% OF TOTAL MACHINES OF INTEREST

ONLY PRE-1970 MACHINES
MIXED PRE-1970 AND
50 - POST-1969 MACHINES
Yf ONLY POST-1969 MACHINES
40
80 F
20F-
10-
- -
0 /),
OWNERS OWNERS OWNERS
OF 1-5 OF 6-15 OF 15

Figure A4-4. Underground Mines — Distribution of Machines of
Interest by Owner Fleet Size and Composition

A4-20



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multiplied. The point is easily illustrated by considering a sphere with
diameter D inside a cube which is Dona side. If the volume of the sphere
is expressed in terms of the length, width and height of the cube, it is D3,
But the actual volume of the sphere is 1/6 rD®. The error is represented
by 7/6 = 0.524, that is to say, the actual volume of the sphere is about
half of what it would be stated to be if the dimensions of the cube were
used to calculate it. Suppose the sphere were an irregular shape, what
"correction constant" would have to be applied to obtain an accurate
volume if only the dimensions of the cube were known? This is the kind

of question for which a reasonable estimated answer was sought. The
method was to obtain nine fallen rocks of various shapes and sizes from
mines for an experiment. The greatest length, width and thickness of
each rock was measured and a volume calculated from these figures. The
amount of water each rock displaced when immersed was measured to the
nearest 0.5 ounce and a volume calculated. The ratio of the second
volume to the first was then calculated. The results are shown in

Table A5-12. The mean V/V value was 0.406. It suggests that the
correction constant which should be employed for volumes calculated

from reported fall dimensions should be about 0.4. However, 0.75 was
used. The reason is that another experiment showed that the test subjects
quite consistently underestimated length, width and thickness when asked
to express these rock dimensions in inches. The resulting error was
0.20 to 0.30 of the volume calculated from the true dimensions. Further,
a weight-volume correlation check was done on the first 21 data sets
received in which fall weight and fall dimensions were given and densities
were known with reasonable accuracy. The check indicated that a cor-
rection factor of about 0.70 applied to the volumes would make the weights
and volumes correlate well. After some discussion of this matter, a

correction constant for volumes of 0.75 was chosen for volumes calculated

WMA.

A5-26


Figure 4-19. Eimco ROPS on Eimco IHD Units



Figure 2-1 summarizes the results of analyzing fall-of-ground
accidents for surface and underground mines. The rock fall kinetic
energy that will be transmitted into the protective structure has been
tabulated and the expected frequency determined. For example, it is
estimated that 40-45% of all rock falls in surface mine areas will trans-
mit kinetic energy levels less than 40,000 ft-lb into the FOPS. Likewise,
it is estimated that about 55-65% of the underground rock falls will have
kinetic energy levels less than 40,000 ft-lb. This information is used
to help evaluate the protection afforded by possible FOPS performance
criteria. Section 4.1 and Appendices A4, A5, and A6 discuss the rock

fall characterization and accident analyses studies in detail.

Table 2-1 lists FOPS performance standards now in effect. A
FOPS performance standard that provides significantly more operator
protection has been developed. This new FOPS performance standard
will provide protection for the operators of "machines of interest" with
gross weights above about 30,000 pounds against large rock falls that trans-
mit energy levels equivalent to 40,000 ft-lb into the FOPS unit. Figure 2-2
illustrates the energy absorption range of FOPS units that are designed to
meet the recommended Woodward Associates, Inc. (WAI) FOPS performance
in addition to the performance criteria required for SAE ROPS units (ROPS
designed to meet Society of Automotive Engineers standards). The
WAI FOPS performance criteria can effectively combine the requirements
of the SAE ROPS performance standard (SAE J1040a) and the SAE FOPS
performance standard (SAE J231) with a minimum top load energy require-
ment to effect a protective structure that will provide excellent operator
protection during vehicle overturn, large rock falls and small "spike"
rock falls. Protection is also provided for side impact accidents.

Table 2-2 reviews this new proposed FOPS performance standard.



$ MACHINE VALUE AND ROPS COST

1
4
.
#4 200
a
a
a
:
MACHINE MARKET F
VALUE :
a
a
:
ROPS RETROFIT e
COST AS % OF e
°
100 3
ROPS RETROFIT COST |
| 0
Ay

AGE —>

Figure 4-34. Machine Value vs. ROPS Retrofit Cost — General

4-104



Table 4-13. Representative ROPS Retrofit Costs

— —
YEAR present [| AVERAGE 9 AVERAGE AVERAGE AVERAGE AVERAGE, ROPS COST
MACHINE MACHINE oF MARKET ROPS: ROPS TRANSPORTATION INSTALLATION TOTAL AS 20F

ee | “ooet puauracrone | "Yatve  f cosr'to8 | serene cost cost nore cost macutve waneer vaue
Tacron | rore soo [isms Ps o0s0 P soe soo +35 carn Tess Ta
raacron ] oeere 200 | 69 1500 100 | 5300 ry as 2 515
raacron | Hessey xe30]1975 $300 700 | 00s a 10 on 16.5
actor J care 500 J 196s 1700 ro] save ss bs 902 sua
reactor | cat e14 170 19,000 x20 | asso % 220 1s 83
raactor J wich 290 119] 1966 14,000 uso J aos B 210 ea 4
rmcron Jim ro-is | 193s 2250 100 J 12008 os 200 be os
voren | car > 1953 1500 io aioe Fo vs use 96.8
voren Pica ore | ass? 600 1290 | a2s0e 0 200 180 2.9
vozer Pacuns | is 25,750 ras J aoe % 20 139 6.0
voxee fvmis | ise 4300 rao Passo 100 25 155 6.2
vorer mma | ses 22,000 13s | an208 162 x0 1937 ba
orn Picar ose | ass 32,750 uaa | ss08 6 200 Lost sa
vorer | terex 62-30] 1970 21,000 vaso | 2osae us 230 aa 39
craven | cat 140 wx 2,000 un | as00e 1os 230 1507 as
cnoen | ca a2 soe 1500 7s J 13000 1os 20 1si0 100.0
craven J cation r500qf 1973 29,730 uso four 4s 130 ins 4s
craoen | deere 5700 | as72 19,000 00 J 14900 106 230 ine oa
caaoen | scans 660 [2955 3500 300 J asr00 % 20 sis o
raver | vabco 7778 | ass 16,000 1300 | as008 “1 200 1391 29
voasen cat 968 1965 37,000 68s | asso ves 250 2100 sa
voanen J car s6ee | as7s $2,000 1500 J 17008 ns 20 1as9 as
voaoen J car 955n | ase2 s2s0 ui%0 | tos08 6 200 146s v8
voasen | cat 950 908 24,000 1500 J aso 9 20 1a 1
roaver | cat 9928 J as J 100,000 sero | aosse 28 250 «403 2s
vonoen Pater 27s sre 50,500 700 aise 133 40 2093 26
wich 751969 29,500 520 | as200 a? 20 1817 6
toaoer J ten 75 1969 15,000 nas | a320r v2 220 1607 no
voaver J nich a2sar [Psst s4so vars | as20n ny 230 a2 a6
voaser Paco mas J asez «aso 0x0 sso “ vs as 2.4
voaser J cere nsssea 1973 25,000 1700 | asso 108 x0 2o«e a
voaser J case ws | as6s 19,500 wa | oso “ 200 sia 1
oroer J teren 2-15 J 197 28,300 vuoo | anroe 2 200 sos 8.
orser | rrosan soo 1966 000 1500 J 1s008 a 220 eit v9
mnie | car 651 967 49,000 2005 | asso i 250 nse 5.0
ore
me [ican J ass 64,000 1250 | te20r us 230 98 26
mare Patcn 210 ses 27,000 rio | aza0 & 200 1625 60
woven
paane | evetse ss-ref 1960 500 v0 J asst % 200 1380 ae
woweR
raise teren s-26 | asre 84,000 2080 | 2x20" 162 20 82 2.0
roves
raise cor war sss 6300 iro | as200 v2 220 2 28.3
roves



USBM Contract No. J0357110 WA Report 76-22F

PROGRAM FINAL REPORT
DESIGN CRITERIA AND GUIDELINES
FOR

FALLING OBJECT PROTECTIVE STRUCTURES (FOPS)

Prepared for

U.S. Bureau of Mines
4800 Forbes Avenue
Pittsburgh, Pennsylvania 15213

By

Woodward Associates, Inc.
225 Redlands Plaza
Redlands, California 92373

The views and conclusions contained in this docu-
ment are those of the authors and should not be
interpreted as necessarily representing the official
policies or recommendations of the Interior Depart-
ment's Bureau or of the U.S. Government.



Fleco Corporation
Jacksonville, Florida 32203
(904) 354-8361

Manufactures retrofit ROPS for many different
Caterpillar vehicles including crawler dozers,
crawler loaders, wheel loaders, scrapers, and
motor graders.

Industrial Cab Company
Essex, Massachusetts 01929
(617) 768-6931

Manufactures ROPS cabs for Fiat-Allis loaders and
dozers, International Harvester/Hough loaders,
GM-Terex loaders and dozers, and Clark- Michigan
loaders.

Medford Steel
Medford, Oregon 97501
(503) 779-1970

Manufactures ROPS and ROPS cabs for broad range
of Caterpillar crawler dozers and crawler loaders,
GM-Terex crawler loaders, and Komatsu crawler
dozers and crawler loaders. Medford supplies ROPS
for both the retrofit market and the new vehicle
market.

Palm Industries, Inc.
Litchfield, Minnesota 55355
(612) 693-2492

Manufactures ROPS and ROPS cabs for equipment
manufactured by Fiat-Allis, Case, GM-Terex,
Galion, Austin Western, Caterpillar, Deere, Ford,
International Harvester, Clark-Michigan, and
others. Supplies both retrofit ROPS and ROPS for
new equipment. Large number of ROPS models
available.



4.2 DEVELOPMENT OF FALLING OBJECT PROTECTIVE
STRUCTURE (FOPS) PERFORMANCE CRITERIA

This section describes the various FOPS performance criteria
now available to guide the FOPS designer and the test procedures used
to demonstrate the attainment of the desired performance. The rock-
fall kinetic energy data presented in Section 4.1, ''Characterization of
Rockfalls'' are reviewed and approaches to protecting against rockfalls
discussed. Structural analysis methods are described which establish
the basis for the recommended energy absorption capability requirement
for the FOPS. Equivalent static load criteria are developed leading

to three alternate methods which are practical for certifying the FOPS.

FOPS Performance Criteria in Use

Several state and federal agencies (including the U.S. Bureau
of Mines) have safety regulations in effect that, under certain circum-
stances, require the installation of a canopy, a FOPS, or some similar
structure to provide overhead operator protection. Before addressing
possible new requirements for FOPS on mining equipment, the existing
regulations should be examined and the level of protection provided
assessed. Table 2-3 listed several state and federal agencies that have
adopted FOPS regulations and indicated the performance criteria or
the design criteria used. As can be seen in that table, in several cases
the FOPS is to be "substantial" in construction. The FOPS criteria

developed by SAE are mentioned in three of the regulations.

Since canopies have been built and installed on mining and con-
struction vehicles to satisfy these requirements, it is important to
understand the relative structural capabilities of FOPS designed to meet
these requirements. Table 4-2 illustrates the test requirements for
SAE J231 and SAE J167. This table also gives the top load capability of
the SAE ROPS criteria and the Corps of Engineers ROPS criteria.

MRA.

4-18



all of the forms pertinent to fall-of-ground accidents could be sorted

economically from the rest.

A manual entitled ''Inspection and Investigation Manual, Public
Law 89-577" prescribes the procedures and report contents for investi-
gations of fatal accidents. Section 9C of the manual requires that "a
formal report shall be prepared and distributed for all fatalities deter-
mined to be chargeable to the mineral industries."' Paragraph 9C(3)
requires that the content shall include a description of the accident in
"detailed narrative" form. It specifies also that ''a suitable sketch of
the accident scene should be prepared and included in the report."
With the permission of Mr. E. Levi Brake, Phoenix Subdistrict Manager,
MESA, and the cooperation of MESA personnel in the Reno Field Office,
WAI staff members examined, in the course of preliminary planning for
this study, a stack of approximately 150 MESA accident investigation
reports. It was observed that, although the reports succeed admirably
in identifying and explaining accident causes, and in presenting recom-
mendations for improved safety, they often do not include all of the
physical details of the fall-of-ground. For example, some state the
weight of the rock which fell, but do not give the fall distance or sufficient
dimensional information in the narrative or sketch from which to deter-
mine fall distance. Some state the fall distance, but do not give the size
or weight of the material that fell. However, they are excellent sources
of information concerning the nature and location of accidents, the people
who witnessed or investigated the accidents, and some of the physical
details. Used collectively, the reports of fatal fall-of-ground accidents
provide much data which, we believed, could easily be augmented through
mail questionnaires which asked for specific physical details. Further,
it was clear that MESA had published a large number of investigation

reports on non-fatal accidents. The WAI staff people observed, from the

WMA.

A5-2


~

It is appropriate to call attention here to three points of special

interest with regard to financial analysis of ROPS retrofit.

First, the cost of ROPS retrofit as a percentage of machine value
is generally lower for heavy machines than for lighter machines. This
point is illustrated by comparing Figure 4-32 to Figure 4-33. Fig-
ure 4-32 relates to a machine in the 50,000 pound class of gross vehicle

weight. Figure 4-33 relates to one in the 6000 pound class.

Second, the ROPS retrofit costs used in this study are for what
may be termed the ''minimum ROPS,"' that is, ROPS which do not have
any of the "options.'' Accordingly, the costs are substantially lower than
those which actually would be incurred if retrofit were required. For
example, the $1920 average ROPS retrofit cost used in the D8 illustration
in Figure 4-32 does not include curved front sweeps, tank guard, back
screen or side screens. Adding these would increase the cost to $2935.
Adding the tank guard only, an option which is very frequently chosen,
increases the ROPS retrofit cost to about $2040. The ROPS used in the
analysis here is the kind usually referred to in the trade literature as
a "ROPS canopy," as distinguished from a ""ROPS cab.'"' A "'ROPS cab"
costs two to four times as much as a ''ROPS canopy,'' depending upon the

type of machine and the manufacturer.

Third, the manufacturers’ prices for new machines and attach-
ments increased substantially in 1975. For example, the Green Guide
reported that ''new price average increases" for wheel tractors of 7%
to 41%, depending upon the manufacturer, had occurred since the section
from which data were taken for this study was printed. Price increases
for attachments were in the range 7% to 48%. Under these conditions,
used machine market values increase also, approximately in proportion

to the new machine price increases. ROPS retrofit cost as a percentage

MRA.

4-102


Since vehicle configuration and mounting location vary widely,
definitive energy absorption capabilities were not obtained. It is safe
to assume, however, that some energy is absorbed in all installations.
For example, bolted joints overcome frictional resistance and slip to
take up dimensional differences between the bolt and the bolt-hole.
Experience gained by Woodward Associates personnel while witnessing
numerous ROPS/FOPS tests has shown that a considerable amount of

energy is absorbed by most vehicle frames.

The energy absorption characteristics of tires were evaluated.
The results indicated that large amounts of energy can be absorbed.
The curve, Figure 4-8, shows the capability of representative tires for
wheeled dozers, motor graders and front end loaders as a function of
gross vehicle weight. Tires on a large vehicle, such as the 180,000 lb
Le Tourneau L-700 front-end loader, can absorb approximately
400,000 ft-lb of energy. The tires on the Caterpillar 112F motor grader,
a 21,600 lb vehicle, can withstand 33,000 ft-lb.

The Caterpillar 988 front-end loader with a gross weight of
67,000 lb will be used as an example to describe the methods used to
determine tire capability. The assumptions used in the evaluations

were as follows:

1) The total impact loading is reacted by two tires. This
assumption is conservative since on most vehicles and
canopy installations at least 25% of the force will be
transferred to the other two tires.

2) The tire will withstand the maximum load as rated by
the manufacturer at the recommended operating pressure.
The tires should actually withstand higher loads because

the manufacturer utilizes a design safety factor.



~

investigation reports, dependent information on fatal accidents was also
extracted. There were 98 fall-of-ground accidents for which fatality
information was available. Table A5-16 shows the number of fatalities
in these 98 accidents by mine type. There were 125 fatal accidents,
fall-of-ground and other types related to ROPS or FOPS considerations,

for which dependent information was given. Table A5-17 shows the number

Table A5-16. Number of Fatalities — Fall-of-Ground
Accidents in This Study from MESA Accident Investigation Reports

No. of No. of
Mine Type Accidents Fatalities
Under ground 67 75
Surface 31 31
TOTAL 98 106

Table A5-17. Number of Dependents of Victims of Fatal Accidents

No. of No. of No. of
Accident Type Accidents Fatalities Surviving Dependents
Fall-of-Ground 83 90 270
Other ROPS/ 42 42 93
FOPS Related
TOTAL 125 132 363

A5-36


Figure 1-3. Rubber-Tired Dozer

Figure 1-4. Industrial Tractor



% OF TOTAL MACHINES OF INTEREST

60

50

cs
-)

w
°

iN)
i)

10

.

|

ONLY PRE-1970
MACHINES

MIXED PRE-1970 AND
POST-1969 MACHINES

ONLY POST-1969
MACHINES

0
OWNERS OWNERS OWNERS
OF 1-5 OF 6-15 OF >15
Figure A4-5. Crushed Stone Mines — Distribution of Machines of

Interest by Owner Fleet Size and Composition

A4-21



APPENDIX A6

ACCIDENT DATA ANALYSIS

This section is a summary of the work done with respect to the
collection and analysis of information about 'fall-of-ground" accidents
incident to the acquisition of data concerning fall-of- ground physical
characteristics. Details are provided in Appendix A5, ‘Accident Data

Survey."

Sources of Accident Information

The information about the time and place of fall-of-ground acci-
dents was obtained principally from four sources. The first was the
fatal accident investigation reports published by MESA and maintained
in a central repository by the MESA Health and Safety Analysis Center
in Denver. The second was the non-fatal accident investigation reports
published by MESA. The third was mines which were surveyed by mail
in the Fall-of-Ground and Equipment Survey (see Appendix A4, ''Equip-
ment Population Survey") and which provided information about ''no
injury" accidents. The fourth was the field visits made to mines of
many types and sizes throughout the United States by WAI staff members,
and discussions with MESA people at several MESA offices. The number

of fall-of-ground accidents identified through these sources was 211.

Physical Data Collection

The minimum data requirement for each accident, to meet the
specific needs of this study, consisted of the general identification of the
material that fell, the fall distance, the dimensions (or weight) of the

material, whether the fall was in an underground or surface mine, and

WA.

A6-1



~

fall-of-ground accidents. The annual fatal and injury rates are greater for
the LHD type in underground mines than for all of the types of machines

of interest specified for this study. The reason is obvious: they are

more often ''where the action is," that is, their exposure rate to areas

in which fall-of-ground occurs most frequently is high relative to that

of the machines of interest. Only in mines which have very high backs
(some lead and salt mines, for example) do the machines of interest

figure prominently in the type of underground operation which have

high fall-of-ground exposure.

Table A6-4. Estimates of Average Annual
Fall-of-Ground Accidents Which Involve Machines of Interest

Surface | Underground Total
Mines Mines M-NM Mines
Number of Active Mines 13,321 668 13,989
FOG Accident Class
Fatal 7 15 22
Non-Fatal Injury 153 570 723
No Injury 169 292 461
Total FOG 329 877 1,206
Fatal, MI 3 1 4
Non-Fatal Injury, MI 62 28 90
No Injury, MI 68 15 83
Total FOG Involving 133 44 177
MI

A6-14


elasticity of these elements with one that reflects the composite effect
of distributed elastic and plastic responses throughout the cross section
of the beam. The effective modulus derived in this manner represents
the secant modulus which would be obtained in the elastic plastic section
when the local loads are reacted. Solutions are obtained by applying the
loads in increments and by iterating each load step to obtain convergence.
This permits evaluation of beam structures through a range of loads
where in the individual beams are partially elastic and partially plastic.
Once a beam becomes incapable of supporting the applied loads, the
convergence process will fail and the solution will terminate. It is
possible to interpret this solution termination as the collapse load for
the structure whenever the primary members are responsible for the
failure. In any event, this failure is indicative of complete failure of

a member to support additional applied loads.

The program also contains a similar modification technique for

the plane stress membrane element.

Comparison of Computer Programs

The computer programs CANOPY, SAP and Elastic/Plastic SAP
are compared in Table A2-1. The information contained in the chart is
important for evaluating the programs for possible use as a certification

method.

It is clear, from the general description and discussion of element
types, that the programs vary widely in complexity and capability. In
general, it is most efficient to use a program which closely matches the
complexity of the problem to be analyzed. Using a general purpose
program to analyze a small specific problem results in wasted machine

time, operator effort for input and operator effort to evaluate the output

A2-15



|
ra

ar ee TT me a an _

Figure 4-26. Saf-T-Cab ROPS Cabs on
Caterpillar Motor Grader and on
Caterpillar Crawler Loader



years with no provision for mounting ROPS or FOPS units on the vehicles.
Since there were no nationwide ROPS or FOPS regulations, the original
equipment manufacturer did not ''design in'' the structural areas neces-
sary for attaching ROPS mounting brackets and necessary for reacting
the loads that might be experienced during a roll-over or during a rock
fall. Thus the question of vehicle structural capability resolves to
determining the year that each original equipment manufacturer began

producing vehicles with chassis and frames designed to accept ROPS.

The original equipment manufacturers, when asked to define which
of their vehicles will accept ROPS, state vehicle manufacture dates that
are consistent with their ROPS development and vehicle chassis modifica-
tion programs. Characteristically, they state that in 1965 or 1966 or
1967, they realized that there would be future requirements to provide
ROPS on construction vehicles and perhaps on mining equipment and that
they began to redesign their vehicle chassis and frames to accommodate
the installation of ROPS. The vehicle chassis were analytically examined
for structural adequacy and, where necessary, they were modified to
provide the necessary strength to accept the structural loads imparted
through the ROPS to the chassis during a roll-over (or at least during

a static laboratory test).

