcst factual information available. If possible, there should be arrangements to have counselors and clergy available to interact 

with family members during the emergency. A suitable 

facility might be necessary for family members who wish 

to remain on site during the response. 

Special Needs of Response Personnel and Others Involved.-In a mine emergency, workers and rescue personnel are faced with riumerous situations thal may result 

in severe emotional strcss and trauma (3). This conditio~:, 

called critical incident stress, can frcqucntly rzs111t in shot tor long-term emotional difficulties that affLw one's ab~liiy 

to function. There should be arrangements to have counseiors, trained in critical incide~lt str~ss de!!ricfin(~ b (GIST?), y 

available for workers who witnessed or wcr2 involvcd in 

the emergency. These counsclors could also assist individuals who participated in the response. ClSD is a technique for helping normal people cope with stress associated with abnormal events. 

Contmunicutiorzs.<ommunications is one of thc most / 

crucial elements in managing a mine emcrgcncy. Quality 

communication links are nceded between a command 

center and the emergency location. Thcre must also be 

good links between a command center and facilities away 

from the minesite. An operator needs to assign a person 

to ensure that mine telephones or other communication 1 

systems are in place and working. It is not uncommon for 

a mine to have only one telephone line servicing the 

operation. Depending on the nature of an ~mergency 

however, additional telephone lines may be necdcd. The 

capability to add additional lines during an emergency 

should be prearranged with the telephone company. 

The purpose of this portion of the paper was to 

stimulate thinking by illustrating some of the many items 

that must be dealt with during a mine cmcrgency. The 

elements of a mine emergency response plan that have 

been mentioned are but a few of the many components 

that could comprise a quality effort. An important point 

to remember is that the time to plan for a mine ernergency is before an event occurs raihcr than in the middle 

of a situation. 

IS HAVING A WRITTEN 

When the planning process has resulted in a final 

document-a mine emcrgency response plan-then the next 

phase of preparation begins. ~veryone who works at the 

minesite should be trained in the plan's contents. They 

DOCUMENT ENOUGH? 

should also be introduced to the various roles included.( 

Individuals must know what they are likely to be asked to 

do if the plan were put into use. They should also be 

aware of company policy on response issues such as site 
security and interactions with the media. If possible, 

miners and responders should be given an opportunity to 

practice carrying out the plan or, at least, some portion of 

it. Less direction and coordination will be needed to start 

up a response if more people are trained to follow the 

plan. During training, the plan will also be tested and can 

be revised and refined to match minesite demands. 

Preparation for a large-scale emergency should be an 

ongoing process. Telephone lists and mine maps should 

be updated routinely. Newly hired workers should be 

introduced to the mine emergency response plan before 

they start to work. On occasion, everyone should be reminded of the plan and of their role(s) in it. When there 

are changes to a mine, mine management, or local resources, the plan should reflect those changes. The result 

would be a work force that is more confident of management's commitment to their safety, inspectors who see that 

the extra step has been taken at this site, and responders 

and decisionmakers who are better prepared. If the worst 

happens, management will know that every effort was 

made to make an emergency response as efficient and 

effective as possible. 

CONCLUSIONS AND RECOMMENDATIONS 

As discussed previously, large-scale mine emergencies 

are infrequent events, and so it is difficult to put daily 

concerns aside to focus attention on them. They do, however, occur with renslts that can be devastating economically for the mining operation, and economically as well 

as emotionally for the individuals involved. These consequences can be mitigated with even limited emergency 

response planning. Planning is particularly important for 

small mining operations that will need to call on outside 

help to mount a sizable response. 

There are a number of resources available at little or 

no cost to the small mine operator who wants to begin 

planning for a mine emergency. One place to begin is 

with the sample emergency response plan provided in the 

appendix to this paper. The plan is a simplified version of 

one prepared for and being used at an underground coal 

mine. It could be used as a model for the development of 

a site-specific plan. 

Another source of information is the National Mine 

Health and Safety Academy at Beckley, WV. The academy is devoted to mine safety training and has both written material and classes on emergency response topics. 

There is also a fire school on the grounds where miners 

are trained to fight underground fires. Information about 

classes being taught at the academy can be obtained by 

calling the Instructional Services Office at 304-256-3211. 

Written materials are promoted in a catalogue, which is 

available through the Business Office at 304-256-3257. 

Assistance is also offered through the Center for Emergency Preparedness, West Virginia University Mining Extension, in Morgantown, WV, at 304-293-4211. Like the 

academy, the center has written materials available and 

conducts training related to emergency response. Staff 

members also act as consultants conducting fire audits for 

mining companies. 

Local resources should not be forgotten. Local experts 

may be needed during an emergency, and those individuals 

will be happy to help. The best time to meet with these 

people and coordinate planning efforts is during the planning process. Local law enforcement may be called on to 

provide site security and should be familiar with the site 

and the individuals who will be in charge. Ambulance 

crews and other medical personnel should be contacted so 

that their part in the response will go smoothly. The 

American Red Cross or a local civic group may be willing 

to coordinate activities, such as feeding responders and 

making family members as comfortable as possible. A 

church, school, or community center may have rooms that 

could be used as offices or a press briefing area. It will be 

much easier for community members to assist in a response if their tasks are defined before an event occurs. 

The probable needs should be considered and then resources sought to fulfill them. The telephone calls and/or 

meetings to set up this coordination of resources may save 

a considerable amount of time and energy and decrease 

confusion inherent in the situation if a response ever needs 

to be put in place. 

REFERENCES 

1. Auf der Heide, E. Disaster Response: Principles of Preparation Proceedings of the 1994 International Emergency Management and 

and Coordination. C. V. Mosby Co., Baltimore, MD, 1989, pp. 3448. Engineering Conference (Miami, FL, Apr. 18-21, 1994). Simulation 

2. Gooch, D., and K Myers. Crisis Communications Manual. Coal Councils, Inc., in press. 

Operators & Assoc., Inc., Pikeville, KY, undated, 13 pp. 4. Lehman, D. A., and E. R. Pauley. Accident Investigation Report: 

3. Kowalski, K M. A Missing Component in Your Emergency Nonfatal Roof Fall Accident. Federal Mine I.D. No. 06289, June 6,1989. 

Management Plans: The Critical Incident Stress Factor. Paper in Commonwealth of Pennsylvania, undated. 
5. Safety in Mines Testing and Research Station. Training of the 

Officials for the Underground Coal Mining Industry. V. 2,1989, pp. 4-1 

to 4-8. 

6. U.S. Code of Federal Regulations. Title 3GMineral Resources; 

Chapter I-Mine Safety and Health Administration, Department of 

Labor; Subchapter 0--Coal Mine Safety and Health; Part 75- 

Mandatory Safety Standards-Underground Coal Mines; Part 77- 

Mandatory Safety StandardsSurface Coal Mines and Surface Work 

Areas of Underground Coal Mines, July 1, 1993. 

7. U.S. Mine Safety and Health Administration (Dep. Labor). 

Advanced Coal Mine Emergency OperationsStudent Text Material and 

Instructor's Guide. Undated, 80 pp. 

8. Vaught, C., and D. G. Wooten. Responding to an Underground 

Mine Fire: A Case Study. Paper in Proceedings of the 'henty-Third 

Annual Institute on Mining Health, Safety, and Research (Blacksburg, 

VA, Aug. 24-26, 1992). Dep. Min. and Miner. Eng., VA Polytech. Inst. 

and State Univ., Blacksburg, VA, 1992, pp. 197-208. 
APPENDIX.-SAMPLE EMERGENCY RESPONSE PLAN 

Weplan Mining Company 

Mine Emergency Preparedness Plan 

Introduction 

Although substantial improvements in the technical aspects of mining and improved examinations have 

been made, mine emergencies continue to occur. Because of this fact, we must continue to search for 

the safest methods to obtain the best results using training and planning skills, and being prepared for 

positive response in the event of an emergency. 

A combination of actions in an emergency many include all of the following: 

1. Hazard Control: The immediate action to eliminate the hazard or limit its scope. 

2. Evacuation: The orderly exit of miners from affected areas, using designated escape routes, and 

emergency breathing devices. 

3. Survival: Alternate means of survival, such as barricading, when escape routes are blocked. 

4. Rescue: The efforts by those outside the mine to locate, communicate with and remove those 

miners trapped underground. 

5. Recovery: The effort to recover missing persons and return the mine to operational or investigative 

status once conditions permit. 

Confusion and disorder after discovery of an emergency is normal. The first few minutes after 

discovery are crucial. Since almost all emergencies are unique, a program detailing every situation is 

not possible. However, there are certain elements common to all and the preparation of a written plan 

can minimize the confusion and disorder associated with the emergency. This program is intended to 

offer some basic guidelines for responding when an emergency occurs. 

Some elements included are: 

1. Communications and notifications immediately after discovery of an emergency and at certain 

intervals thereafter. 

2. Responsibilities of certain personnel during the emergency. 

3. Selection of a person to be in overall control. 

4. Development of an advisory and control group. 

5. Evacuation and survival procedures. 
INTRODUCTION 

Page 2 

6. Rescue and recovery procedures. 

7. Surface organization, facilities, and outside sources of assistance for support purposes. 

8. Control of outside elements with an interest in the emergency, but not involved with the operation 

such as news media, relatives and the general public. 

It is intended that all persons who have a part in the emergency will review the entire plan and be 

aware of the contents. If anything is noted that should be changed, it should be brought to the 

attention of "the Safety Department" for revision as necessary. 

Waiting until an emergency to review this plan may be too late to organize an effective emergency 

operation. Study it frequently. 

INSTRUCTIONS 

The actions taken in this manual are color coded. 

When implementing any step of these instructions, identify the color highlighted and turn to the corresponding color tab for detailed information. 

[In the original plan, the underlined words in the following summary were highlighted with colors. 

The notebook which held the plan included corresponding color tabs. These tabs separated sections 

consisting of detailed informution on each item and blank fonns that would be needed to complete the 

tasks. Headings are used here instead of the colors.] 
RESPONSE PLAN SUMMARY 

Page 1 

UNDERGROUND MINE EMERGENCY PLAN 

Upon notification or indication of a mine emergency: 

IMMEDIATELY ... 

1. Initiate Event Log 

2. Notify personnel adversely affected and document their intentions 

3. Notify on-site person in charge 

4. Activate on-shift mine emergency or fire fighting procedures 

PRIOR TO 15 MINUTES 

1. Initiate mine monitoring procedures 

2. Notify personnel outby affected area for evacuation or assistance 

3. Notify person in charge of mine 

4. Notify person in charge of safety 

5. Notify critical company manpower 

PRIOR TO 1 HOUR 

1. Evaluate underground conditions 

A. Determine emergency location and extent 

B. Effect of emergency on evacuation, escape and barricading 

C. Determine fire fighting, mine rescue or other emergency needs 

2. Evaluate underground utilities 

A. Communications 

B. Ventilation 

C. Power 

D. Water 

3. Initiate check-inlcheck-out procedures 

4. Provide critical supplies 

5. Notify Mine Rescue Team 

6. Notify Fire Brigade 
RESPONSE PLAN SUMMARY 

Page 2 

7. Notify EMT's on shift and other medical assistance as needed 

8. Notify essential manpower 

9. Notify MSHA 

10. Notify State Division of Mines 

1 1. Notify Local Law Enforcement 

PRIOR TO 4 HOURS 

1. Activate gas sampling and fan evaluation procedures 

2. Provide essential supplies and services 

A. Shop 

B. Engineering 

C. Other Corporate operations 

D. Other mines 

E. Vendors 

3. Activate control group organization 

4. Notify additional fire brigade members or mine rescue teams 

5. Provide for technical assistance from other corporate operations and other local mines 

AFTER 4 HOURS 

1. Activate advisory group organization 

2. Provide additional outside communications 

3. Provide maximum number of mine emergency teams needed 

4. Activate facility needs procedures 

A. Control Group area 

B. Advisory Group area 

C. Mine rescue briefing area 

D. Mine rescue benching area 

E. Mine rescue housing 

F. Family relations area 

G. Press and public relations area 

5. Provide necessary supplies and services 

A. Food services arrangements 
RESPONSE PLAN SUMMARY 

Page 3 

B. Press and family briefing procedures 

6. Initiate mine rescue logs 
INITIATE 

Page 1 

Mine Emergency 

Weplan Mining Company 

TIME 

COMPLETED 

WHEN 

Immediately 

Prior to 15 minutes 

Prior to 1 hour 

After 4 hours 

WHERE 

Logs and Records 

Form - See 

Page 2 

Fan 

Underground 

Logs and Records 

See Page 3 

Operations Center 

Mine Rescue 

Briefing Room Area 

Logs and Records 

See Page 4 

HOW 

As Events Occur 

Mine Monitors 

Utilize Log for 

Response Personnel 

Per Available Mine 

Rescue Teams 

INITIATE 

Event Log 

Mine Monitoring 

Check-In and 

Check-Out Log 

Mine Rescue Team 

Logs 

WHO 

Person who learns 

of problem until 

assigned person 

takes over 

Assigned person 

Assign person at 

Operations Center 

Advisory Group 
INITIATE 

Logs and Records 

Page 2 

Weplan Mining Company 

Emergency Command Center Activity Log 

Person Keeping Log 

TIME Instructions to (Person) Information recieved or instructions given 
INITIATE 

Logs and Records 

Page 3 

Weplan Mining Company 

Emergency Check-In / Check-Out 

NAME Social 

Security # 

Date and 

Time In 

Date and 

Time Out 

COMPANY 
IIII 

I I IIII 

2 z 6 

122 a ob 

Z 5' 

a u, 

Z Y 

a TJI 

Z T 

a cl 

E" 

2 5 2 

Z 5 

b ob 

Z ~0 

b 6 

Z 

< 4 

5 2 

Z 2 

b - 

E 

(3 

G 

I 
NOTIFICATION 

Page 1 

Mine Emergency 

Weplan Mining Company 

" 

TIME 

COMPLETED 

HOW 

Mine phone, 

Electrical Power, 

Belt Shutdown 

Mine phone, 

Electrical Power, 

Belt Shutdown 

Mine phone, 

Physical Inspection 

"Phone #" 

"Phone #" 

"Phone #" 

"Phone #" 

WHERE 

"Sections" 

Operations Center, 

or in the Mine 

Throughout the 

Mine 

Home 

Work 

Home 

Work 

WHO 

Working Sections 

and Outby Crews 

Mine Superintendent 

or Maintenance 

Superintendent 

Working Sections 

and Outby Crews 

"Names" 

"Names" 

WHEN 

Immediately 

Immediately 

Prior to 15 minutes 

Prior to 15 minutes 

Prior to 15 minutes 

NOTIFY 

Persons Affected 

On site person in 

charge or person 

outside 

Persons outby 

affected area 

Person in charge of 

Mine (Call until one 

is reached, then go 

to Safety list) 

Person in charge of 

Safety (Call until 

one is reached, then 

go to Critical 

Manpower list) 
NOTIFICATION 

Page 2 

" L 

WHEN 

Prior to 15 minutes 

Prior to 1 hour 

Prior to 1 hour 

Prior to 1 hour 

Prior to 1 hour 

Prior to 1 hour 

Prior to 1 hour 

NOTIFY 

Critical Company 

Manpower (Do not 

repeat if notified 

above) 

Mine Rescue Team 

Members 

Fire Brigade Team 

Members 

Emergency Medical 

Technicians or other 

medical assistance 

as needed 

Essential Manpower 

as instructed or as 

needed 

Company personnel 

MSHA 

Note: should be 

called in order by a 

Safety or Mine 

official until one is 

contacted. 

TIME 

COMPLETED 

WHO 

"Names" 

"Names" 

"Names" 

"Names" 

Local Ambulance 

"Names" 

"Names" 

"Local" Office 

Field Office 

Subdistrict Office 

District Office 

Response Coord. - 

Ron Keaton 

WHERE 

Home 

Work 

Home 

Work 

Home 

Work 

Mine Site 

Hospital 

Home 

Home 

Office 

"Location" 

"Location" 

"Location" 

"Location" 

Morgantown, WV 

HOW 

"Phone #" 

"Phone #" 

"Phone #" 

"Phone #" 

"Phone #" 

"Phone #" 

Mine Phone 

"Phone #" 

"Phone #" 

"Phone #" 

"Phone #" 

"Phone #" 

"Phone #" 

"Phone #" 

"Phone #" 

304-296-2079 
NOTIFICATION 

Page 3 

TIME 

COMPLETED 

WHEN 

Prior to 1 hour 

Prior to 1 hour 

Prior to 4 hours 

NOTIFY 

State Mine Officials 

Note: Should be 

called in order by a 

Safety or Mine 

official until one is 

contacted 

Local Law 

Enforcement as 

needed 

Additional Mine 

Rescue and Fire 

Brigade Teams 

HOW 

"Phone #" 

"Phone #" 

"Phone #" 

"Phone #" 

"Phone #s" 

WHO 

"Main Office" 

Emergency Number 

"Names" 

Sheriff's Office 

"Team Names" 

WHERE 

"Location" 

"Location" 

"Location" 

"Location" 

"Location" 
ACTIVATE 

Page 1 

Mine Emergency Plan 

Weplan Mining Company 

TIME 

COMPLETED 

HOW 

Fire Fighting and 

Evacuation 

Procedures 

Mine Monitor and 

Detectors 

Sample Bags 

Command System 

Structure 

"Phone #" 

See Procedures 

See Procedures 

See Procedures 

See Procedures 

WHEN 

Immediately 

Prior to 4 hours 

Prior to 4 hours 

After 4 hours 

After 4 hours 

After 4 hours 

After 4 hours 

After 4 hours 

ACTIVATE 

Mine Emergency 

Procedure 

Gas Sampling and 

Fan Evaluation 

Procedures 

Control Group 

Organization 

Advisory Group 

Organization 

Command Center 

Advisory Group 

Area 

Mine Rescue 

Brigade Area 

Mine Rescue 

Benching Area 

WHO 

Underground 

Personnel 

"Name" 

"Names" 

"Names" 

"Name" 

"Name" 

"Name" 

"Name" 

WHERE 

At or Inby Affected 

Area 

Fans and Sampling 

Points 

Command Center 

Advisory Group 

Location 

Operations Center 

"Location" 

"Location" 

"Local Hotels" 

Weplan Mining Company 

Facility Needs Procedures 

ACTIVATE 

Page 3 

1. Command Center 

2. Staging Area for Teams 

Building Name 

Location 

Phone Number 

Building Name 

Location 

Phone Number 

i 

3. Work Area for Apparatus Maintenance 

Building Name 

Location 

Phone Number 

4. Briefing Area for Teams 

Building Name 

Location 

A Phone Number 

5. Waiting Area for Relatives and Friends 

Building Name 

Location 

Phone Number - - - -- 

6. Press Room and Information Center 

Building Name 

Location 

_ Phone Number 

7. Food and Sleeping Quarters 

Building Name 

Location 

Phone Number 

EVALUATE 

Page 1 

WHEN 

Prior to 1 hour 

Mine Emergency 

Evaluate Conditions for Decision Making 

Weplan Mining Company 

EVALUATE 

1. Emergency 

location and extent 

2. Effect of 

emergency on 

evacuating and 

barricading 

3. Firefighting, Mine 

Rescue, or other 

emergency needs 

WHO 

Person in charge of 

mine 

WHERE 

Mine monitor or 

mine site 

HOW 

1. Review event log 

2. Review 

notification log 

3. Review Current 

Monitoring - CO 

levels and their 

locations 

4. Prior monitor 

print-outs 

5. Mine maps at 

display board 

TIME 

COMPLETED 

EVALUATE 

Page 3 

WHEN 

Prior to 1 hour 

Prior to 1 hour 

EVALUATE 

Electrical Power 

Water System 

WHO 

1. Person assigned 

by person in charge 

of mine 

2. Electricians, 

"Names" 

3. Facility 

Technician 

1. Person assigned 

by person in charge 

of mine 

2. "Name" 

3. Mine monitor 

operator 

WHERE 

Mine 

Mine monitor 

Outside water 

storage (tank and 

ponds) 