As is normal in a manufacturing concern, these design changes
were not immediately reflected in changes to the vehicles on the pro-
duction line. Some models of vehicles were modified soon after the
decision to accommodate ROPS, but some other models were not. The
time from the decision to modify the vehicle chassis to accept ROPS to
the time when the production vehicles are delivered off the end of the
production line with the redesigned chassis can be as short as one year

but could be as long as four to six years.

4-84


Table A5-10. Density of Materials (Cont)

(Lb. Per Cu. Ft.)

Density Average
Material Range Density Source
Lead Ore
Galena 456-475 465 2
Galena 460-470 3
Limestone 131-178 155 2
167-171 3
168-178 4
Bank 148-163 1
Loose 89-104 1
Manganese Ore
Pyrolusite 231-288 259 2
Marble 160-177 3
163-179 170 2
Phosphate Rock
Apatite 200 2
Porphyry 162-181 3
163-181 172 2
Quartz 165 3
Flint 165 2
Riprap
Limestone 80-85 2
Sandstone 90 2
Shale 105 2
Sand
Dry, Bank 100-111 1
Dry, Loose 89-111 1
Damp, Bank 119-130 1
Damp, Loose 111-122 1
And Gravel, Dry, Loose 90-105 2
And Gravel, Wet 118-135 126 2

A5-20



for a unidirectional applied stress, but becomes more complicated for

combined stresses. For the unidirectional case:

SF

where

F =

n

1"
|

Allowable stress

Induced stress

For the combined stress condition:

where

fa fy 1 *p 2

= R = R = R=

Fy bl Fy be FY s

= Axial, bending and shear stress ratios

= Minimum tensile yield strength of material

= Induced bending stress in 1 and 2 directions
= Minimum ultimate shear strength of material

= Induced shear stress due to direct shear and
torsional moment

A2-7



Material Requirements

The material used in the fabrication of the canopy and attachment
structure must meet the Charpy V-notch impact strengths specified in
Section 7.0 of the ''Performance Criteria for Roll-Over Protective
Structures (ROPS) for Earthmoving, Construction, Logging, and Indus -
trial Vehicles - SAE Recommended Practice J1040."" These values are
repeated in Table Al-1. Structural members of the canopy and attach-
ment to the vehicle shall be made of steels that have Charpy V-notch
impact strengths as shown in Table A1l-1 at -30°C (-20°F). Specimens

are to be "longitudinal" and taken from flat stock, tubular, or structural

Table Al-1. Charpy V-Notch Impact Strengths

Specimen Size, mm J | Ft-Lb
10 x 10 11.0 8.0
10x 9 10.0 7.5
10x 8 9.5 7.0
10 x 7.53 9.5 7.0 |
10x 7 9.0 6.5
10x 6.7 8.5 6.5
10x6 8.0 6.0
10 x 52 7.5 5.5
10x 4 7.0 5.0
10x 3.3 6.0 4.5
10x 3 6.0 4.5
10x 2.5% 5.5 4.0

3Indicates preferred size. Specimen size shall be no less than the
largest preferred size that the material will permit.

Reference: ASTM A 370-68, Standard Methods and Definitions for
Mechanical Testing of Steel Products.

WMA.

Al-2


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4-24


geometry of the wall collapses suggest that the effective thickness of the
portion which might have impacted on top of a machine located at a mini-
mum working distance from the wall was no greater than about 10 feet.

All of large collapses examined involved material of density <150 pounds
per cubic foot. A maximum thickness value of 10 feet was used in the
model, making the estimate for the maximum protective structure impact
volume 70 inches by 90 inches by 120 inches = 756,000 cubic inches or
437.5 cubic feet. In the data analyses and the presentations of kinetic
energy at the protection level, no greater value than this was considered
for impact volume relevant to the protective structure. In those accidents
in which fall distance was less than 18 feet, the volume was calculated
from the protective structure area (43.75 square feet) multiplied by (f - p),
and appropriate related adjustments were made in the weight for those
cases. The basis for this procedure is the protective structure height, p,
which was taken to be a minimum of 8 feet for the model (but 6 feet in the
underground model). In fact, some of the machines of primary interest

in this study are equipped with ROPS which have heights in the 10 to 14 foot
range. When the machine involved was known, appropriate values were
found in manufacturer's data and p was usually taken to be the given value
minus one foot. Table A5-11 shows ROPS heights for some of the machines

of interest.

It was suspected early in the study that there might be large errors
in weight and dimension estimates. It was clear from discussions during
the mine visits with safety officials and with MESA inspectors on several
occasions that sometimes the dimensions reported were merely "eyeball
estimates.'' In cases where measurements were made, the measurement
was of the void from which the fall came. Even if one assumes that the
length, width and thickness dimensions given are accurate, the volume

of the rock they describe will not be correct if the dimensions are simply

WA.



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2-10


~

Table A4-7 shows the estimates for the population of machines of
interest by machine type and age group. The methods of estimating are

summarized below.

The numbers of machines of interest reported by each respondent
who owned one or more were used to calculate a sample mean and sample
standard deviation. The sample mean was used as the estimator of the
population mean. The 95% confidence interval for the population mean

was calculated as:

A
o

ar

-d

where

kis the confidence multiplier (1.96 in this case)

a>

is the sample standard deviation

nis the sample size (number of respondents with one or
more machines of interest)

1

is the sample mean

The estimated population mean and confidence limits were used with the
number of mines in the Mine Reference File which had one or more
machines of interest to estimate the population. The population used in
Sections 4.3 and 4.6 of this report is the mid-point of the 95% confidence
interval, which is 44,827 to 53,759.

Proportions of the population representing various machine age

groups, fleet sizes and installed protective structures (and the owners

A4-15


FRONT END LOADERS
27,934
58.1%

DOZERS
9,102
18.9%

GRADERS
3,114
6.5%

TRACTORS
4,963
10.3%

PRIME
MOVERS
2,961

6.2%

Figure 4-13. Machines of Interest Used in Surface Operations



of 30,000 pounds and above. A method of providing the same level of
protection for operators of these small tractors is not defined in this

report.

There is considerable evidence in the form of MESA mining acci-
dent records that supports the need for operator protection structures
on specific types of mobile equipment used in metal-nonmetal mining
operations. These MESA accident records describe deaths and injuries
due to vehicle overturns, vehicle-vehicle collisions, vehicle-object
collisions, fall-of-ground on machines, fly rock striking operators, and
vehicles caught in rock slides. A properly designed protective structure,
incorporating roll-over protection, falling object protection, and some
measure of side protection, would save the machine operator in many
of these accidents. This "all-protective'’ canopy or cab need not be a
totally enclosed, uncomfortable fortress that limits visibility and creates

new problems.

The ROPS/FOPS now used in the construction industry were
resisted by both management forces and by the equipment operators when
first introduced. Now, several years after these units have been in use,
many of the construction contractors are very positive in their comments
on the usefulness of ROPS/FOPS. The protection from the weather
(rain, snow, etc.) afforded by a canopy or cab has resulted in increased
productivity during inclement weather. Vehicle operators have become
aware of the life-saving record of ROPS and are now accepting the fact

that it is better to "ride out" a roll rather than trying to jump.

The ROPS/FOPS used on construction equipment can be used on
similar mining equipment with the same positive effects on safety and
production. Changes in FOPS performance criteria can be made to
accommodate the higher energy rock falls experienced in mining opera-

tions with little or no change in ROPS/FOPS cost or appearance. Since

WA.

3-3



Table A5-10. Density of Materials

(Lb. Per Cu. Ft.)

Density Average
Material Range Density Source
Asbestos Ore or Rock
Bank 141 1
Loose 81 1
Basalt 169-200 184 2
150-190 3
171-201 181 4
Clay 112-162 3
Dry 63 2
And Gravel, Dry 100 2
Compact Bank 111 1
Loose, Dry 70 4
Marl 112-162 137 2
Concrete
Cement, Stone, Sand 137-150 144 2
Copper Ore
Sulfides and Up to
10% Copper, Bank 163-178 1
Loose 113-120 1
Pyrites 256-269 262 2
Dolomite 181 2
177 3
Bank 148-163 1
Loose 90-104 1
Earth
Dry, Packed 95 2
Moist, Packed 96 2
Dry, Clayey 110 1

A5-18



interviews, were imperfect in many respects. It was necessary to
develop guidelines and correction constants with which to treat the
reported data. The objective was to accurately characterize the falls

with respect to the energy which would be ''seen" by a protective structure.
The procedures and corrections chosen were those which would attain

the objective, but never underestimate factors which affect energy cal-
culations. The bias which exists in the final data is in the direction of
overestimation. The degree of bias is judged in Section 4.1 and reflected

in Figure 4-5.

Early in the study interest focused on the surface accidents
because the size of some falls, as reported in weight terms, was very
large. Data were available for a few accidents from which analyses
could be made to judge the maximum weight and volume that would actually
affect a protective structure. It quickly became apparent that the kinetic
energy with which a protective structure could have been affected was
usually very much smaller than that of the total fall. Several models for
analyses purposes were considered. One is discussed below to illustrate

how the physical data on fall-of-ground accidents were treated.

Model for Surface Mine Ground Falls

Not all of the weight in a large volume fall of non-cohesive material
can impact in a small area. It would be inappropriate to estimate the
kinetic energy a protective structure must transform by assuming that
all of the falling material would impact on it. A method which provides
more accurate estimates is needed. If the details of the fall geometry
were known in each case, a very accurate estimate could be made. How-
ever, as explained earlier, in many cases little about the physical details
of the accident is known. It is sometimes difficult to obtain good infor-

mation even about such fundamental things as the fall distance and volume

WMA.



SECTION 5.0

REFERENCES

The following list of publications is presented for the reader who
is interested in the details of many of the reports, performance standards,

regulations, etc. , that are referenced in this report.

ROPS/FOPS REPORTS

1) CANOPY — A Computer Program for the Structural
Analysis of Space Frame Protective Canopies, Bureau
of Mines Information Circular IC 8546, by Dr. Stephen

Sawyer

2) Design and Installation of ROPS for Army Retrofit
Program, by Paul D. Hopler and William O. Stewart
(SAE Paper 730752)

3) Dynamic Testing of Tractor Protection Cabs, by

Harold Ason Moberg (SAE Paper 730761)

4) Earthmoving Equipment Cab Design, by Gardner P.
Burton (SAE Paper 730433)

5) Elastic Plane Frame Analysis of Semisymmetric Cabs
and Canopies Used on Underground Electric Face
Equipment, Bureau of Mines Report of Investiga-
tions RI 7799, by Dr. Stephen Sawyer and Darryl

Brogan



PERCENT OF ANNUAL FALL-OF-GROUND ACCIDENTS

70

60

50

40

30

20

10

wee UNDERGROUND MINES
weee SURFACE MINES

|
|
|
|
1

L 1

10

Figure 4-6.

20 30 40 50 60
KINETIC ENERGY (1000 FT-LB)

Prediction of Kinetic Energy at Protection Level



protection level. The machines involved, and other information, are

provided as in the table for surface mine accidents.

Graphs which summarize the data in Tables A5-13 and A5-14

are in Section 4.2, "Characterization of Rockfalls."

As noted under the ''Data Requirements" section above, the
second type of data needed is related to "point loading" of the protective
structure. Unfortunately, the information obtained for this study pro-
vided few data points from which to estimate the characteristics of ground
falls in this respect. There were only 11 accidents from which sufficient
data were available to make a general assessment of the matter. For
these 11 accidents, estimates were made of the smallest impact area
which seemed likely. Neglected, of course, were the possibilities that
an irregular-shaped rock would fall so that a sharp "'tip'' would impact
on the protective structure with an impact area <1 square inch. Using
narrative descriptions of the rocks which actually fell in accidents, and
observations of many rocks in mine environments, a judgment was formed
about a likely area of impact. The results are shown in Table A5-15. It
deserves to be repeated that these are judgments only. They are carefully
considered judgments, but they have no sound foundation in test or care-
fully measured empirical data. The judgments are related to SAE J231
in the table. The symbol "+" indicates that the fallen weight or the
impact area is greater than the SAE J231 specified value. The last
column, ''Possible Problem," is checked in appropriate cases to indi-
cate that a machine operator might not have been protected by a commer -
cial ROPS. The SAE J231 test weight is 500 pounds; the test impact area

is 50.26 square inches; the kinetic energy is 8500 feet-pounds.

Although this study was directed to the physical characteristics

of accidents, in the course of taking accident data from MESA accident

WA.

A5-34


APPENDIX A3

FOPS TEST PROCEDURE

The testing procedure specified in this document was developed
as a method of certifying the structural integrity of falling object pro-
tective structures (FOPS) for use in metal-nonmetal mines. The pro-
cedure is applicable to FOPS installed on the following type of equipment

used in surface mines and surface areas of underground mines:
e Track-type or wheeled front-end loaders
e Dozers
e Tractors (excluding over the road type tractors)
e Motor graders
° Prime movers

Two testing procedure options are presented. Option A includes
a static test of the entire FOPS including protective canopy, attachment
joints, vehicle chassis and axles. Testing of some of the FOPS compo-
nents or the canopy alone is required with Option B. The remainder of
components must be certified with engineering calculations or by meeting

certain specified and required design guidelines.

Option A

A static test of the entire FOPS including protective canopy,
attachment joints, vehicle chassis and axles is specified. In addition,

several design and fabrication requirements must be met. The

A3-1



generally have the tools and the skills required to do the installation
work very efficiently. No costs were included in the total ROPS cost
estimate for lost production time. It was assumed that installation
would be done during a time when machines were out of service for
other reasons. The ROPS prices used in the calculations are averages
of selected high and low ROPS manufacturer's catalog prices (FOB) in
effect during the first quarter of 1975. Some representative ROPS
retrofit costs are given in Table 4-13. The method of using the ROPS
costs was to construct a machine "type profile’ for each machine age
group in both underground and surface mine categories. The profile

is a list of models which, in terms of ROPS costs and machine values,
properly represent the machines in a given age group. A proportion
was assigned to each model, from the survey data, so that a weighted
average of machine value and ROPS retrofit cost could be calculated for

each age group,

Figures 4-32 and 4-33 illustrate the relationship between ROPS
retrofit cost and machine value. Figure 4-32 pertains to the Caterpillar
D8 crawler tractor. A commercial ROPS is available for machines of
this general model designation which are more than 20 years old. In the
illustration, the years 1953-1973 were used. The average ROPS retrofit
cost for 1972 and 1973 machines is $1510; the average for the older
machines is $1920. The difference is related principally to the fact that
many of the newest machines are manufactured with ROPS mountings
installed. Although the ROPS retrofit cost is constant over many model
years, the market value of the older machines is steadily decreasing,
as shown by the market value curve. Thus, for older machines, ROPS
retrofit may represent a large proportion of machine value. In the
illustration, ROPS retrofit cost for a 1957 machine is 35% of the market

value of the machine; for a 1953 machine it is 48%.



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4-17


The resulting safety factor is:

1
2 2)1/2
[(R, +R, + Ry) +(R,) ]

SF =

Buckling
The support columns of the canopy must be checked for collapse
due to buckling. A simplified approximate method of addressing the

buckling problem is presented below.

The bending moment in a beam column with a compressive load P
is derived from the bending moment in a simple beam with no axial load

by the following relationship:

1
M = M
1-(P/P_)
cr
where
M = Bending moment in the beam column
ul = Bending moment in a simple beam resisting
the same loading without compressive load P
P = Applied compressive load
. 2 2
P., * Euler buckling load, 7 El/L

E = Modulus of elasticity

I = Moment of inertia

L = Column length

A2-8



systems. Elastic/Plastic SAP also includes routines to analyze
nonlinear deformation of beams and plates and geometric corrections
for large displacements. The program is written to analyze structures

which are idealized by combinations of structural element type as follows:

1) Three-dimensional truss member

2) Three-dimensional beam element

3) Plane stress membrane element

4) Two-dimensional finite element

5) Three-dimensional solid element: 8 nodal brick

6) Plate and shell elements (quodrilateral)

7) Boundary element

8) Three-dimensional thick shell element (16 notes)

9) Three-dimensional beam element (plastic modification)
10) Plane stress membrane element (plastic modification)

There is practially no restriction on the number of elements used,
the number of load cases or the bandwidth of the stiffness matrix. Each
nodal point in the system can have from zero to six displacement degrees

of freedom.

The elastic solution routine begins by forming a structural stiff-
ness matrix. The analysis is continued by solving the equations of

equilibrium followed by computation of element stresses.

The program contains an element modification technique which
causes specified three-dimensional beam elements to respond as elastic/

plastic beams. This is accomplished by replacing the modulus of

A2-14



>

costs, ROPS transportation costs, and ROPS cost/machine value

information.

Figure 4-14 shows the percentage of machines of each type which
presently have some form of protective structure installed. With few
exceptions, machines which were reported to have a ''ROPS" installed
had a commercial ROPS which was designed and manufactured to either
SAE or Corps of Engineers standards. However, many machines which
reported protective structures other than ROPS had non-commercial
structures, usually designed and built in mine shops, or some form of
commercial cab or canopy locally modified to provide additional falling
object protection. The figure reflects all installations which, in the
judgment of the reporting mines, provide falling object and/or roll-over

protection.

Figure 4-15 shows the estimate of the distribution of the machines
of interest according to the year of manufacture groupings used in this
study. Approximately 46% of the total population is composed of
machines manufactured in the years 1970 through 1975. There are
a few machines in the population which are more than 25 years old.
Three-quarters of the machines manufactured in 1949, or earlier, are
in two type categories, dozers and graders. Wheeled front-end loaders
were not made in large numbers until the late fifties. Crawler loaders
were available earlier, but only a few models were available in the forties.
The estimates for machines in the ''1949 or earlier’ age category may be
high, primarily because the sample for that category was small and the
proportion estimators in the range below 0.05 do not permit the construc-

tion of good confidence intervals.

Figure 4-16 shows the approximate percentages of machines of

interest, by the ''vear of manufacture" groups, which have protective

WMA.



6) Occupational Safety and Health Administration,
Subpart W, Roll-Over Protection Structures; Overhead
Protection — paragraphs 1926.1000 thru 1926.1003
(ROPS, FOPS)

ROPS/FOPS — PERFORMANCE STANDARDS

Society of Automotive Engineers, Inc. , 400 Commonwealth

Drive, Warrendale, Pennsylvania 15096

SAE J167 — Protective Frame with Overhead
Protection — Test Procedures and

Performance Requirements

SAE J168 — Protective Enclosures — Test Procedures

and Performance Requirements

SAE J231 — Minimum Performance Criteria for
Falling Object Protective Structure
(FOPS)

SAE J333a — Operator Protection for Wheel Type

Agricultural and Industrial Tractors

SAE J334a — Protective Frame Test Procedures and

Performance Requirements

SAE J1040a — Performance Criteria for Roll-Over
Protective Structures (ROPS) for
Earthmoving, Construction, Logging,

and Industrial Vehicles



Figure 4-23. Palm Industries ROPS Cab on
GM-Terex Rubber-Tired Loader

Figure 4-24. Sequoia ROPS Cab on
Caterpillar Prime Mover (Scraper)



Table A5-10.
(Lb. Per Cu. Ft.)

Density of Materials (Cont)

Density Average
Material Range Density Source
Feldspar 159-172 3
Bank 152-167 1
Loose 100-111 1
Orthoclase 156-169 162 2
Granite 160-170 166 4
163-169 165 2
165-173 3
Bank 148-163 1
Loose 96-104 1
Gravel
Wet 125 4
Dry 112 4
Bank, Wet 111-126 1
Loose, Wet 100-120 1
Bank, Dry 104-115 1
Loose, Dry 90-100 1
Gypsum 144-145 3
Loose 90-100 1
Alabaster 144-175 159 2
Iron Ore
Hemotite 325 2
Limonite 225-250 237 2
Magnetite 306-325 315 2
Hematite 306-330 3
Magnetite 306-324 3
Ore, 60% Iron
Bank 237-259 1
Loose 156-170 1
Ore, 50% Iron
Bank 211-230 1
Loose 141-152 1
Ore, 30% Iron
Bank 167-185 1
Loose 119-137 1

A5-19



Table 3-2, Conclusions ~ ROPS/FOPS Technical Area

A FOPS meeting SAE J231 criteria provides acceptable
operator protection for minimum of 21% of the rock falls in
surface metal-nonmetal mines and approximately 33% of the
rock falls in underground metal-nonmetal mines,

A FOPS meeting structural performance criteria developed
by WAI will provide operator protection for at least 40% of
the rock falls in surface metal-nonmetal mine areas and
60% of the rock falls in underground metal-nonmetal mines,
This FOPS performance criteria represents the maximum
energy absorption design that is practical for tnese types
of equipment,

The WAI rock fall data collection technique recorded all

rock falls reported and thus does not include many of the
smaller rock falls that are not reported anywhere, The true
percentage of actual rock falls for which these FOPS would
provide protection is probably greater than the above numbers
indicate,

Providing significant levels of overhead protection for light
industrial tractors is impractical, The FOPS capability
normally provided with industrial tractor ROPS (SAE J167)
does not provide adequate protection for the surface or
underground rock fall environment, Light industrial
tractors do not have the frame strengths necessary to
survive the loads transmitted by rock falls,

Test procedures and analytical methods are available that
provide satisfactory verification of FOPS performance.
Existing certification procedures are valid in some areas;
a FOPS certification procedure for the WAI FOPS per-
formance criteria has been prepared,

The ROPS manufacturing industry has sufficient production
capacity to meet the demands of the ROPS/FOPS regula-
tions being considered by MESA and other federal and state
regulatory agencies, Production capacity exceeds

300,000 ROPS/FOPS units per year.