Mine monitor 

HOW 

1. Physical check of 

outside and 

underground power 

2. Current mine 

monitoring 

1. Physical 

inspection 

a. levels 

b. rate of drop 

2. Current mine 

monitoring 

3. Check sprinkler 

a1 arms 

TIME 

COMPLETED - 
PROVIDE 

Page 1 

Mine Emergency 

Provide for Materials and Equipment 

Weplan Mining Company 

TIME 

COMPLETED 

HOW 

Deliver to 

emergency site 

1. Deliver to portal 

2. Deliver to 

emergency site 

1. Dispatch 

ambulance to mine 

site 

2. EMT list 

Deliver to operations 

center 

WHERE 

1. Underground 

a. section safety 

trailer 

b. outby locations 

2. Warehouse 

Electrical Shop 

1. Warehouse 

2. Mine monitor 

room 

3. Command center 

Safety Office 

WHO 

Assigned persons 

1. Persons assigned 

2. Fire brigade 

members 

1. Facilities 

technician 

2. Person in charge 

3. Safety department 

1. Assigned person 

2. Safety 

Department 

WHEN 

Prior to 1 hour 

Prior to 1 hour 

Prior to 1 hour 

Prior to 1 hour 

PROVIDE 

1. Fire fighting 

2. Foam generator 

and foam 

3. First aid andlor 

medical assistance if 

needed 

4. Gas detection 

supplies 
PROVIDE 

Page 2 

+ 

WHEN 

Prior to 1 hour 

Prior to 1 hour 

Prior to 1 hour 

Prior to 4 hours 

Prior to 4 hours 

PROVIDE 

5. Respiratory 

protection SCSR 

6. Mine rescue 

breating apparatus 

7. Ventilations 

supplies and/or 

urethane foam 

Essential supplies and 

services 

Chromatograph 

analysis - 

WHO 

Assigned person 

Qualified mine rescue 

team member if 

available 

Person assigned 

1. Warehouse/ 

purchasing - "Names" 

2. Engineering - "Names" 

3. Other Corporate 

Operations 

4. Other Mines 

5. Vendors 

"Name" 

WHERE 

1. Operations 

centerlmantrips 

2. Warehouse 

Mine rescue station 

Warehouse 

Warehouse 

Office 

"Mine Names - Contact Person" 

"Mine Names - Contact Person" 

"Vendor List" 

"Location" 

HOW 

Deliver to operations 

center 

Quick bench and 

respond with or 

without full team 

Deliver to emergency 

location 

"Phone #" 

"Phone #" 

TIME 

COMPLETED I 
PROVIDE 

Page 3 

WHEN 

Prior to 4 hours 

After 4 hours 

After 4 hours 

After 4 hours 

PROVIDE 

Technical assistance 

from corporate 

office 

Additional outside 

communication 

Maximum number 

of mine rescue 

teams 

Necessary supplies 

and services 

1. Food service 

2. Press and family 

briefing procedure 

HOW 

"Phone #" 

"Phone #" 

See Notification 

Procedure 

"Phone #" 

TIME 

COMPLETED 

WHO 

"Names" 

"Names" 

"Names" 

"Names" 

WHERE 

"Location" 

"Location" 

See Notification 

Procedure 

Family facility 

Press facility 
EXPERIMENTAL TRAINING TO REDUCE VARIABILITY 

IN THE INTERPRETATION AND APPLICATION 

OF MACHINE GUARDING REQUIREMENTS 

By Lynn L. ~ethi' and William J. wiehagen2 

ABSTRACT 

The use of machine guards for industrial equipment is 

commonly accepted as a primary means of injury prevention. Often the interpretations of rules pertaining to 

machine guarding lead to a variety of guarding applications 

at the worksite. The consequences of this variability between regulatory intent and practice are evidenced by the 

frequency of guarding citations by inspectors, litigation 

seeking to ameliorate judgment of the inspectors, injuries 

that may be sustained because of workers' misunderstanding of safe guarding practices, misinterpretations of 

guarding requirements, or failure to comply with guarding 

mandates. 

Training is a common method used for reducing this 

variability. This paper describes a U.S. Bureau of Minesdeveloped training intervention that might begin to define 

and identify this variability within the inspectorate, work 

force, or management. The fidelity of the training is enhanced through the use of three-dimensional slides and the 

structure of the classroom exercise. The classroom simulation moves beyond traditional safety training by offering 

an opportunity to apply general guarding rules and regulations to a specific situation. It is suggested that this type 

of training may be useful in defining and seeking solutions 

to the apparent variability in both the interpretation and 

application of guarding requirements. 

INTRODUCTION 

The reason behind a machine guard seems simple 

enough-to prevent employees from coming in contact with 

moving parts. The method of providing that protection 

appears equally simple-install a barrier. Machine guarding is not a new concept. The first patent issued for a machine guard was registered in 1868 Since then, the 

guarding of moving parts has become much more sophisticated. A major influence on present machine guarding 

practices was the Occupational Safety and Health Act of 

1970 (OSHAct) (2). Within a few years of the OSHAct, 

 rainin in^ research specialist. 

2~ndustrial engineer. 

Pittsburgh Research Center, U.S. Bureau of Mines, Pittsburgh, PA. 

3~talic numbers in parentheses refer to items in the list of references 

at the end of this paper. 

the National Safety Council asserted: "One of the major 

goals of the [Act] is the guarding of all machinery and 

equipment to eliminate personnel hazards created by point 

of operations, in-going nip points, rotating parts, flying 

chips and sparks. These hazards have been responsible for 

countless numbers of injuries, and fatalities of personnel. 

If the now required guarding had been required back then 

[prior to the OSHAct], many if not most of these accidents 

might have never occurred and even . . . [the Act itselfl 

would probably not be the law of the land" (3). These remarks imply a widely accepted recognition of the irnportance and application of machine guarding requirements. 

What can be done today to better apply a proven technique for loss prevention? While the solution may be 

elusive, the U.S. Bureau of Mines (USBM) conducted this 

research to learn more about the sources of variability 
between guarding theories, regulations, and everyday experiments," in defining variability, may lead to innovapractice. This approach would involve the collection of tions in guarding practices, work procedures, and training 

data. These data could define the variability within the protocols. Benefits could include a further reduction in 

inspectorate, management, and work force concerning the the number of injuries related to improper guarding pracpractical understanding and application of guarding re- tices, reduced levels of violations, and lesser reliance on 

quirements. Defining variability, through structured the judicial system to resolve a variety of interpretations of 

training experiments, may lead to a shift in the way one machine guarding regulations. 

thinks about traditional safety training. These "training 

EVIDENCE OF VARIABILITY 

Although the sensible notion of "good guarding practices" is fairly common within general industry, other 

factors suggest that variability exists in the regulatory 

interpretation and use of machine guards at the workplace. 

How can this variability be described? Does it fall within 

the literature relating to perception and recognition, motivation, judgment and decisionmaking, ergonomic design, 

or the adherence of workers to safe job procedures? 

Understanding and describing this variability may offer 

insight to solutions that embody all these concepts. This 

knowledge could assist in the design of training, the design 

of guarding components, or regulatory policy. The evidence of variability is manifested by the information obtained from injury reports, legal controversies, and 

violations-citations associated with machine guarding 

practices. 

INJURY DATA 

One important consequence of variability between regulatory intent and practice is the frequency of serious 

injuries. A variety of questions might be posed based on 

any one of these incidents. To illustrate, in 1993, a beltman was fatally injured while cleaning an area around an 

underground belt drive. The U.S. Mine Safety and Health 

Administration (MSHA) investigative report (4) notes: 

A beltman was fatally injured when he partially removed a guard from the side of a stationary roller and entered the take-up area with 

the belt in motion. Guarding for the belt and 

take-up assembly was constructed with four foot 

wide by eight foot long sheets of expanded metal 

welded in angle iron frames and bolted onto a 

main frame. The guarding was then secured to 

the entire length of the drive and take-up assembly on both sides. Evidence indicated that 

the victim partially removed the stationary guard 

in an attempt to gain access to the take-up area. 

While shoveling loose coal, he became caught in 

the roller and was fatally injured. 

Assuming the guard was "adequate" prior to its removal, 

what are some questions that might be asked to explore 

the contributing factors? 

1. Was there an appropriate machine guarding policy 

at the mine? 

2. How was the employee trained? Were there any 

follow-up observations of his performance? 

3. Was there a lockout-tagout procedure? 

4. Was the hazard recognizable? 

5. Was this a safe practice? 

Responses to these questions highlight variability. 

These include perceptions of what constitutes (1) an appropriate policy, (2) quality training, (3) an adequate procedure, (4) a recognizable hazard, and (5) a safe practice. 

These perceptions would be expected to vary within and 

across the inspectorate, work force, and management. 

Outside of mining, the importance of researching these 

questions is magnified. For example, within the agricultural sector, Etherton (5) estimates that 20,000 occupational amputations occur annually. Ninety percent of these 

serious injuries are traced to machinery and equipment. 

The magnitude and severity of these injuries ampllfy the 

need to pose serious questions. The careful consideration 

of these questions might lead to a better understanding of 

the variability between regulatory intent and everyday 

practice. 

LITIGATION 

Another indication of variability is perhaps evident in 

the number of legal controversies surrounding safe or unsafe guarding practices. In more than a few cases, the 

final determination of "compliance" with guarding regulations is a product of the judicial system. In one case, 

involving a piece of mobile equipment, it was determined 

that failure to properly guard the cooling fan blades and 

air compressor belts and pulleys located on the front of 

the engine was a valid violation. The parts in question 

were located in the center of the engine compartment in 
front of the engine. In order for an individual to contact 

the parts, it would be necessary to reach over the truck 

frame, which is approximately 76.20 cm high, and extend 

one's arm a distance of approximately 76.20 to 91.44 cm. 

The judge ruled that "given the physical accessibility of the 

engine compartment, the fact that mechanics could check 

and work on running equipment, and that contact with the 

cited machine parts could occur, we conclude that a reasonable possibility of contact existed (6). In litigation, 

variability is exhibited by the opposing views of those 

involved in the case. 

VIOLATION AND CITATION DATA 

Violation and citation data may also imply large levels 

of variability within and across the inspectorate, general 

work force, and management. In 1991, for general industry, OSHA reported over 4,000 violations issucd for unsafe 

machine guarding practices, with an initial dollar penalty 

of $6.64 million (7). The direct costs resulting from citations of unsafe machine guarding ranked third, behind 

hazard communication and electrical lockout-tagout 

procedures. 

A review of MSHA data indicated that from 1991 

through 1993 there were 20,517 significant and substantial 

violations issued for unsafe guarding practices in the 

mining industry (8). These numbers may be directly 

linked to the undefined variability that surrounds safe 

guarding practices. 

How one interprets machine guarding regulations, how 

one determines if a guard is adequate (or, in compliance 

with the regulations), how one maintains or modifies a 

guard, or how one adheres to safe guarding practices can 

all contribute to large levels of variability. 

For the regulators, the violation data explicitly imply 

variability in compliance profiles. Implicitly, is the issue 

one of adherence (motivation and skills)? Is it one of how 

workers and managers interpret the regulations? Or, a 

combination of both? Knowledge does not guarantee a 

decision to act, nor does it obligate the appropriate action. 

What can be learned from studies of traditional mine safety training that could offer insight to these questions? 

TRADITIONAL METHODS FOR MINE SAFETY TRAINING 

Safety training is a common method to inform and motivate workers to adhere to safety procedures and requirements. Its widespread acceptance to loss prevention is ingrained within regulations, company policies, and culture 

of the workplace. Training implies increased competence; 

competence suggests some means to measure; and measurement implies a connection between the training intervention and goals of the organization. Improved competence, in turn, cannot be defined without some means of 

evaluation. The concept of training (and performance) 

evaluation is consequential, as it suggests a means for 

improvement. 

USBM-sponsored studies of mine safety training were 

described in a series of research reports by Adkins (9), 

Digman (lo), Short, (11), and Cole (12) spanning the 

period of 1976 to 1986. These evaluative studies of mine 

safety training, coupled with the general safety training 

literature, offer insight into methods to understand the 

limitations of traditional safety training. Combined, these 

studies suggest a shift to instructional procedures that can 

better tie investments in training to the performance of the 

workforce. Performance measures imply a reliable means 

to evaluate, both within the context of the training and 

how those skills are transferred to the worksite. 

Two of the more recent studies (10, 12) observed a 

noticeable level of variability in both the conduct and 

outcomes of classroom health and safety training. This 

variability was observed during annual refresher training 

sessions. Researchers noted several of the reasons for this 

variability: 

1. There was confusion among the trainers and participants concerning the expected outcomes of safety 

training. 

2. There is limited availability of good test designs to 

assess health and safety knowledge and the application of 

that knowledge. 

3. Miners were more attentive when participation was 

encouraged or instructors used stories or examples to 

ground the instruction. 

4. The preponderance of concern was more apt to relate to quantity of instruction (i.e., hours of training) as 

opposed to outcomes (quality). 

5. The use of innovative teaching techniques (games or 

simulations) was fairly common but usually limited to the 

factual recall of safety information. 

6. Trainees appeared most attentive when discussions 

involved the resolution of a safety problem in a work procedure or emergency protocol. 

These studies suggest that traditional mine safety training could benefit by more objective and reliable data. 

These data would better connect safety training interventions to the performance of the work force. It is within 

this con text that the following training exercise was 

developed. 
A NEW APPROACH 

The "Raggs and Curly" machine guarding exercise is a 

three-dimensional (3-D) latent image ~imulation.~ The 

idea of combining 3-D slides with latent image simulation 

was first introduced in 1989 (13-14). The Raggs and Curly 

exercise embeds teaching with evaluation, makes use of 

3-D slides to enhance the fidelity of the simulation, and is 

administered in small group settings. It is similar in 

structure and complements the growing set of interactive, 

latent-image, problem-solving simulations described elsewhere (e.g., 12, 15). 

Raggs and Curly is an eight-question, seven-slide exercise that deals with machine guarding hazards and unsafe 

practices. The Raggs and Curly exercise is set at a surface 

coal mine. The situation is as follows: 

You, Earl E. Raggs, are the chief mechanic at the main mine complex of the AB 

Coal Company. You have been called to the 

Jake's Run surface nine. The mine supplies 

coal directly to rail cars by means of a 48" 

mobile conveyor. The superintendent explains 

that during a recent insurance company inspection, some potentially dangerous situations concerning improper guarding practices 

were noticed. He instructs you to conduct a 

survey and document the guarding problems 

you observe around the mobile conveyor. 

Your recommendations will be part of a 

planned company wide guarding policy. He 

assigns Noah "Curly" Hair, who just recently 

became a mechanic's helper at this operation, 

to accompany you. The superintendent stresses the fact that Curly is not too familiar with 

safe guarding practices and asks that you take 

this opportunity to share your knowledge concerning guarding. You and Curly are to report back to the superintendent with your 

findings. 

Skills developed through this classroom simulation include machine and equipment guarding strategies and procedures; hazard identification; warning and caution sign 

'?he authors are indebted to D. L. Garry, mining industry specialist, 

and R A. Dorton, safety and occupational health specialist, both at the 

USBM's Pittsburgh Research Center, Pittsburgh, PA, for their invaluable 

assistance in designing this exercise. 

usage; safe work habits; safe guarding practices; and decisions involved in the use of factual, regulatory information .in their application to specific machinery and 

equipment. 

The exercise follows Raggs and Curly as they evaluate 

machine guards and discuss safe guarding practices. The 

efficiency of the training is noted through the opportunities 

to experience real-life situations and the application of 

factual knowledge often reserved for on-the-job learning. 

The classroom training and discussion provides a controlled setting for trainees to experience the consequences 

of both good and bad decisionmaking. The exercise itself 

is designed to reinforce good decisions and to correct errors when inappropriate decisions are made. 

The exercise seeks to apply and reinforce important 

characteristics in guard design and construction. These 

characteristics of guard design are summarized in the 

widely distributed "MSHA Guide to Equipment Guarding 

for Metal and Nonmetal Mining" (16). As MSHA notes: 

"Such guards should: 

1. Bc considered a permanent part of the equipment or 

machine. 

2. Afford maximum protection. 

3. Prevent access to the danger zone. 

4. Be convenient-they must not interfere with efficient 

operation. 

5. Be designed for the specific machine, with provisions 

made for oiling, inspecting, adjusting, and repairinq 

machine parts. 

6. Be durable and constructed strongly enongh to resist 

normal wear. 

7. Not present a hazard in itself." 

The guard might also be constructed to contain those parts 

that may fail or be propelled to possibly strike employees. 

As participants work through the exercise, they begin to 

discover the difficulties that can exist in the interpretation 

of regulations, the necessity for safe guarding practices, 

and common misperceptions about guarding requirements. 

It is within this context that this exercise approaches 

training. (See the appendix for problem example.) 

The exercise is now being field tested and will be 

revised as needed. Once completed, the exercise will be 

sent to the Mine Safety and Health Academy located in 

Beckly, WV, for distribution to those mining compznies 

requesting machine guarding training exercises. 
SUMMARY AND CONCLUSIONS 

Variability within the applied interpretations of rules, fidelity of safety training, thus aiding in the transfer of 

regulations, and actual work practices may be a major con- safety skills. The benefits of this and similar exercises 

tributing factor in machine guarding injuries, violations, could be a further reduction in the number of injuries reand litigation. The experimental training simulation dis- lated to improper guarding practices, less reliance on the 

cussed in this paper is an attempt to better define and judicial system to resolve a variety of interpretations of 

understand differences in the interpretation and applica- machine guarding regulations, and a reduced level of 

tion of machine guarding regulations. The use of the 3-D violations. 

slides within a realistic problem setting can improve the 

REFERENCES 

1. Smith, C. 0. Problems in Machine Guarding. Paper in American 

Society of Mechanical Engineers Annual Conference (Boston, MA, Dec. 

13-18, 1987). ASME, New York, 1987. 

2. McElroy, E E. Accident Prevention Manual for Industrial Operations. Natl. Saf. Council, Chicago, IL, 8th ed., 1980, pp. 285-313. 

3. National Safety Council (Chicago, IL). Accidcnt Prevention Manual for Industrial Operations. 7th ed., 1980, 795 pp. 

4. Shortridge, D. C. Accident Investigation Report. U.S. Mine Saf. 

and Health Admin., Sept. 1993. 

5. Etherton, J. R, and M. L. Myers. Machine Safety Research at 

NIOSH and Future Directions. Int. J. Ind. Ergon., v. 6, No. 2, 1989, 

pp. 163-174. 

6. Federal Mine Safety and Health Review Commission. Docket 

PENN 81171, Sept. 1984, pp. 2094-2098. 

7. Wienstock, M. P. Avoiding the Top Ten. Occup. Hazards, Sept. 

1992, pp. 36-39. 

8. U.S. Mine Safety and Health Administration. R-63, Violation 

Counts by Standard and Type of Assessment. Jan. 26, 1994. 

9. Adkins, J., R Akeley, P. Chase, L. Marrus, W. Prince, R Redick, 

C. Rogne, J. Saalberg, and L. Szempruch. Review and Evaluation of 

Current Training Programs Found in Various Mining Environments; 

Volume I, Summary (contract S0144010, Bendix Corp.). BuMines OFR 

llO(1)-76, 1976, 67 pp.; NITS PB 259 410. 

10. Digman, R M., and J. T. Grasso. An Observational Study of 

Classroom Health and Safety Training in Coal Mining (contract 

J0188069, WV Univ.) BuMines OFR 99-83,1982, 65 pp.; NTIS PB 83- 

210518. 

11. Short, J., J. Hams, J. Waldo, and S. Barber. A Study To Determine the Manpower and Training Needs of the Coal Mining Industry 

(contract J0395038, John Short & Assoc., Inc.). BuMines OFR 14-80, 

1979, 145 pp.; NTIS PB 80-164742. 

12. Cole, H. P., L. G. Mallett, J. V. Haley, P. K. Berger, W. E. Lacefield, R D. Wasielewski, G. T. Linebeny, and A. M. Wala. Research 

and Evaluation Methods for Measuring Nonroutine Mine Health and 

Safety Skills (contract H0348040, Univ. KY). Volume I. BuMines OFR 

18(1)-89, 1988, 229 pp.; PB 89-196ffl6; Volume XI: Appendices. 

BuMines OFR 18(2)-89, 1988, 348 pp.; PB 89-196653. 

13. Barrctt, E. A. Innovative Idea for Teaching Hazard Recognition 

Skills to Miners. BuMines Technol. News 409, Oct. 1992, 2 pp. 

14. Barrett, E. A., W. J. Wiehagen, and C. Vaught. Roof and Rib 

Hazard Recognition Training Using 3-D Slides. Paper in Mine Safety 

Education and Training Seminar. BuMines IC 9185, 1988, pp. 23-30. 

15. Cole, H. P., G. T. Linebeny, A. M. Wala, J. V. Haley, P. K. Berger, and R D. Wasielewski. Simulation Exercises for Training Miners 

and Mining Engineers. Min. Eng., v. 45, No. 11, Nov. 1993, pp. 1397- 

1401. 

16. U.S. Mine Safety and Health Administration. MSHA Guide to 

Equipment Guarding for Metal and Nonmetal Mining. Rev. 1992, reprinted 1993, 32 pp. 
APPENDIX 

The appendix consists of a problem workbook and a master answer sheet. These items represent a completed exercise. 
Raggs & Curly Guarding Exercise 

Raggs and Curly Guarding Exercise 

Problem Booklet 

Mining Systems and Human Engineering 

U.S. Bureau of Mines 

Pittsburgh, PA 

July 1994 
109 

Raggs & Curly Guarding Exercise 

Instructions 

Read the problem situation described on the next page. Then answer each of the eight questions. Do them one at a 

time. Some questions will ask you to look at one or more three-dimensional slides. Look at the appropriate slide or 

slides, then continue on with the exercise. Don't jump ahead, but look only at the questions and slides to which you are 

directed. However, you may look back to earlier questions and answers at any time. Follow the directions for each 

question. 

After you have selected a choice to a question, look up its number on the answer sheet. Select your answer(s) to each 

question by slowly and gently rubbing the special pen between the brackets on the answer sheet. A hidden message will 

appear and tell you if you are right. When you have finished, you will learn how to score your performance. 
Raggs & Curly Guarding Exercise 

The Situation 

You, Earl E. Raggs, are the chief mechanic at the main mine complex of the AB Coal Co. You have been called to the 

Jake's Run Surface Mine. The mine supplies coal directly to rail cars by means of a 121.92-cm (48-in) mobile conveyor. 

The superintendent explains that during a recent insurance company inspection, some potentially dangerous situations 

concerning impropdr guarding practices were noticed. He instructs you to conduct a survey and document some of the 

guarding problems you observe around the mobile conveyor and make recommendations for correcting these problems. 

Your recommendations will be part of a planned company-wide guarding policy. He assigns Noah "Curly" Hair, who was 

just recently reassigned as a mechanic's helper at this operation, to accompany you. The superintendent stresses the fact 

that Curly is not too familiar with safe guarding practices and asks that you take this opportunity to share your knowledge 

concerning guarding. You and Curly are to report 'back to the superintendent with your findings. Turn to Question A. 
Raggs & Curly Guarding Exercise 

Question A 

You and Curly take a camera and notebook and begin to document the status of the guards located at the mobile 

conveyor area. Look at slide 1. You are looking for unsafe guarding practices and related problems. What should you 

point out to Curly? (Select as MANY as you think are correct.) 

1. A dirty warning sign. 

2. A missing guard. 

3. Altered guard. 

4. Coal spillage. 

5. A missing guard around the electrical box. 

When you have made your selection(s), do the next question. 
Raggs & Curly Guarding Exercise 

Question B 

Continuing your survey, you and Curly go to the rear of the bin. Look at slide 2. What hazards would you note and point 

out to Curly at this location? (Select as MANY as you think are correct.) 

6. The salamander is located too close to the fuel depot. 

7. There are holes in the guards. 

8. The guard is not extended far enough to enclose all pinch points. 

9. Warning signs are inadequate. 

10. Coal has built up here. 

11. Guard screens are not aligned. 

When you have made your selection(s), do the next question. 
Raggs & Curly Guarding Exercise 

Question C 

The next place you stop is a conveyor dump point. Look at slide 3. Other than repairing the holes in the guards and 

cleaning up obvious spillage, what corrective measures should you recommend to the superintendent for this area? (Select 

as MANY as you think are correct..) 

12. Replace the missing triangular guard on the near side. 

13. Display warning signs. 

14. Investigate the cause of the large coal chunks underneath the equipment. 

When you have made your selection(s), do the next question. 
Rags & Curly Guarding Exercise 

Question D 

You walk around the dump point to look at the other side. This is what you see. Look at slide 4. What corrective 

measures should you and Curly recommend to the superintendent for this area? (Select as MANY as you think are 

correct.) 

15. Display warning signs. 

16. Repair the holes in the guard. 

17. Investigate the cause of the large coal chunks underneath the equipment. 

When you have made your selection(s), do the next question. 
Raggs & Curly Guarding Exercise 

Question E 

You and Curly travel to the mobile conveyor. Look at slide 5. You ask Curly to assess this piece of equipment. What 

positive guarding practices would you expect Curly to note? (Select as MANY as you think are correct.) 

18. Effective use of multiple guarding materials. 

19. Extended grease fittings. 

20. Handrail and toe boards. 

21. Walkway is clear of all slip and trip hazards. 

22. Guarding for machinery parts that are out of reach. 

When you have made your selection(s), do the next question. 
Raggs & Curly Guarding Erercise 

Question F 

Curly mentions to you that he saw another example of guarding on a piece of mobile equipment. Look at slide 6. This 

is a refurbished piece of equipment that arrived from the factory not too long ago. After new tires are put on it, what 

guarding changes, if any, do you think should be made before the equipment is put into use? (Select as MANY as you 

think are correct.) 

23. No changes should be made because this is the way it came from the 

factory. 

24. Extend the height of the guard around the engine compartment. 

25. Paint the engine compartment guards a different color than the equipment. 

26. Extend the guarding down to cover the top of the tire. 

27. Install warning signs and reflective materials on the step. 

When you have made your selection(s), do the next question. 
Raggs di Curly Guarding Erercise 

Question G 

You decide to conclude this initial phase of the survey by asking Curly to survey his work area near where the compressed 

gas is stored. Look at slide 7. You see quite a few potential hazards at this site and decide to have Curly point them 

out to you. What should Curly point out as potential hazards? (Select as MANY as you think are correct.) 

28. The handrail is lying of[ to the side and not attached to the steps. 

29. Combustible materials are stored too close to the compressed gas. 

30. There are no signs indicating compressed gas storage. 

31. Batteries are not stored properly and are placed too near the compressed gas. 

32. Compressed gases are not secured in place. 

33. Compressed gases should be stored in metal sheds. 

34. Housekeeping is poor in this area. 

35. There are no fire extinguishers here. 

When you have made your selection(s), do the next question. 
Raggs & Curly Guarding Exercise 

Question H 

You meet with the superintendent to brief him on your findings. Besides the condition of the guards themselves, what 

are some other safety practices that you might recommend to support safe work procedures around moving parts? (Select 

as MANY as you think are correct.) 

36. Warning signs placed in close proximity to moving parts. 

37. Materials used for guarding should be substantial and heavy. 

38. Written procedures such as SOP'S and JSA's that address specific tasks. 

39. A maintenance and inspection program specifically aimed at guarding. 

4-0. Removal of a guard only after a piece of equipment has been deenergized or locked and tagged out. 

41. Guards should be designed and modified to protect maintenance personnel as well as to make their job easier. 

End of Problem 

Scoring your performance 

1. Count the total number of responses you colored in that were marked "correct." Write this number in the first 

blank on the answer sheet. 

2. Count the total number of incorrect responses you colored in. Subtract this number from 9. Write the 

difference in the second blank on the answer sheet. 

3. The best score is 41. The worst score is 0. 
Rags & Curly Guarding Exercise 

Master Answer Sheet for the Raggs & Curly Guarding Exercise 

Use this answer sheet to mark your selections. Rub the special pen gently and smoothly between the brackets. Don't 

scrub the pen since the message may blur. Be sure to color in the entire message once you have made a selection. 

Otherwise, you may not get the information you need. The last part of the message will tell you what to do next. 

Question A (Select as MANY as you think are correct.) 

1. [Correct. It is a good idea to clean the illegible sign. A comprehensive 1 

[guarding policy should include periodic cleaning of warning and 

[caution signs. 

1 

1 

2. [Correct. A missing guard exposes a hazard. ]i 

3. [In many circumstances it may be necessary to alter existing guards. 1 

[The addition of straps to this.guard strengthen and protect it. 1 

4. [Correct. Coal buildup can be a fire and tripping hazard. The amount 1 

[of coal may indicate that additional malntenancc is necessary here. 1 

5. [The electrical box does not require additional guarding in this situation. 1 

Question B (Select as MANY as you think are correct.) 

6. [The distance between the salamander and the fuel depot is adequate 1 

[and poses no hazard. 1 

7. [Correct. Holes in guards present a hazard because they make it ]I 

[possible for persons to come into contact with moving parts. 4 

8. [Correct. Even if the guard was in good condition, the rollers would not 

[be completely enclosed by the guard. Contact with moving parts is nOh 1 

[prevented here. I] 

9. [Correct. Warning and/or caution signs are a good safcty practice. 1 

LO. [Correct. Coal buildup is a potential fire and tripping hazard. The 

[amount of coal seen here may indicate that equipment 

[modifications may be necessary to prevent continued spillage. 

PI. [Correct. Space left between the frames of guards allows openings 

[where fingers could contact moving parts. 
Raggs & Curly Guarding Exercise 

Question C (Select as MANY as you think are correct.) 

12. [Correct. If you look closely, you can see a triangular guard on the opposite 

[side of the structure. It may be a possible violation if a similar guard is 

[not in place on this side of the structure. 

13. [Correct. It is a good policy to include caution and warning signs as 

[part of the guarding program. 

14. [Correct. This problem needs to be addressed. Either the area should 

[be guarded so that the large pieces can be confined or the source of 

[the problem should be remedied. 

Question D (Select as MANY as you think are correct.) 

15. [Correct. It is a good policy to include caution and warning signs as part of 

[the guarding program. 

16. [Correct. Holes in guards present a hazard because they make it possible for 

[persons to come into contact with moving parts. 

17. [Correct. This problem needs to be addressed. 

Question E (Select as hlANY as you think are correct.) 

18. [Correct. Materials used include screen, belting, and manufacturer equipped 

[guards. 

19. [Correct. Extended grease fittings and cups allow for easy greasing of 

[moving parts and are required. 

20. [Correct. Sometimes we forget that guarding includes handrails to 

[guard against the employee falling from an elevated position. 

21. [Correct. There is no problem here. 

22. [Correct. Even though they are out of reach, moving parts may break 

[and pieces may fly out and hit someone if not guarded. 
Rags & Curly Guarding Exercise 

Question F (Select as MANY as you think are correct.) 

23. [This is not necessarily true. Manufacturer's specifications do not always meet 1 

[company, State, and Federal regulatory agency guarding specifications. 1 

24. [Correct. The existing guard does not adequately stop access to 

[potential hazards. 

1 

1 

25. [Correct. This is recommended to make guards more obvious. ]I 

26. [This is not practical. If guards were there they could restrict movement 1 

[of the wheels and could be a hazard. 1 

27. [Correct. Warning signs are good guarding practice. The use of reflective 9 

[materials along the catwalk of the machine and around the other guards can ] 

[draw attention to potentially hazardous areas, such as the step as a tripping ] 

[hazard. 1 
Raggs & Curly Guarding Exercise 

Question G (Select as MANY as you think are correct.) 

28. [Correct. Handrails provide a means of support and guard against 

[accidental slips and falls. 

29. [Correct. Combustible materials may be an ignition source and a fire 

[could easily develop. 

30. [This is not required. The only sign required is a "NO SMOKING-NO 

[OPEN FLAMES" sign. 

31. [Correct. Batteries may be a source of hydrogen gas, which is highly 

[explosive. Batteries should be kept in a secure location to guard 

[against chemical burns. 

32. [The safety chains shown are adequate and the door is locked. 

33. [That is not a problem here. It is not recommended that compressed 

[gas be stored in metal sheds because of the potential heat buildup. 

34. [Correct. Side of stairs is broken and steps are not anchored solidly to 

[the shed. Accumulations of unmarked drums and debris create a 

[potential fie hazard. 

35. [Correct. Fire extinguishers are required because it is a wooden 

[structure that presents a fire hazard. 
123 

Raggs & Curly Guarding Exercise 

Question H (Select as MANY as you think are correct.) 

36. [Correct. Warning signs alert personnel to potential hazards associated 

[with moving parts. 

a 

I 

37. [This doesn't make a good guard. Additional hazards may be 

[introduced when trying to remove a heavy guard. 

I 

I 

38. [Correct. These procedures clarify safe practices to be followed 

[including guarding issues. 

39. [Correct. Through a preventive maintenance schedule and regular 

[inspection, guarding problems can be documented and corrected. 

40. [Correct. This is always a good practice. In addition, thought 

[should be given to other forces, such as belt tension and pressurized 

[liquids and gases. 

41. [Correct. One example is extended grease fittings and cups, which 

[eliminate the need to work close to moving parts when lubricating. 

3 

I 

End of Problem 

Scoring your performance 

1. Count the total number of responses you colored in that were marked "correct." Write this number in 

the first blank on the answer sheet. 

2. Count the total number of incorrect responses you colored in. Subtract this number from 9. Write the 

difference in the second blank on the answer sheet. 

3. The best score is 41. The worst score is 0. 
ERGONOMIC AND STATISTICAL ASSESSMENT OF SAFETY 

IN DEEP-CUT MINING 

By Lisa J. ~teiner,' Fred C. ~urin,' and Christopher A. amr rick' 

ABSTRACT 

This U.S. Bureau of Mines paper examines the occupational safety concerns associated with deep-cut mining. 

Mining deeper cuts may have some unknown effects on 

how miners position themselves for visibility, the types of 

accidents that can occur, and the new interactions between 

the equipment and the continuous miner operator. This 

preliminary report utilizes data from the U.S. Mine Safety 

and Health Administration accident database, interviews 

with mine workers and mine operators, and conversations 

with State, local, and union representatives. A statistical 

analysis was performed to compare injurics and fatalities 

that occurred in mines with deep-cut approval to mines 

that did not have deep-cut approval. The data were categorized by mine size. A series of interviews with over 

50 mine workers in 5 States was also conducted. A preliminary task analysis study revealed some concern in the 

following areas: the bolting cycle, continuous miner operator positioning and ~{sibility, mine conditions and depth 

of cut, cable handling, and remote-control unit design. 

Methods that will be used to study these tasks are 

discussed. 

INTRODUCTION 

Like many other industries, mining companies implement new technologies as they are developed to increase 

productivity and/or increase safety. These technologies 

require research to explore what unintended effects these 

new methods, machinery, and interfaces will have on mine 

workers. Deep-cut mining refers to mining a cut of coal 

with a continuous miner deeper than the standard 6.1-m 

(20-ft) cut. A standard cut may be mined with the miner 

operator using controls on the deck of a continuous mincr 

or by using a remote-control unit for a continuous mining 

machine. In either case, the miner operator is protected 

under a roof that has been bolted. With the development 

of the remote control and better dust control and ventilation methods, miner operators are able to mine more than 

6.1 m (20 ft) while still remaining under a supported roof 

area (fig. 1). These deeper cuts allow the miner operator 

to mine coal for a longer period of time without moving 

the machinery as often, which in turn is expected to increase productivity and safety. To be permitted to perform deep cuts, a mine must apply for U.S. Mine Safety 

and Health Administration (MSHA) approval. MSHA has 

various conditions and equipment updates that must be 

met bcfore approval is given. Currently, MSHA information states that approximately 22.3% of U.S. underground 

coal mines have deep-cut approvals. 

Bauer, Pappas, and Listak examined fatal coal 

mining accident data from 1988 through 1990. They reported that the rate of fatal roof falls is 2.5 times higher in 

mines with deep-cut approval, considerably larger roof falls 

occur when deep-cut mining is practiced, and geologyinfluenced roof fall fatalities occur about equally in deepcut and nondeep-cut mining. However, they reported that 

'Industrial engineer, Pittsburgh Research Center, U.S. Bureau of 'Italic numbers in parentheses refer to items in the list of references 

Mines, Pittsburgh, PA. at the end of this paper. 
Figure 1 .-Diagram of deep-cut mining method. 

nearly half of the fatalities for deep-cut mining were the 

result of illegal deep cutting. These were classified as 

illegal because the mines either exceeded the approved 

length of cut or did not have MSHA deep-cut approval. 

The rate of Iegal deep-cut fatalities was found to be at a 

rate slightly below that of nondeep-cut fatalities. 

Davis (4) conducted a detailed analysis of roof fall 

fatalities in 1990. It was found that 7 of 20 (approximately 

31%) fatalities occurred in a deep cut. However, only one 

fatality occurred in a deep cut made in compliance with an 

approved plan. The remaining six fatalities occurred while 

illegal deep cuts were being taken. 

Bauer, Steiner, and Hamrick (2) examined 1990 and 

1991 MSHA accident data to compare reported accidents 

in deep-cut and nondeep-cut mines by mine size. The 

data indicated that the reported accident rate and the rate 

of accidents at the face were higher for all mines taking 

deep cuts in all size categories, with the exception of those 

mines with a 150- to 250-employee range. Overall, deepcut mines had a 23% higher reported accident rate at the 

face and a 12% higher rate of accidents. Reported accidents included those which did not result in injury. 

Fatality rates were found to be lower in deep-cut mines, 

with the exception of mines in the 50- to 150-employee 

range. The overall fatality rate was 37% lower for deepcut mines. 

Many studies have explored the overall productivity effects of deep-cut mining. It is believed that taking deep 

cuts will improve productivity through decreased tramming 

time since the machine will stay longer in each working 

face. In a U.S. Bureau of Mines (USBM) study (11) of 25 

mines to assess the reasons for high productivity, 2 mine 

operators said that their productivity per section increased 

by about 25% by using deep cuts. The 4 mines that had 

depths of cut of 9.14 m (30 ft) or more had an average 

section production of 1,067 t (1,050 st) per shift while the 

21 mines with a depth of cut of less than 9.14 m (30 ft) averaged 892 t (878 st) per shift. However, in a mine with 

1,476 t (1,452 st) per shift, it was found that deep-cut 

mining did not improve overall productivity. This might 

mean that as maximum productivity for a given mining system is approached, small technological changes become 

less important and major technological innovation, such as 

longwall mining, is needed for major production increases. 

In other words, mines that have a higher production rate 

may not see as much of a production rate change by irnplementing deep-cut technology as would a mine with a 

lower production rate. In mines with lower productivity 

rates, however, implementation of technological change, 

such as deep-cut mining, may result in a substantial 

improvement. 
Deep-cut mining has not only shown improvements at 

the productivity level, but has also been attributed to 

improving safety by removing the continuous miner operator from inherent dangers at the mine face and decreasing 

the respirable dust levels through the required use of 

scrubber and fan-spray systems. By relocating the continuous miner operator from the face return air position to 

the face intake air position, a 94% reduction in respirable 

dust was evidenced (6). 

Though deep-cut mining has introduced new safety features, it may have introduced new hazards. Vertical visibility may be limited when cutting the deeper cuts, which 

may cause some extraction of the roof and floor (3). 

Another study, performed by the USBM, revealed that 

continuous miner operators were standing in positions that 

were not recommended by their standard operating procedures because of the inability to see from these recommended positions (8). The study concluded that the positions used were not in accordance with the safe operating 

procedures of the mine and that there was a problem with 

determining a safe position with adequate visibility. The 

results of the study are magnified as the variance is 

granted for deeper cuts. As the length of cut increases, 

visibility, staying on the sight line, and watching the roof 

changes become more difficult. The continuous miner operator is removed from the machine through the use of the 

remote control and has to rely heavily on sound and sight 

senses instead of vibration for condition and position cues. 

The further the miner operator is away from the face, the 

potential for misreading cues increases and, therefore, the 

potential for mistakes and accidents increases. 

Though deep-cut mining has been embraced by the 

mining industry as a way to avoid the obvious safety and 

efficiency drawbacks of the machine-mounted compartment, research addressing the new issues is still relatively 

new and scarce. There is a lack of information regarding 

training for miners who will be or are using deep cuts. 

Because of varying mine conditions, not all mines will have 

the same problems and their experiences with deep-cut 

mining will vary. The USBM is taking a systematic look 

at the new technology to help identify problems associated 

with deep-cut mining and to address problems associated 

with standard-cut mining. A first step in identifying problems is to take a look at current available accident data. 

In this paper, the USBM examines the occupational safety 

concerns associated with deep-cut mining. This work was 

done in support of the USBM's goal to enhance the safety 

of the Nation's underground miners. 

STATISTICAL ANALYSIS 

Introduction Method 

The most objective measures of mine safety are the frequency and severity rates of mining accidents. An important element of the research to assess the safety of deepcut mining operations has been an evaluation of mine 

accident data collected by MSHA. In particular, accident 

data of mines that had MSHA approval to take deep cuts 

have been compared with accident data of mines that did 

not have approval to take deep cuts. 

Title 30, part 50 of the U.S. Code of Federal Regulations (14) requires mine operators to notify MSHA immediately of mine accidents and to investigate accidents. 