ROPS and FOPS designs are generally available for the
machines of interest manufactured after 1965 and for many
of the ''heavy'’ machines from 1960, :



structure which can withstand a static load of 74,000 lb uniformly dis-
tributed over the plan view area of the canopy top without yielding will

be capable of absorbing at least 40,000 ft-lb of kinetic energy.

The 40,000 ft-lb energy absorption requirement was estab-
lished because it represented a level which could be accommodated by
the majority of ROPS/FOPS structures for vehicles under consideration,
and because it would provide operator protection for a significant number
of rock falls. A review of Table 4-4 shows that vehicles with gross
weights ranging from 30,200 lb to 180,000 lb have ROPS with energy
absorption capabilities of 40,000 to 288,000 ft-lb. Since these ROPS
are representative of existing units within this weight range, it is
expected that very few design modifications will be needed to meet these
structural requirements. Therefore, the cost of ROPS manufactured
to present standards should not have to be significantly increased to meet

the 40,000 ft-lb energy absorption requirement.

An energy absorption capability of 40,000 ft-lb will give pro-
tection in at least 47% of the rock falls in surface mines and 66% of the
rock falls in underground mines as shown in Figure 4-6. This represents
protection for over twice the rock falls covered by meeting the SAE J231

requirements.

However, as stated previously, the 40,000 ft-lb energy ab-
sorption capability is limited to vehicles with gross weights above
30,000 lb. This lower limit does not appreciably reduce the predicted
protection percentages as the value was established primarily for three

reasons:

1) A study of the accident statistics shown in Table A5-13
indicated that approximately 70% of the vehicles involved

in rock fall accidents had gross vehicle weights above

30,000 lb.

WMA.



TABLE

2-3

2-4

2-6

3-2
3-3

3-4

LIST OF TABLES

Falling Object Protective Structure (FOPS)
Performance Standards . :

Proposed FOPS Performance Standard
(WAI)

Federal and State FOPS Regulations

Equipment Population — Machines of
Interest

ROPS/FOPS Retrofit Costs (SAE or COE
ROPS with J231 FOPS)

Costs of Alternative ROPS/FOPS Retrofit
Policies .

Conclusions — Accident Analysis/Rock Fall
Characteristics

Conclusions — ROPS/FOPS Technical Area
Conclusions — ROPS/FOPS Economic Area
Recommendations

Summary Statistics — Fall-of-Ground
Accidents

Falling Object Protective Structure (FOPS)
Performance Standards

ROPS/FOPS Certification Costs

PAGE

xi





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A5-32


$ (000'S)

60

50-

40

30

20-

Vv

MACHINE MARKET

ALUE

«a
’
ROPS RETROFIT ?
COST AS % OF e
MACHINE VALUE

60

450

30

20

10

75

Figure 4-32.

1
67 65 63 61 59 57 55
YEAR OF MANUFACTURE

Machine Value vs. ROPS Retrofit Cost —
Caterpillar D8

4-100



~

about 4 per year and the accidents which cause some degree of non-fatal
injury by 90. This estimate must be qualified by several factors. The

two most important of these are:

1) Protective structures protect the machine operators
only when they are in the operators! normal operating
positions. In some of the fall-of-ground accidents
which involve machines of interest, the operator is

not in his normal operating position.

2) The degree of protection afforded a machine operator
by a protective structure depends upon the energy
absorption capability of the structure relative to the
energy involved in the ground fall. It is clear that there
are some fall-of-ground accidents for which no con-
ceivable machine-mounted protective structure could

provide complete operator protection.

Supplementary Note Concerning Machines of the Load-Haul-Dump Type

The low profile load-haul-dump (LHD) machines are commonly
used in underground mines in areas in which the larger machines of
interest cannot be employed. Indeed, the LHD and similar types were

developed largely for that reason.

In the sample, Table A6-3, there were 8 fall-of-ground accidents
in underground mines which involved machines of the LHD type. Three
of these were fatals and 2 produced some degree of non-fatal injury.

The LHD type was involved in nearly 6% of the underground mine

A6-13



attempt to provide operator protection in underground mines. The
installation of a FOPS type structure that does not unacceptably increase

the machine height is desirable.

During mine visits, examples of protective structures that
attempted to satisfy the need for low profile operator protection were
examined. Figure 3-1 illustrates this type of protective structure.
Before proceeding with a requirement to install some such device on
underground equipment, the structural performance requirements needed
to protect against side impacts must be defined. Since the machine mass
is moving during many of these side impact accidents, it would appear that
the performance criteria should cause the designer to prepare protective
structure designs that have energy absorption capability directly related
to equipment gross weight, A performance criterion for a side impact
protective structure has not been developed during this study. A regula-
tion requiring protective structures on underground mining equipment
should contain a side impact performance criterion in addition to a top

load performance criterion,

The use (or non-use) of seat belts in ROPS-equipped machines
is a source of mine safety personnel concern. A seat belt must be worn
by the operator to gain the maximum effectiveness of the ROPS system.
Woodward Associates personnel have examined many construction industry
accident reports where the operator of a ROPS equipped machine was
thrown out and crushed by the ROPS during a roll-over. Seat belts are

necessary to keep the operator inside the protected area.

Table 3-1 summarizes the conclusions reached in the accident
analysis/rock fall characterization area. Table 3-2 reviews the conclu-
sions relative to FOPS performance criteria and Table 3-3 presents the
economic effects of possible ROPS/FOPS retrofit policies. These con-

clusions form the basis for the recommendations.

WA.



such owners might be relatively much greater than for any other owner

group.

Based on the survey data, it is estimated that approximately 7%
of all of the owners had fleets of one to five composed of machines of
interest only, all of which were manufactured before 1970. In other,
more precise, terms, there are approximately 980 mines which have
self-propelled machine fleets (except trucks) composed only of machines
of interest manufactured before 1970. Approximately 60% of these
owners have no protective structures on any of their machines of interest.
So, there are about 600 owners of 1 to 5 machines of interest for whom
a ROPS retrofit requirement which covered all pre-1970 machines would
represent a financial burden of 15% to 60% of the market value of the
machines. The majority of these owners are in the sand and gravel
industry. For avery small number of owners, ROPS retrofit would
represent a cost of 90% to 100% of the market value of the machines.
This does not mean, of course, that the greatest financial impact in
dollar terms of ROPS retrofit would be on the small fleet owners. Some
large fleet owners also have large numbers of machines which are not
equipped with protective structures. One company, which operates
several mines, reported nearly 90 machines of interest. More than 60
were pre-1970 machines which had no protective structures installed.
The cost of total retrofit of ROPS to this company would exceed $120,000

for the pre-1970 machines alone,

4-111


a
= 200,000 L
a Po Pl i
U u ’
oe ' 1
eo) ‘ '
& | '
4 P
<= 100,000 YF- 1 1
v fl t U 1
i= 1 1 '
o ! ‘ 1
aa ' ‘ '
> ' ! 1
' ! i)
0 i | L 1
by Out du2
0 2.0 4.0

VERTICAL DEFLECTION (IN.)

DEFINITION OF SYMBOLS

Py = VERTICAL LOAD AT BENDING YIELD STRESS (LB)

by = VERTICAL DEFLECTION AT BENDING YIELD STRESS (IN.)

PL = MAXIMUM LOAD AT ULTIMATE BENDING STRESS (LB)

ot = DEFLECTION AT INITIATION OF MAXIMUM LOAD (IN.)

Lae = MAXIMUM ALLOWABLE DEFLECTION

U = ENERGY ABSORBED BY ROPS AT 4.0 IN, DEFLECTION (FT-LB)

Figure 4-7. Predicted Vertical Force-Deflection Curve for
Representative Canopies (Example: Caterpillar D8 ROPS)

methods and empirical relationships presented in the Reference Section
under "Plastic Design Principles". The derivations of each of the

parameters presented in Table 4-4 are discussed below.

The yield loads and deflections, Py and dy, were determined
from computer analyses using the program CANOPY. A uniform ver-
tical load was applied to all beam members in the plane of the canopy
Ne WA.

4-23



to 400,000 ft-lb depending on the gross weight of the vehicle. The energy
capability of the tires is not included in the criteria development leading

to the 40,000 ft-lb FOPS energy capability.

a PROTECTIVE CANOPY
r |t U = 6,000 - 300,000 I T-1.13

TIRES
U = 50,000 - 400,000 I T-T.B

Figure 4-9. Energy Absorption Capability of Vehicle
Equipped With Protective Canopy

Non- Uniform Loads

It should be emphasized that all previous discussions of energy
absorption capability were based on the assumption of a uniformly dis-
tributed force application over the plan view area of the canopy top.

The energy absorption capability is very different for other loading
assumptions. Figure 4-10 and Table 4-5 summarize the structural
capability of a representative FOPS for the Caterpillar D8 tractor under

various loading conditions. Rock falls matching these loading condition

~

WMA.


DESIGN CRITERIA AND GUIDELINES

FOR

FALLING OBJECT PROTECTIVE STRUCTURES (FOPS)

(FOR RUBBER-TIRED AND CRAWLER-MOUNTED FRONT-END LOADERS, DOZERS, AND TRACTORS; AND FOR MOTOP
GRADERS AND WHEELED PRIME MOVERS)

PREPARED FOR
UNITED STATES DEPARTMENT OF THE INTERIOR
BUREAU OF MINES

BY

WOODWARD ASSOCIATES, INC.
225 REDLANDS PLAZA

REDLANDS, CALIFORNIA 92373

PROGRAM FINAL REPORT

USBM CONTRACT NO. JO357110
WA REPORT 78-22F

FEBRUARY 26, 1976


structures installed. The pie charts in this figure are drawn so that
the area of each is approximately proportional to the percentage of the

population to which it relates.

In summary, the following can be stated about the effort in this

section:

1) The survey of approximately 4% of all of the active metal
and nonmetal mines provided the basis for the estimate
of the population of machines of interest. The total popu-
lation was estimated to be about 49,000 machines, of

which all but 1200 are used in surface operations.

2) Nearly 46% of the machines were manufactured after
1969; nearly 32% in 1965 through 1969; and approximately
22% before 1965.

3) Nearly three-fourths of the machines manufactured after
1969 have protective structures installed; approximately
one-third of those manufactured in 1965 through 1969
have protective structures; and less than one-fifth of

those manufactured before 1965 have protective structures.

It should not be inferred that all of the machines in the population
are used exclusively for mining, or even for work directly related to
mining. In fact, many of the machines, particularly in sand and gravel
operations, are used in work not directly related to mining much of the
time. The survey did not attempt to determine the proportion of operating
time a machine was used in mining. Many telephone inquiries were
received about whether a machine which was used only ''a small fraction

of the time"' or "'a few weeks a year" should be reported in Section 3 of

the survey form. The answer was to report all machines used at the



elastically support a static load of 36,000 pounds applied to the plan view
area of the canopy top within the middle ninth of the plan view area.
Specified safety factors are required for the attachment joints. If the
canopy is mounted to the main vehicle frame and meets specified design

guidelines, no analysis of the vehicle frame is required.

Method 4 — A computer analysis of the canopy and noncomputer
analysis of the attachment structure and vehicle chassis is required with
Method 4. This method of certifying the static top load requirement is
outlined in the FOPS Design Guide (Computer Method) (Appendix A2).

As described in the Design Guide, the computer program CANOPY can
be utilized if the program is modified to include plate elements and

buckling checks of the structural members.

A1-6

.



Figure 4-29. Young Corporation ROPS on
Massey-Ferguson Industrial Tractor;
ROPS on Massey-Ferguson Rubber-Tired Loader



Table 4-16. Estimate of Machines of Interest
Used Only Underground or Underground and Surface

No

ROPS ROPS Total Percent
Front-End Loaders 241 509 750 61.7%
Dozers 36 44 80 6.6%
Graders 10 62 72 5.9%
Tractors 9 268 277 22.8%
Prime Movers 27 9 36 3.0%

Total 323 892 1215
Percent 26.6% 73.4% 100.0%

used in certain underground mines. Under those circumstances, it
would be appropriate to estimate the cost of implementing the policy by
subtracting from the total population some proportion of the numbers in
Table 4-16 which represents the machines used in underground low back
mines. The discussion above does not apply to room and pillar mines
which have very high backs (as in some salt mines and lead mines con-

tacted during this study) or at least does not apply to the same degree.

Figure 4-35 shows the total estimated population of machines of
interest by fleet size and composition. Of special interest is the estimate
that nearly 15% of the owners have fleets of 1 to 5 which contain only pre-
1970 machines. Some additional analysis was made of the sample data
for these small fleets with a view to estimating what proportion of the
owners of fleets of 1 to 5 machines of interest owned only machines of

interest and only pre-1970 machines because the financial impact on

WA.

4-109


PREFACE

This report describes the results of the activities of Woodward
Associates, Inc. in performing U.S. Bureau of Mines Contract
No. J035711, ''Design Criteria and Guidelines for Falling Object

'

Protective Structures.'' The effort funded by this contract was com-

pleted during the period from June 13, 1975 to January 30, 1976.

This contract was directed by Mr. James Ault, Technical Project
Officer, Pittsburgh Mining and Safety Research Center, and Mr. Bill
Pickens, Contracting Specialist, Pittsburgh Mining and Safety Research

Center.

iii



The example, Figure A2-2, further illustrates the approach:

u!

Oo > — ee ) <P

|

Ro
Ry

Figure A2-2. Beam Buckling. Example

3.0 in. steel pipe

L = 80 in.
A = 21,228 in.?
I = 3.017 in.*
Cc = 1.75 in.
6 .
E = 29x10 psi
Pry = 36,000 psi
Loads and reactions
P = 25,000 lb
1 .
M~ = 40,000 in. -1b
_ M! _ 40,000 _
R, = Ry = TF 30 = 500 lb

A2-9



~\

Reporting to Mining Enforcement Administration in 1974." These listings
had a total of 7369 mines. They were compared to the Mine Reference
File in several ways and the differences analyzed. The conclusion was
that the HSAC list, although not a complete frame as the Mine Reference
File is, was a satisfactory surrogate for a complete frame with respect

to the survey for this particular study.

Table A4-1 shows the survey sample selected. Systematic selec-
tion was employed on the HSAC list, which was arranged by states.
Every kth item in each mine category (underground, open pit, crushed
rock, sand and gravel) was selected from a random start. For under-

ground mines, k was 4; for all surface mines, k was 8.

Table A4-2 shows the overall response achieved by the survey by
state. One of the several reasons for using systematic sampling was to
make certain that all mining regions and all states were represented in
the sample. It was clear from early discussions of the study with mining

people that this feature would be desirable.

Table A4-1. Composition of Survey Sample
(Equipment Survey)

Number of Number of
Mines on Mines Selected | Sampling
Mine Class HSAC List for Sample Ratio
Underground (RS-U) 444 111 1/4
Open Pit (RS-O) 1441 182 1/8
Crushed Stone (RS-C) 2320 291 1/8
Sand and Gravel (RS-S) 3164 396 1/8
TOTAL 7369 980 13/100

WMA.

A4-2


mine, regardless of the amount of time used there. The machines of
interest are types which have great work versatility. None is distinctly
identified with the mining industry. It is likely the relatively high pro-
portion of machines which have protective structures installed is related
to their versatility, that is, they are also used in work in which OSHA

or state ROPS requirements apply.



Table 2-3 lists current state and federal ROPS regulations.

These regulations often refer to SAE Standards and Recommended
Practices that were in effect on the date that the particular regulation was
promulgated. The SAE ROPS Recommended Practice currently in effect
is SAE J1040a, This SAE Recommended Practice incorporates material
previously published as SAE J320, J394, J395, J396, and J1011,

Section 5.0, References, lists SAE ROPS Standards and Recommended

Practices that have been and/or are in effect at tnis time.

Table 2-4 describes the mining equipment population that could be
affected by a ROPS/FOPS regulation, The results of the USBM Fall-of-
Ground and Equipment Survey have been analyzed and estimates of the total
numbers of mining machines have been prepared. These estimates are
given by machine type and by date of manufacture, The equipment numbers
given in the front-end loader category do not include load-haul-dump
machines, The total number of LHD units in use in underground mines
is estimated at about 600 of which about 60% have some form of protective

structure installed,

Tables 2-5 and 2-6 provide estimates of the costs involved in

complying with ROPS/FOPS regulations.



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A4-4


The groundrule for establishing the load level for alternate
approaches is that stresses in critical areas of the structure must du-
plicate stresses imposed during a 74,000 lb load application distributed
over the entire canopy top. Table 4-6 shows a comparison of yield load
and deflection for a four-post ROPS configuration for the Caterpillar D8
tractor. A 106,000 lb yield load is predicted for the distributed load
condition over the entire plan view area of the ROPS top. The corre-
sponding yield prediction for a distributed load over the middle ninth of
the plan view area is 52,000 lb. By using this relationship, a yield
prediction of 36,000 lb is obtained for a four-post unit with a center
ninth loading Goxtooo X 74 000 = 36,000). Therefore, the stresses at
critical points in the protective structure are equivalent for the 74,000 lb
fully distributed load and the 36 ,000 lb load over the center ninth of the

top.

This relationship appears to be valid for typical four-post
configurations since the more concentrated loading produces higher
stresses in the structure. The relationship does not hold for two-post
ROPS. In this case the critical stress is located along the entire support

column and is not affected by changing the top loading from fully

Table 4-6. Yield Predictions for the Caterpillar D8 Tractor ROPS/FOPS

Yield Load, Yield Deflection,
Loading Condition Py by
Distributed load over entire 106 ,000 0.258
plan view area of ROPS top
Distributed load over 52,000 0.320
middle ninth of plan view
area



data. In contrast, using a program of inadequate capability will result
in an inaccurate solution or excessive input time while attempting to

formulate a realistic mathematical model.

The program CANOPY is limited to beam members as contrasted
to ten element types in Elastic/Plastic SAP. The computer analyses
conducted during this study indicated that beam and plate elements are
necessary to adequately evaluate a cab or canopy. Protective canopies
are generally constructed with rectangular tubing, square tubing, round
tubing, square bar stock, or round bar stock. In any case, these can

be modeled as beam members.

FOPS canopies also usually have steel plates covering their tops.
Enclosed cabs utilize plates extensively. Since almost all cabs and
canopies use plates in their construction, it is apparent that a plate
element is a very useful computer analysis tool. The computer program
CANOPY does not have a plate element; therefore plates must be modeled
as equivalent beams or not included in the analysis. Both of these alter-
nates can result in poor accuracy and extra input effort. SAP includes
a plate element which can be effectively used in the analysis of cabs

and canopies.

The required computer size is important since it affects the use-
fulness of the program because of geographical location. The very large
computers and data terminals are generally only available in large
metropolitan areas. The program SAP requires a large CDC, IBM or
UNIV AC machine to handle the core storage requirements. A smaller
computer can be used with CANOPY since only a 40K core storage is
needed. This is an important factor if the computer analyses are going
to be conducted by mine companies which are commonly located in remote

geographical areas.

A2-17



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4-34


3)

4)

5)

8)

The future promulgation of a ROPS regulation for
metal-nonmetal mining equipment is expected to cause

a significant reduction in deaths and injuries to the

operators of the subject mobile equipment. Though the
proposed ROPS regulations would only apply to equipment

used in surface areas of underground mines and surface mines,
it is recognized that in underground mining, and certain areas
of surface mines, operators of the same equipment types could

be exposed to death or injury from falling objects,

This report defines the "rock fall environment" in
underground and surface mines and examines the opera-
tor protection available through the use of FOPS and
combination ROPS/FOPS units.

If it is determined that a FOPS requirement is necessary
in surface and underground mines, a performance cri-
terion will have to be developed to guide the design of
acceptable FOPS. This report outlines a certification
procedure, and the analytical and test methods that

verify the structural performance of the FOPS.

A question exists as to the feasibility of installing ROPS/
FOPS on "machines of interest" that were manufactured
before 1970. This report examines the availability of
ROPS designs for pre-1970 equipment and reviews the

concern about the frame strengths of pre-1970 equipment.

The installation of ROPS/FOPS on mining equipment may
in some way interfere with the machine's ability to
perform its intended work function. The operation of
FOPS-equipped machines in underground mines has been

examined.

1-3

WMA.


established procedures. The test specimen will include
all of the major load carrying structural members in

the load train between the canopy top and the axles.

The axles of the vehicle shall be mounted to a rigid
platform. A rigid platform is defined as a surface of
such firmness that it cannot be penetrated or appreciably
deflected during loading. Other support points beyond
the axle locations must be accompanied by engineering
calculations which show that they do not react more than

10% of the applied static test load.

Test Loading

The canopy will be loaded within the middle ninth of its
plan view area with a load equal to 36 ,000 pounds.
Detailed examples of this loading criterion are shown
in MESA Information Report IR 1002, ''A Testing Pro-
cedure for the Certification of Underground Protective

Cabs and Canopies."

The loading requirements described above are adequate
for certifying most canopies. In some instances,
however, this loading location does not represent a
reasonable verification of the canopies functional charac-
teristics. An example is a canopy in which the vehicle
operator is located under a cantilevered overhang portion
of the roof. It is apparent from this example that a test
with the load applied over the middle ninth of the plan
view area does not demonstrate the structural adequacy

of the design to protect the operator.

A3-3



Data Analysis and Inferences

lm order to deal properly with the reported information, it was
necessary first to decide upon certain conventions which would be used
in processing the data. Insofar as possible, data about each accident
was expressed in terms which made it possible to perform some para-
metric analyses. Correction constants were employed in some cases
to make the data more accurately reflect the true energy levels involved.
The "ground rule" for selecting these constants was simply to choose
those which would be most appropriate to obtain true energy levels within
the constraint that no energy-related factor would ever be understated.
All of the data processing procedures have been consistently conservative,
that is, whatever bias exists in the final data is in the direction of higher
than actual energy values. The details concerning the selection of cor-
rection constants appear in Appendix A5. An estimate of bias is included

in the appendix cited.

In processing the data, the weight of the fall, as reported by the
mine management or by the MESA accident investigation was always
used as reported. No "correction constant'' was applied to weight for

two reasons:

1) No sound basis could be found for using a correction
constant. A few of the respondents to the accident
questionnaires gave fall volume information in addition
to weight. In some of these cases, a calculation would
show that one or the other was incorrect because, in order
to have the weight reported, the density would have to be greater

than it possibly could be in the ore body concerned. There

4-4



APPENDIX

Al

A2

A3

\4

AS

A6

APPENDICES
TABLE OF CONTENTS

FOPS CERTIFICATION PROCEDURES

FOPS DESIGN GUIDES

FOPS TEST PROCEDURE

EQUIPMENT POPULATION SURVEY

ACCIDENT DATA SURVEY

ACCIDENT DATA ANALYSIS

PAGE

Al-1

A4-1

A5-1

A6-1

A-iii



4.3 EQUIPMENT POPULATION

This section is a summary of the work done with respect to
defining the population of the ''machines of interest'' and estimating the
characteristics of that population. The characteristics included machine

age, ROPS installation status, size of fleet and others.

Sources of Population Information

The machine data were obtained by means of a survey of metal
and nonmetal mines. The sample to be surveyed was selected from a
listing provided by the MESA Health and Safety Analysis Center (HSAC)
in Denver. The list was in two parts. One part was formally entitled
"Surface Metal-Nonmetal Mines Reporting to Mining Enforcement and
Safety Administration in 1974,'' the second was "Underground Metal-
Nonmetal Mines Reporting to Mining Enforcement and Safety Administra-
tion in 1974,'' The total number of mines listed, less those which were
deleted by WAI because they were mines which would receive accident
questionnaires, was 7369, (See Appendices A4 and A5 for survey back-
ground.) The very cooperative MESA people also provided a second type
of listing. It was entitled 'Metal-Nonmetal Mine Reference File." It had
an effective date of August 8, 1975. The file showed the most recent MESA
inspection date for each mine, the number of employees, and other infor-
mation which indicated that some mines were not presently active. The
file included some details about mine locations, but not about company or
mine mailing addresses. Some cross-checking of the two listing types led
to the conclusion that the HSAC lists could be used as the frame for survey
sample selection. The HSAC list, although not a complete listing of active
mines, and therefore not a complete frame, was judged to be a satis-
factory surrogate for a complete frame. (A more detailed discussion

of the survey matters, including frame considerations, is contained in

WMA.

4-46



beams. These approximations ignore the moments at the ends of internal
top members, which introduce small errors in calculation of resultant
stresses. To account for these errors safety factors must be applied

to the computed elastic strength. Safety factors ranging from 1.05 to
1.33 are recommended depending on the geometrical configuration of the

canopy.

Two-post protective canopies are increasingly popular on these
equipment types. The two-post configuration does not meet the geometric
requirements as described previously. In most cases, however, these

designs are easier to evaluate since the degree of redundancy is lower.

Generally the support columns, members AB and CD shown in

Figure A2-1, can be evaluated using the following approach.

Figure A2-1. Two-Post Canopy

A2-3



tan 40° = 0.839 = we
h = 29.37 in.
Vv = 4£(70 x 70)(29.37) +4 (70 x 20)(29.37)
= 47,971 + 20,559 = 68,530 cu. in. = 39.66 cu. ft.
Ww = Vd = 39.66 cu. ft. x 150 Ibs./cu. ft. = 5,949 Ibs.

This calculation is important only in that it shows that a relatively small
fall of loose material, up to about 6000 pounds, might be retained entirely
on the protective structure, provided that the initial contact area was

somewhat smaller than 70 inches by 90 inches = 43.75 square feet.

An estimate may be made of the maximum weight and volume which
might impact upon the protective structure. The mean thickness (vertical
dimension) of the near vertical (>65°) falls for which the vertical dimen-
sion was reported was 4.5 feet. The range was 0.5 to 10 feet. However,
there were some falls with a vertical dimension of 50 feet, judging from

the accident investigation data. These all involved wall collapse. The

WMA.

A5-23



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" a tesous oostues cont one's our suvter n oot er ot fc-zesa se
x a seek *ra3ur n ono st0"te suc oseten a dato stones: “
‘ ssove9 eat 000" 966 " ores or 609 cones ot so9 su
« a sents rst'ost 000*000*001 sue casita , svorspues ator | ot Pecoose sm
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s ° ° oo0'e6 ooo 9st 00's 7 svorepaes oot n une
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e x a 4a Ove 99S'T stety nos*oe > om ”
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* n resous 200" 0008 ort one
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" a venous ooy't 000" ovr n sneavenr oor oz 100 88
s a weraaeg soon 00007 000" 9c 000"? ot puyeeas voate ar Poeece ow
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. ° ° 000" 861 000" 017 oo" x auoresua ot
* ° ° ovo" tt o00"t a svornser oon" «

sp09 Kantor | worszex024 Pestoaut s0
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os 4

(qUOD) SJUEPTOOY puNoIy-jo-][ey SUT, Voejung s0j
suolje[nojep Asaeuq pue eyeq payoday

“eT-SV PTdeL

A5-30




Table A5-4, Accident History (AH) Questionnaires
Mailed and Numbers of Accidents Involved

AH Fatal Non- Fatal Total
Mine Type Mailings Accidents Accidents Accidents
Underground 76 56 37 93
Surface 37 29 8 37
TOTAL 113 85 45 130

reports. There are fewer questionnaires than accidents because several
underground mines had more than one accident about which inquiries

were made.

The questionnaire used is shown in Figure A5-1. It is Section 1
of the survey form which is discussed in more detail in Appendix A4.
Three illustrative inquiries are shown on the questionnaire. The 130 acci-
dents were numbered serially starting with AH-101. The ''AH" referred
to mines which had an "accident history" reflected in the MESA accident
investigation reports. Equipment data which was also obtained on the
AH survey forms were compiled separately from those obtained on forms

with other designations, as discussed in Appendix A4.

Table A5-5 shows the numbers of fatal and non-fatal accidents
for which the data required were obtained from responses to the mail
questionnaires. The total is 86. The ''success rate" of the questionnaire
was 86/130 = 0.662, or about 66%. The overall response rate was higher.

Some respondents did not provide the information requested, and a few

A5-9



top. The maximum values of Py and bye were limited to levels
corresponding to the bending yield stress allowable at the highest
stressed point in the structure. The allowable bending yield stress

was obtained by increasing the 36,000 psi normal minimum tensile yield
stress of ROPS steels by an appropriate bending modulus of yield factor.
The bending modulus of yield factor ranged from 1.16 to 1.28 depending
on the shape configuration of the beam bending cross-section. This
factor was computed using the methods outlined in the text, "Strength

of Materials" by F. Shanley. The deflections presented are for the point

on the structure with maximum vertical deformation at the PY load level.

As shown in Figure 4-7, PL is the maximum load capability
predicted for the canopy and corresponds to the ultimate bending stress
allowable of the material. The bending allowable was determined by
multiplying the 55,000 psi material minimum ultimate bending strength
by a bending modulus of rupture factor. The factor, depending on the
cross-section configuration, ranged from 1.27 to 1.50. The deflection,
Suze was obtained from the force-deflection curve assuming a stiffness
between the yield and ultimate load equal to one-half that of the linear

elastic portion of the curve.

The deflection over the operator at the center of the canopy
was limited to 4.0 inches as depicted by bo: In general, the analyses
results indicated that the protective structures could deform 7.0 to
8.0 inches before collapsing. However, it was assumed that this amount
of deformation was excessive since the canopy top would probably impact

the operator's head during a rock fall.

The useful energy absorption capability, U, was determined
by computing the total area under the force-deflection curve out to 59°

This method assumes that all of the kinetic impact energy of the rock

WA.



where
Ex = kinetic energy in foot-pounds
m = mass in slugs

v= velocity in feet per second

It is the kinetic energy of the falling object which the protective
structure must transform in one way or another. If the energy loss due
to air friction is ignored, because it is very small, the principle of con-
servation of energy requires that the kinetic energy of a falling object at
any point in its fall be equal to the potential energy it has lost. An object
of weight ''w'' which is held at a height "h'' above some reference plane
(such as the floor of a mine) has potential energy equal to the product of

its weight and height (Ex = wh).

The kinetic energy of a rock fall can be defined at a reference plane
that is the same as the level at the top of the FOPS. This level may be
from about five feet to thirteen feet above the surface on which the machine
is operating. The reference plane defined by the FOPS top is called the
"protection level''. How the "protection level" was selected for each
accident in the data analyses is discussed in later paragraphs. Of course,
the total kinetic energy at the protection level is not necessarily the amount
with which the design of the protective structure must be concerned. In
many cases, only a part of the energy affects the structure. The method
of handling this fact in the data analysis is also discussed in later para-

graphs of this appendix.

The second of the two needed types of energy data is that related
to small area (point) loading of the protective structure. For some fall-
of-ground accidents, the provision of protection depends upon the capability

of the structure to resist extensive deformation, or top plate rupture.

WMA.

A5-5



Explanatory Notes:
tion 2

— "TMDimensi
_ “Material”

— if mo equipment involved, state

Section 3
— "Equipment 1) pe”: (EXAMPLE: FE
_ "Year Mad "

Use”:
underground, on Te surface, or both.

to protect the ‘operator in FO ‘over

u

designed and Built IP your facilities.
_weRemaining Life
same WO! Kit IS doing Now.

Figure A4-2.

as”: State length, width, and thicknes in feet.

state type of basic mine ore (EXAMPLE: ‘luorspar, timestoner salt, gold)

— agelt From” might ‘ye back, face, Piles bencl
“Not

. numt

_ “Primary Use Check one of the three locks tO indicate whether the machine 'S used

= "ROPS installation” refers to any, “protect canopy’
jin roll

Name commerc

Your estimate Of time, in years, the equipment ca” PP sed to do the

BUSINESS REPLY MAIL
irst Class Permit NO 4, Genoa, NV,

atrer compretion of 108 piease ford, seal an mail

USBM F.
. all-of-G
R round and Equi
everse Side) pment Survey F
y Form

" shovel bucket shaft, etc:
spe state type (E AMPLE cE loader, dozer

loader, doze", tractor, grader fork lift, LHD. truck).
ber.

A4-9

WA.


000‘ 000‘ S#$ %OO1 OSL‘ SZ SourTYyoe!, IV
000‘ 000‘8E$ 16 G2S° 1S 0961 ‘1 Azenuer
000‘ 000‘ 0E$ YL oss‘ ot S961 ‘1 Avenues
000‘ 000‘ II$ %09 006°S OL6L ‘1 Auenuer
AdTPOd JOLY paddinbgy -SdOu AoTpOd aatpeusaiy JIWV
jo ysoy ST }eu4} Aq payajjy peanjoejnue Ay
uorjepndog auryoeyy souryoeyy JO saquiny SOULYORI
9L61 ‘1 Adenuer ayeutxouddy uo }1jO119Y
1e}O.L JO WITIT SdOu/SdOU

(Sault punousaapun puke adejuns ul ,,}Se4a}UL JO Sauryoeur,, JO

sed4} 11V)

SOLTOd WJOLIOY SdOM/SdOU PAT eUsayY JO SISOD ~9-% ALAEL

2-14


Method 1 — A static test of the entire FOPS including protective
canopy, attachment joints, vehicle chassis, and axles is required with
Method 1. The procedure involves the distribution of static loads near
the center of the protective structure's top and the measurement of
vertical deflection at the center of the load application. The canopy is
tested while mounted on the vehicle chassis which is rigidly attached to

the test platform at the axles.

With Method 1 all of the load carrying FOPS components are
tested; therefore structural analysis is not required. Option A of the
FOPS Test Procedure (Appendix A3) presents a step-by-step sequence

for conducting this test.

Method 2 — A static test of the canopy attached to a rigid plat-
form, engineering computations of the attachment structure and adherence
to certain design guidelines is required with Method 2. The test pro-
cedure is identical to that described in Method 1 except the test specimen
includes only the canopy. Since the joint and the structure attaching the
canopy to the vehicle are not tested, an engineering analysis is required.
If the canopy is mounted to the main vehicle frame and meets specified
design guidelines, no analysis of the vehicle frame is required. An
engineering analysis of the vehicle frame is required for designs not

meeting these requirements.

Option B of the FOPS Test Procedure (Appendix A3) presents a

step-by-step sequence for conducting this test.

Method 3 — A noncomputer analysis of the canopy, attachment
joints and vehicle chassis is required with Method 3. The details of the
analysis procedure are described in the FOPS Design Guide (Appendix A2).

In general the analysis results must demonstrate that the FOPS can

WMA.

Al-5


United States Department of the Interior
BUREAU OF MINES

AVENUE

pITTSBURGHY

pittsburgh Mining and Safety Research Center

industrial Hazards
and Communications

as a part of the continuing research in mine safety, the Bureae of
tines is conducting ce eudy of metal and non metallic mines. contract
‘0357110 has beet warded tO Woodward Assochates of Redlands, Calif-
ornia, to perform aeme of the Study work.

one part of the study pertains %° gali-of-ground accidents. The te7TM
ome agent” referss Rhis study, tO any unplanned OF unforesee?

cvent that Mays OF may not, have

or damage t° property: We seek to augment ‘and up- date fall-of-ground
Secident data bY obtaining sfgormation from YOU Pag from others +" the
mining industtY+

the second part of the study relates to self-propelled machines presently
in use in mining operations » pxcept machines Pech are remotely operated-
We seek tO authenticate Cmrjous estimates es seh have been made by means
bE sample machine viwentories from @ few mining FATMS-

we would greatly appreciate Your assistance in the gtuay. spechfical’Ys
ye would be Very heipful $f YOU would provide the information identified
on the enclosed survey form at Your a hiest convensenee Should YoU
wish to ask questions about the form, please call (702) 32-5815 OF
wigre to Woodward cegociates, Nevads operations OFFICE? pox 116, Genoa
Nevada, 89411 OF contact me at (il2) 892-2400

thank you fF your cooperation #7 this matter.

respectfully

oWwtlon
“ns
: 4 C. At
g, Zz james: c, Ault
~ . General Engineet

it Technical project FFEECE

@,
8
3
3

Figure A4-3.

USBM Co
ve
wey vr Letter for USBM F
quipment Survey atbrol Ground

A4-11


~\

cause undue and unwarranted financial hardships for some equipment
owners. Generally it can be stated that the older machines are not worked
as many hours per year as newer machines and therefore are not subjected

to falling object or roll-over risk situations as much as newer equipment,

The selection of a later date of manufacture, Januay 1, 1970 for
instance, would result in coverage of only 60% of the machines currently

in use,

The regulation should state a date (January 1, 1978 is suggested)
after which the ROPS/FOPS that are installed on new machines must meet
the SAE ROPS performance criteria (SAE J1040a), the SAE FOPS per-
formance criteria (SAE J231), and a new MESA FOPS performance standard,
The time lag will allow ROPS/FOPS manufacturers the time necessary to
verify that their current ROPS/FOPS meet this new USBM FOPS per-
formance standard. Machines with gross vehicle weights under 30, 000 pounds
will not be fitted with FOPS that provide the minimum desired protection but

no solution to this problem is readily available,

Table 3-4 summarizes the WAI recommendations,



Table 4-12.

ROPS/FOPS Model Availability (Cont)
(Furnished by Saf-T-Cab, Inc. , Fresno, California)

Ravgo/Wagner
Rollers

2.96

ae

Compactors Wa
spay
Tampo
Rollers
RS-16
Riran
SP-950
Terex

Crawler Tract

-15/72-10
30
2-40

Teagan

Wheel Loaders

104

154

tos

2000
000

Vibro Plus Hbynapach
Roller

cues

45
600

west

RS-28

Ress

na
164
100
1500
3000

‘erapers (Le Tournea

c-Patt
Rezo

BiH

wert

Jotor Graters | \tams|

220
a
312
860

450
660-7

60 400

woeaT

Sa AS-166.

Sp-31g | $P-T50

A240 2-80.

1-20

1-25

1-30

31

Tsld S18

T2500 S28
451

124 14

204 208-4

104 400

1700 100

4000 5000

101 nes
300)

oe

330 330-15

HO aa

833 610

666 655-1,

Vibra Plus "benapac) ‘cont

Untor Graders (dams) Cont
m” T77-RARR

Off Highway Trucks

Wheel Loaders

1 Ha np
Lp-sP A Ler
Lp-150 300 350
son 1200

Wagner (See Raygo Wagner
Waldo
5000
Wheel Tractor

G6

HPD
Lasts,

4008

4-67



addition, some accurate information about the shape of the fallen material
would be necessary and, if it is non-cohesive, data which define its
character should be known. Shape might be expressed as initial impact
area in square inches. And finally, it should be known whether the
material fell in a free-fall mode or as a sliding, pivoting or tumbling
mass. If the fall was not a free fall, information about angles and fric-
tion losses would be required. Of course, data of these kinds which are
accurate and detailed are possible only from controlled field tests or
laboratory experiments. It is actual events with which this report is
concerned and those events occurred in environments which are greatly

different from the controlled test environment.

What are usually measured in an accident, if anything is actually
measured at all, are the dimensions of the void created by the fallen
material and the distance from what was believed to be the base of the
material before it fell to the surface on which it came to rest. If the
fall involved only one rock, or a few, the measurements might be made
on the fallen material. Sometimes actual measurements are taken by
mine safety officials or by federal and state mine inspectors. In many
cases the information is estimated, and the dimensions used are feet of
fall distance and size, and tons or hundreds of pounds of weight. More
often, only a few of the needed data items are estimated at the time of
the accident, or the time of the formal investigation, and the others are
not estimated (or at least not recorded in the accident records). Only 22
of 152 MESA accident investigation reports used in this study had all of
the needed data. The reason seems clear: neither the company safety
officials nor the MESA officials need these data to form the judgments
they normally must make regarding accident causes and accident pre-

vention techniques for effective safety administration.

~\



Va

requirements are briefly summarized below and described in the FOPS

Certification Procedure (Appendix A1).

e The canopy and attachment structure must be fabricated
with steel meeting specified Charpy V-notch impact

strengths.

e The American Welding Society specification for welding
roll-over and falling object protective structures must
be followed during fabrication and installation of the

canopy and attachment structure.

e The top of the canopy must meet minimum design guide-
lines or be tested to SAE Recommended Practices J231
which specifies the minimum performance criteria

for FOPS.

e A static load must be applied near the center of the
protective structure's top. The canopy will be installed
on the vehicle in the normal manner and supported in

the test bay at the axle location.

Step-by-Step Test Procedure (Option A)

Protective canopies are required to elastically support a static
load of 36,000 pounds applied within the middle ninth of the plan view
area of the canopy top. Detailed test requirements are presented in the

following paragraphs:

a. Test Preparation

The canopy shall be mounted to the vehicle chassis in
the same manner as it is for normal operation. All
attachment methods such as welding, bolt types and

installation torque values shall be in accordance with

WA.

A3-2


ribbed structures to spread the load out over a larger reaction area.
The smaller industrial- or agricultural-type tractor used in mining as
personnel carriers or to tow small ore trailers present a more difficult
retrofit problem than the larger units. Some of the small farm-type
tractors manufactured up to the late 1960's and early 1970's have very
limited attachment areas; indeed on some units the only potential attach-
ment areas are on the rear axle housings. These areas are of known
weakness in some vehicles and have, at times, exhibited failure when

subjected to ROPS testing.

_As was shown in Section 4.4, there are commercial ROPS avail-
able for a broad range of vehicle models and dates of manufacture. The
conclusion of the OSHA review of retrofit problems on pre-1970 equip-
ment was that ROPS were available and could be installed on most "heavy"
construction equipment manufactured after 1960, and on many light

industrial tractors manufactured after 1965.

Operational Viewpoint

The installation of a ROPS/FOPS on a mining machine can cause
problems that are far-reaching and that can have effects on the mining
procedures and on the use of the machine and its new ROPS/FOPS. A
different set of potential problems exist for the case of equipment used

in surface areas and the case of equipment used underground.

In the surface area application, the negative aspects of ROPS/
FOPS installation begin with the installation procedure itself. Inthe
instance where a machine is being retrofitted with a ROPS/FOPS at the
mine site, provision must be made to have a crane of sufficient capacity
available to lift the ROPS/FOPS into position on the machine. The

mounting brackets must be welded to the proper areas of the machine



Table 3-4, Recommendations

ROPS/FOPS in Surface Areas — A MESA ROPS/FOPS
regulation should require ROPS/FOPS on machines used in
surface mines and surface areas of underground mines,

ROPS/FOPS Retrofit Policy - A ROPS/FOPS regulation
should be promulgated by MESA that requires the installation
of ROPS and FOPS on all "machines of interest'’ manu-
factured after 1964, These ROPS should comply with the
performance requirements given in SAE J1040a or in Corps
of Engineers Manual EM385-1-1, March 27, 1972. The FOPS
should comply with the performance requirements of

SAE J231,

ROPS/FOPS for New Machines — The ROPS/FOPS regulation
should state that new machines manufactured after 1977 must
have ROPS installed that comply with SAE J1040a and FOPS
that comply witha MESA FOPS performance standard
(developed from the WAI FOPS criteria included in this
report), Anew MESA certification procedure (developed
from WAI procedure included herein) should be referenced
as the performance verification method.