Mine operators must file reports with MSHA pertaining to 

accidents, occupational injuries, and occupational illnesses 

using form 7000-1. Mine operators must also report employment and production data using form 7000-2. MSHA 

generates yearly data files containing employment and production data, as well as reported accident, injury, and illness information. In recent years, the MSHA data files 

have included estimated accident costs, as determined by 

the USBM's accident cost indicator model (ACIM). 

ACIM considers the type of accident and other factors, 

such as regional medical treatment rates to estimate costs 

to the public, industry, and family (5). 

Mines that had approval to take deep cuts were 

compared with mines that did not have approval using 

MSHA employment, production, and accident data. The 

data were classified and selected as follows: First, mines 

that had obtained approval to take deep cuts for 1990 and 

1991 were identified in the data files. Second, mines that 

used longwall technology in these 2 years were identified 

in the data files. The list of longwall mines was obtained 

from Merritt (9-10). Third, data for mines without longwall operations, with underground coal production greater 

than zero tons, and with at least 16,000 underground employee hours were selected [16,000 equates to approximately 8 underground workers (a minimal face crew), 

working for a year]. Fourth, accident records for underground workers who were fatally injured or had losttime injuries were selected. 

Results 

Table 1 presents the number of mines, underground 

hours worked, and productivity data for mines with and 

without approval to take deep cuts. Data are presented for four mine size categories: average number of 
employees less than 50, average number of employees between 50 and 150, average number of employees between 

150 and 250, and average number of employees greater 

than 250. ' Overall results are presented as well. 

Table 2 displays fatality rates and nonfatal lost-time 

injury rates for mines with and without deep-cut approvals. 

Rates are normalized to 200,000 underground hours 

worked. In addition, the average number of days lost per 

nonfatal lost-time injury and average estimated cost per 

nonfatal lost-time injury are displayed. Results are categorized by mine size in the same manner as in table 1. 

Additional incidence rates were calculated for small 

(average number of employees less than 50) mines with 

and without deep-cut approvals. These rates were broken 

down according to "accident-injury-illness" type, mine 

worker activity, and job title. These results are displayed 

graphically in figures 2 through 4, respectively. 

Limitations 

It would be desirable to compare the characteristics of 

accidents that occur when a deep cut is taken to those that 

occur when a cut of 6.1 m (20 ft) or less is taken. Unfortunately, MSHA data files do not identify whether a mine 

was taking a deep cut at the time of an accident. The only 

information available is the identity of mines with MSHA 

approval to take deep cuts for the years 1990 and 1991. 

For this reason, the analyses compare mines with and 

without deep-cut approvals for 1990 and 1991. It is not 

known what percentage of deep-cut mining is done at 

mines with deep-cut approval. It is also known that some 

deep-cut mining is done at mines without deep-cut approval (1, 4). However, it is assumed that deep-cut mining 

is more prevalent at mines with deep-cut approval. 

Data that are reported to MSHA on the 7000-1 and 

7000-2 forms are not always complete. The most accurately reported accidents are those that resulted in a fatality. 

It is also more likely that accidents that result in lost work 

time will be reported accurately. This analysis only examines accidents that resulted in a fatality or a lost-time 

injury. 

Longwall mining and mine size are two factors that 

greatly influence the data, and each were addressed in this 

analysis. However, other factors that influence safety in 

underground mining that were not addressed include mining conditions, seam height, geology, type of ventilation 

system used, makeup of the work force, and management 

structure. Because of the limitations discussed, definitive 

conclusions about the comparisons that are presented are 

difficult to make and the interpretation of many of the results will be left to the reader. 

Table 1.-Summary of 1990 and 1991 employment and production data for underground coal 

mines without longwall operations, categorized by mine size and deep-cut approval status 

Mine 

Number of mines (sum of Work time, lo3 h Coal productivity, t/h 

size (average number each year's total) underground underground 

of employees) Deep-cut No approval Deep-cut No approval Beep-cut No approval 

Less than or equal to 50 ... 162 1,298 9,657 51,212 3.80 3.21 

50 to 150 .............. 130 156 20,309 22,041 3.46 3.04 

150 to 250 ............. 50 22 17,796 6,995 2.87 3.09 

More than 250.. ........ 32 13 22,699 6,710 2.76 3.09 

Overall ............. 374 1,553 70,461 86,958 3.13 3.15 

Table 2.--Summary of 1990 and 1991 fatal and nonfatal lost-time injury rates, average days lost, 

and average total cost for underground coal mines without longwall operations, categorized 

by mine size and deep-cut approval ststus 

Fatal injuries per Nonfatal lost-time in- Average days lost per Average total cost per 

Mine size 200,000 h underground juries per 200,000 h nonfatal lost-time injury nonfatal lost-time 

(average number ~eep-cut NO approval underground Deep-cut No approval injury, $ 

of employees) approval Deep-cut No approval approval Deep-cut No approval 

approval approval 

Less than or 0.12 0.13 12.28 1 1.76 42 46 10,719 12,282 

equal to 50 ... 50to150 ...... 0.06 0.05 13.32 12.61 41 42 10,355 1 0,737 

150to250 ..... 0.04 0.06 15.01 15.73 45 50 9,826 9,037 

More than 250 . . 0.00 0.06 15.08 14.04 42 36 10,208 10,559 

Overall ..... 0.05 0.10 14.17 12.47 43 44 10,206 1 1,407 
KEY 

Nondeep-cut mining 

MDeep-cut mining 

Handling Machinery Powered Fall of Hand tools Slip-fall Other 

material haulage roof 

ACCIDENT-INJURY-ILLNESS TYPE 

Flgure 2.-lncldence rates (serious accidents per 200,000 underground hours worked) by accldentinjury-Illness type for small mines (average number of employees less than 50). 

KEY 

Nondeep-cut mining 

EQ Deep-cu t mining 

Roof bolting Handling Moving cable Machine Hand tools Load-haul- Other 

supplies maintenance dump 

WORKER ACTIVITY 

Figure 3.--Incidence rates (serious accidents per 200,000 underground hours worked) by mine 

worker activity for small mines (average number of employees less than 50). 
KEY 

INondeep-cut mining 

BDeep-cut mining 

Roof bolter Shuttle car Scoop car Laborer Continuous Belt operaror Other 

operator operator miner operalor 

JOB TITLE 

Figure 4.-Incidence rates (serious accidents per 200,000 underground hours worked) by job 

title for small mines (average number of employees less than 50). 

Discussion 

The calculations from data in table 1 indicate that deepcut mines report more than three times the number of employee hours per mine than mines without deep-cut approval. This fact highlights the need to normalize accidents to exposure hours; any analysis that fails to do so 

may provide misleading information. 

In smaller mines (less than 150 employees), those with 

deep-cut approval had a higher productivity rate than 

those without approval. In the larger mines, however, the 

converse is true. Perhaps this indicates that as mine size 

increases, the impact on total productivity of taking deep 

cuts is lessened and other factors that impact on productivity play a more prominent role. When the productivity for 

all mine sizes are compared, mines with and without deepcut approval had nearly the same rates. 

Table 2 indicates that the overall fatality rate of mines 

with deep-cut approval was about half that of mines without deep-cut approval (0.05 versus 0.10). However, fatality 

rates within each mine size category, with the exception of 

mines with average number of employees greater than 250, 

were very similar. Fatality rates were higher in the smaller 

mine categories than in larger mine categories. This indicates that mine size had more impact on fatality rates than 

deep-cut approval status. 

The opposite effect is seen when comparing the nonfatal lost-time injury rates. Mines with deep-cut approval 

have a slightly higher accident rate than those without 

approval (14.17 versus 12.47). It appears that mine size 

played a significant role in this difference as well. Larger 

mines reported lost-time injuries at a higher rate than 

smaller mines. 

Two measures of accident severity are days lost and 

cost per accident. Average number of days lost is approximately the same for mines with and without deep-cut approval. Mine size does not seem to have a significant impact on average days lost. The estimated average cost per 

nonfatal lost-time injury is slightly higher in mines without 

deep-cut approval than in those that do have approval 

($11,407 versus $10,206). Mine size does appear to have 

some impact on the average cost data. In particular, 

mines with fewer than 50 employees appear to have the 

highest average cost per injury. 

According to figure 2, "handling materials" was the 

largest single category of accidents in small mines, accounting for more than 30% of all accidents, and deep-cut 

mines had an almost 20% higher rate of material handling 

accidents than nondeep-cut mines. One possible explanation for this statistic is that as deeper cuts are taken, the 

trailing length of cable of continuous mining machines is 

longer and, therefore, the lengths of cable to be handled 

are longer. The longer cable is more difficult to move and 

is more likely to result in an injury. This explanation is 

also supported by figure 3, which shows that moving cable 

is associated with a 26% higher incidence rate in deep-cut 

mines than in nondeep-cut mines. The accident rate due 

to handling supplies also is higher in deep-cut mines by 
about 22% than in nondeep-cut mines (fig. 3). Slip-fall accidents have a substantially higher rate in deep-cut mines 

by about 82% than in nondsep-cut mines; however, these 

accidents only accourit for about 7% of p!l accidents in 

small mines. 

One finding of note is that the activity of roof bolting 

has a lower reported accident rate in deep-cut mines than 

in nondeep-cut mines (fig. 3). Furthermore, the incidence 

rate for roof bolters is lower in deep-cut mines by about 

22% than in nondeep-cut mines (fig. 4). This finding is interesting because roof bolting is often thought of as one of 

the most dangerous tasks in mining. Special concerns have 

been associated with this task in deep cuts. These discrepancies about the bolting task indicate that this area warrants further investigation through task analysis. 

It appears from figure 4 that the job titles of "shuttle 

car operator" and "continuous miner operator" have higher 

accident rates in deep-cut mines by 20% and 63%, respectively, than in nondeep-cut mines. The duties performed 

by these job classifications also should be examined 

through task analysis so the reasons for these increased 

rates can be determined and countermeasures suggested. 

UNDERGROUND MINE INTERVIEWS 

A questionnaire was used to determine what aspects of 

deep-cut inining arc considered the most critical to the 

mining industry. To date, over 50 mine workers, including 

mine operators and supervisors, have been questioned at 

various mines with deep-cut approvals throughout Pennsylvania, Kentucky, Maryland, and Ohio. The questionnaire 

addresses various aspects of the worker's experience, mine 

conditions, and the mine worker's view of safety of deep 

cuts. Topics included in the questionnaire are miner experience, deep-cut methods and procedures, roof control, 

accidents and injuries, manual materials handling, control 

layout and design of equipment, visibility, ventilation, 

continuous miner operator protection, breaker tripping, 

maintenance, and general safety questions. The USBM's 

goal is to cover as many areas as possible to identify any 

problems particular to deep-cut mining. 

In general, the results reflect a positive attitude from 

the miners and the mine operators toward deeper cuts. 

Seventy-four percent of the large mine (more than 100 

employees) workers and 95% of the small mine (less than 

100 employees) workers said that deep-cut mining improved or maintained their productivity levels. The miners 

believe deep-cut mining is safer because they move the 

equipment less, thus decreasing the probability of moving 

accidents. Twenty-two percent of continuous miner operators interviewed felt there was increased safety with 

remote control in general. They commented that they 

were more mobile and therefore able to get out of the way 

of the continuous miner quicker and more safely than 

when on the deck of the continuous miner. They also felt 

they were exposed to less noise and dust. Nearly one-half 

of miner operators thought it would be worthwhile to examine the design of the remote-control unit because of its 

weight and bulkiness. 

Several concerns with deep cuts were raised. Sixtyseven percent of continuous miner operators interviewed 

said that there were visibility problems and 29% said that 

it was at least sometimes difficult to stay on the sight line 

in the deep cuts. Several of these continuous miner 

operators stated that a 12.2-m (40-ft) cut is the maximum 

safe cut because visibility problems begin to occur after 

that point. Scrubber systems are necessary at any length 

to help improve visibility. As the roof and rib conditions 

worsen, miners expressed more concern, especially when 

taking deep cuts and with any length of cut for that matter. 

Also, the miner operator's position when operating the 

continuous miner has become an important safety concern 

in deep cuts, as voiced by many of the interviewees. 

There were varying opinions among the roof bolters of 

the increased danger of bolting deep cuts. It was difficult 

for some bolters to keep up with the mining cycle in deep 

cuts because the extent of roof to be bolted is larger than 

the standard cut. The cutting task and the bolting task 

have become more efficient because of decreases in tramming time, but it is not known whether the tramming time 

has decreased proportionately for both. The bolting task 

time is heavily dependent on several variables. If there are 

poor roof and rib conditions, the bolting slows down. Pillar dimensions also affect the bolting cycle. If the pillars 

are larger, there is less bolting to be done and it is easier 

for the bolter to keep up. If the mine is wet, bolting becomes a more difficult task. 

The bolters' workload has been described as the heaviest of all of the job positions. Bolter operators are concerned that the continuous miner operator will have to 

wait on them to finish bolting the section (13). One-third 

of the roof bolter operators in the study of six mines with 

deep-cut approval said that they find themselves hurrying 

to stay ahead of the continuous miner every day, and 

another 24% said that this happens to them a few times a 

week (12). This workload may encourage the bolter to 

take shortcuts, either to keep up with the miner operator 

or to get a break. The type of shortcuts mentioned were 

spacing bolts further apart than the roof plan allows, neglecting to do methane checks, neglecting to drill test 

holes, and neglecting to check the torques on bolts. 

Another important concern is the length of time between bolting. Some believe that the longer the top sits 
unbolted, the greater the probability of the roof sagging 

and possibly falling. Fifty-seven percent of continuous 

miner operators interviewed were concerned that roof falls 

in deep cuts were both deeper and have larger surface 

areas than roof falls in standard cuts. Thirty-seven percent 

of roof bolters interviewed thought that ground falls may 

be larger in deep cuts. According to Bauer, Pappas, and 

Listak (I), deep-cut roof falls averaged 3.0 times larger in 

area and 1.5 times greater in thickness than nondeep-cut 

roof falls. Love and Peters (7) found that roof bolter 

operators thought that the increase in lengths of cuts was 

causing an increase in the frequency of high roof falls. 

Bolting in deep-cut sections is considered to be the most 

dangerous of the mining job categories because of increase 

in roof fall size and frequency combined with temptations 

to take dangerous shortcuts to keep up with the miner 

operator and to go under unsupported roof. 

Some areas to be looked into more closely are ventilation, cable handling, roof fall protection, remote reset of 

the continuous miner, maintenance, safe operating procedures, and remote-control unit design. Hanging ventilation 

curtain and extending the ventilation tubing in deep-cut 

sections could result in miners going under unsupported 

roof (13). This occurrence also depends on the ventilation 

plan and type of ventilation available. Cable handling, 

though it is the same task as in a standard cut, may be 

more difficult because of the longer length of cable to be 

handled with the deeper cut. Several miner operators 

thought that they would like to have some protection from 

roof and rib falls when operating the continuous miner, 

but were not sure of the practicality of such a structure. 

There is si&cant interest in the ability to remotely reset 

the breaker on a continuous miner when it trips under unsupported roof during deep-cut mining. Erecting temporary supports is time consuming and places the worker in 

close proximity to unsupported roof. The temptation is 

great to quickly go out and reset the breaker because it 

takes a fraction of the time required to set temporary 

supports. The USBM has developed alternate methods to 

remotely reset the machine and test sights are being 

established. 

Currently, the USBM is taking a systematic look at 

safety issues in deep-cut mining through the use of the 

questionnaire. The results of these interviews are being 

used to determine what areas need further examination. 

The USBM plans to perform task analyses to break down 

the problem and develop possible solutions. One outcome 

the USBM plans to develop from this research is a method for mine management to use when implementing new 

mining technology, whether it is equipment or methods. 

This will provide them with a tool for evaluating the 

human factors aspects of technological changes and to better plan and design for these changes. Because of the nature of the data presented here, it would be a mistake to 

rely solely on these data to make inferences as to the 

safety of deep-cut mining or to point out all of the areas 

where problems are occurring. 

CONCLUSIONS 

The preliminary task analysis questionnaire has helped 

to point out several areas of concern with deep-cut mining 

safety. Several discrepancies were found between the statistical analysis and the questionnaire results, but both can 

be useful in pointing out areas of concern. The information helps to better define the factors contributing to injuries and fatalities involved in deep-cut sections. The 

interviews with miners reflect the way they feel about the 

issues discussed. Many limitations and biases may shape 

their perceptions, but their viewpoints are considered 

informative and insightful and are a valuable source of 

information. This sample was relatively small and was not 

randomly selected and, for that reason, should not be 

considered representative of the entire industry. 

The USBM is also taking into account discussions with 

State, Federal, and United Mine Workers of America officials to develop a task analysis approach to researching the 

controversial aspects of deep-cut mining. The USBM 

plans to use several types of task analysis methods at two 

or more mines with varying conditions. As part of the 

study, the USBM apects to develop a method for mine 

operators to evaluate, their mine before, during, and after 

the implementation of the new technology or method to 

diminish possible human interface problems. In this way, 

problems can be identified before they show themselves as 

statistics. 

To take a closer look at the visibility aspects of continuous miner operators, the USBM plans to initiate a 

work sampling-work activity analysis. This will help to 

determine where the miner operator is positioned in the 

different phases of the cycle and why. The bolter workload is another area that requires special attention. Since 

interview data have indicated that the bolter may be taking 

shortcuts or may be under pressure and hurried, we plan 

to check the loadings on the bolter, both physical and 

mental, through ergonomic checklists, task decomposition, 

and human error analysis. We expect these studies will 

help to point out the amount of exposure to dangerous 

work situations, the amount of workload, the most effective type of training needed, and to identify potential 

errors and their likelihood of occurrence. 
REFERENCES 

1. Bauer, E. R, D. M. Pappas, and J. M. Listak. Ground Control 

Safety Analysis of Extended Cut Mining. BuMines IC 9372,1993,24 pp. 

2. Bauer, E. R, E. J. Steiner, and C. A. Hamrick. An Update on 

Extended Cut Mining. Coal Mag., in press. 

3. Campbell, J. A., R Riffey, and P. D. Risner. Deep Cut Remote 

Control Mining. Paper in Proceedings of the AIME Annual Meeting 

(Denver, CO, Sept. 1989). AIME, 1989, pp. 101-112. 

4. Davis, A. Extended Cuts: An Accident Analysis and Inventory of 

Approvals. U.S. Mine Saf. and Health Admin., Div. Saf., Coal Mine Saf. 

and Health, Internal Rep., Apr. 15, 1991, 32 pp. 

5. DiCanio, D. G., A. H. Nakata, D. Colvert, and E. G. LaVcque. 

Accident Cost Indicator Model To Estimate Costs to Industry and Society From Work-Related Injuries and Deaths in Underground Coal Mining. Volume I. Development and Application of Cost Model (contract 

J0255031, FMC Corp.). BuMines OFR 39(1)-77, 1976, 202 pp.; NTIS 

PB 264 438. 

6. Jayarman, N. I., R Jankowski, and D. Stritzel. Improving Health, 

Safety, and Productivity Through the Use of Machine-Mounted Scrubbers. Paper in Proceedings of the Illinois Mining Institute 95th Annual 

Meeting (Mt. Vernon, IL, Oct. 1, 1987). IMI, 1987, pp. 62-75. 

7. Love, A. C., and R H. Peters. Deep Cuts Present Some New 

Challenges to Avoiding Unsupported Roof. Holmes Saf. Assoc. Bull., 

Mar. 1993, pp. 28-30. 

8. Love, A. C., and R F. Randolph. Radio Remote Control Continuous Miner Operator Positioning. New Technology in Mine Health and 

Safety. Paper in Proceedings of Symposium of Annual SME Meeting 

(Phoenix, AZ, Feb. 24-27, 1992). SME, 1992, pp. 357-360. 

9. Merritt, P. C. As Time Changes, So Do Longwalls. Coal, Feb. 

1991, pp. 40-49. 

10. . Longwalls Having Their Ups and Downs. Coal, Feb. 1992, 

pp. 26-37. 

11. Page, S. J., J. C. Volkwein, and I.'. N. Kissell. Achieving 435-2540 

Tonnes Per Shift From Continuous Miner Sections: A Report on the 

USA's Most Productive Coal Mining Systems. Paper in Proceedings of 

the AusIMM Illawarra Branch, 21st Century Higher Production Coal 

Mining Systems-Their Implications (Wollongong, NSW, Australia, Apr. 

1988). AusIMM, 1988, 9 pp. 

12. Peters, R H., and A. C. Love. Roof Bolter Operators: Preventers 

and Victims of Roof Fall Accidents. IIolmes SafetyAssociation Bulletin, 

Jan. 1993, pp. 9-12. 