Seat Belts — The ROPS/FOPS regulation should contain a
requirement that seat belts be installed in machines and that
it is the employees’ responsibility to wear them,

ROPS/FOPS in Underground Mines — It is recommended that
crawler loaders, crawler dozers, rubber-tired dozers, motor
graders, and scraper prime movers be exempt from any future
ROPS/FOPS regulation effecting mobile equipment used
underground,

USBM should continue investigation into the need for FOPS on
underground mining equipment, Mining macnines that work
in unsupported roof areas (roof bolters, gathering arm j
loaders, front-end loaders, LHD units, etc.) experience far
more accidents of the type that a FOPS or side impact pro-
tective structure will protect against than do the front-end
loaders, dozers, graders that generally work in supported
roof areas,

The use of FOPS in underground mines should not be viewed
as a substitute for sound roof control engineering. Mobile
temporary roof supports are an important part of the overall
approach to providing protection for underground mining
personnel,



Table A4-3 shows the "usable data'' response rates. For the
sample shown in Table A4-1 (referred to as the 'RS'' sample) the usable
data response rate was 50%. Responses that reported the mines sold
were the subject of follow-up actions when the new owner could be identi-
fied. These were few in number; most of the responses in the ''closed
or sold" column were closed. Table A4-3 also includes data obtained
from the accident history inquiries (referred to as the ''AH'' sample).
These data were used only for comparison analyses with the RS sample.
In the table, "RS-U'' is the underground mine data. ''RS-O"' is open pit
mines; ''RS-C" refers to crushed stone and "RS-S" to sand and gravel.
The AH data are divided into ''AH-U" for underground mines and '"AH- A"

for all other.

The survey instrument used is shown in Figures A4-1 and A4-2.
Figure A4-1 is the face side with illustrative entries. When received
by the addressee, the only entries were the identifying number in the
upper left-hand corner and check marks in the squares in front of

' The numbers were assigned

"Section 2'' and "Equipment, Section 3.'
in district blocks for each mine category and, in addition, the RS and

U, O, C, or S blocks were color coded for each mine category. This

was done to minimize initial data processing errors and the time expended
by research assistants in data sorting and recording. The equipment

and accident entries shown on the form for illustration are some actually
received, although not from a single mine. Of course, not all responses
were as clear or as complete as those shown here. The "estimated

remaining life" data were used only to form some estimates about the

average machine life in different mining operations.

Figure A4-2 shows the reverse or mailing side of the survey

form. It is self-explanatory.

A4-6



main vehicle frame must be certified with engineering
calculations. The attachment structure loads should
be obtained by determining the reactions of the canopy
as a free body subjected to the applied top load of
Option A, Step b. A factor of safety of 2.0 above the
minimum yield strength of the material is required
for primary weld and bolt joints. A factor of safety
of 1.0 must be shown for all other parts of the attach-

ment structure.

Vehicle Frame Requirements

Analysis of the vehicle frame is not required if the
canopy is attached to a main structural frame member.
If the canopy is mounted to a secondary frame member,
a detailed engineering analysis is required to show a
factor of safety of 1.0 compared to the minimum yield

strength of the vehicle frame material.

A3-7



MTS BS SI 89 EGG 969 e601 IVLOL
6S HEL 8 9 19 18 SIL reqoqans HV
ES %89 I v 02 GZ Lg V-HV
%%9 rh L z Lb 9s 9L O-HV
0G LG L 29 98b fexere 086 yeqorqns SU
6b GG T 61 961 91g 96 S-SU
DLP Sb € Il BLT ZEl 16% O-SUu
% 9 %6 9 z al raat 921 B81 O-su
PS EL if 02 09 18 Ill a-su
oyey arey posnjoy POs 10 ayejdui0,) asuodsay aZzIg apo) ssei)

asuodsa y asuodsay *ojuy paso,) yeqoL, ye1OL aydures oul,
eyed [TLW4aaO aul0g

arqesn,
L_

soyey asuodsoy eyed e1qesn,, “§-PV O1deL

A4-7


These points constitute an important basis for ROPS/FOPS designs.

A configuration which is too flexible or soft will deform into the operator
protection zone under vertical impact loading from a rock fall and crush
the operator. An extremely soft ROPS/FOPS system is therefore ob-
viously inadequate. Although it is not so immediately apparent, a

canopy which is too stiff can also be unacceptable since it introduces
other possible failure modes. The cause of the problem, as discussed
previously, is that the vertical distributed load must be very high to
absorb the kinetic energy of the rock fall. This load must be transferred
to the vehicle frame through an attachment joint and an attachment
structure. The ROPS is usually bolted to the attachment structure which
is welded to the vehicle frame. Bolted and welded joints are the most
common source of structural failures. Therefore, a balanced ROPS/FOPS
design is required which is flexible enough to limit the load going into the
attachment structure, but is sufficiently rigid to withstand the impact

loads and limit the deflection to acceptable limits for the operator.

The energy absorption capability of the vehicle chassis and
related components is very difficult to determine accurately. It is
apparent that the vehicle frame contribution is very different for an
industrial tractor with the canopy mounted to the trumpet housing and
for a front-end loader with the canopy attached a considerable distance
from the axles. In the case of the small tractor chassis, very little
energy is absorbed in the vehicle frame since loads are transmitted
almost directly into the tires. In contrast, vehicles with canopies
installed to members with long lengths loaded in bending will deform
appreciably and absorb a considerable amount of energy. Many canopies
are mounted on fenders and fender support brackets which also deform

quite easily.



~

2) The survey of equipment population showed that over 60%
of vehicles had gross weights above 30,000 lb.
3) It is believed that the heavier vehicles are generally more

subject to rock fall exposure because of their work function.

Selecting a limit below 30,000 lb would actually result in lower
overall operator protection from rock fall. The reduction in protection
level would occur because the lighter vehicles can not withstand the
40,000 ft-lb energy requirement or the analogous static load require-
ments. Therefore, the requirement would have to be reduced. Lowering
the 40,000 ft-lb specification would result in lighter ROPS/FOPS struc-
tures being put on larger vehicles which are more numerous and accident
prone. Alternate performance criteria are recommended for vehicles

with gross weights under 30,000 lb.

The minimum predicted yield load, Po for canopies with
energy absorption capabilities above 40,000 ft-lb as shown in Table 4-4
is 74,000 lb. This value represents the distributed load which can be
applied over the entire plan view area of the ROPS top without causing
yielding. A unit with a yield load capability of 74,000 lb or greater and
fabricated with a high elongation material will have sufficient reserve
ultimate load and deflection capacity to absorb at least 40,000 ft-lb of
elastic-plastic strain energy. Loads below 74, 000 1b will not cause

permanent deformation of the ROPS/FOPS,

Any static load criterion must therefore induce stresses in
critical areas of the protective structure which correspond to stresses
induced during a 74,000 lb distributed load over the entire top. Obvi-
ously, a test or analytical procedure with a distributed load meets this
requirement. Sometimes it is very difficult to accurately apply a uni-
formly distributed load over a large area. Therefore, alternate

approaches were considered.



Figure 3-1. Protective Structures



Figure 4-27. Tube-l.ok ROPS Cab on
Caterpillar Rubber-Tired Loader;
ROPS on Caterpillar Crawler Dozer



Table 4-11.

(Incomplete)

ROPS Availability for Pre-1970 Vehicles

Crawlers Wheeled Loaders Scrapers
Caterpillar Caterpillar Caterpillar
D4-4G = (1936) 944 (1959) 619 (1959)
D4 -7U- (1947) 966 (1960) DW-20 (1955)
D6 - 8U_ (1947) DW-21 (1953)
D7 -3T (1944) Hough 632 (1962)
D8 -2U (1946) 641 (1962)
D9 - 18A (1954) H30F & R= (1960) 630 (1962)
H60 (1961)
H70 (1959) 631 (1960)
Allis-Chalmers 657 (1962)
490 (1959) 660 (1962)
HD-6B (1955) H100 (1962) 666 1962)
HD-9 (1953) (
HD-9B (1956) Trojan
HD-11B_ (1955) Motor Graders
HD-11E (1958) 134 (1959)
HD-16D (1959) .
HD-21 = (1954) Crawler Loaders Caterpillar
112 (1962)
International Caterpillar 13-9K (3338)
TD-24 (1956)
933C (1955)
TD-25 (1962)
955C (1955)
TD-30 (1962) 977D (1955)
TD-20 (1958)
TD-15 (1958) :
TD-9 (1953) Allis-Chalmers
HD-7G (1962)
HD-11G (1959)
HD-21GC (1956)



Table A5-18. ROPS/FOPS-Related Accidents,
Except Fall-of-Ground, for Which Data Recorded

Accident Type

Number

Roll Over
(ROPS and SB status unknown)

Roll Over
(No ROPS, no SB)

Roll Over
(ROPS, no SB)

Roll Over
(ROPS and SB)

Roll Over
(No ROPS, but SB)

Machine Fall
(ROPS and SB status unknown)

Machine Fall
(ROPS, no SB)

Machine Operator Struck Object
(No ROPS, no SB)

Machine Operator Struck Object
(ROPS, SB unknown)

Fly Rock
Operator Thrown from Machine

Machine Struck by Other Machine

Machine Operator Struck by Drill Steel

16

24

vy wn

TOTAL

68

n

Key: SB Seat Belt

ROPS

Roll-Over Protective Structure

A5-39



Figure 4-17. Egging ROPS Cab on
Caterpillar Crawler Dozer

Figure 4-18. Industrial Cab Company ROPS Cab
on GM-Terex Crawler



APPENDIX A4

EQUIPMENT POPULATION SURVEY

Survey sampling was the means of obtaining data from which to
make inferences about the population of the ''machines of interest" used
in metal and nonmetal mining operations.

MESA provided a computer listing, called ''Metal-Nonmetal Mine

' It listed all of the mines, their locations, and data about

Reference File.'
number of employees, last MESA inspection, product by SIC code, and
other factors. It was dated August 8, 1975. There were 13,989 mines
identified as active. Six hundred sixty-eight of these were underground
mines; 1756 were open pit mines; 4029 were crushed rock mines; and

7536 were sand and gravel mines.

A visit to MESA in Washington and to the offices of the staff of the
Minerals Yearbook produced the information that mine lists used in the
annual ''canvas'' for Minerals Yearbook data were available, but only after
several weeks and at considerable expense for the machine time to produce
them. The lists were large compared to the Mine Reference File. There
were approximately 13,000 on the Minerals Yearbook sand and gravel
list alone; the Mine Reference File had a total of 8913 in this category
(7536 active). Discussions on the Minerals Yearbook list suggested that
it included more inactive and sporadic operations than the Mine Reference
File and that the latter was a very satisfactory frame for a survey of the

type planned.

The MESA Health and Safety Analysis Center (HSAC) provided

two other machine listings entitled ''Surface Metal-Nonmetal Mines

WA.

A4-1



Figure 4-25. Saf-T-Cab ROPS on Euclid
Off-Road Dump Trucks;
ROPS Cab on Ford Industrial Tractor



APPENDIX A5

ACCIDENT DATA SURVEY

During the preliminary planning related to this study, WAI staff
members familiarized themselves with the MESA accident reporting and
investigation procedures. Particular attention was given to the prepar-
ation and processing of USBM Form 6-1555-S, ''Metal and Nonmetal
Mine Injury and Illness Report" and to the contents of accident investi-
gation reports made pursuant to clause (1) of Section 4 of the Federal

Metal and Nonmetallic Mine Safety Act (80 Stat. 772).

The USBM Form 6-1555-S has, in Section C, space in which
accident occurrence data is to be reported. The instructions require
that the reporting official ''describe fully the circumstances under which
the accident, injury or illness occurred" and "name equipment, material,
or tool involved," including model number. Although the descriptions
given are usually adequate to give the reader an understanding of the
nature of the accident, they seldom provide all of the physical details
needed to calculate the energy levels involved. Accident frequency data
by type of accident, and lost time data, are readily obtained from an
analysis of the forms submitted during a given period. However, for
the specific purposes of this study, the principal value of the forms
seemed to be the identification of the locations and companies which
had experienced fall-of-ground accidents. The initial study planning
included procedures for using the forms in this way, provided that

access to a central collection file could be obtained and provided that

A5-1



Table A4-5. Equipment Survey Response

Responses Follow-Up

Mine Sample Before Letters Total
Class Code Size Follow-Up Sent Responses
RS-U 111 57 53 81
RS-O 182 73 107 126
RS-C 291 91 200 132
RS-S 396 140 255 216
RS Subtotal 980 361 615 555

—
AH-U 76 42 34 56
AH-A 37 19 18 25
|

AH Subtotal 113 61 52 81

TOTAL | 1093 422 667 636

mines receiving survey forms provided usable information, As with
previous surveys, it is expected that responses will continue for two to

three months after this report is published,

Table A4-6 summarizes a survey problem area for which we can
provide no satisfactory explanation. There were 16 cases in which the
USPS returned the initial mailing as undeliverable, although the addresses
were correct according to the HSAC list. These 16 letters were put in
new envelopes and sent out with the same address. None was ever

returned and several reached their intended destinations because survey

WA.

A4-13


$ (000'S)

240

COST AS % OF

a

ROPS RETROFIT d
a
MACHINE VALUE —

VALUE

a
’
’
a
e
MACHINE MARKET Fd
a
a
0
e
*

ROPS
RETROFIT
COST

oer"
»

1 1 i= i as 4 i i —_

4220
4200
+4180
+160
4140
4120

4100

40

73

71 69 67 65 63 61 59 57 55 53
YEAR OF MANUFACTURE

Figure 4-33. Machine Value vs. ROPS Retrofit Cost —
Light Industrial Tractor

4-101

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4-105




Strictly speaking, ''density'' is the mass per unit volume of a
material. Its units are slugs per cubic foot or Ib-sec2-ft"*. The weight

‘or "relative weight" expressed in

per unit volume is "weight density,'
pounds per cubic foot. However, ''density'' is commonly used to mean
weight per unit volume, and it is so used here. Table A5-10 gives density
values for some of the materials in the accident samples and the sources
from which these values were taken. In most cases, the highest value
given in standard references for the material being considered was used.
In the few cases for which the material was not known, and could not be
estimated from available information, a density of 150 pounds per cubic
foot was used. It was always assumed that the material which fell had

the same density as the ore being mined, although in some cases it was

clear that the fallen material (overburden) actually was lighter than the

ore.

It was assumed that falls from a face or wall occurred from a

single place, rather than from a long lateral area of the wall.

The general model is illustrated in Figure A5-2, which also shows

the symbols used in the discussion and tables which follow.

Consider now what is the maximum volume of "loose" material
which could rest entirely on the top of a protective structure after falling,
given the conditions of the model. The volume is, of course, dependent
upon the area of the top of the protective structure and whether it is flat.
Examination of design data for ROPS presently available commercially
shows that one of those with the largest top area is a ROPS for the
D9 Caterpillar crawler tractor. It is a nearly flat top with dimensions
approximately 70 inches by 90 inches. This area, 6300 square inches,

or 43.75 square feet, is used in the analysis here.

A5-17



Table A5-10. Density of Materials (Cont)
(Lb. Per Cu. Ft.)

Density Average
Material Range Density Source

Salt

Granular, Bank 111-119 1

Granular, Loose 70-78 1

Rock 136
Slate 162-205 3

Shale 163-181 172 2
Sylvite 125 3
Talc 168-174

Bank 126-133 1

Loose 85-89 1
Tremolite 181-200 3
Trona 132-134 3
Uraninite 406-606 3
Zinc Ore

Blende 244-263 253 2
Sources:

1. SME Mining Engineering Handbook; Cummins, Arthur B. and

Given, Ivan A.; Society of Mining Engineers; American
Institute of Mining, Metallurgical and Petroleum Engineers,
Inc., N.Y., 1973.

Marks! Standard Handbook for Mechanical Engineers;
Baumeister, Theodore (ed.); 7th Edition; McGraw-Hill Book
Company, N.Y., 1967.

Handbook of Chemistry and Physics, 54th Edition; Chemical/
Rubber Publishing Co., Cleveland, 1973.

Mining Engineer's Handbook; Peele, Robert (ed.), John Wiley
and Sons, N.Y., 1961.

A5-21



Data Analysis and Inferences

As emphasized above, the principal thrust of the accident
analyses in this study related to the physical characteristics of the
fall-of-ground accidents. However, it was also desirable to know the
importance of fall-of-ground accidents relative to all accidents, and
to know the importance of fall-of-ground accidents which involved
machines of primary interest, relative to all fall-of-ground accidents.
These things cannot be known exactly, but they can be estimated

satisfactorily.

In the course of reviewing MESA fatal and non-fatal accident
investigation reports, a total of 1005 reports was examined. These
reports do not constitute a random sample of all accidents in metal and
nonmetal mines to which the laws of probability would properly apply.
The MESA reports do not include all accidents, as the term "accident"
is used here. Instead, they cover all fatals and some selected non-fatals
which were investigated in the interest of safety administration. Further,
the set of reports reviewed is complete only with respect to 1972 through
1974 fatals, and other factors, as discussed above under ''Limitations of
the Accidents Data,'' apply. The sample is, in the terminology of
statistical analysis, a judgment" or "'purposive'' sample. The WAI
staff believes it to be reasonably representative of the metal and non-
metal mine accident total population with respect to the proportion
involving fall-of-ground phenomena. This belief derives from examina-
tions of available accident analyses which suggest that the proportion of
fall-of-ground accidents is, considering the definitional limits employed
by different analyses, approximately 0.15 for non-fatal as well as for
fatal accidents. Accordingly, the estimate used in this study is that
15% of all accidents in metal and nonmetal mines involve fall-of-ground

phenomena. Table A6-2 provides some comparative data concerning

WA.

A6-6


performance criteria. As time passes and the older machines are
phased out, the percentage of machines covered with ROPS that meet
the more optimum SAE criteria grows larger and larger. This same

approach could be used on FOPS.



1965-1969
15,746
31.9%

APTER 1969
22,498
45.7%

1960-1964
5,860
11.9%

1950-1959
4,293
8.7%

1949 OR
EARLIER
891

1.8%

Figure 4-15. Date of Manufacture,
Total Population, Machines of Interest



falls in kinetic energy and in state of material. A FOPS test procedure
that simulated the rock fall as a large solid competent mass with great
structural integrity would be only representing a small portion of the

actual rock falls.

Table 4-1 is a summary of some important information which

characterizes fall-of-ground accidents.



4.1 CHARACTERIZATION OF ROCK FALLS

This section is a summary of the work done to quantify the
dimensions of rock falls experienced in metal-nonmetal mines. The
data on rock falls is divided into surface and underground categories.
Kinetic energy of rock falls is determined for use in FOPS performance

requirement calculations.

Sources of Accident Information

The sources of information about the time and place of fall-of-
ground accidents in metal and nonmetal mines are discussed in detail

in Appendix A5.

Physical Data Collection

The methods of data collection are treated in detail in Appen-

dices A4 and A5.

Important Definitions

The definitions of "accident", "fall-of-ground", and ''machines

of interest", as used consistently in this study, are given in Appendix A5.

Limitations of the Accident Data

A discussion of data limitations is given in Appendix A5.

There are other limitations which should be taken into account.
They relate primarily to the accuracy of the basic data about the physical

characteristics of falls, that is, to weight and distance data.

Consider how one would describe a fall ideally for energy calcula-
tions. The fall distance would be measured quite accurately, say to the

nearest inch. The weight would be measured to the nearest pound. In

WMA.



in the working environment, rather than as accidents.

Cases were mentioned in which routine barring down,

scaling or skimming activities produced "unplanned or
unforeseen" falls, in addition to those deliberately

induced.

3) A special category of Paragraph 2) above, which would
be particularly pertinent to this study if it could be
quantified properly, is those accidents in which no
injuries occurred because the machines involved were
equipped with ROPS or some other operator protection
structure. Several cases of this kind were mentioned
during mine visits but, because of the dearth of informa-
tion available, no good estimates could be made about

them.

4) Falls of ground which produced minor injuries which
were treated at the mine first aid station, with no

recorded "lost time."

During a few of the field visits
to mines, opportunities were available to examine
treatment logs in dispensary or aid station facilities.
It was observed that treatments for minor injuries
identified with causes such as "struck by rock'' were
included, but that there were no physical data about

the accidents recorded there or in any other records.

Although there are a few mines which record all known ground
falls, as evidenced by the detailed information received from some
survey respondents, it is clear that most do not. Generally, accurate
physical data are available only for accidents which resulted in serious

injuries, but not for all such accidents.



FIGURE

A2-1

A2-2

A4-1

A4-2

A4-3

A4-4

A4-5

A4-6

A4-7

A5-1

A5-2

APPENDICES
LIST OF ILLUSTRATIONS

Two-Post Canopy.
Beam Buckling Example

USBM Fall-of-Ground and Equipment
Survey Form.

USBM Fall-of-Ground and Equipment
Survey Form (Reverse Side) . .

USBM Cover Letter for USBM Fall-of-
Ground and Equipment Survey

Underground Mines — Distribution of
Machines of Interest by Owner Fleet Size
and Composition

Crushed Stone Mines — Distribution of
Machines of Interest by Owner Fleet Size
and Composition

Sand and Gravel Mines — Distribution of
Machines of Interest by Owner Fleet Size
and Composition . . . .

Open Pit M-NM Mines — Distribution of
Machines of Interest by Owner Fleet Size

Accident History Questionnaire (Section 1 —
USBM Fall-of-Ground and Equipment

Survey . . . : . .

General Model of Rock Fall

PAGE

A2-3

A2-9

A4-8

A4-9

A4-11

A4-20

A4-21

A4-22

A4-23

A5-10

A5-22

A-v



the mid-point of the confidence interval for the estimate. Only a small
percentage of the population (2.5%) is used in underground operations.
The term "used in'' is employed here to call attention to the fact that
some of the machines of interest which belong to underground mines are
not used underground, but rather in the surface operations associated
with underground mines. There are approximately 600 machines in this

category.

Figure 4-12 shows the estimates of the numbers of machines, and
percentages of the total, used in underground mines, for each of the
five types of machines of interest. As one would expect, more than half
of the total is composed of front-end loaders. Jt should be noted that the
numbers of machines given in Figure 4-12 are based on the responses to
the survey and, in cases where the survey response indicated a small
number of a machine type, the confidence interval is wide, The
survey produced mid-interval estimates of 72 for graders and 36 for
prime movers used underground. While it is known that both types of
machines are used in underground operations, the validity of the absolute

numbers estimated is not high.

Figure 4-13 shows the estimates of numbers of machines, and
percentages of the total, used in surface metal-nonmetal mining, for
each of the five types of machines of interest. Again, front-end loaders

are more than half of the total.

The different models of machine types reported in the survey were
of interest to enable the calculation of estimates of the financial implica-
tions of possible ROPS/FOPS retrofit policies, as discussed in Sec-
tion 4.6. The estimating method used did not require detailed analysis
of every model reported. The most frequently reported models were

identified and used to prepare ROPS acquisition costs, ROPS installation

WMA.



Table A5-12.

Mine-Run Rock Volume Sample

m0 |
Sample Dimensions V1 Disp. V2
No. (In.) (In. 3) (Oz.) (In.3) | Vo/V4q
1 6.125 149.30 36.0 64.97 | 0.435
4.875
5.0
2 3.375 94.68 18.0 32.48 | 0.323
3.375
8.3125
3 8.75 141.64 34.0 61.36 | 0.433
4.625
3.5
4 5.25 144.95 32.5 58.65 | 0.405
3.875
7.125
5 5.9375 206.65 44.0 79.41 | 0.384
5.0625
6.875
6 15.5 3,796.29 900.5 1,625.12 | 0.428
20.625
11.875
7 34.25 10,971.77 | 2,468.5 4,454.88 | 0.406
12.75
25.125
8 16.375 4,709.60 | 1,145.63 | 2,067.51 | 0.439
29.125
9.875
9 37.9375 7,939.61 1,750.98 | 3,159.98 | 0.398
18.5
11.3125
V9
Mean —— = 0.406
vy

A5-27



PERCENT OF ANNUAL FALIL-OF-GROUND ACCIDENTS

T0-

60-

50L

40-

30-

|
'
1
|
'
10 |
!
1
!
'
1

mumees UNDERGROUND MINES

seme SURFACE MINES

4 1

is) 10

Figure 2-1. Rock Fall Kinetic Energy vs. Percent of Total Rock Falls

20 30 40
KINETIC ENERGY (1000 FT-LB)

WMA.

2-4


a

Table A4-8. Estimates of LHD Type and Forklifts Used Underground
Some Form of No
Protective Structure Protective Structure Total
LHD Type 357 241 598
Forklift Type 98 250 348
TOTAL 455 491 946
48.1% 51.9% 100%

A4-19



In the course of the work, a few reports of interest on accidents which
occurred prior to 1972 were found and were included in the study. Tables
and discussion in later paragraphs of this appendix relate the accidents
examined to the years in which they occurred. Also, when the final design
of the equipment survey was being considered, it was decided to combine
the survey with the accident questionnaire and to add a section inwhich
respondents could identify fall-of-ground accidents which did not involve
injuries. Such accidents would, with a few exceptions, not have been
included in the MESA data. Later tables and discussion show how much

information for the study was obtained in this way.

Data Requirement

One of the objectives of this study was to determine the structural
requirements for FOPS to be used on underground and surface equipment
for metal-nonmetal mines. This required that a determination be made
of the size of rock falls most often experienced and the distance they fell.
The mining equipment that was of particular interest is defined early in

this report.

The data requirement, in other words, is to obtain data which show
the energy transformation capability a protective structure must have to
protect the operators of certain machines from injuries due to "'fall-of-

ground" accidents.

One of the two needed types of energy data is that related to a
nearly uniform loading of the protective structure. Kinetic energy is the
quantity desired:

Ex = 1/2mv?

A5-4



N.L. Industries,
Newcomb, New York

St. Joe Minerals Corp.,
Balmat, New York

Southern Talc Corp.,
Chatsworth, Georgia

Sunshine Mining Co.,
Kellogg, Idaho

Union Carbide,
Grand Junction, Colorado

White Pine Copper Co.,
White Pine, Michigan

Tahawus Mine

Balmat-Edwards Mine

Earnst Mine
Rock Cliff Mine

Sunshine Mine

Deremo-Snyder Mine
Sunday Mine

White Pine Mine



r

FRONT-END LOADERS

TRACTORS

DOZERS

GRADERS

PS = PROTECTIVE
STRUCTURE

PRIME MOVERS

PS

INSTALL
47%

Figure 4-14. Protective Structure Status — 1975
Total Population, Machines of Interest

by Machine Type

4-55



Figure 4-36 summarizes the industry costs of complying with
five policy alternatives related to providing ROPS/ROPS capability.

The five policies are:

1) No retrofit requirement, consider only ROPS on new

equipment.

2) Retrofit with commercial ROPS all machines of interest

manufactured after January 1, 1970.

3) Retrofit all machines of interest manufactured after

January 1, 1965.

4) Retrofit all machines of interest manufactured after

January 1, 1960.
5) Retrofit all machines.

Figure 4-36 displays the estimated cost to equip with ROPS all machines
of interest not already so equipped. Approximately 48% already have
ROPS. The estimates are for fourth quarter 1974 prices and values
except for 1975 machines. An appropriate multiplier must be used to
estimate costs for the time period in which retrofit may be considered.

The machine population estimates are for fourth quarter 1975.

4-112



6)

7)

8)

9)

10)

11)

12)

13)

Engineering Basics of Roll Over Protective Structures,

by G. L. Klose (SAE Paper 690569)

European Legislative Requirements for Agricultural
Tractors and Farm Machines, by Horace F. Howell

(SAE Paper 730788)

Experimental Verification of the Computer Program
CANOPY by the Static Testing of a Continuous Miner
Canopy, MESA Informational Report IR 1004, by

Dr. Stephen Sawyer, Darryl D. Brogan, John L. Dahle,

and George J. Karabin, Jr.

Nebraska Tractor Test — Programs and Philosophy,
by W. E. Spinter, G. W. Steinbruegge, D. E. Lane,
and L. F. Larson (SAE Paper 730763)

A North European Tractor Cab, by E. Gunner Ahlastrom
(SAE Paper 730792)

Roll-Over Protective Structures for Farm and Con-
struction Tractors — A 50-Year Review, by James F.

Arndt (SAE Paper 710508)

ROPS Safety Compliance Testing, by Robert W. Weed
and Hartwell C. Davis (SAE Paper 710694)

Study to Determine the Engineering and Economic
Feasibility of Retrofitting ROPS on Pre-July 1, 1969
Construction Equipment, by Woodward Associates

(DOL Contract No. L-73-158)



USBM Contract No. J0357110 WA Report 76-22F
February 20, 1976

APPENDICES
TO
PROGRAM FINAL REPORT

"Design Criteria and Guidelines
for
Falling Object Protective Structure"

U.S. Bureau of Mines
Pittsburgh, PA


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TABLE

A5-4

A5-5

A5-6

A5-7

A5-8

A5-9

A5-10

A5-11

A5-12

A5-13

A5-14

A5-15

AS-16

A5-17

APPENDICES
LIST OF TABLES (CONT)

Accident History (AH) Questionnaires
Mailed and Numbers of Accidents Involved

Fall-of-Ground Accident Data Obtained
Through Use of Accident History

Questionnaire

Accident Data Obtained by Mine Type and
Extent of Injury .

"AH" Questionnaire Response Information
Angle of Repose, Some Common Materials
Angle of Slide . : : . .
Density of Materials

Protection Levels, Selected Machines,
Approximate Height of Machine Plus ROPS

Mine-Run Rock Volume Sample.

Reported Data and Energy Calculations for
Surface Mine Fall-of-Ground Accidents .

Reported Data and Energy Calculations for
Underground Mine Fall-of-Ground
Accidents

Summary of "Point Load" Falls
Number of Fatalities — Fall-of-Ground
Accidents in This Study from MESA

Accident Investigation Reports .

Number of Dependents of Victims of Fatal
Accidents

PAGE

A5-9

A5-11

A5-12

A5-13

A5-16

A5-16

A5-18

A5S-25

A5-27

A5-29

A5-31

A5-35

A5-36

A-viii



attachments."

The load-haul-dump type machine, although a form of
front-end loader, was not specifically included. However, WAI decided

to include data about them in parts of the analyses.

Limitations of the Accident Data

There are several limitations of the accident data, in addition to
those inherent in the sampling procedures used, which should be taken

into account in making inferences from the data obtained.

First, it is a fact, verified by comments on the questionnaires
and survey forms received from mine officials, by field visits to mines
and examination of records, and by discussions with MESA mine inspec-
tors, that many "accidents," as defined above, are not recorded by
anyone and, consequently, were not reported in this study. Some of the

known examples of such unreported accidents are:

1) Falls of ground which occurred during periods when no
persons or machinery were inthe area. Several under-
ground mines stated that falls had been observed to have
taken place during times when no shift was working.
Many surface mines, particularly sand and gravel opera-
tions, remarked about falls which occurred during
periods of inclement weather when the pit was not being

worked.

2) Falls of ground which occurred during active work
periods, but which produced no injuries to persons
or serious damage to equipment. Several mines

remarked about "occasional," "frequent" or '

"regular"
falls, mostly small in size, which occur in underground

mines. These are usually regarded as normal events

A6-4



% OF TOTAL MACHINES OF INTEREST

ONLY PRE-1970 MACHINES

MIXED PRE-1970 AND
POST-1969 MACHINES

Y ONLY POST-1969 MACHINES

40 F-

30 -

20 -

10 -

3 TM
OWNERS OWNERS OWNERS
OF 1-5 OF 6-15 OF >15

Figure A4-6. Sand and Gravel Mines — Distribution of Machines of
Interest by Owner Fleet Size and Composition

A4-22



Table 4-12.

ROPS/FOPS Model Availability (Cont)

(Furnished by Saf-T-Cab, Inc. , Fresno, California)

Curtis Wright

Scrapers

6 320

Deere
Crawler Tractors
400 450
2010
Wheel Tractors
40 300 301
400 410 420
510 544 620
760 860 1010
2010 2510 3010
Scrapers
760. 860
Motor Grader
Dynahoe
Loader Backhne
ww 140
110 200
Fimeo
Crawler ‘Dover
103-¢
Buelia
Off-Highway Trucks
R35 R30 Reva
R70 p-100 etn
Ford

00 20 21

Aso 2000 000
3500 4000 4022
5000, 7000 aa
400 1000

\gricultural Tractors

2N aN waa

ey Bat 600
701 740 oo
4900 4300 3400
5000 7000

110

a0
500
644
1520
510

Ras

Fordson Super Mayor]
Fordson Dexta
County Super 4

Counts Super 6

Golden Fubilee
601
2000
400

Motor Graders

101 104
We 11a RAC
1601 303
T-400\ T5900
r-600 T6008,

Rollers

3-5 Ton Tandem
a-12 Tan Tandem

10-12 Ton 3-Wheel

9-Wheel

Hancock (Michigan)

Scrapers

2n2 209

Motor Graders
Mes I-50
\850 aD
e100, b-1300
P- b-1700
Hyster
cay 4511
5300-550
ingersall Rand
Rollers
<par spas
gram
Rollers
3-5 Ton 5-8 Ton

A Ton 4-wheel
10 Ton 3-wheel

14 Ton 3-wneel

Crawler Tractors

rh Th?
Tptd 9 Thets
Th2d | Th-25,

104 RAC 1041! Serves

500

5-8 Ton Tandem

10-14 Ton

‘ander

12-14 Ton 3-Wheel

550-800

rob

b-1400 p50

b-1900

B12 Tan 10-14 To

.2800P 11-2700

0-3409-P 13-2300

rw ry
rea Tp-20

rp-30

4-65



(qUOD) SqUeplooy punosy-jo-{[ey] SUT, PUNOASIapuy) 103

suotje[nolTe) ASszauyq pue eyeq payuoday

“PT-SV PLdeL

A5-33


Since the axial stress ratio does not change, the safety factor is,

1 = 1 = 1.046

SF R_+R 0.312 + 0.644

Recompute the allowable axial load,

= (SF)(P) = (1.046)(25,000) = 26,150 lb
allow.

The maximum allowable axial compression load as predicted by
the procedure not including a buckling correction is 26,150 pounds; or
about 5% over the induced load of 25,000 pounds. An analyst would
therefore incorrectly certify that the member had a 1.046 positive safety
factor when in fact the safety factor is 0.907 and the member would likely

fail at a load 15% below prediction.

This example clearly shows the need for a buckling analysis.
Structural members with higher slenderness ratios will show consider-
ably greater differences between analyses which do and do not include

buckling correction.

Computer Method of FOPS Analysis

The results of this study indicate that a computer method of
certifying canopy structures is feasible. A cost effective and technically
acceptable method would, however, require additional computer program

development effort.
Two computer programs were evaluated during the study:

1) CANOPY — A computer program for the structural

analysis of a space-frame protective canopy.

A2-12



+ a9 °
e “ ‘ ‘ o

sjuaplooy punosy-jo-[1eJ eUTA, punousaapuy 10j
“PT-SV e142

suoljzetnojeg Asuauq pue eyeq payzoday

A5-31


Table A5-11. Protection Levels, Selected Machines,
Approximate Height of Machine Plus ROPS

Protection Level

Machine (Feet)
Dozers
Caterpillar D-8 11.4
Allis-Chalmers HD21 11.0
Loaders
Hough H-400 14.6
Michigan 175 12.5
Michigan 275 13.3
Allis-Chalmers 745 11.7
Allis-Chalmers 945 13.8
Terex 72-71 13.3
Caterpillar 950 10.8
Caterpillar 977 11.3
Caterpillar 988 12.5
Scrapers
Michigan 210 11.4
Wabco 333 13.1
Terex TS24 12.6
Allis-Chalmers 261 11.8
Caterpillar 627 10.8
Caterpillar 637 11.9
Graders
Allis-Chalmers 200C 11.4
Wabco 444 10.8
Caterpillar 16 11.8

A5-25



4)

imbedded drill steel, etc.) or another machine (conveyor,
bucket arm, etc.), a protective structure will greatly

reduce the probability of serious injury.

A carefully designed training program to increase
machine operators! knowledge of the benefits and limita-
tions of protective structures and seat belts seems highly

desirable.

A5-40



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40 SONAUGGAIG x

¥SOLSS7Z ¥97S SET 6zL zor cos‘e | 98% zL9‘y | sett zy9*oT} vOr's 16'S yes‘ oT S1VLOL

SUTAON

€6S‘T Ors 0 0 ol x4 Sov 80T 76S 6S 92E slo aW1Ud

€98°7 “LEZ 18 18 slg 18 yze 0Lz SOv‘T Ise Ble y6S‘T BOLOVEL

Tis $19 Ble id 76S 80T fats oS 6zL oS £62 zey waavyd

zL9'y omsty £92 Lz weet | z9T €so't | sce sot | 0g0't 6s £98°% wazoa

yaqvot

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sdou sdou sdou SdOU SdOX Sd0U SdOU SdOu SdOU SdOu SdOu SdOU
LAOHLIM MLIM | Laonin} LIM | LNOWLIM| fot | LAONLIN LAOULIM WIM =| LaouLim | HLM
SIVLOL WAITUVE 2 66T 6S6T ~ OS6T y96T - 096T 6961 - S96T 6961 - LSod

sajyeulljsy uoTye[ndog jsauayy jo sauryoe

(€62‘ 6h UoTye[ndog 1301)

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A4-16


vehicles that are now in use that were manufactured before that date

have had ROPS installed is really not a paradox at all. The equipment
manufacturer is correct in stating that he knows, through engineering
analysis, that vehicles manufactured after a certain date are structurally
capable of withstanding the rigors of a roll-over. These vehicles were
designed with ROPS as a known accessory and, in fact, have been sub-
jected to static laboratory tests. The equipment manufacturer is also
saying, though not directly, that the reason he is not confident about
earlier vehicle models accepting ROPS is because no engineering analysis
has been conducted to define the vehicle chassis or frame capability. It
is probable that many of these vehicle frames would be capable of success-
fully supporting the ROPS dynamic loads transferred during a roll-over.
It is also probable that some would not. The cost of reanalyzing each
vehicle model produced in the United States would be prohibitive and

probably not entirely conclusive.

Even if all previously manufactured vehicles were analytically
examined for chassis strength, the serious question of in-use chassis
strength degradation is still unanswered. The in-use or service related
chassis strength degradation is not easily determined. Discussions
with mine operators, construction contractors and dealers of used mining
and construction equipment reveal that it is not uncommon for an owner to
"modify" a vehicle to fit his particular needs. He may "drill a hole here”
and ''weld a bracket there'' as required for attaching a sun shade or adding
an accessory. This owner modification could have very detrimental im-
pact on the vehicle chassis strength in local areas. If these local areas
of chassis weakening are coincident with a structural load path required
to absorb the force and energy imparted during a roll over, a failure in

those areas is possible.



APPENDIX Al

FOPS CERTIFICATION PROCEDURES

A falling object protective structure (FOPS) must be designed to
strict standards to achieve a structure which will perform satisfactorily
under the complex loading environment during a rock fall. A rock fall
imparts dynamic loads to the FOPS which are reacted by the elastic and
sometimes plastic deformation of the canopy, vehicle chassis, axles and
tires. An extensive engineering study was performed to establish practi-
cal methods of certifying FOPS. Designs certified to these standards
have been shown to exhibit energy absorbing characteristics needed to

withstand the rock fall kinetic energy requirement.

Certification Requirements

FOPS may be required on the following equipment used in surface
metal-nonmetal mines and the surface areas of underground metal-

nonmetal mines:
e Track-type or wheeled front-end loaders
e Dozers
e Tractors (excluding over the road type tractors)
e Motor graders
e Prime movers

FOPS installed on these vehicles must meet material, welding,
impact resistance, and static load/deflection requirements specified in

the following paragraphs.

\ WMA.

Al-1



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Ladd ‘3 ‘FONVISIG TIVvd

99-19 ,O9-LS |9S-ES |7S-64 |BY-SY 7Y-TY OY-LE | 9E-C£

7E-67

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09

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of ROPS manufacturer tends to produce large quantities of relatively

few models of ROPS. The ROPS may be shipped to the equipment manu-
facturer where they are installed on new vehicles and then delivered to
dealers. The second classification of ROPS manufacturers may also
have ROPS production contracts with equipment manufacturers but tends
to depend more heavily on supplying retrofit ROPS or after-market ROPS
direct to the equipment owner. This manufacturer must have a large
selection of ROPS designs available for production. Table 4-11 has been
extracted from the previously referenced ROPS study conducted for
OSHA. While admittedly incomplete, it serves to indicate that ROPS

are available for equipment manufactured as early as the 1940's and
1950's. There are several ROPS manufacturers that have over 500 designs
available; a few companies have over 400 designs available for pre-1970
equipment alone. This extensive selection of ROPS models is illustrated
in Table 4-12. This table is a partial list of ROPS models available from
a ROPS manufacturer that supplies both the retrofit market and the equip-
ment manufacturer. This listing is somewhat representative of the scope

of equipment models covered by the ROPS industry.

The ROPS manufacturers contacted during this study commented
on the increase in requests for ROPS units to be installed on machines
manufactured before 1969. One ROPS manufacturer stated that about
40% of his ROPS retrofit business in the first six months of 1975 was
for pre-1969 units. This particular manufacturer has over 900 ROPS
designs available. Designs are available for some machines manufac-
tured back as far as 1938. Many ROPS manufacturers have ROPS designs

available for machines manufactured in the 1950's.

4-62



fall is absorbed by the elastic-plastic strain energy of the canopy
structure. In reality this assumption is conservative since some of the
energy is dissipated by the inertia of the canopy members and deforma-

tion of the rock fall material.

Energy Absorption Capability

The kinetic energy from a rock fall impacting a protective
canopy is absorbed by all of components between the point of impact and
the supporting ground. The energy absorption characteristics of several

of the important components are discussed below.
1) Protective canopy

2) Vehicle chassis including canopy attachment structure

and axles
3) Tires

The results of analyses to determine energy absorption capa-
bilities of protective canopies have been previously summarized in
Figure 4-7 and Table 4-4. It is apparent from this table that the pre-
dicted energy absorption capability of the ROPS to withstand a vertical
impact loading depends generally on the gross weight of the vehicle for
which the ROPS was designed. For example, a four-post ROPS designed
for the Le Tourneau L-700 front-end loader will withstand 288,000 ft-lb
of energy as compared to 6000 ft-lb predicted for a light industrial

tractor.

As discussed previously the assumptions used in these analyses

were as follows:

1) The rock fall is not of competent rock. The fall energy
is transmitted into the ROPS structure as a uniformly

distributed load.

WMA.



surajshS aT91YaA/SdOU Jo Aq tiqedey uoljduosqy Adaaug

q1-13 000‘08 -000‘0S Tews

Q1-33 000‘00L-000‘00€ 41-33 000‘ 00%-000‘ 002

Q1-33 000‘00Z-000‘0ZI 41-33 000‘ 021-000‘ 08

q1-13 000‘SS -000‘ST q1-13 000‘0% -000‘OI

a1-143 000‘08 -000‘0¢

41-13 000‘ 00-000‘ 00T

Q1-33 00008 -000‘OF

q1-33 000‘ST -000‘9

uoljdaosqy Asaouq uoljduosqy Asuauq uoijdsosqy ASaaugq
uw1a}SAS sadly /awedy SdOwW
a1-La 00000% - 000‘0e =
SHULL

aT-Lel 000‘ 00 - 0009 =n
AdONVO FZALLOGLOUd

*G-% aansiy

(41 000‘ 09

= MAD)

J3z0q JaTMed,)

(a1 000‘0S1

= MAD)

dapeo'y pugy-jUod,}

(41 000‘ 0€

= MAD)

dapeo'] pugy-}UOdy|

(QL 000°S

= MAD)

sopra, perarsnpuy 7st"

STOTUaA



to have the best balance between reasonably demonstrating the ability
of the FOPS structure to meet the 40,000 ft-lb energy absorption re-
quirement and being practical to conduct as a widely used certification

method.