13. Peters, R H., and R F. Randolph. Miners' Views About Why 

Peoplz Go Under Unsupported Roof and 1Iow To Stop Them. 

BuMines IC 9300,1991,59 pp. 

14. U.S. Code of Federal Regulations. Title 30-Mineral Resources; 

Chapter I-Mine Safety and Health Administration, Department of Labor; Subchapter M-Accidents, Injuries, Illnesses, Employn~ent, and Production in Mines; Part 50-Notification, Investigation, Reports and Records of Accidents, Injuries, Illnesses, Employment, and Coal Production 

in Mines; Subpart A--General; Section 50.1-Pupose and Scope; 1993. 
CREWSTATION ANALYSIS PROGRAMS-AN EASY TO USE PERSONAL 

COMPUTER-BASED LIGHTING AND VISIBILITY ANALYSIS 

SOFTWARE PACKAGE FOR UNDERGROUND MINING EQUIPMENT 

By Richard L. ungerl 

ABSTRACT 

Restricted fields of vision are a common problem to use gcrsonal computer-bascd software package to aid in 

with the operator of underground mining equipment, par- the analysis of the visibility and illumination aspects of 

ticularly in lower seams. Also, when lighting systcms are mining equipmcnt design. The software is widely available 

provided underground, they arc often positioned where for use by mine operators and equipment manufacturers 

they cause cxcesslve glare. This restricts the visibility to design new machine illumination systems, as well as 

around the machines even further. To help address thcse to evaluate proposed modifications to existing machines 

problems, the U.S. Bureau of Mines has developed an easy already in use. 

Designing operator compartments (crewstations) for 

underground mining equipment can be a formidable task. 

Massive machinery is required to meet production goals 

while the confined environment imposes severe space 

restrictions in every direction, most critically in hcight. 

As a result of the space limitations, mining equipment 

operator compartmcnts are frequently smaller than recommended to adequately accommodate most of the population. In fact, crewstatioils that provide operator 

accommodations of less than 76 cm (30 in) in height and 

60 cm (24 in) in width are not uncommon. In these 

cramped quarters, visibility is often severely impaired, 

forcing operators to lean outside of the protection of their 

crewstations to see. When lighting systems are provided 

to meet regulatory requirements, they may be positioned 

where they cause glare, which creates additional problems 

for miners operating or working around the machines. 

Given the difficulty of implementing human factors into 

mining equipment design, the U.S. Bureau of Mines 

(USBM) has been attempting to provide the industry with 

products to assist in the equipment design process. 

Several recommendations documents have been dzveloped, 

including a maintainability design reference (I)' and a 

textbook on human factors in mining (2). In addition, a 

database containing abstracts of human factors research 

applicable to mining was developed and made available to 

anyone with a Digital Equipment Corp. VAX-compatible 

terminal and modem. One of the most recent USBh4 research projects that shows promise of impacting how 

engineers think about the mining equipment design process is the development of the Crewstation Analysis Programs (CAP) package. CAP is a set of computer programs that can be used to analyze some of the human engineering aspects of crewstation design that have particular 

significance in underground mining. These programs currently include assessments of visibility and illumination in 

the surrounding work area. Graphics-oriented procedures 

allow the user to input information needed for the analyses, such as type of mining machinery, lighting systems, 

and mine layouts. Once this information is identified, 

'civil engineer, Pittsburgh Research Center, U.S. Bureau of Mines, '1talic numbers in parentheses refer to items in the list of references 

Pittsburgh, PA. at the end of this paper. 
the user may select any of the available analyses. By experiment with novel crewstation layouts for mining 

automating the task of evaluating human factors design equipment. 

issues, CAP will allow engineers to more quickly and easily 

ACKNOWLEDGMENTS 

A software projecl such as CAP requires the expertise engineer; Alan Mayton, mining engineer; James Rider, 

of many professionals. The author wishes to acknowledge operations research analyst; E. W. Rossi, industrial engithe contributions of USBM's Pittsburgh Research Center neering technician; Paul Sonier, computer programmer; 

employees Sean Gallagher, research physiologist; Audrey and Tris Betts, computer programmer during the developGlowacki, program analyst; Chris Hamrick, industrial ment of CAP. 

DESIGN OF CAP 

The original version oT!be software, completed in 1990, 

was written in FORTIZAN for a Digital MicroVAX I1 

computer and reqi;iicd a Tektronk graphics display terminal and mouse, a graphics tablet, and an optional hardcopy unit. The programs have recently been updated and 

translated to the C language and are now targeted for the 

widely used 386/486 processors. However, the programs 

have been designed so that they can be easily transported 

to other, more powerful platforms, such as work stations. 

A great deal of effort was expended to develop interactive 

graphic displays that are "user friendly" to assist in the 

placement of machines, lamps, and other objects needed 

to perform the various ergonomic analyses. 

CAP is designed much like a simple computer-aided 

drafting (CAD) program, such as AutoCAD. The center 

of the screen is taken up by a large view port into the 

"world," where the user positions three-dimensional modcls 

of mines, machines, lamps, glare shields, or any object that 

is needed by the analysis (fig. 1). The lower right portion 

of the screen contains the viewing controls, which allow 

users to change their point of view with respect to the 

objects in the scene. These controls are always available 

and activate several zooming, panning, and camera positioning functions. The lower left portion of the screen 

contains controls for the activation of utilities and positioning aids. These include changing the color or visibility 

of objects in the scene, turning on a grid to help position 

objects, toggling the scene from a wire frame to a solid 

mode, and activating the help screen. 

The upper right portion of the screen contains the main 

menu area of the program. This is a changeable menu 

several levels deep that controls access to the majority of 

the functions of the program. From this menu you can 

open and save files; input mines, machines, and lamps; edit 

and delete objects; run the analyses; and change the program settings. 

The upper left portion of the screen contains a user 

defined menu. If the users determine that there are functions in the main menu that they use more often than 

most, the controls for those functions can be permanently 

displayed here so they are readily available. 

Prompts to the user and other pertinent information are 

displayed in the banncr across the top of the screen. Information about what the program is currently doing is 

generally displayed here. Input into the program is often 

made through dialog boxes, such as the one presented in 

figure 2. This particular dialog box allows the user to 

position a lamp, change its type, or turn it on or off. 

The models of machines and lamps used by CAP are 

usually created with AutoCAD. The AutoCAD DXF file 

is translated to the CAP file format with a utility program 

supplied with CAP. However, simple machine models can 

be created by using either a text editor or a separate model build utility supplied with CAP. Actual mine layouts 

can be input to CAP by scanning existing mine maps and 

vectorizing the resultant image into AutoCAD. Mines can 

also be created from scratch in AutoCAD. 

CAP'S VISIBILITY ANALYSIS 

Visibility is a significant problem in the underground chines: shuttle cars, scoops, and continuous miners. 

mining environment. During thc 1980's, the USBM- Using structured interviews and on-site task analyses 

sponsored research (3) to determine minimum visibility re- involving approximately 100 subjects, the researchers first 

quirements for three classes of underground mining ma- identified the tasks involved in the operation of each class 
of vehicle, such as loading, hauling, or unloading. Then, 

the machine operators were interviewed to identify the 

visual information required to perform each of these tasks. 

For example, a shuttle car operator performing a loading 

task would need to see the positioning of the shuttle car 

under the tail boom of the continuous miner. While hauling, the location of the shuttle car and any obstacles in the 

roadway would be required. Following the interviews, the 

operators were observed while performing the tasks to verify the visual information requirements established in the 

interviews. 

Once the requirements were determined, a methodology was developed to identify specific points in the frontto-back, side-to-side, and vertical planes that must be 

visible to the operator to satisfy the visual requirements. 

These points, called visual attention locations (VAL's), 

were defined in reference to generic locations on the 

machine. This alluir'cd the VAL'S to apply to all configurations of a particular equipment class. For instance, 

while tramming, a shuttlc car operator must be able to 

spot an obstruction on the ground, while there is enough 

time to stop thc vehicle. The location of one of the VAL's 

associated with this requirement is describcd in table I. 

Using this methodology, the procedure involved in computing the location of the VAL is the same even if the 

length of the equipment, the operator's position, or the 

height of the equipment is modified. 

The results of this VAL research have been incorporated into the CAP package. The CAP visibility model 

automates the task of determining whether or not the required VAL's are visible to a selected human operator, 

currently either a 5th percentile female or 95th percentile male. The output is a relative visibility rating for 

the machine, which can be compared with results of alternative machine designs. CAP also provides both graphical 

(figs. 3-4) and tabular output to pinpoint any machine 

parts that obstruct visibility. 

Table 1 .-Location of VAL associated 

with tramming shuttle car 

Coordinate 

plane 

Position of VAL 

Front to back . . Front edge of machine plus necessary stopping distance. 

Side to side . . . Machine centerline. 

Vertical ...... Floor. 

CAP'S ILLUMINATION ANALYSIS 

Due to the perpetual darkness of the underground 

environment, illumination is a factor that must be considered when designing equipment for optimal visibility. 

Federal regulations specify that certain surfaces within 

a miner's normal field of vision must be illuminated to 

0.21 cd/m2 (0.06-fL) while self-propelled mining equipment is being operated. The 0.21-cd/m2 (0.06-fL) level is 

a measure of luminance, or photometric brightness. It is 

a product of the level of illumination (incident light) 

impinging on a surface and the reflectivity of the surface. 

USBM research has shown that the 0.21 cd/m2 (0.06%) 

level is adequate for most mining tasks and is low enough 

so that operaLois will not cxpcricncc severe adaptation 

problems when moving from illuminated to nonilluminated 

areas of thc mine (1-5). 

Unfortunately, in attempting to mcet these illumination 

standards, mine equipment designers sometimes aggravate 

another mine lighting problem-glare. There are currently 

no standards related to glare in underground mining. The 

regulations state only that designers should attempt to 

minimize glare when developing machine illumination systems. Obviously, performing all of the calculations required to compute glare for a multitude of machine and 

lamp types, with the possible combinations running into 

the thousands, is too tedious and costly to be practical 

using manual methods. The result is that the designer is 

impeded significantly in solving for an optimal illumination 

system that minimizes glare. 

The CAP illumination model eliminates these problems 

by turning the computational portion of the lighting design 

task over to the computer. The software allows the lighting designer to concentrate on adjusting the configuration 

of the illumination system to minimize the potential for 

glare while still providing enough illumination to conform 

to the Federal regulations. 

To perform an illumination analysis using CAP, the 

user lays out a lighting system on a machine model. Each 

lamp has associated with it an illumination profile, previously measured along selected angular orientations from 

the lens of the lamp. Using these profiles, the software 

can calculate the light output at any location in the scene. 

The model does not take into account reflected light, but 

it can correct for the shadowing effects of machines or 

other objects in the scene. 

In CAP, illumination measurement panels represent the 

areas (roof, ribs, floor, and face) that must be illuminated 

to 21.52 lx (2.0 fc) to meet the Federal regulations. These 

panels can be sized and positioned around a machine 

model (fig. 5). The output of the illumination analysis can 

be displayed on these panels so that quick comparisons 

can be made between lamp layouts (fig. 6). 
14:ll VIEW REAR RIGHT ZOOM: 1.250 Cur Mach: BATSCOOP SNAP HN HIDE 

-- - 

Figure 1.-Default screen layout of CAP with solid model of battery-powered scoop displayed. 

15:IS VIEW: FRONT ZOOM: 7.451 Cur Mach. BATSCOOP SNAP HIV HIDE-1 

Figure 2.--Screen layout switches to three view modes when objects are being positioned. Dialog box allows Input of preclse lnformatlon for objects. 
(r VIEW: REAR RIGHT ZOOM: 0.356 Cur Mach: lO2HP SNAP HIV HIDE 

Figure 3.-Shuttle car and continuous miner in entry. Pillars are from scanned mine map. 

I-- VIEW ***** LOOM 0336 CwMach 10211P SNAP kW HIDE 

Figure 4.-View from inside shuttle car cab. VAL'S are represented as blocks. 
Figure 5.--Continuous mining machine with three of its lamps turned on. There are four illumination measurement panels-ane on floor, one at face, and two at sides. 

- - .. . - - - - . . . . . . . . .. . - . - .. - - - - - - . . - - - -- - 

!i) .h X= 46h.(KH) Yr(,3 (Hni bl( )L )I 1x1 0 %(Oh1 I Wl C'ur Panel- I:I.ONK SNAI' HIDE 

l'u~n~ \,.Itite~i l(195 i.( ' Ell,,, k J\L.IJL.,~ 11 Xi 1 ('. 1 

Psss 

Figure 6.-Illumination measurement panels are unfolded to display results. Crosshatched 

blocks indicate an average Illumination of at least 21.52 lx (2.0 fc). 
SUMMARY 

The hardware and software requirements for CAP are 

listed below. 

Hardware: 

1. IBM-compatible 3861486 computer. 

2. Math coprocessor. 

3. 8 Mb of random access memory (RAM) (16 Mb is 

preferred). 

4. At least 10-Mb hard-disk space. 

5. Video graphics adaptor (VGA) with 256 color capability (super VGA is preferred), 

6. VGA monitor. 

7. Microsoft-compatible mouse. 

1. DOS 5.0 or greater. 

2. Optional AutoCAD release 11 or 12 with or without 

advanced modeling extension. 

AutoCAD release 11 or 12 with or without the advanced 

modeling extension (AME) is also necessary to generate 

complex machine models. However, CAP is supplied with 

a library of generic mining machines that suit most needs. 

There is a charge to cover the USBM's licensing fees for 

the graphics toolkits used by the software. 

There are many advantages to using computers to assist 

in the design of mining equipment. Computers permit 

quick evaluation and cornparisoil of different systems, such 

as when trying to optimally position lamps. Information 

that is difficult or tedious ro incorporate into a design with 

manual methods, such as anthropometric data, call be 

conveniently accessed. Graphical feedback not only enables the designer lo quickly identify potential problems, 

but also enhances his or her ability to con~municate ideas 

to the client, increasing fhc lihclihoad ill acceptance of 

novel designs. 

In the future, the TJSHhl plans to enhance CAP with 

additional capabilities. Work is already underway to autoniatlcally gznerate the path network composed of the entries and cros~cuts of the mine model. This will allow 

computerized t~min,g sstudies to be performed, such as tl~e 

tiinc ncedcd for pcrsonilel to escape from a scctiou. Operator reach and accommodation models may- idso be addcd, Thcse progr,iIns would bclp the dcsigner to determine 

whether operators from a sclccted populrition would bc 

able to fit into the crewstation and reach the controls. As 

with t1:c illumination and virlliility models, the unique requirements of the underground mine worker would be taken into account, including provisions for miners wearing 

hardhatb, metatarsal t)c)cjis, and self-contained breathing 

apparatus. 

REFERENCES 

1. Conway, E. J., and R L. Unger. Maintainability Design of Under- 30387213, Canyon Ices. Group, Inc.). BuMincs OI;R 29(2)-82, 1981, 

ground Mining Equipment (contract 50145034, VRC Corp.). Volume 1- 67 pp.; Xl'IS PL3 82-16?9.49. 

Final Report. BuMines OFR 39-91-V1, 1988, 35 pp; Volume 11- 4. Lewis. W. I!. I.:ndcrg;.i?unii Coal Mine 1,ighting IIandbook. (In 

Maintainability Design Guidelines. BuMines OFR 39-91-V2, 1988, two parts 1. !3ack;round. 1iu'llir:cs IC 9073, 1986, 42 pp. 

181 pp. 5. . lirldergrcjund Cual Xline 1,ighting IIandbook. (In Two 

2. Sanders, M. S., and J. M. Peay. Iluman Factors in Mining. Bu- Parts.) 3. Applicatio~~. 13u:llines I(: 0074, 1986, 89 pp. 

Mines IC 9182, 1988, 153 pp. 

3. Sanders, M. S. Visual Attention Locations for Operating Continuous Miners, Shuttle Cars, and Scoops: A Summary (contract 
IMPACT OF MAINTAINABILITY DESIGN ON INJURY 

RATES AND MAINTENANCE COSTS FOR 

UNDERGROUND MINING EQUIPMENT 

By Richard L. ungerl and Kirk ~onwa? 

ABSTRACT 

In the U.S. underground coal mining industry, maintenance of the mining equipment accounts for over 30% of 

the lost-time injuries. In addition, the steadily increasing 

cost of maintaining this equipment has focused attention 

on the need to find ways to contain or reduce these 

expenses. To obtain a better understanding of why maintenance injuries occur, the U.S. Bureau of Mines has 

conducted a research project to analyze the design of 

underground mining equipment with respect to ease of 

maintenance and maintainer safety. The objective was to 

identify design factors contributing to these high injury 

rates and maintenance costs. The work included a review 

of relevant maintainability design literature, analysis of 

maintenance-related accident data, field reviews of equipment design in underground operating environments, and 

interviews with mine maintenance personnel and equipment manufacturers. Based on the findings, a set of maintainability design recommendations have been prepared 

and published. The documents include basic maintainability engineering information for equipment designers, as 

well as a buyers' guide to assist purchasers of mining 

machinery in evaluating the maintainability of equipment. 

INTRODUCTION 

In the 1950's underground coal mining equipment consisted of relatively simple but rugged machines powered by 

electric motors and hydraulics. These machines were used 

to cut, dig, load, and transport coal from the mine face to 

the surface. The machines were maintained by mine 

maintenance personnel armed with a basic knowledge of 

hydraulics, electricity, and mechanical design. These 

maintainers were expected to repair all of the equipment 

at the minesite using only simple hand tools. 

Over the years, the basic mining machine has been 

transformed into powerful, complex mining systems. To 

boost productivity, the horsepower and size of the original 

machines have been increased. To enhance unit productivity, machines were designed to perform multiple functions. 

'civil engineer, Pittsburgh Research Center, U.S. Bureau of Mines, 

Pittsburgh, PA. 

%enior staff scientist, VRC Corp., Monterey, CA. 

To increase throughput, continuous miners, longwall and 

shortwall systems, and continuous haulage were introduced. To reduce injuries, numerous safety features have 

been added to the machines. To protect the miners' 

health, environmental control systems have been tacked 

on. 

With few exceptions, however, little improvement in the 

basic design of equipment for maintainability has been 

made. In many cases, equipment maintainability has been 

sharply decreased. Many of the above design changes 

were achieved by simply modifying existing machine designs. On certain mining machines, sharp reductions in 

maintainability and, consequently, maintainer safety were 

experienced as a result of added-on safety and environmental systems designed only with the machine operator 

in mind. 
Even with all of the above changes, the maintainer is 

still expected to service and repair these ever more complex machines. This must be accomplished in an operational setting providing little in the way of new maintenance tools, procedures, automatic test equipment, or 

other technology-based maintenance aids and in an environment that usually lacks proper lighting and clearances. 

All in all, there has been little concern directed at the well 

being of the maintainer. It is no wonder that equipment 

maintenance has traditionally accounted for one-third of 

all lost-time injuries in underground mines. This injury 

rate persists in spite of concerted efforts on the part of 

mine management to minimize accidents, U.S. Mine Safety 

and Health Administration (MSHA) efforts to enforce 

health and safety rules, and USBM efforts to conduct 

safety research. 

In addition to the safety of the maintainer, another area 

of concern has been the escalating cost of mining equipment maintenance. Underground equipment maintenance 

typically accounts for 25% to 35% of the total mine operating costs. These costs have continued to rise over the 

years despite efforts to contain them. Mine operators 

have attempted to gain control of these steadily increasing 

costs through (1) optimization of scheduled maintenance 

operations, (2) reductions in maintenance staff, (3) reduction and better control of spare parts inventories, 

(4) contracting for maintenance support, and (5) deferring 

nonessential maintenance. 

Unfortunately, little attention has been focused on 

the design of the mining machine itself with respect to 

maintenance costs. The cost of maintaining a machine is, 

after all, a direct function of1. Maintenance frequency and failure interval for the 

machine and major components. 

2. Time and labor required to complete unscheduled 

maintenance actions. 

3. Time and labor required to complete routine maintenance tasks. 

A review of current mining equipment design suggests 

that considerable improvements in safety, as well as substantial cost savings, could be achieved with relatively 

simple design improvements. For example, by relocating 

difficult to access, but frequently replaced hydraulic valves 

and hoses on certain roof bolters, this 1-h plus removal 

and replacement (R/R) task is reduced to a 5-min operation. Improved component accessibility and increased ease 

of R/R tasks reduces the maintainer's risk of injury. Numerous other maintenance improvements could be realized 

with minor design changes on new or existing equipment. 