Methods of conducting the elastic load test are described in
detail in Appendix A3. The test requires applying a 36,000 lb force
within the center ninth of the canopy plan view top. The permanent
deflection remaining after the test can not exceed 10% of the maximum
deflection measured during the test. Two testing procedure options
are specified in Appendix A3. The first includes a static test of the
entire FOPS including protective canopy, attachment joints, vehicle
chassis and axles. The second option includes testing of some of the
FOPS components or the canopy alone with the remainder of the com-
ponents being certified with engineering calculations or by meeting certain

specified and required design guidelines.

An elastic computer analysis, the second recommended cer-
tification procedure, is described in Appendix A2. Several computer
programs were compared and the program CANOPY was selected as the
best approach. It is recommended that the program be modified by
adding a plate element and a beam buckling prediction before using it as
a certification procedure. With this method, a load of 74,000 lb is
input as a uniformly distributed load over all of the beam members in
the canopy top. The resulting stress output can not exceed the vield

stress of the material.

Guidelines for the engineering analysis certification procedure
are included in Appendix A2. With this method a non-computer analysis
is conducted for a 74,000 lb load distributed over the entire canopy top

or a 36,000 lb load over the center ninth of the plan view area.

4-44



LIST OF TABLES (CONT)

Summary of Energy Absorption
Calculations for Representative ROPS

Energy Absorption Capability Predictions
for the Caterpillar D8 Tractor ROPS/FOPS

Under Non-Uniform Loading Conditions .

Yield Predictions for the Caterpillar D8
Tractor ROPS/FOPS

Summary of Static Load Criteria .
Certification Procedure Alternatives

Composition of Survey Sample (Equipment
Survey)

Responses as Percentage of Total Metal-
Nonmetal Mines

ROPS Availability for Pre-1970 Vehicles
(Incomplete) : : :

ROPS/FOPS Model Availability
Representative ROPS Retrofit Costs
ROPS/FOPS Retrofit Costs

ROPS Retrofit Costs as Percentage of
Machine Value . . : .

Estimate of Machines of Interest Used Only
Under ground or Underground and Surface

4-47

xii



2) Maximum deflection of 4 inches is permitted over the
operator's head,

3) Material properties of the ROPS steel are 36,000 psi
yield and 55,000 psi ultimate.

The energy absorption capability also depends on the configura-
tion of the ROPS design. As shown in the table, a two-post ROPS and a
four-post ROPS for the Le Tourneau L-700 front-end loader were evalu-
ated. Energy absorption capabilities of 149,000 ft-lb and 288,000 ft-lb
were predicted for the two and four-post designs, respectively. By
looking at this comparison, one could reach the conclusion that a four-
post configuration is a much better energy absorber. Infact, however,
the opposite is probably true. As presented in Table 4-4, the more
rigid four-post ROPS reaches a maximum force of 871,000 lb while the
two-post maximum load limit is 527,000 lb. To illustrate the compari-
son in another way, the predicted energy absorption of the four-post
design at the 527,000 lb maximum distributed load level shown for two-
post ROPS is only 800 ft-lb. The high energy absorption capability of
the four-post ROPS (288,000 ft-lb) is realized at very high load levels.

This example and the information shown in Table 4-4 for other

representative ROPS demonsirates two important points:

1) A rigid type ROPS generally has the greatest total
energy absorption capacity. ROPS designed for large
gross vehicle weight machines and four-post configura-
tions usually have these characteristics.

2) A flexible ROPS minimizes the load being transmitted
into the vehicle frame. Two-post configurations and
ROPS designed for small vehicles are examples of

flexible units.

4-27



LEGEND: LETTERS REFER TO JOINTS.
NUMERALS REFER TO BEAMS.

Figure 4-10. Caterpillar D8 Tractor ROPS/FOPS
Structural Model



0.2236 (0.7764) 9/49,293 - 1,825
1,825 49,292

0.2236 + 1.86 ¥

0.2236 + 1.96 (0.0098)(0.9813)

0.2236 + 0.0188

or 0.2048 to 0.2424

The 95% confidence interval for machines with attributes i, j and k would

be 10,095 to 11,949. The finite population correction factor,

varies little within the confidence limits of N.

[44,827 - 1,825 _
44,826 = 0.9794

53,759 - 1,825 _
Von = 0.9829

Estimates of the LHD type machines and forklifts used underground
are given in Table A4-8. The total of these two machine types is nearly
78% of the total of all machines of interest used underground and their
exposure to fall-of-ground danger areas is generally greater than for the

machines of interest.

Figures A4-4, A4-5, A4-6 and A4-7 show the estimates of the
numbers of owners who have 1-5 machines of interest, 6-15 and >15
for the four mine classes used in the study. Note that there is a greater
proportion of machines in large fleets in underground mines than in the

other three classes.

A4-18



FIGURE

4-6

LIST OF ILLUSTRATIONS (CONT)

Total Rock Fall Kinetic Energy

Rock Fall Kinetic Energy at FOPS
Protection Level .

Predicted Kinetic Energy at Protection
Level — Surface and Underground Mines

Prediction of Kinetic Energy at Protection
Level

Predicted Vertical Force-Deflection Curve
for Representative Canopies

Energy Absorption Capability of
Representative Tires .

Energy Absorption Capability of Vehicle
Equipped With Protective Canopy

Caterpillar D8 Tractor ROPS/FOPS
Structural Model . . :

Metal-Nonmetal Mines Estimates of
Population, Machines of Interest
Total: 49,293 . . . . .

Machines of Interest Used in Underground
Work Areas . . . . : .

Machines of Interest Used in Surface
Operations . . . . : .

Protective Structure Status — 1975 Total
Population, Machines of Interest by
Machine Type ©

Date of Manufacture, Total Population,
Machines of Interest

4-55

4-56

viii



Current ROPS/FOPS Production Capability

There are approximately 50-60 manufacturing concerns in the
United States that produce ROPS/FOPS as a primary business product
line. These companies range in production capacity from the level of
100-200 units per year up to firms that produce 10,000-15,000 per year.
The top ten ROPS/FOPS manufacturers produce a yearly production of
50 ,000-60,000 units and have the facility capacity to produce close to
100,000 units per year. In addition to the independent ROPS/FOPS
manufacturers, the original equipment manufacturers also produce

ROPS for many of their own new vehicles.

The total ROPS production capacity in 1973 was estimated at
360,000 units/year by Woodward Associates in a program conducted
for the Occupational Safety and Health Administration. This capacity
has not been required since the demand for ROPS has not reached the
estimates made by industry during the 1970-1972 period when OSHA was
formulating and promulgating ROPS regulations for the construction
industry. The ROPS manufacturers contacted during the current study
for the U.S. Bureau of Mines expressed the opinion that this production
capacity is still available but has not expanded significantly. Since the
total production of machines of interest, for all applications (mining,
construction, logging, etc.) is approximately 250,000 - 270,000 per
year, there is sufficient ROPS production capacity to supply ROPS or
FOPS for any conceivable new ROPS or FOPS regulation that might be
promulgated by MESA.

The ROPS/FOPS manufacturers tend to divide into two general
classifications. The first classification contains the manufacturers that

supply ROPS/FOPS directly to the equipment manufacturer. This class

WA.

4-61


.

3) The force remains constant until the tire is compressed.
The force would actually increase due to the decreased
volume and increased pressure. The pressure increase
is not sufficient to burst the tire.

4) The tire does not fail until it deflects to the rim.

Therefore, for the Caterpillar 988,

Gross vehicle weight - 67,000 lb
Tire diameter - 73,0 in.
Tire size - 26.5-29
Load rating - 34,860 lb

Deflection to rim

(73.0 - 29.0) +2 = 22.0 in.
Energy absorption capability - (34,860)(22.0) +12 = 63,900 ft-lb

All of the parameters used in the evaluation of the energy
absorption capability of tires appear to be conservative. The range of
predicted capability between 33,000 and 400,000 ft-lb is therefore

realistic.

It should be noted that tracked vehicles, as a class, can not
take advantage of the large energy absorption capability of tires. The
configuration of a tracked vehicle does permit some deformation, but

the magnitude is very small compared to a rubber-tired vehicle.

A summary of the range of energy absorption capabilities
for a typical vehicle and FOPS is shown pictorially in Figure 4-9. The
predicted range for the protective canopy under a uniformly distributed
top load is 6,000 to 288,000 ft-lb. Predicted levels for the vehicle
chassis and canopy attachment structure are not included, even though
they are significant, since the magnitudes vary widely due to configuration.

The contribution of tires for a rubber-tired vehicle is 33,000 ft-lb



"Elastic Plane Frame Analyses of Semisymmetric Cab and Canopies
Used on Underground Electric Face Equipment,'' pages 36 and 37.
Equation D-1 establishes H, the parameter indicating the strength of
supporting beam with respect to the plate, which is required to define
the edge fixity condition of the plate. The maximum stress in a rectan-
gular plate supported along all four edges can be computed from
formula D-2. Equation D-3 defines the relationship for determining the
maximum stress for a plate supported on two opposite sides and free on

the others which is equivalent to the relationship for a pinned end beam.

A safety factor of 1.0 or greater based on the minimum tensile
yield strength of material is required for the top plate. The safety factor

is computed as follows:

F
sp = —Y
o
P
where
Py = Material minimum tensile strength
% = Maximum stress in plate

Evaluation of Stresses

Stresses should be computed for all critical points in the FOPS
structure. The applied or induced stresses must be determined and
compared to the allowable stress of the material to establish the safety

factor. The procedure for obtaining the safety factor is straightforward

A2-6



AFTER 1969
TOTAL 22,498

1960-1964
TOTAL 5,860

1950-1959
TOTAL 4,293

1965-1969
TOTAL 15,746

1949 OR LARLILR*
TOTAL 891

SHADED ARLAS INDICATE
PROTECTIVE STRUCTURE
INSTALLED
*PERCLNTAGES OF PS FOR
THIS AGE GROUP WOULD
bE UNRELIABLE

Figure 4-16. Protective Structure Status — 1975

(Machines of Interest by Year of Manufacture) WZA.

4-57


Several certification procedure alternates are described in
Table 4-8. It is apparent that a drop test with non-competent material
very closely simulates the actual conditions of the recommended rock
fall requirement. Although this test is practical as a controlled
experiment, it does not appear feasible as a widely used certification
test. The test would be difficult to conduct and costly due to the special
requirement of non-competency of the drop weight and the destruction

of the canopy and vehicle frame.

The other methods described in the table are further removed
from the conditions of an actual rock fall. The drop test with competent
material, the pendulum test, and the energy absorption static test all
demonstrate energy absorption capability. However, these three tests
do not match the loading distribution application of a non-competent
rock fall. Some members of the canopy are therefore overloaded while
others are underloaded. This leads to a condition which does not com-
pletely demonstrate the capability of all individual members within the
FOPS structure. A disadvantage of all of these tests is that they are

destructive to the test specimen.

The elastic/plastic computer analysis method, as described
in Appendix A2, is a good simulation of the actual rock fall. (The pro-
cedure is currently being evaluated by SAE as an alternate to the SAE
J1040a side load energy test for ROPS). However, this certification
method has disadvantages of high computer costs, complex input require-
ments for the analyst, and the need for a large computer which is not

widely available.

Woodward Associates has recommended the elastic load static
test, the elastic computer analysis, or the engineering analysis approach

as the alternate procedures for certification. These procedures appear

WA.



with bar stock can also be used. With either of the design concepts, the
maximum unsupported span distance between roof reinforcement members
cannot be greater than 24 inches. A dynamic drop test is not required

for designs meeting these configuration requirements.

Jynamic Drop Test — Designs not meeting the guidelines specified

above can be certified by a dynamic drop test. The test must be con-
ducted in accordance with SAE Recommended Practice J231 which speci-
fies the minimum performance criteria for falling object protective
structure (FOPS). The test requires that a 500-pound weight with an
impact diameter of 8.0 inches be dropped onto the center of the canopy.
All of the references to the critical zone in SAE J231 shall be deleted.
Instead, a requirement that the maximum deflection at the point of impact
shall not exceed 4.0 inches under the first or any subsequent impacts of

the drop test object shall be added.

Static Top Load Requirement

Protective canopies are required to elastically support a static
load of 36,000 pounds applied to the plan view area of the canopy top
applied within the middle ninth of the plan view area. Four acceptable

methods of certification have been developed as follows:

1) Static test of the canopy, attachment joints, vehicle

chassis and axle structure.

2) Static test of the canopy and noncomputer analysis of

the attachment joints and vehicle chassis.

3) Noncomputer analysis of the canopy, attachment joints

and vehicle chassis.

4) Computer analysis of the canopy and noncomputer analysis

of the attachment structure and vehicle chassis.

WMA.

Al-4


APPENDEIX A2

FOPS DESIGN GUIDES

The procedures presented in this appendix were developed as
guidelines for analytically certifying the structural integrity of falling
object protective structures (FOPS) for use in metal-nonmetal mines.
The procedures are applicable to FOPS installed on the following type
of equipment used in surface mines and surface areas of underground

mines:
e Track-type or wheeled front-end loaders
e Dozers
e Tractors (excluding over the road type tractors)
e Motor graders
e Prime movers

Methods of determining internal loads and stresses in the canopy
top plate, beam members and support columns are described. Safety
factor requirements for the canopy and attachment joints are also speci-
fied. Several computer programs are compared and a practical method

of computer analysis is recommended.

General Approach for Determining Internal Loads of FOPS Designs

Most protective canopies are statically indeterminate structures.

Therefore reactions and internal loads cannot be determined from the

A2-1



adjusted where necessary by volume corrections), to the frequency of
occurrence for accidents in the sample. As in the previous graph,
underground mine accidents are distinguished from surface mine

accidents.

The calculated kinetic energy values for accidents in the sample
are portrayed in two cumulative percentage graphs, principally so that
one may observe easily what percentage of the falls are below any
selected kinetic energy value. Figure 4-3 gives the total fall kinetic
energy data for fall-of-ground accidents in the sample. One curve is
for underground mine accidents, the other for surface mine accidents.
Figure 4-4 gives the fall kinetic energy at the "protection level." The
upper curve is for underground mine accidents and the lower is for

surface mine accidents.

The kinetic energy values for the estimated total annual number
of fall-of-ground accidents are portrayed in cumulative percentage
graphs in Figures 4-5 and 4-6. First, the annual population of fall-of-
ground accidents was related to the sample data and to WAI estimates
of the distribution by kinetic energy levels of the non-fatal injury and
no injury accidents. This analysis produced the lower limit of each
curve band in Figure 4-5. Then, estimates of the bias which exists in
the kinetic energy calculations for the sample and for the population were
made. These estimates produced the upper limits of the curve bands in
Figure 4-5. Ina sense, these curve bands are prediction curves. They
predict what percentages of fall-of-ground accidents each year will be
below any chosen kinetic energy value at the protection level, assuming
that mining techniques and conditions do not change. Figure 4-6 presents
the same information as Figure 4-5 ina slightly different form. The

scale of the horizontal axis has been changed so that kinetic energy



The fall distances were reported in one of two ways: ''total fall

' In order

distance" or "distance material fell before striking victim.'
to express the total fall distance for kinetic energy calculations when
only the fall distance to victim was given, it was necessary to add a
correction constant of 6 feet. If the victim was operating a machine in
a sitting position, the height of the top of the victim's head, as extracted
from manufacturer's data on the machines, was used. Ina few cases,
information from the accident report was used to estimate the height of
the top of the victim's head above the mine floor. For example, one
accident report described the victim as being in a scaling tower which

was 14 feet above the floor. The height of the top of the victim's head

above the floor was taken to be 20 feet.

The "protection level" was defined as the height of the top of a
protective structure above the plane on which a machine's wheels rest.
In accidents which involved machines, a height was selected from the
machine manufacturer's data or from ROPS manufacturers! data. It
was, in the case of existing ROPS, the height of the top of the ROPS.

If no ROPS data were available, the height of the top of the operator's
head was used. If a non-riding machine was involved, or no machine
was involved, the protection level was taken to be 6 feet, or 1 foot less
than the fall distance, whichever was smaller, for underground accidents

and 8 feet, or 1 foot less than fall distance, for surface accidents.

In order to estimate the portion of total kinetic energy which a
protective structure must transform to be effective, it was necessary
to model the fall and to make certain assumptions about the area of the
top of the structure. This correction was required because some reported
falls had plan form areas which were much larger than the canopy top.

One of the largest of the existing ROPS was chosen for the model. It



~

In the text of this report the terms ''equipment", ''vehicles",
"machines" and "machines of interest'' are used somewhat interchangeably
in describing the different pieces of equipment studied. The types of
equipment covered by this study could also be referred to as "construction

equipment used in mining."

The protective structures referred to in this report are of two gen-
eral functional types — a roll-over protective structure or ''ROPS" that
provides operator protection in the event that the vehicle overturns, and
a falling object protection structure or ''FOPS" that protects the operator
from falling objects. The terms ''cab"' and ''canopy" are often used to
describe the physical construction and appearance of the protective struc-
ture; ''ROPS" or 'FOPS" describes the structural design of the protective
structure. In some cases (for instance, a sheet metal cab designed for
protection against weather) the cab or canopy is not protecting against
accidents but serves some other purpose. A cab is usually a fully
enclosed operator area and a canopy is a covering over the operator's
area. Figure 1-9 depicts a ROPS canopy; Figure 1-10 shows a ROPS
cab. In the case of these two illustrations, a FOPS capability is also

built into the top of each unit.

Many mines have purchased or fabricated protective structures
for their mining equipment. These structures are often designed to meet
specific requirements in the mines in which they are used. Figure 1-11

illustrates three examples of canopies installed by mine operators.

MINE VISITS

During the performance of this program it was necessary to visit
several mines to discuss specific rock fall hazards, review detailed

accident information, assess operational impacts of FOPS regulations,

WA.

1-9



~

sample included in the reports available for review in the Reno Field Office,
that these were, for the purposes of this study, quite as useful as the fatal
accident reports. Accordingly, it was decided to use the MESA accident
investigation reports, fatal and non-fatal, as the principal source of needed
fall-of-ground accident data, and to obtain the data not given in the reports
through mail inquiries to individual mines in which the accidents had

occurred.

This preliminary planning also included a literature review, parti-
cularly of pertinent documents available in the MESA and Bureau of Mines
facilities in Reno; the library of the Mackay School of Mines, University
of Nevada; and the Nevada State Library. One document, entitled

Administration of Public Law 89-577 in 1973, Annual Report to Congres3

of the Secretary of Interior, stated that there were 568 fatal accidents in

the period 1971 through 1973 in all mines and mills. Of these, approxi-
mately 90 involved some '"'fall-of-ground" or closely related phenomena.
MESA Safety Reviews indicated that there were approximately three times
as many reported (Form 6-1555-S) fall-of-ground non-fatal accidents as
fatals. There was no way found to determine readily what percentage of
the reported non-fatals were covered by formal MESA accident investigation
reports. Conversations with various MESA people and a count of the non-
fatals in the chance sample of reports examined in the Reno Field Office
suggested that as many as 25% might have been the subject of formal
MESA investigation reports. Accordingly, it was estimated that there
would be an average of about 50 available MESA accident investigation
reports a year. If this estimate was correct, it was expected that data on
about 175 fall-of-ground accidents might be obtained if only those which
had occurred since January 1972 were considered. Thus, when the study
began, emphasis was placed on receiving all available formal MESA

accident investigation reports for the years 1972 through mid-1975.

WMA.

A5-3


3.2 RECOMMENDATIONS

It is recognized that increased safety for miners is a primary
goal for the U.S. Bureau of Mines and for the Mining Enforcement and
Safety Administration. The implementation of the following recommenda-
tions will help achieve that goal. It has been demonstrated that, through
evaluation of the operational and economic implications of different
approaches to increased safety, a path can be defined that produces
the desired increases in work place safety at minimum disruption of
production and at acceptable cost levels. The effect of the recommenda-
tions presented in this section will not be to eliminate completely deaths
and injuries due to accidents involving the machines studied. These
recommendations, if implemented, will significantly reduce the deaths
and injuries experienced in surface mines and surface areas of under-
ground mines due to fall-of-ground, vehicle overturns, vehicle falls,
and vehicle-object collisions. The costs to comply with these recommenda-

tions are judged to be reasonable, The effects on production are negligible,

The primary recommendation resulting from this study is to
promulgate a MESA regulation similar to that proposed in the Federal
Register, Volume 39, Number 207, dated October 24, 1974 but modified

as the result of this investigation.

This regulation should only apply to surface mines and surface
areas of underground mines. The ROPS and FOPS performance standards
now available should be used as guidelines in requiring ROPS/FOPS on

all ''machines of interest'' manufactured since January 1, 1965,

The selection of January 1, 1965 as the "date of manufacture" for
machines that must have ROPS/FOPS will result in over 80% of the machines
now in use being fitted with ROPS/FOPS. The selection of an earlier date

would not add significantly to the number of macnines covered but would

WMA.



Va

of fatalities and the number of surviving dependents of the victims in

these 125 fatal accidents. These data are not from random samples, but

three general observations seem valid:

1)

2)

3)

There is a greater probability of multiple fatalities in
an underground fall-of-ground accident than in a surface

fall-of-ground accident.

There is a greater probability of multiple fatalities in
fall-of-ground accidents than in machine roll-over
accidents and other accidents in which ROPS might have

provided operator protection.

A fatal accident is very costly in any terms in which

one wishes to measure cost.

While extracting fall-of-ground accident physical data, information

on other accidents related to operator protective structures was also

recorded.

1)

2)

The reasons were two:

Review of the first 150 accident reports in the MESA
offices in Reno suggested that the frequency of fatal
roll-over and other fatal accidents in which a ROPS
might have protected the operator was greater than
the frequency of fatal fall-of-ground accidents. Some
comparisons would be interesting to the reader of this

report.

Protective structures on heavy machines are an area
of special WAI interest. Some additional data about
their relevance in mining operations might make
possible some observations of value to the Bureau of

Mines.