As part of its program to enhance the safety of mine 

workers, the U.S. Bureau of Mines (USBM) completed a 

project entitled "Assessment of the Maintainability Design 

of Underground Mobile Mining Equipment," which was 

performed by VRC Corp. The final report was published 

in 1988 Other papers published by the USBM based 

on this work are listed in the references (2-6). 

DESIGN-INDUCED MAINTAINABILITY PROBLEMS 

The USBM analyzed underground coal mining equipment with respect to design for maintenance and maintenance personnel safety. A maintainability design review 

and human factors analysis of equipment was completed 

at nine operational coal mines. Mining machines in large 

and small mines operating in high- and low-seam coal 

were surveyed. Conventional, continuous, and longwall operations were included. Shuttle cars, scoops, roof bolters, 

continuous miners, longwall equipment, undercut machines, face drills, utility vehicles, and personnel carriers 

were reviewed. The survey identified the following design 

limitations that directly impacted maintenance time, cost, 

and personnel safety. 

1. Accessibility problems: Inability of maintenance 

personnel to access failed or suspected components to inspect or remove and replace them. Accessibility problems 

resulted froma. Inadequate access opening size. 

b. Poor layout of components in a compartment, 

necessitating R/R of nonaffected parts to access the 

failed units. 

c. Inability to access mounting bolts or connectors 

or to use required tools. 

d. Installing components in inaccessible interior 

cavities and running cables inside the frame or chassis 

where they cannot be reached. 

e. Locating fasteners and mechanical interfaces 

where they physically cannot be reached unless the machine is partially or completely disassembled. 

2. Inadequate component-handling capability and 

component-machine interface design. 

3. Inadequate design for routine maintenance: Inability 

to quickly remove and replace leaking hydraulic hoses and 

water lines, to remove and replace failed hydraulic valves, 

3~talic numbers in parentheses refer to items in the list of references 

at the end of this paper. 

HUMAN ERROR AND DESIGN FOR MAINTENANCE 

So-called human error is a problem that must be ad- of the component-machine interface. Although not directdressed in design as well as during operation and main- ly applicable to underground mining operations, the above 

tenance of complex equipment (9-13). Errors may occur error rates are suggestive of the types, frequencies, and 

in operating mining machines, performing maintenance sources of human errors in maintenance. It is reasonable 

tasks, or in making management decisions. Fortunately, to assume that similar error-rate patterns could be exmost human errors result in limited negative consequences pected in mine maintenance operations. 

(e.g.; lost time and production waste). In many cases, the 

error ends up costing the party involved time or money. 

Unfortunately, in a smaller percentage of cases, people are 

injured or killed and equipment destroyed. 

Dramatic evidence of the impact of a maintenance error was the 1979 American Airlines DClO crash that killed 

272 people. This crash was directly attributed to maintenance error. The probability of recurrence of this type of 

error was reduced substantially by means of a simple component design change. 

OPERATIONALLY INDUCED ERRORS 

Table 2.-Representative maintenance task 

error rates (13) 

Action Object Error description Error 

rate1 

Observe .. Chart Improper switch action ..... 1,128 

Fiead .... Gage ..... Incorrectly read ...... 5,000 

Read .... Instruction Procedural error ...... 64,500 

Connect .. Hose ..... Improperly connected 4,700 

Torque ... Fluid lines incorrectly torqued .... 104 

Tighten .. Nuts, bolts Not tightened ........ 4,800 

Install .... Nuts, bolts Not installed ......... 600 

Install .... 0 rings ... Improperly installed ... 66,700 

Solder ... Connection Improper solder joint .. 6,460 

........... What does human error have to do with mining equip- Assemble Connector Bent pins 1,500 

Assemble Connector Missing part ......... 1,000 

ment maintainability? .... ..... ... In an interesting review of the sub- Close valve Not closed properly 

ject, researchers report that a significant percentage of all Adjust ... Linkage ... Improperly adjusted ... 16,700 

operational equipment failures are human error induced Install .... Orifice .... Incorrect size installed 5,000 

.. ..... (11-12). In fact, human error accounted lor- Machine Valve Wrong size drill and tap 2,083 

'per million operations. 

1. Fifty to seventy percent of all electronics failures. 

2. Sixty to seventy percent of all aircralt and missile 

failures. 

3. Twenty to thirty percent of all mechanical failures. 

ERRORS IN UNDERGROUND MINING 

EQUIPMENT MAINTENANCE 

Representative underground mining maintenance errors 

Many of these are operator induced errors resulting in have been identified, with the major types summarized in 

machine damage Or prolonged down time. Maintenance table 3. It was also possible to identify a number of fatrequirements be reduced designing Out these tors to maintenance-related human error. 

types of errors. Other errors are made by maintenance includepersonnel while performing maintenance tasks (13). 

MAINTENANCE-INDUCED ERROR RATES 

The above study also reports that 20% to 25% of all 

failures are directly traceable to maintenance errors. A 

separate study found 25% of all maintenance problems to 

be human error induced during maintenance operations 

(11). Another study reports human error rates lor specific 

types of maintenance tasks. These data, summarized in 

table 2, were derived from an earlier study (13). The 

values are indicative of the error rates found in many 

industrial and military settings. 

Another maintenance study reports that the average 

human reliability in adjusting or aligning tasks is 0.0987 

(13). This value suggests that out of every 1,000 attempts 

to adjust a component, you can expect 13 errors. Many of 

these errors could be eliminated through improved design 

1. Confined workspaces: Crowded equipment bays. 

2. Inability to make visual inspections. 

3. ~naccesiible components: - 

a. Lube points that could not be reached. 

b. Adjustment points that are hard to access. 

c. Major components that could not be reached. 

4. Poor layout of components in a compartment. 

5. Inappropriate placement of components on machine. 

6. Poor or no provision for hose and cable 

management. 

7. Lack of troubleshooting guides and tools. 

8. Lack of positive component installation guide pins 

and other installation controls. 

9. Insufficient task inspection and check-out time. 

10. Cumbersome or inadequate manuals. 

11. Excessive weight of components being manually 

handled. 
Table 8.-Typical mining equipment maintenance errors b. Provide mounting pins and other devices to supFrequency Type of enor 

I . . . . . . . . Install incorrect component. 

S . . . . . . . Omitting a component. 

Parts installed backwards. 

Failure to properly torque. 

Failure to align, check, or calibrate. 

Use of incorrect fluids, lubricants, or greases. 

Reassemble error. 

Failure to seal or close. 

O... 

port a component while it is being bolted or unbolted. 

2. Improved fault isolation design: 

a. Designate test points and procedures. 

b. Provide built-in test capability. 

c. Clearly indicate direction of fault. 

3. Improved indicators, warning devices, and readouts 

to minimize human decisionmaking. 

4. Use of operational interlocks so that subsystems canError resulting from failure to complete task due to not be activated if they are incorrectly assembled-installed. 

shift change. 5. Use of positive decision guides to minimize human 

Failure to detect while inspecting. guesswork: Failure to lubricate. 

Failure to act on indicators of problems due to a. Arrows to indicate direction of flow. 

workload, priorities, or time constraints. b. Correct type of fluids or lubricants. 

Failure to follow prescribed instructions. c. Correct hydraulic pressures. 

I Infrequent (less than once per year). 

S Somewhat frequently f2 to 5 times per year!. 

0 Often (over 5 times per year). 

Listed below are several engineering design improvements 

that reduce maintenance errors: 

1. Improved component-machine interface: 

a. Design interface so that the component can only 

be installed correctly (e.g.; irregular bolt pattern). 

6. Design to facilitate detection of errors: 

a. Locate connections on front of component to facilitate visual inspections. 

b. Lay equipment out in a logical flow sequence. 

If maintainer-induced errors could be reduced by 50%, 

overall equipment availability would be increased by more 

than 10%. These reductions can be achieved through 

improved design. 

MAINTENANCE SAFETY COSTS 

Maintenance operations account for a significant percentage of all coal mining accidents and injuries. MSHA 

accident statistics for 1984 suggest that maintenance-related injuries account for 33% of all lost-time accidents 

(14). These accidents impact mine operating costs in the 

form of decreased productivity, increased benefits costs, 

and increased insurance rates. 

Many injury accidents can be directly traced to equipment design in this and other studies (6). Inadequate 

accessibility, lack of meails to lift and maneuver heavy 

components, inability to visually observe the maintenance 

task being performed, inadequate maintenance safeguards, 

and other design-induced problems account for a significant percentage of maintenance accidents. Improved accessibility, enhanced component-machine interface, and 

simplified maintenance procedures could have a positive 

impact on these statistics. Improved maintenance safety 

will reduce maintenance as well as overall operating costs. 

COST OF MINING EQUIPMENT MAINTENANCE 

Reliable maintenance cost data are not currently avail- to over 35% of total mine operating costs. Actual values 

able across the underground coal mining industry, although varied based on the size and type of mine, mining technolseveral industry estimates are available. These estimates, ogy employed, management attitude toward maintenance, 

however, vary substantially from source to source. and other factors. 

Informal data gathered over the past several years 

reveal that equipment maintenance costs range from 20% 
FACTORS CONTRIBUTING TO MAINTENANCE COSTS 

The current review of mine maintenance operations 

suggested that the following factors contribute to equipment maintenance costs: 

1. Management attitude towards maintenance: Attitudes range from "when it breaks-fuc it" to strong top 

management support for professionally planned and implemented preventive maintenance (PM) programs geared 

to reducing unscheduled equipment down time and to controlling maintenance costs. 

2. Skill of maintenance management personnel: The 

skills required to organize and manage an effec~ive mine 

maintenance program differ from the skills required to 

perform "hands on" maintenance of mining equipment. 

Poor maintenance management contributes to increased 

costs. 

3. Maintenance training and experience: Poor maintenance skills on the part of maintainers resulting from inadequate training; lack of job performance aids, manuals 

and guides; and complexity of maintenance tasks. 

4. Maintenance environment: It is an entirely different 

task to maintain a continuous miner in a 91-cm (36-in) 

coal seam than it is to maintain one in a well-equipped 

standing height underground repair shop. 

5. Age of equipment: Older equipment tends to be 

smaller and inherently simpler in design. As a result, older machines are somewhat simpler to maintain. Newer 

equipment tends to be larger, more complex, and overlaid 

with numerous "add-on" systems and components, making 

accessibility and the basic maintenance process more 

difficult. 

6. Maintenance errors: Reliable data are not available, 

but most maintenance personnel interviewed informally 

concede that maintenance errors contribute substantially 

to overall maintenance costs. Removing and replacing 

nonfailed items, troubleshooting one system too long, not 

replacing suspected components during a previous maintenance opportunity, failing to install or repair a component 

correctly, failing to test a component prior to reassembly, 

and related errors account for an estimated 10% to 25% 

of all maintenance time. 

7. Design of equipment itself: Certain makes and 

models of mining equipment are designed to facilitate 

maintenance and repair, while the basic design of other 

models hinder maintenance actions. 

8. Regulatory compliance: Safety and environmental 

control devices required for regulatory compliance add to 

the complexity and increase maintenance costs. 

COST OF DESIGN FOR MAINTAINABILITY 

The value or worth of any machine resides in its ability 

to generate a return on investment. If a machine has an 

initial cost of "Y dollars, it must produce "Y plus" dollars 

of coal to have a positive worth or value. On this assumption, it is possible to illustrate the cost savings derived 

from improved design for maintainability using simple economic models. 

There are many economic models that can be used to 

compute the worth of equipment. For this discussion, a 

simplified model will suffice. Figure 1 presents an overview of this model. (Readers interested in a more comprehensive treatment are referred to references 8, 15, 16, and 

17.) The following model suggests that the worth (W) of 

a piece of mining equipment can be defined aswhere L = initial purchase price of machine, 

The initial purchase price of the piece of equipment is 

fued or "inelastic." It is set at the time of purchase. The 

price is simply amortized per hour over the useful life of 

the machine. Of course, the more hours of production it 

sees, the lower the amortized cost per hour. 

The cost per hour to operat~ the machine is relatively , 

fured or "inelastic" and composed of the following cost 

elements: 

1. Labor costs for the machine operator(s), support 

personnel, and immediate production supervision. 

2. General overhead costs, which include insurance, 

utilities, royalties, brokerage, and related costs. 

3. Cost of mining supplies and materials. 

4. Other management and administrative costs. 

The cost to maintain consists of the followine; cost ele- - ments, some of which are fuced and some of which are relatively "elastic": 

C = cost per hour to operate machine, 1. Labor costs for maintenance personnel. 

2. Cost of spares, replacement parts, and supplies. 

M = maintenance costs per hour of operation, 3. Loss of production during maintenance. 

4. Cost per hour of idled machine operators. 

and P = production value per hour of operation. 5. Other maintenance-related costs. 
The costs of replacement parts and maintenance supplies are also relatively inelastic. Certain savings can be 

realized with careful buying. The cost of labor and other 

overhead items, on the other hand, are a function of the 

duration of repair time for unscheduled corrective mainte- I 

nance (CM) actions. F 

rY 

More importantly, a reduction in repair time for 0 

downed equipment contributes positively to the overall 3 

worth equation by increasing the time available for pro- 2 duction. Thus, decreased time to repair not only reduces w 

direct maintenance costs, but also increases the production F 

per hour, thereby offsetting other costs. If we look at the C/) 

> maintenance process again, we observe many points at y.) 

which time can be saved through improved design for 

maintenance (fig. 2). Several of these points include1. Prediction of pending failures to facilitate PM 

scheduling. 

2. Decreased fault isolation time. 

3. Reduced component access time. 

4. Decreased inspection and diagnosis time. 

5. Diminished component R/R time. 

6. Reduced test and alignment time. 

A review of underground maintenance task completion 

times at two large mining operations revealed that the 

time required to change hydraulic hoses on continuous 

miners and shuttle cars ranged from 15 min to over 3 h. 

The estimated average time for a failed hydraulic hose 

R/R was over 35 min. Examination of these machines revealed that the time differences were directly linked to 

accessibility of the hose connectors. In several cases, two 

or more nonfailed components had to be removed to access a failed hose connection. 

By relocating several components or rerouting hoses, 

maintenance personnel could directly access over 90% of 

all hydraulic line connections on the surveyed machines. 

This would have reduced the average hydraulic line R/R 

time to well under 15 min per replacement. 

If a maintainability design standard for new or rebuilt 

machines specified that all hydraulic hoses had to be 

7 Logistics 

I su~~ortabilitv A 

MAINTAINABILITY 

Figure 1.-System worth versus maintainability (13). 

Operation KEY 

t Fault detection Task where design 

I 

Improvement reduces 

Equipment down time 

I Fault isolation 

Access part 

Disassemble machine 

I Remove-replace part 

I Reassemble machine V///////////1 

I Test and align 

I Return to service 

MAINTENANCE TASK SEQUENCE 

Figure 2.-Sample maintenance task sequence. 

removed oi replaced in less than 15 min, the average 

repair time for this task could be reduced 50%. Similar Evidence from other civilian and military research efforts 

performance criteria could be developed for other suggest that PM and CM task time reductions of from 

maintenance tasks. The result would be significant 40% up to 70% are achievable with planned maintainreductions in all maintenance task completion times. ability design efforts (15-16). 

PRODUCTIVITY 

Productivity represents the other side of the maintain- and ease with which the mining machine can be repaired 

ability issue. Productivity is a function of the machine pro- and returned to service. The more rapidly a machine can 

ducing coal. Hence, it is directly impacted by the speed be returned to production, the more productive it will be. 
Productivity is expressed in terins of the units (of coal) 600 h/yr x 90,000 kg/h (100 st/h) = 54 million kg/yr 

produced by a machine per unit of time. The greater the 

number of hours the machine is available to produce coal, (60,000 st/yr) per machine increase. 

the more productive it is going to be. For example, suppose that a continuous miner has a rated production ca- If the mine were operating eight miners, this 54 million 

pacity of '07 kg/h (loo st/h). Further, that the kg/yr (60,000 per machine increase would be the 

same miner requires an average of- equivalent of adding another miner with no additional 

1. One hour of PM per shift, and 

2. One hour of CM per shift. 

increase in cost. 

54 million kg/yr (60,000 st/yr) x 8 miners 

Assume that the mine operates the equipment during 

two production shifts per day for 300 d/yr. Hence- = 432 million kg (480,000 st) annual increase. 

(300 h PM + 300 h CM) x 2 shifts = 1,200 h/yr. Actual analysis of the design of three different continuous mining machines during this project suggested that If the CM and PM time could be reduced by 50%, this productivity improvements exceeding the above example would result in the following increase in productivity: could be achieved with relatively simple redesign efforts. 

(1,200 CM and PM h/y) x 0.5 = 600 h/yr savings 

CONCLUSIONS 

The following conclusions were derived from this study 

of maintainability in the underground mining industry: 

1. There is little evidence of the systematic application 

of maintainability design principles, concepts, or criteria 

to the design of operational underground coal mining 

equipment. 

2. Similarly, there is little evidence of systematic 

application of human factors engineering principles, concepts, or criteria being applied to the design of this equipment with respect to maintenance. 

3. Reduced task completion times and fewer maintenance problems were reported for the 10 most frequently 

performed maintenance tasks on older and smaller machines than for newer more complex equipment. This appears to be the result of simpler design on the older 

equipment. 

4. Increased task complexity and completion times 

were generally reported for the newer, larger mining machines. This appears to be the result of increased design 

complexity, larger and heavier components to be handled, 

overlaying of safety and environmental control systems 

over the basic machine design, and inadequate accessibility 

to components. 

5. For certain machines, heavy maintenance tasks could 

be performed on the surface or in high roof underground 

shops equipped with requisite lifting devices. The same 

maintenance tasks were extremely difficult, time consuming, and risky to perform at the mine face, where they 

often have to be completed. 

6. With the exception of machines produced by 1 small 

mining equipment manufacturer, maintenance task completion times for the 10 most frequently performed maintenance tasks could be reduced from 10% to 30% or more 

with relatively simple design improvements. 

7. Application of accepted human engineering design 

standards and criteria could substantially reduce maintenance risk. Over one-third of the reviewed maintenance 

lost-time injuries were traceab!e to equipment design deficiencies. Estimates of actual maintenance risk reduction 

resulting from redesign of the equipment could not be derived from the data. 

REFERENCES 

1. Conway, E. Y., and R L. Unger. Maintainability Design of 3. Conway, E. Y., and R L. Unger. Maintainability Design of 

Underground Mining Equipment (contract 30145034, VRC Corp.). Underground Mobile Mining Equipment. Paper in Annual Review of 

Volume I-Final Technical Report. BuMines OFR 39-91-V1, 1988, Internatio~ial Mining Technology and Development. MINECH 1989. 

35 pp., NTIS PB 91-241885. Volume 11-Maintainability Design 4. Unger, R. L., and E. J. Conway. Maintainability Design of UnderGuidelines. BuMines OFR 39-91-V2,1988,181 pp., NTIS PB 91-241893. ground Mining Machinery. Proceedings of the AL4A/NASA Symposium 

2. . Maintainability Design of Mobile Underground Mining on the Maintainability of Aerospace Systems (Anaheim, CA, July 26-27, 

Equipment. Paper in Human Engineering and Human Resources Man- 1989). AM, 1989. 

agement in Mining. BuMines IC 9145, 1987, pp. 61-65. 
5. Conway, K, and R L. Unger. Design of Mining Equipment for 

Maintainability, Industrial Ergonomics--Case Studies. Ind. Eng. and 

Manage. Press, 1991, pp. 317-334. 

6. Conway, E. J., and R L. Unger. Recommendations Concerning 

the Maintainability of Underground Coal Mining Equipment. Paper in 

Proceedings of the SME Annual Meeting (Phoenix, AZ, 1992). SME, 

1992, pp. 297-308. 

7. Conway, E. J., and W. A. Elliott. Mine Maintenance Material 

Handling: Volume I-Final Technical Report (contract H0113018, Canyon Res. Group, Inc.). BuMines OFR 13(1)-89, 1988, 44 pp.; NTIS PB 

89-168967. 

8. Foster, J., D. Phillips, and T. Rodgers. Reliability, Availability and 

Maintainability. MIA Press, 1981, 265 pp. 

9. Conway, E. J., and M. S. Sanders. Recommendations for Human 

Factors Research and Development Projects in Surface Mining (contract 

J0395080, Canyon Res. Group, Inc.). BuMines OFR 211-83,1982,86 pp.; 

NTIS PB 84-143650. 

10. Taylor, R J. An Introduction to Error Analysis. Oxford Univ. 

Press, 1982, 270 pp. 

11. Christensen, J. M., J. H. Howard, and B. S. Stevens. Field Experience in Maintenance, in Human Detection and Diagnosis of System 

Failures, ed. by J. Rasmussen and W. B. Rouse. Plenum, 1981,363 pp. 

12. U.S. Government Accounting Office. Effectiveness of U.S. Forces 

Can Be Increased Through Improved Weapon System Design. GAO 

Rep. to Congr. PSAD-81-17, 1981, 23 pp. 

13. Rasmussen, J., and W. Rouse (eds.). Diagnosis of System Failures. Plenum, 1981, 363 pp. 

14. U.S. Mine Enforcement and SafetyAdministration (Dep. Interior). 

Analysis of Injuries Associated With Maintenance and Repair in Metal 

and Non-Metal Mines. MESA Inf. Rep. 1058, 1985, 34 pp. 

15. Dhillon, B. S. Human Reliability. Pergamon, 1986, 239 pp. 

16. Dhillon, B. S., and H. Reiche. Reliability and Maintainability 

Management. Van Nostrand Reinhold, 1985, 240 pp. 

17. Bird Engineering-Research Associates, Inc. Maintainability Engineering Handbook. Nav. Ordnance Syst. Command contract 

N00017-68-4403, 1969, 310 pp. 
APPENDIX.-MAINTAINABILITY DESIGN CHECKLIST 

This appendix presents an example maintainability design checklist for coal mining equipment. The purpose of 

the checklist is to provide a summary of design review 

points for the maintainability assessment of new or existing 

underground equipment. It specifically focuses on the 

identification of equipment design features, tasks, or procedures that impact equipment down time, repair costs, labor hours, and maintainer skill level requirements. 

Some of the checklist points are general in nature. The 

checklist was designed to be used across all categories of 

underground equipment. The intent is to draw attention 

to design features and maintenance procedures that will 

increase maintainability requirements. The reader is encouraged to adapt this checklist to site-specific or machinespecific requirements by1. Inserting specific performance criteria for various 

categories of maintenance tasks. For example, all hydraulic lines on a shuttle car should be replaceable in 15 or 

25 min. 

2. Adding or deleting checklist items for different categories of equipment. Environmental control equipment, 

for example, would be included on face equipmen1 and not 

on shuttle cars or mantrips. 

3. Adding additional checklist items based on site or 

equipment specific maintenance histories or experience, 

company maintenance standards, or other factors. 

Guidance on how to develop local maintenance standards is provided in the USBM final report "Maintainability 

Design of Underground Mining Equipment" (1). Several 

definitions are provided to clarify items in the actual 

checklist. These includeI. Primary maintenance zone: The zone or area 

from the side or the end of a mining machine inward 45 

cm (18 in). 

2. Secondary maintenance zone: The area from a 

point 45 cm (18 in) from the side or end of the machine 

to a point 45 cm (18 in) from the opposite side or end of 

the machine. 

3. Tertiary maintenance point: A maintenance point 

outside the primary and secondary maintenance zone. An 

example would be a lubrication point on the end of a conveyer boom. 

4. Immediately accessible: A component that can be 

reached, removed or repaired without having to open access covers, remove other components, or disassemble 

other components. 

5. Maintenance point: Any point on the machine 

wherea. Two components are joined, or 

b. A component is mounted on the machine 

chassis, or 

c. Where hoses, cables, and lines are attached to a 

component. 
MAINTAINABILITY DESIGN CHECKLIST FOR UNDERGROUND COAL 

MINING EQUIPMENT 

GENERAL MAINTENANCE REDUCTION 

Hydraulic hoses, electrical cables, and water hoses are securely attached along their length to protect 

against abrasive wear, pinching, or other damage. 

All cables and hoses are protected to minimize exposure to impact or fall of roof damage. 

Power feed cables enter the machine or the cable reel from the side to minimize exposure to vehicle 

wheels or tracks. 

All components, systems, and devices are located where they are protected from fall of roof damage. 

All exterior mounted machine features and components are protected from impact, scraping, or 

collision damage. 

Operator controls and displays are protected from impact, fall of roof damage, or inadvertent 

activation. 

Components subject to wear are designed for self-adjustment where possible. 

Where self-adjustment is not practical, the design provides components that can be manually adjusted 

for wear to minimize the need to tear down. 

Design provides for a self-lubricating system for all bearings, joints, and other wear points on the 

machine. 

Design provides for bearings and seals with wear or failure monitoring capability to permit 

scheduling of maintenance prior to actual component failure or component damage. 

Design provides hour meters (e.g., on conveyer circuits), volt meters and ammeters (e.g., on electric 

drive motors) to assist in wear assessment and maintenance management. 

Design provides for gears, bearing, hydraulic cylinders, and other impact or load-absorbing 

components of sufficient size or rating to handle peak impact loads. 

Design provides for adequate derating for bearings, motors, and hydraulic systems to minimize 

overload related failures. 

Vehicle frame is adequately designed to prevent cracking or other fatigue-induced failures at: 

Hydraulic cylinder attachment points. 

. Articulation polnts. 

YES 

ADEQUATE 

NO 
MAINTAINABILITY DESIGN CHECKLIST FOR UNDERGROUND COAL 

MINING EQUIPMENT 

GENERAL MAINTENANCE REDUCTION (Cont.) 

Other frame load-bearing points. 

b Welded seams. 

Provides for shock and vibration isolation of critical components. 

Interlocks are provided to prevent vehicle from being trammed or moved with components deployed 

or extended that are easily damaged: 

Stab jacks. 

b Drill booms. 

b Tail booms. 

b Automated temporary roof support (ATRS) components. 

b Cutting heads. 

b Canopies. 

Protective covers are over all body cavities containing components, hoses, lines, or maintenance 

points to prevent buildup of muck and debris. 

Expanded metal grating is used for floors or other designs to prevent accumulation of water, mud, 

and other materials in equipment bays, crevices, and body cavities. 

Rubber tires are protected by fenders, bumpers, or guards from collision and rib impact. 

Mechanical linkage systems are protected from impact and fall of roof. 

Roof bolter geometry is designed to prevent overelevation damage to boom lift mechanism. 

Disc and drum-type brake systems and components are protected from coal dust, rock, and other 

debris to minimize wear and damage. 

Mounting holes and brackets are designed to permit installation of functionally similar parts 

produced by different manufacturers. 

ADEQUATE 

YES NO 
MAINTAINABILITY DESIGN CHECKLIST FOR UNDERGROUND COAL 

MINING EQUIPMENT 

SAFETY AND ENVIRONMENTAL SYSTEM DESIGN ADEQUATE 

FEATURES 

YES NO 

Required safety equipment is properly installed and protected, but easily accessed for repair: 

. MSHA-required lighting. 

. Fire suppression system. 

. Panic bars. 

. Methane detectors. 

Dust control equipment is located for easy inspection and servicing: 

. Dust bins and filters are easily accessed, opened, and serviced. 

. Water spray nozzles are easily accessed for adjustment or replacement. 

. Fan motors are readily accessed for repair or replacement. 
MAINTAINABILITY DESIGN CHECKLIST FOR UNDERGROUND COAL 

MINING EQUIPMENT 

DESIGN STANDARDIZATION FEATURES 

Design provides for standardization of the following items throughout the machine: 

. All mechanical components. 

. Hydraulic connectors, valves, hoses. 

Electrical components and connectors. 

. Water hoses and connectors. 

. Fasteners and other attachment devices. 

. Bolts, nuts, and fasteners. 

ADEQUATE 

YES NO 
MAINTAINABILITY DESIGN CHECKLIST FOR UNDERGROUND COAL 

MINING EQUIPMENT 

ADEQUATE 

DESIGN FEATURES FOR ROUTINE MAINTENANCE 

YES NO 

Routine service points are clustered in one or two service locations in the primary maintenance zone 

including: 

Lube points. 

. Hydraulic reservoir tank fill points. 

. Hydraulic filters. 

Environmental system filters. 

Fuel tanks on diesel-powered equipment. 

. Belt or chain adjustments. 

Line bleed valves. 

Fluid-level indicators are provided on fluid reservoirs and in the primary maintenance zone for ease 

of inspection. 

Routine inspection points are all clearly visible and labeled including: 

. Relief valves. 

. Drain plugs. 

Wear points. 

. Hydraulic line connections. 

. Personnel safety equipment. 

Test points for stand-alone or built-in test equipment are located in the primary maintenance zone. 

All mechanical adjustment points are located in primary maintenance zones. 

Quick connect type couplers are installed on frequently changed hydraulic lines, water hoses, and 

cables. 
MAINTAINABILITY DESIGN CHECKLIST FOR UNDERGROUND COAL 

MINING EQUIPMENT 

DESIGN FEATURES FOR ROUTINE MAINTENANCE 

(Cont.) 

Quick-release fasteners are used on doors or covers for routine inspection points. 

Only one type of hydraulic fluid is used on the machine. 

Oil seals are easy replaceable types. 

Design reduces to a minimum the number of spare parts and components required to support 

maintenance: 

. Common hoses. 

. Connectors. 

. Valves. 

. Drive belts, chain, etc. 

. Cables. 

. Nuts and bolts. 

. Washers. 

Routine service points are not located behind other components or structural members, in enclosed 

spaces. or in the secondary maintenance zone (e.g., more than 46 cm (1 8 in) from the side or the end 

of the machine). 

ADEQUATE 

YES NO 
MAINTAINABILITY DESIGN CHECKLIST FOR UNDERGROUND COAL 

MINING EQUIPMENT 

DESIGN FEATURES FOR TROUBLESHOOTING 

General design and layout provides for rapid and positive identification of component malfunction: 

. Fluid leaks. 

. Pressure loss. 

. Shorts. 

General layout facilitates visual inspection of major components, connections, couplers, interfaces, 

and potential damage points. 

Hydraulic, electrical, and mechanical system schematics permanently affixed to machine to facilitate 

troubleshooting. 

Hydraulic, electrical, and other systems can be easily traced throughout the machine. 

The following pertinent information is immediately available to the maintainer: 

. Component or system identification. 

. Proper direction of motion or fluid flow. 

. Proper adjustment, pressure level, or setting. 

. Correct fluids. 

Amperage and other electrical information. 

Self-checking features are designed into critical components or systems where possible: 

. Major hydraulic systems. 

. Cooling systems. 

. Electrical circuits. 

All mechanical interfaces are visible froni the sides or end of the machine. 

ADEQUATE 

YES NO 
MAINTAINABILITY DESIGN CHECKLIST FOR UNDERGROUND COAL 

MINING EQUIPMENT 

DESIGN FEATURES FOR TROUBLESHOOTING (Cont.) ADEQUATE 

YES NO 

Manual test points are located in the primary maintenance zone for all critical systems or subsystems. 

Test points are designed to eliminate or minimize the need to remove components for testing. 

Locate test points in one or two locations where practical or in a single test panel. 

Test points are coded or labeled to identify recommended or acceptable pressure, temperature, or 

voltage ranges. 

Test points are labeled and are located close to the control or display they are associated with. 

Built-in test capability andlor test equipment provided to monitor wear on critical bearings or other 

wear points such as: 

. Continuous miner cutterhead. 

. Gathering arms. 

. Articulation bearings on scoops. 

. Hydraulic pumps. 

Test set instructions for built-in test equipment (BITE) are attached to the machine at the point of 

service. 

Automatic test equipment (ATE) sensors are provided that operate without disturbing or loading the 

system under test. 

Fail-safe design for all ATE where failure of test equipment will not cause failure of the mining 

machine. 
MAINTAINABILITY DESIGN CHECKLIST FOR UNDERGROUND COAL 

MINING EQUIPMENT 

DESIGN FEATURES FOR REPAIR AND REPLACEMENT ADEQUATE 

YES NO 

Provisions are made for adequate towing or movement of disabled machine to maintenance area: 

Tow cable attachment points. 

t Designated push points. 

. Tow bar attachment points. 

Design features are incorporated to facilitate jacking, hoisting, or lifting of machine to expedite 

maintenance and repair: - 

. Designated jack points with jack plates designed to prevent jack slippage. 

Attachment points for overhead lifting devices. 

Design features are incorporated to facilitate lifting, hoisting, or manipulating heavy components and 

machine features: 

. Built-in attachment hooks. 

. Lift bolt attachment points. 

Lifting guides or pins. 

Provisioris for forklift arms. 

. Built in swing boom arm. 

. Designat~A lift points. 

All areas of the machine are designed to be self-cleaning and designed to eliminate (minimize) the 

accumulation of rock, coal, mud, and water. 

All components are labeled to positiS:ely identify part number-type, component ratings, types of 

lubricant-fuel required, direction of flow, and orher pertinent information. 

All components and interfaces are designed to be installed only one way - the correct way. 
MAINTAINABILITY DESIGN CHECKLIST FOR UNDERGROUND COAL 

MINING EQUIPMENT 

DESIGN FEATURES FOR REPAIR AND REPLACEMENT 

(Cont.) 

Design eliminates the need for special tools or jigs to perform required maintenance. 

All major parts used are readily available from local suppliers or vendors. 

All mounting bolts are directly accessible and unobstructed to permit use of required hand tools 

without having to remove or disassemble adjoining components. 

ADEQUATE 

YES NO 
MAINTAINABILITY DESIGN CHECKLIST FOR UNDERGROUND COAL 

MINING EQUIPMENT 

VISUAL INSPECTIONS AND ACCESSIBILITY 

All maintenance points should be visually accessible from the side or the end of the machine and 

should provide line-of-sight inspection capability. 

Design provides for clear and rapid visual identification of parts that may have to be replaced or 

repaired. 

Approved glass covers should be installed in all access opening covers if routine visual inspection of 

maintenance points are required. 

Access openings should be large enough to permit visual contact with the component being worked 

on while the work is being performed. 

Visual access openings should not be located on the top of machines unless the average roof height 

I 

above the top of the machine is 61 cm (24 in) or more. 

Visual access openings should never be located under the main chassis of the machine or behind 

other components that may restrict visibility. 

For less frequently performed maintenance tasks, the maintenance point may be located behind a 

protective cover. The component, however, should be directly visible when the pro:ective cover is 

removed. 

Maintenance and service points should be located no further than 91 cm (36 in) from the 

maintainer's head at time of inspection. 

ADEQUATE 

YES NO 

-- 
MAINTAINABILITY DESIGN CHECKLIST FOR UNDERGROUND COAL 

MINING EQUIPMENT 

DESIGN FOR PHYSICAL ACCESSIBILITY ADEQUATE 1-1 - - - -- 

All components are accessible from the side or the end of the machine. 

All drain valves for compressor tanks, reservoirs, and sumps are accessible from the slde or end of 

the machine. 

All other maintenance points are accessible from the sides or ends of the machine. I I 

A11 components that require repair, replacement, or adjustment every 2,000 h or less should be 

directly accessible (can be removed-replaced without having to remove other components) from the 

sides or ends of the machine. 

For components that must be disassembled to be repaired or inspected (e.g., bearings), no more than 

four R/R task steps (e.g., remove par? A, remove part B, etc.) should be required to access the 

targeted part. 

i 

For components with an expected service life of over 2,000 h, only one other component should 

have to be removed to access for removal or replacement (RIR). 

All components weighing more than 23 kg (50 Ib) or more should be removed frorri the side or the 

end of the machine and should not have to be lifted up and over the machine frame or other 

componen ts. 

I 

Hinged or quick-release access opening covers should be used where practical with the hinges on the 

side or bottom so that door will remain open during maintenance. I 

A minimum number of bolts or fasteners should be used on access covers, equipment bay doors, or 

other pr0tective:shielding. 

I For components weighing more than 45 kg (100 Ib), access openings and workspace should be 

sufficient tc permit the attachment of hoisting or lifting devices. I 

Access openings should be sufficiently large to permit removal and replacement of all components 

contained in that area. 

Screws, nuts, and bolts should be located to permit use of requisite hand tools to remove or replace 

them. 

Nonhinged access opening covers weighing more than 23 kg (50 Ib) are designed with built-in 

handles or lifting device attachment points. 

1 

I All components can be removed and replaced in a straight line from their place of attachment. 

(Components do not have to be maneuvered around or over structural features or components.) - - 

Design provisions are made to support components weigh~ng over 23 kg (50 lb) while they are being 

unbolted or bolted into place. 

i - 
1 MAINTAINABILITY DESIGN CHECKLIST FOR UNDERGROUND COAL 

MINING EQUIPMENT 

HYDRAULIC SYSTEM MAINTENANCE DESIGN 

Fluid reservoirs have adequate storage capacity to ensure uninterrupted operation between shifts. 

Dual in-tank or stand-alone filters are installed on each fluid system to minimize component and 

control valve wear. 

Hydraulic system filters are located in the primary maintenance zone and use permanent or cartridgetype filters. 

Hydraulic meters and gauges are located in the primary maintenance zone. 

Quick-disconnect-type hydraulic line connectors are used where practical. 

Hydraulic systems are designed to be fail safe with the system or components reverting to a safe or 

neutral position in event of loss of power. 

Hydraulic circuits are permanently labeled to identify circuit, direction of fluid flow, recommended 

pressure settings, and high- and low-pressure lines. 

All hydraulic valves are labeled to positively identify the system-subsystem operated by that valve; 

the label should not be on the valve itself. 

Design uses seals that are visible after installation to ensure that they are not inadvertently left out 

during maintenance. 

Design uses armor-coated flex hoses where hoses are subject to abrasive wear or impact damage. 

Design provides for automatic bleeding of major hydraulic system(s). 

Physically incompatible connectors are specified where there is a danger or mismating connectors 

from adjoining systems. 

Design provides metal shielding to protect electrical and other sensitive equipment in the event of 

hydraulic fluid leak. 

Design prevents the accumulation of hydraulic fluids in the event of leaks or hose breaks. 

Design provides for hydraulic system drains at the lowest physical level in the system. 

Hydraulic system fittings and valves are staggered to provide improved access to each system's 

connectors. 

YES 

ADEQUATE 

NO 
MAINTAINABILITY DESIGN CHECKLIST FOR UNDERGROUND COAL 

MINING EQUIPMENT 

MECHANICAL SYSTEM MAINTENANCE DESIGN 

Design provides for minimum manual adjustment of all mechanical systems, except to correct for 

wear. 

Self-adjustment designs are incorporated where practical. 

Adjustments that cannot be designed out should: 

Be completed without the requirement to disassemble the unit. 

Be reduced to the minimum number of steps possible to complete. 

Not require removal or replacement (RR) of other components to complete. 

c Be incorporated into other required maintenance on the same component. 

Incorporate range limits to prevent over-adjustment damage. 

Design precludes the need for special tools or hardware to install, adjust, or align mechanical 

components. 

Components and mechanical interfaces are designed with the minimum number or pivots, bearing 

surfaces, and other moving part wear points to minimize maintenance requirements. 

Mechanical system locks or locking devices are incorporated wherever mechanical locking is 

required for maintenance. 

Design avoids the use of through bolts for installation or assembly where the nuts are not accessible 

to the maintainer. 

Design locates high-failure-rate components outboard in the primary maintenance zone. 

Design provides for coverings or boots for exposed connectors, universal joints, and other 

interacting mechanical parts to protect them from mud, coal dust, and other debris. 

ADEQUATE 

YES NO 
MAINTAINABILITY DESIGN CHECKLIST FOR UNDERGROUND COAL 

MINING EQUIPMENT 

ELECTRICAL SYSTEM MAINTENANCE DESIGN ADEQUATE 

YES NO 

Design provides overload or other electrical protective devices for all major electrical circuits, each 

of which is equipped with a "kickout" indicator light for easy troubleshooting on: 

Drive, conveyor, cutterhead, and gathering arm motors. 

Lighting. 

r Electric power takeoffs. 

Design routes all electrical cables on machine to avoid damage from abrasion, pinching, or cutting. 

All electrical cabling is routed to permit easy removal and replacement. Cabling is not routed under 

machine chassis, in the center of boom arms, or in other difficult-to-access locations. 

Electrical connectors are isolated from hydraulic fluid leaks, fuels, water, and other liquids. 

Quick-disconnect-type electrical connectors are used where possible. 

All electrical equipment cabinets are equipped with interlock that terminates power to the unit when 

the access cover is removed. 

A manual override is provided for all cabinets equipped with shutoff interlock. 

Breakers and other overload protective devices are in a central location in the primary maintenance 

zone. 

Electrical connector pin patterns are coded to permit connecting cables only to the appropriate 

receptacle. 

Uses electrical plugs in which the alignment pins extend beyond the electrical pins. 

Design makes receptacles "hot" or "cold." 

Uses contact pins no larger than 30 cm (12 in) to resist being bent upon insertion and withdrawal of 

the connector. 

Design uses right-angle plugs to avoid sharp bends in the electrical cable. 
MAINTAINABILITY DESIGN CHECKLIST FOR UNDERGROUND COAL 

MINING EQUIPMENT 

PERSONNEL PROTECTIVE EQUIPMENT MAINTENANCE ADEQUATE 

YES NO 

Personnel protective equipment is designed and located to facilitate inspection, repair, and 

replacement of the following systems: 

t Dust control. 

Methane monitoring. 

Operator protective canopy (as required). 

Operator panic bars. 

Emergency power cutoff devices. 

.................... 
MAINTAINABILITY DESIGN CHECKLIST FOR UNDERGROUND COAL 

MINING EQUIPMENT 

DESIGN FOR MECHANICAL SAFETY 

Protective guards are provided on or around all moving mechanical parts adjoining to where 

maintenance personnel will be working. 

Mechanical lockout devices are provided where maintenance must be performed at location that 

exposes maintainer to moving components (e.g., under a cutterhead). 

Design prevents components from slipping or falling as they are being unbolted for repair or 

replacement. 

Mechanical components are located to prevent maintainer from being exposed to energized 

equipment, hazardous fumes, hot surfaces, or other hazards during repair operations. 

Mechanical components that require the use of heavy springs are designed so that the springs cannot 

inadvertently dislodge, causing damage or personnel injury. 

Design provides for warning plates where mechanical assemblies, linkages, or components are under 

high strain or loading. 

Design routes hot exhaust pipes away from locations where routine maintenance will be performed. 

Design prevents failure of high-stress-loaded component from damaging other components or 

injuring personnel. 

ADEQUATE 

YES NO 
167 

MAINTAINABILITY DESIGN CHECKLIST FOR UNDERGROUND COAL 

MINING EQUIPMENT 

STORAGE BATTERY MAINTENANCE ADEQUATE 

YES NO 

I Design isolates routine machine maintenance paints from battery fumes. I 1 

Design prevents leaking battery acid from accumulating in equipment compartments or operator 

station. 

I 

Batteries are installed in a location that permits use of overhead lifting device to remove or replace 

them. 
INEXPENSIVE, EASY TO CONSTRUCT MATERIALS-HANDLING 

DEVICES FOR UNDERGROUND MINES 

By Richard L. ungerl and Kirk conwayz 

ABSTRACT 

The U.S. Bureau of Mines (USBhI) has developed and site. The six devices include scoop-mounted lift boom, 

tested designs for six materials-handling devices for use in swing-arm boom, heavy component lift-transport, mine 

underground mines to redilce materials-handling injuries. mud cart, container-work station cart, and timber car. 

Particular attention was focused on making the designs This paper presents a brief discussion of that work and 

practical, low cost, and easily fabricated to be broadly the six devices. It is intended for mine operators who wish 

applicable in underground operations. Where possible, the to make use of the design concepts to manufacture similar 

designs were simplified so that off-the-shelf components devices for use in their mines. 

could be used to permit fabrication by mine personnel on 

Manual materials handling represents a critical and per- evaluation. Complete plans for the devices are available 

sistent source of personnel injuries in undcrground coal in USBM Information Circular (IC) 9212.3 

mining operations. On an annual basis, such injuries 3~onway, E. J., and R. L. Unger. Material Handling Devices for Unrepresent the largest category of nonfatal, lost-time in- derground Mines. BuMines IC 9212, 1989, 48 pp. 

juries, accounting for 35% of all lost-time injuries in 1983 

and 1984, according to an analysis of U.S. Mine Safety and 

Health Administration (MSHA) data. Approximately 26% 

of all injuries related to manual materials handling are 

associated with the performance of mine maintenance or 

equipment maintenance tasks (fig. 1). 

In the mid-19809s, as part of its program to improve health and safety conditions in mines, the 

USBM conducted a research program that addressed the 

materials-handling problems of mine maintenance and 

equipment maintenance. During the course of the project, 

a detailed analysis of mine- and machine-related tasks was 

completed and sources of injuries were identified. Concepts for simple materials-handling devices that could 

replace manual handling were then developed and evaluated. Six of these devices were fabricated and delivered 

to operational underground coal mines for testing and 

'civil engineer, Pittsburgh Research Center, U.S. Bureau of Mines, Figure 1.-Most materials handling IS done manually in unPittsburgh, PA. derground coal mlnes, whlch Is part of the reason It is the leading 

2~enior staff scientist, VRC Corp., Monterey, CA. cause of Injuries year after year. 
SUMMARY OF DESIGN RATIONALE 

The work described in USBM IC 9212 specifically addressed materials-handling tasks related to mine maintenance and equipment maintenance performed in underground coal mines. Surface materials-handling tasks and 

the transporting of supplies or materials from the surface 

to the operating section were outside the scope of this 

effort. 

MINE AND EQUIPMENT MAINTENANCE 

Representative mine maintenance tasks included1. Installation or removal of ventilation, electrical, 

communications, or compressed-air systems. 

2. Installation of timbers, cribbing, and other supplemental materials used in roof or rib control. 

3 Track installation, repair, and retrieval. 

4. Rock dusting, installation of air-control screens, and 

electrical wiring installation of warning or other systems. 

Typical machine maintenance tasks falling within the scope 

of this project included1. Removal or rcplacenlent of bclt drives, head, pumps, 

drive motors, and other major machine parts on stationary 

equipment. 

2. Assembly, installation, and repair to mine equipment, including mobile face equipment. 

3. Routine servicing of mining equipment. 

All underground coal mine seam heights were included 

in this study. However, emphasis was placed on midseam 

to lower seam coal mines (under 147-cm (58-in) seam 

height) because preliminary data suggested that the highest 

risks of manual materials-handling injuries were to be 

found in those seam heights. The study included a review 

of relevant materials-handling literature and past USBM 

programs, visits to six operating coal mines, and an 

extensive analysis of MSHA's accident database. 

The mine maintenance and equipment maintenance 

tasks investigated involved, by their very nature, the 

manual handling of supplies and equipment components. 

Individual modules of items handled might range in weight 

from a few to several thousand kilograms. Because of the 

operational constraints in underground coal mines, these 

materials and components often have to be manually 

moved from the supply dropoff point to the place where 

they will actually be used or installed. 

Components used in equipment maintenance are typically hoisted onto a railroad car, scoop bucket, or maintenance jeep on the surface. They are then transported to 

the section where the disabled machine is located. At that 

point, they are manually lifted off the rail car or jeep or 

ejected out of the scoop bucket and manually carried to 

the installation position. Occasionally, hoists or comealongs are attached to roof bolts to aid in this process. 

Replaced components are then manually loaded into the 

transport vehicle for shipment to the surface. 

Mine maintenance materials (e.g., timbers, rock dust 

bags, roof bolts, etc.) are typically loaded in bales or via 

pailets onto railcars or into scoop buckets for shipment to 

or near the working section. At the end of the rail line, 

the bales or pallets are broken down for manual loading 

into scoops or onto other transport vehicles for delivery to 

work locations. (One mine visited had rubber-tireequipped railcars that could be detached at the end of the 

rail line and towed by battery-powered vchicle to the work 

locations or section supply areas.) Once the materials are 

dumped near the work location, miners manually carry 

them to the maintcnance point for use. These maintenance personnel may lift materials weighing 23 to 226 kg 

(50 to 500 Ib) continually on a daily basis. They handle 

materials (sections of rail or steel arches) weighing 454 kg 

(1,000 lb) or more on a monthly or more frequent basis. 

Analyses of materials-handling injuries in the six mines 

visited indicated that1. Thirty-nine percent of all mine maintenance and 

35% of all machine maintenance injuries involved the 

lower back. 

2. Forty-five percent of all mine and 39% of all machine maintenance accidents were the result of overexertion. 

3. Sixty-eight percent of mine maintenance injuries 

involvcd handling timbers, posts, caps, and cribbing materials, while 32% of the machine-related accidents involved 

handling metal machine components. 

MECHANIZATION REQUIREMENTS 

The desigil implications of these and other findings 

revealed during studies of materials-handling tasks related 

to mine and equipment maintenance can be summarized 

by the lollowing mechanization needs: 

I. Devices to lift or lower and rotate machine components weighing up to 1,361 kg (3,000 lb) for removal from 

and replacement on mining equipment. 

2. Devices to lift or lower components of up to 226 kg 

(500 Ib) in and out of scoops, off railcars, and on or off 

other mobile vehicles. 

3. Carts or other devices to transport small quantities 

of materials weighing up to 226 kg (500 Ib) from storage 

areas or railheads to working sections. 

4. A device to raise and support crossbeams for temporary roof support while permanent roof supports are 

installed. 
Six materials-handling devices were developed to fulfid 

these needs. Particular attention was focused on making 

the designs practical, low cost, and easily fabricated so 

as to be broadly applicable in underground operations. 

Where possible, the designs were simplified and off-theshelf components used to permit fabrication of the devices 

by mine personnel on site. 

The devices discussed in this paper are not intended to 

be final designs. Rather, they are working prototypes that 

have been field evaluated and are presented herein in the 

hopes of stimulating other innovative designs on the part 

of mine personnel. 

The six devices include1. Scoop-mounted lift boom. 

2. Swing-arm boom. 

3. Heavy component lift-transport. 

4. Mine mud car. 

5. Container-work station vehicle. 

6. Timber car. 

Functions performed by, and design specifications for, each 

of these devices are discussed in the following section. 

PROTOTYPE MATERIALS-HANDLING DEVICES 

SCOOP-MOUNTED LIFT BOOM To address these requirements, a lightweight, removable, 

storable lift boom was designed (figs. 4-5). This boom can 

One of the major identified needs was for a simple be installed at various locations on maintenance carts or 

boom device to lift and transport components weighing up on mining machines themselves. The height of the boom 

to 1,361 kg (3,000 Ib) in the underground environment. can be varied by quickly changing the boom leg. The 

The device had to be mounted on a powered mobile ma- inexpensive mounts can be permanently welded at varichine and installed and removed quickly to minimize ous locations on the machine frame and are designed to 

production down time for the machine. This tool would 

be used for transporting and maneuvering heavy machine 

components such as a continuous miner head. 

A quick-mount-dismount lift boom device was developed for installation on the front of a small scoop with its 

bucket removed (figs. 2-3). 

The design features of the scoop-mounted lift boom 

include1. A 1,361-kg (3,000-lb) lift capacity. 

2. Manual or powered lift capability. 

3. Installation and removal in 5 min or less. 

4. Ready storage in working section or on mobile 

machinery. 

Four attachment points secure the lift boom to the 

scoop lift mechanism by means of four pins. The pins 

correspond in size and location to the pins used to secure 

the scoop bucket. The overhead design of the lift boom 

permits lifting or lowering of components being handled. 

The bucket tilt mechanism provides up and down maneuvering of the components, while the scoop's normal steering permits lateral and forward and reverse maneuvering. 

SWING-ARM BOOM 

Accident and biomechanical analyses suggested the 

need for a simple swivel crane or boom device to lift components on and off transport vehicles and to assist in ma- Figure 2.-Testing rcoopmounted lift boom at Pittsburgh Ra 

neuvering heavy machine components in confined spaces. search Center. 
Figure 3.--Scoop-mounted lift boom during surface tests. 

Flgure 5.--Crane Is easily mounted In Its removable base. 

Figure 4.--Machine-mounted swivel crane during underground 

tests. 

resist damage during normal machine operation. Two or 

more quick mounts can be installed on the same machine 

to permit access to all machine locations. 

Design features of the swing-arm boom include1. Load capacity of 227 kg (500 lb). 

2. Boom height range from 61 to 173 cm (24 to 68 in), 

depending on leg length. 

3. Arm radius of 61 to 122 cm (24 to 48 in). 

4. Mounting and stowing without tools. 

5. Light weight for carrying by one person. 

HEAVY COMPONENT LIFT-TRANSPORT 

Another identified need was for a floor-type maintenance jack that could be used to lift heavy machine 

components from the bottom, transport them over short 

distances, and lift them into position for installation. 

Saddles on the lift point could be designed to permit 

additional maneuvering of the component during actual 

installation. This type of device could be used, for 

example, to install drive motors under the nonremovable 

fenders in shuttle cars. 

The heavy component lift-transport prototype is shown 

in figures 6 and 7. The device utilizes a standard hydraulic 

floor jack to provide the lift mechanism. The jack head 

itself is tiltable and rotatable to permit close-in maneuvering. The jack mechanism travels along the device frame 

by means of a sump drive mechanism. This motion permits forward-backward movement of handled components 

and balancing of components over the lift-transport device 

wheels during travel. The long handle permits the use 

leverage by which to maneuver loads up and down or sideways, as required. Dual tires or oversized balloon tires 

increase the device's stability and permit easy movement 

over uneven floors. 
MINE MUD CART 

One of the basic problems faced by all miners is that of 

moving machine components or supplies such as concrete 

blocks from the supply storage area to 'the point of use. 

If a powered vehicle is not available, the task must be accomplished manually. The intent of this concept was to 

design a small, manually pulled cart that could transport 

up to 408 kg (900 Ib) of materials over a short distance. 

The mine mud cart has the following design features: 

1. Narrow width to permit passage by a parked mining 

machine. 

2. Tandem design to prevent tipover if one unit is 

loaded and the second is empty. 

Flgure 6.4eavy component lift-transport durlng testing wlth 3. Balloon tires for transit through mud or water and 

680-kg (1,500-lb) concrete block. over mine floors. 

4. Handle designed for pulling by one or two people. 

Flgure 7.-llre-changlng attachment ellmlnates manual handllng of heavy wheels durlng replacement 

The design features of the heavy component lifttransport include1. Up to 454-kg (1,000-lb) lift capacity. 

2. Balloon tires for ease of transporting manually. 

3. A standard automotive floor jack for the lift 

mechanism. 

4. Ability to lift and maneuver a heavy component as 

it is being removed or replaced on a mining machine. 

5. Jack head that can be trammed forward or back on 

the frame for close-in maneuvering or for load balancing. 

Figure 8 illustrates a tandem cart concept using eight 

wheels. The vehicle can also be fabricated as a single cart. 

CONTAINER-WORK STATION VEHICLE 

Hand tools and supplies required to perform most 

maintenance tasks in a section can be mounted on a transportable container. This concept is for a device that 

allows a single manually powered mechanism to lift and 

transport such containers (figs. 9-10). There are many 

uses for the containers themselves, such as tool station, 

lubrication module, rock dust unit, fire and safety equipment storage, repair work station, and cable-splicing 

module. 

To move the container around the working section, the 

transporter is positioned around the container and a lift 

mechanism raises it off the floor and positions the load 

sightly ahead of the axle. The load is carried by the 

wheels while the operator controls motion by pulling, 

steering, and balancing the unit on its axle. 

~esign features of the container-work station include1. Rapidly interchangeable containers that can be 

picked up or dropped off as required. 

2. Containers that can be used as secured storage units 

when dismounted from the vehicle. 

3. Up to 454-kg (1,000-lb) load capacity. 

4. Adjustable ground clearance. 

5. Balloon-type tires for easy transporting on unimproved mine floor. 

6. A tow bar that can be adapted for towing behind 

utility vehicles. 
TIMBER CAR 

One of the most hazardous materials-handling tasks in 

underground mining is that of installing crossbeams for 

roof support. A need was identified for a mechanism to 

lift beams weighing up to 227 kg (500 lb) to the roof, 

where they could be held in place until permanent supports could be installed (figs. 11-12). The device shown in 

the figures utilizes a modifred hydraulic floor jack to provide the lift. The jack mechanism is moved manually 

along a track down the center of the car. This forwardbackward movement permits easy positioning of the load. 

In addition, the jack head rotates to ease positioning of 

extra-long members. 

Figure 8.4ine mud caR 

Figure 11.-Timber car durlng underground tests at Pittsburgh 

Research Center's safety research coal mine. 

Figure S.-Contalner-work statlon vehicle. 

Flgure lO.-Contalner is easily removed from frame of vehicle. 

Containers with specialized functions may then be attached. 

Figure 12.4iners using tlmber car to raise 39-kg (85-lb) rail 

for roof support in an eastern Ohio coal mine. 
Design features of the timber car include1. Up to 227-kg (500-lb) lift capacity with a 152-cm 

(60-in) lift height (suitable for low- to medium-seam 

mines). 

2. Mounting on a low-profile flatcar, which serves double duty as a 36,287-kg (40-st) capacity supply car. 

CONCLUSIONS AND 

On-site visits, task analyses, and interviews suggest that 

the majority of the risk exposure associated with materials 

handling in underground coal mines results from the lack 

of properly designed and easily accessible materialshandling tools, devices, and vehicles. Mine personnel traditionally rely on a "couple of extra hands" or on crowbars, 

come-dongs, and other makeshift tools to handle even the 

largest components of mining machinery. Similarly, due to 

the lack of appropriate tools, carts, and other handling 

devices, mine personnel manually move timbers, posts, 

beams, and other heavy materials on a continual basis. In 

most instances, tools are simply not available for these 

heavy lifting, transporting, and positioning tasks. 

These investigations also revealed that what is needed 

is not another complex, powered vehicle designed to perform any and all maintenance jobs. Rather, what is required is a series of simple, task-specific tools, aids, and 

devices to be housed and used in the working sections and 

maintenance areas. Mine personnel tend not to wait 30 to 

60 min while a special vehicle or tool is brought in from 

another area of the mine. The materials-handling hardware should be relatively easy to fabricate and should, 

where possible, utilize off-the-shelf components. The 

hardware should be relatively inexpensive and designed for 

fabrication in mine shops. The prototypes of six such 

devices that were developed and tested by the USBM are 

described in this paper. 

There appears to be a sincere interest on the part of 

mine management and safety and production personnel in 

reducing injuries related to materials handling. There is 

also a need for exposure to new ideas, products, and 

materials-handling mechanization concepts to assist mine 

personnel in identifying their own unique handling requirements and developing appropriate mechanical solutions to 

these problems. The concepts presented here were designed to stimulate the development of other mechanization concepts to address mine-specific materials-handling 

problems. 

Three major recommendations are suggested with respect to development of materials-handling devices: 

1. Systems Approach to Materials Handling.-Many 

larger mines have developed so-called systems for moving 

huge quantities of supplies and materials from surface 

storage areas to in-mine drop points or supply depots. 

These systems, however, have many missing elements and 

3. A modified automotive floor jack for the lift mechanism. 

4. Jack that can be maneuvered forward or back in its 

track for close-in maneuvering. 

RECOMMENDATIONS 

built-in problems. For example, pallets are utilized to load 

quantities of 41-kg (90-lb) cement blocks or 45-kg (100-lb) 

bags of rock dust from the storage onto the supply train. 

Forklifts or hoists may be used to offload the pallets at the 

dropoff points. However, person~el must manually load 

these supplies onto battery-powered vehicles or physically 

lug them to the point of use. This systems-approach thinking has failed to account for the fact that the blocks still 

weigh 41 kg (90 lb) and the bags 45 kg (100 lb) apiece 

when they get into the mine. These loads are too heavy 

for personnel working in confined workspaces and on unimproved mine floors. If a systems approach is to be used, 

it should start with the end user or task and work backward from there. 

2. Task-Spec@ Tools.-As in any industry, the design 

of special tools to perform specific tasks is often overlooked. In underground mining, few if any tools or devices have been developed to cope with specific materialshandling tasks. Exposure to high-risk tasks could be substantially reduced if appropriate task-specific tools were 

available. For example, the transporting of materials 

through a 91- by 91-cm (3- by 3-ft) door requires the 

miner to lift a 23- to 45-kg (50- to 100-lb) (or heavier) 

object, rotate his or her body, and heave the object 

through the door opening. Exposure to overexertion-type 

injuries is very high. If a simple slide. or materials 

conveyor was available, the miner could simply pass the 

material through the opening. Similar aids and mechanical 

tools are required for handling rail sections, timbers, posts, 

cribbing materials, etc. 

3. New Teclznologies. The search for new technologies 

is an ongoing process in any industry. In underground 

mining, however, it is even more important since so little 

completely new technology has been introduced to this 

sector. With respect to materials-handling, this search 

should focus on new, low-cost, reduced-weight materials 

for mine maintenance and safety applications. It should 

address improved designs and packaging for manual handling in operational environments. It should cover improved methods of installation and maintenance of the 

mine and the mining equipment. It should focus on ways 

of reducing mine maintenance (e.g., cleaning up along belt 

lines) and machine maintenance (e.g., autolubing systems). 

It should attempt to replace muscle power (particularly 

back muscles) with mechanical or hydraulic power. 

*U.S. GOVERNWENT PRINTING OFFICEi991-509-021/05014 IhT.BU.3F MN?S,PGFI.,PA 29970