A5-37



SECTION 4.0

PROGRAM ACTIVITIES

The effort performed on this program has been divided, for
reporting purposes, into six different subsections. Each subsection
describes an area of research that was undertaken to gain information
toward two general objectives. These primary objectives were:

(1) definition of technical aspects of ROPS/FOPS usage on "machines

of interest", including determination of a FOPS performance criteria
that would provide operator protection superior to that provided by FOPS
meeting the SAE J231 performance criteria, and (2) preparation of
estimates of the equipment population that could be affected by ROPS/
FOPS regulations and of the predicted costs to retrofit equipment with

ROPS/FOPS.

The results of this effort were summarized in Section 2.0,
Summary of Program Study Areas, and in Section 3.0, Conclusions and

Recommendations.

The subsections are organized as follows:

|

e Subsection 4.1 Characterization of Rock Falls

e Subsection 4.2 — Development of FOPS Design Criteria

e Subsection 4.3 — Equipment Population

e Subsection 4.4 — Commercial Availability of ROPS/FOPS
e Subsection 4.5 — ROPS/FOPS Retrofit Considerations

e Subsection 4.6 — Economic Effects of Possible Protective

Structure Retrofit Policies

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A5-29



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4-30


Figure 4-30. Underground Mine
Vent Bag Clearance Problems



The original equipment manufacturers have set 'ROPS
accommodation" dates that are consistent with their modification pro-
grams and that reflect their confidence in the ability of their machines
to accept an approved ROPS. These dates vary from 1965 to as late as
early 1972. A few manufacturers have indicated that they think (but
don't know) that some of their machines manufactured as early as 1961

could accept ROPS.

All original equipment manufacturers express concern about
installing ROPS on machines that have been in use for any significant
length of time. The unknown condition of the vehicle frame after expo-
sure to the mining or construction work environment prompts the manu-
facturer to state that their confidence about installing ROPS on their

vehicles only applies to new vehicles.

In conflict with the technical judgment offered by the equipment
manufacturers is the fact that many vehicles manufactured prior to their
specified ''ROPS accommodation" date have ROPS installed on them now
and are in use in the field. Many scrapers and front-end loaders manu-
factured in 1967, 1968 and 1969 and used in California have ROPS installed
because the California Construction Safety Orders have required ROPS
on these vehicles if manufactured after August 8, 1966. Many types of
vehicles used on construction projects managed by the U.S. Army Corps
of Engineers have had ROPS installed since the Corps started requiring
overturn protection in addition to falling object protection in 1959. The
U.S. Department of Interior, the states of California, Oregon, and
Washington also had some requirements for overturn and falling object

protection in 1959.

This apparent paradox where (1) the vehicle manufacturer states
that his vehicle is not designed to accept the possible structural loads

produced by a roll-over event before a certain date and (2) the fact that

WA.



Ne

.

The following descriptions of equipment and protective structures
are given to assist the reader in understanding the material presented
in this report. The equipment types studied during this effort are defined
in MESA's proposed standard for roll-over protective structures (ROPS)
as published in the Federal Register, Volume 39, No. 207, dated
October 24, 1974. The proposed standards are to apply to "self-propelled,
track-type (crawler mounted) or wheeled (rubber-tired) front-end loaders;
dozers; tractors, including industrial and agricultural tractors but not
including over-the-road type tractors; motor graders; and prime movers,
all with or without attachments, with the exception of such self-propelled
equipment that is operated by remote control.'' The above description of

equipment types can also be categorized as follows:
e Front-End Loaders

Rubber-tired (Figure 1-1)

Crawler mounted (Figure 1-2)
e Dozers

Rubber-tired (Figure 1-3)

Crawler mounted (Figure 1-2)
e Tractors

Rubber-tired (Figure 1-4)

Crawler mounted (Figure 1-2)
e Motor Graders (Figure 1-5)

e Prime Movers (such as the off-road type used to

pull scrapers, water wagons, etc.) (Figure 1-6)

The low-profile type of rubber-tired front-end loader called a Load-Haul-
Dump (LHD) as shown in Figures 1-7 and 1-8 is not included as a

"machine of interest'' but is treated separately in this report.

1-4


were due to "sliding or falling material."' The number of fatals was
small (4), so the overall percentage of fall-of-ground injuries was
about 3%. There are no comparable data on accidents, as defined for
this study, but it is possible that such data might show fall-of-ground
to represent as much as 6% to 8% of the total sand and gravel industry

accidents.

In discussing this study with mining people in government and in
the industry, it became clear that some take the position that all fall-
of-ground accidents should be considered. The merit of this view resides
principally in the idea that some no-injury accidents could well have

produced injuries but for "fate,'' ''good luck," etc. One miner said,
"The reason I'm alive instead of dead is that I moved eight inches to the
left at the right time.'' Another credited his survival without injury to
the fact that his D-8 ripper had a ROPS. On the other hand, some
people took the more pragmatic view that only accidents which resulted
in fatalities or serious injuries need be considered. This view has the
merit of dealing only with "hard" data, however incomplete. The MESA
non-fatal accident investigation reports do not cover all serious injury
accidents, but they include some accidents in which there were no
injuries.

In this report, WAI has tried to accommodate both points of view
insofar as available data and supplementary subjective information
permit. This is particularly true with respect to the physical charac-

teristics of fall-of-ground accidents.

The WAI review of MESA accident investigation reports (all
fatals published in 1972-1974 plus available non-fatals and selected fatals
for other years) identified 152 fall-of-ground accidents. Ninety-eight

of these were fatal accidents. Information about the victims was

A6-8



An important facet of the equipment manufacturer's reluctance
to confirm the structural capability of earlier vehicle frames to accept
ROPS may be related to an understandable desire to refrain from

"blessing" a questionable structure for product liability reasons.

Another fact to remember is that the vehicle manufacturer is
usually stating that he cannot predict the ability of his older vehicle
frames to pass successfully an SAE ROPS static test. Only the SAE
ROPS performance standards, through the static testing required, bring
the vehicle chassis or frame directly into the ROPS system. The "Corps
of Engineers" type of ROPS requirement ignores the fact that the vehicle

frame may be the weak link in the ROPS system.

Since the Corps of Engineers type of ROPS is acceptable for retro-
fitting pre-1970 equipment to many Federal and State agencies (including
MESA and OSHA) without static testing or field roll-over testing, this
potential weak link could remain hidden until an actual roll-over accident.
This may be of less concern than is obvious. To date, WAI has not
reviewed any mining or construction accident records that discuss the
failure of an approved ROPS system during a ''normal" roll-over.
Further, in conversations with industry personnel, no mention of this
type of occurrence has been made. This lack of information on failure
of ROPS systems during actual field overturns is a very positive indica-
tion that the great concern over vehicle frame structural capability may
be overstated. Certainly it is not a factor to be ignored, but on the
larger mining and construction vehicles, the frames are generally
designed to survive use in a very rugged, demanding environment.
Perhaps more important than the concern about the inherent strength of
the vehicle frame is a concern about the possible limited attachment
areas afforded on some vehicles. It may be necessary to provide some

local reinforcing of the vehicle frame through use of doubler plates or

WA.

4-87


is very good evidence that volume (or length, width and
thickness) is usually overestimated. However, in those
few cases where there occurred this data anomaly,

weight was taken to be correct.

2) Mining people customarily express production figures
in weight terms. The majority of the questionnaires
were answered in weight terms. A miner who moves
a fallen rock, by hand or with a machine, will, because ©
of his experience, make a more reasonable estimate

of the weight than of any other descriptive factor.

Reported volume was available for many of the accidents. It is
a good survey surrogate for weight if it is accurate and if the density of
the material is known or can be satisfactorily estimated. The question
of volume accuracy was given much careful consideration. The basic
problem arises from the way in which the volume of an irregular object
is usually measured or estimated. Typically, the points of greatest
width, height and thickness are measured. The dimensional data were
commonly given in feet, but with some words to express the shape,
such as "egg-shaped rock." If the three dimensional numbers were
simply multiplied to estimate volume, the volume figure would be much
larger than the true volume. How this matter was treated is described

in detail in Appendix A5.

The density of the fallen material was usually not known. It was
estimated using data from standard references about ore densities,
using the assumption that the material which fell had the same density
as the ore being mined. This procedure produces a high estimate of
the rock fall weight since the falling rock is of lower density than the

ore in many cases.



SECTION

TABLE OF CONTENTS

PREFACE
INTRODUCTION
SUMMARY OF PROGRAM STUDY AREAS

CONCLUSIONS AND RECOMMENDATIONS
Conclusions

Recommendations

PROGRAM ACTIVITIES
Characterization of Rock Falls

Development of Falling Object Protective
Structure (FOPS) Performance Criteria

Equipment Population .
Commercial Availability of ROPS/FOPS
ROPS/FOPS Retrofit Considerations

Economic Effects of Possible Protective
Structure Retrofit Policies

REFERENCES

APPENDICES

PAGE

iii



APPENDICES
LIST OF TABLES

TABLE PAGE
Al-1 Charpy V-Notch Impact Strengths . : . Al-2
A2-1 Comparison of ROPS/FOPS Computer

Programs . . : : . . . . A2-16
A4-1 Composition of Survey Sample (Equipment

Survey) . . . : . . : : . A4-2
A4-2 Survey Response Summary by State . . A4-3
A4-3 "Usable Data'' Response Rates . : . . A4-7
A4-4 Survey Problem Situations — Individual

Follow-Up Letters Sent . . : . : A4-12
A4-5 Equipment Survey Response : . . : A4-13
A4-6 Survey Problem Situations — Second

Mailings Required . : . . : : A4-14
A4-7 Machines of Interest Population Estimates

(Total Population 49,293) . . . : . A4-16
A4-8 Estimates of LHD Type and Forklifts Used

Underground . : : : . . : . A4-19
A5-1 MESA Accident Investigation Reports

(Pre-Survey Review) . . . : . . A5-7
A5-2 Fall-of-Ground Accidents — Identified from

MESA Accident Investigation Reports : . A5-8
A5-3 Fall-of-Ground Accidents — Physical Data

Complete in MESA Reports . . . : A5-8

A-vii



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A2-16


Table A4-4.

Survey Problem

Situations — Individual Follow-Up Letters Sent

Problem Area

Number of Cases

Incomplete information provided 28
Addressee declared survey form lost 5
Addressee declared survey form 28
never received
Addressee declared form sent, but 1
not received by WAI
Special circumstances:
Data included in report on other 1
operation
Operation limited to 3-5 days/ 1
3 years
Declared no machinery used 1
Mine sold 7
Form referred to another party 2
Addressee refused to provide any 2
data |
Addressee refused to provide any 1
data unless compensated |
Definitional questions 22 |
Verification of survey authority 1
requested
Protest of "government surveys" 1
TOTAL 101 |

A4-12



100/- os
o4

sob 33
70}-
60- 02

505

20;-

(JANUARY 1, 1976 POPULATION)

0 L
0 10 20 30 40 50

PERCENT OF MACHINES OF INTEREST THAT ARE
ROPS/FOPS-EQUIPPED

ROPS/FOPS RETROFIT COSTS
(IN MILLIONS OF DOLLARS)

POLICY 1 — NO RETROFIT REQUIREMENTS, CONSIDER ONLY ROPS/
FOPS ON NEW EQUIPMENT

POLICY 2 — RETROFIT ALL MACHINES OF INTEREST MANUFACTURED
AFTER JANUARY 1, 1970

POLICY 3 — RETROFIT ALL MACHINES OF INTEREST MANUFACTURED
AFTER JANUARY 1, 1965

POLICY 4 — RETROFIT ALL MACHINES OF INTEREST MANUFACTURED
AFTER JANUARY 1, 1960

POLICY 5 — RETROFIT ALL MACHINES

Figure 4-36. ROPS/FOPS Retrofit Costs vs. Percent of
Vehicle Population (January 1, 1976) ROPS/FOPS Equipped

we WMA.

4-113



Table 4-3. ROPS/FOPS Certification Costs

Vehicle Gross Weight Test Certification Cost
20,000 - 40,000 lb $ 16,000 - $ 20,000
75,000 - 100,000 lb $ 25,000 - $ 40,000

150,000 - 200,000 lb $ 50,000 - $ 75,000

over 200,000 lb $100,000 - $300,000

experienced in underground mines. To attain protection in 70% of the
surface mine rock falls would require a FOPS that could absorb about
75,000 ft-lb. These energy levels are very high compared to the energy
absorption requirements of SAE J231 and SAE J167, which are 8500 ft-lb and
1000 ft-lb respectively. The protection afforded through use of FOPS
meeting the SAE J231 performance criteria is about 33% of the expected
rock falls in underground mines and about 21% of the surface mine rock

falls. The protection provided by the SAE.J167 FOPS is much lower.

Can FOPS be designed and manufactured to meet the high
energy absorption levels necessary to protect operators from the rock
falls occurring in metal-nonmetal mines? To attempt to answer this
question, WAI has structurally analyzed and examined the energy absorp-

tion capability of several representative commercial ROPS.

Description of Structural Analysis Methods

The structural characteristics of representative canopies
described in Figure 4-7 and summarized in Table 4-4 were derived
using computer aided elastic/plastic analysis methods. The computer
program CANOPY, developed by the Bureau of Mines and described in
Reference 3, was used extensively to determine elastic force and de-

formation static response. Plastic behavior was evaluated using the

WA.



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All vehicles with approved ROPS have top load carrying capability
of at least one times the vehicle gross weight and many have substan-
tially greater capability. Gross weights of machines of interest range
from a low of 5000 - 6000 pounds for the small industrial tractors up to
over 350,000 pounds for the largest front-end loaders. The "built-in"
top load capability of ROPS designed for these machines can be assumed
to be approximately the same as the gross weight. This fact presents
an interesting dilemma. This top load capability is required for ROPS
since the machine may come to rest on its top after a roll-over. The
ROPS needs to support the vehicle weight to protect the operator from
being crushed. It is fairly obvious that many of the structural loads
experienced by the ROPS are related or dependent on the machine gross
weight. This is not so ina rock fall. There is no direct relationship
between the particular machine under a rock fall and the size of the rock
fall. Small rocks fall on large machines and large rock falls occur on
small machines. And vice versa. The "built-in"! structural capability
of a machine with ROPS installed will help protect the operator against
rock falls but to a much lesser extent in a small machine than a large

machine. The following examples illustrate this fact.

Assume that a light industrial tractor is outfitted with a ROPS and
that the ROPS has a FOPS capability as required by SAE J167. The rock
fall kinetic energy level that this ROPS/FOPS is expected to accommodate
is at least the 1000 ft-lb experienced in the SAE J167 falling sphere test.
Using the data presented in Figure 4-6 of Section 4.1, it can be seen
that a very small percentage of the surface and underground rock falls
are expected at this low kinetic energy level. Conversely, a large front-
end loader may have a ROPS installed that has a large "built-in'' energy

absorption capability. If its kinetic energy capability is 50,000 ft-lb then

WA.



4.6 ECONOMIC EFFECTS OF POSSIBLE PROTECTIVE STRUCTURE
RETROFIT POLICIES
This section deals with the financial implications of four possible
policies relative to retrofitting protective structures on the machines
of interest. It was shown in Section 4.4 that approximately 48% of the
population of the machines of interest already are equipped with some
form of protective structure. A very large proportion of these structures
is composed of what are commonly called "commercial ROPS'": they
were purchased as installed equipment on the machines, purchased from
the machine manufacturer and installed in the field, or purchased from
a ROPS manufacturer for field installation. (''Field installation," as
used here, includes installation by a dealer, as distinguished from factory
installation.) Most of these "commercial ROPS" are designed and con-
structed so as to meet or exceed the SAE J231 FOPS performance stand-
ard. That is to say, most have the SAE J231 capability and more. How
much more is related closely to the gross vehicle weight of the machine
for which the ROPS is designed. Accordingly, for this analysis, it was
assumed that the proportion of the machine population which was esti-
mated, based on the survey discussed in Section 4.3, to have ROPS

"and therefore also had at least the

installed, had "commercial ROPS,
SAE J231 FOPS capability. In fact, some commercial ROPS for small
machines do not have SAE J231 capability and some machines in the
population have "shop built ROPS'' which were constructed to design
standards known only to the mines which built them. However, the
numbers of these are not sufficiently large to invalidate the assumption
stated above with respect to estimation of total costs to retrofit large

numbers of machines.

The estimate for the population of machines of interest is

49,293 machines; 23,524 of those were estimated to have ROPS installed.

WA.



PERCENT OF ACCIDENTS ANNUALLY

80

40

30-

ESTIMATED ANNUAL
ACCIDENTS

20

10 wees UNDERGROUND MINE FOG
semee SURFACE MINE FOG

| l 1
0 25 50 75 100 125

KINETIC ENERGY (1000 FT-LB)

Figure 4-5. Predicted Kinetic Energy at Protection Level —
Surface and Underground Mines ZA.

4-13


Figure 1-11. Falling Object Protective Structures (FOPS)



SECTION 3.0

CONCLUSIONS AND RECOMMENDATIONS

3.1 CONCLUSIONS

This study has developed information in the three general areas
of accident analysis/rock fall characterization, ROPS/FOPS performance,

and economic effects.

In general it can be stated that it is impractical to attempt to
require FOPS or ROPS that will protect the machine operator against

all possible rock falls or vehicle overturns.

There are accidents in which no practical protective structure
will protect the operator; in some accidents the vehicle itself is com-
pletely destroyed. Massive rock falls have occurred in both surface
and underground mines where thousands of tons of rock have fallen on
equipment. The protective structures discussed in this report provide
protection against rock falls up to a magnitude of two to three tons falling

7 to 10 feet or one ton falling about 20 feet.

In actual practice these protective structures would provide much
greater protection than expected from the design calculations because a
portion of the rock fall energy will be absorbed into the vehicle frame
and tires. In the case of a large front-end loader, the actual rock fall
energy that the FOPS could withstand could be over twice the energy
absorption capability of the FOPS alone. Another important factor in
predicting the protection afforded by FOPS is the structural integrity of

the falling rock. Often the section of rock that falls is termed ''bad

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4-107


Table A5-6 shows the total number of accidents for which data
were obtained in this study. The table separates the accidents by year,
by type of mine and by injury category. The data from the total of 198 fall-

of-ground accidents were those on which the analyses were based.

Table A5-6. Accident Data Obtained by
Mine Type and Extent of Injury

Under ground Surface Totals

F I N F I N F I N
1975 2 0 22 2 ie) 10 4 0 32
1974 11 8 26 6 2 8 17 10 34
1973 10 11 9 5 0 9 15 11 18
1972 8 3 3 5 4 2 13 7 5
Earlier 17 4 4 1 1 5 18 5 9
and
No Date
TOTALS 48 26 64 19 7 | 34 67 33 98

Total Underground 138
Total Surface 60
198

Key: F = Fatal
Injury
N = No Injury

"

A5-12



is a Young Corporation ROPS for the D9G Caterpillar dozer. The top

of the ROPS is 66 inches wide and 90 inches long. However, 20 inches
on one end of the length slopes downward at an angle of about 60 degrees.
In the model and in the kinetic energy calculations for the protection
level, the plan form area was taken to be 70 x 90 = 6300 square inches,

or 43.75 square feet, and it was assumed that the entire area was flat.

The effective vertical dimension of the falling material is also
necessary to calculate the load volume and the kinetic energy which a
protective structure must transform. The vertical dimension of the
load volume was taken to be the thickness of the fallen material as
reported or, in the case of loose material falls in which no thickness
was given, as 120 inches or 10 feet. The reasoning for this assumption

is explained in some detail in Appendix A5.

All of the fall-of-ground data, as reported on the questionnaire
or as extracted from MESA accident investigation reports, are shown
in two tables in Appendix A5. One table gives the reported data for
surface mines, the other for underground mines. Each of these tables
also shows the results of the energy calculations for each accident and,
in addition, identifies the machines involved in cases in which this
information is known. The tables indicate whether the accident produced

a fatality (Ff), a non-fatal injury (I), or no injury (N).

Fall-of-ground characterization data are portrayed in graphical
form in this section. Figure 4-1 is a histogram which relates reported
total fall distances, f, to the frequency of occurrence for fall-of-ground
accidents in the sample of 198 accidents. The graph distinguishes
between data from underground mine accidents and data from surface
mine accidents so that the difference in frequency distribution is

apparent. Figure 4-2 is a histogram which relates fall weight, Wo (as

WMA.



Table A5-5. Fall-of-Ground Accident Data
Obtained Through Use of Accident History Questionnaire

Year Fatal Non- Fatal | Total

of Accident Accidents Accidents Accidents
1975 4 5 9
1974 10 13 23
1973 13 8 21
1972 13 2 15
Prior to 1972 16 2 18

TOTAL 56 30 86

86
Success Rate: T30 0.662

provided it in a form which could not be quantified accurately for energy

calculations.

In addition to the data obtained from the questionnaire, from
Section 1 of the survey form, and from the MESA reports which had com-
plete accident information, 90 fall-of-ground accidents which produced
no injuries were obtained in Section 2 of the survey form. (See Fig-
ure A5-1.) Onthe ''AH" survey forms mailed as well as on the ''RS"'
forms, recipients were requested to complete both Sections 2 and 3.

Data for six accidents were obtained through field trips to mines.

A5-11



SECTION 2.0

SUMMARY OF PROGRAM STUDY AREAS

Falling Object Protective Structures (FOPS), cabs, or canopies
are required on electric face equipment used in underground coal mines.
These operator protective structures have proved their worth in under-
ground coal mines with over one hundred saved lives credited to their
use. The structural performance requirements for these canopies were
developed after detailed investigation of the nature of roof falls in coal

mines and an extensive laboratory test program.

Equipment operators working in surface and underground metal-
nonmetal mines are also exposed to injury or death from falling objects.
The Bureau of Mines, recognizing the differences in rock fall charac-
teristics between underground coal mines and the surface and underground
metal-nonmetal mines, planned an investigation to determine the struc-
tural performance requirements of Falling Object Protective Structures

(FOPS) to be used in the metal-nonmetal mines.

Concurrent with the effort to develop the structural criteria for
FOPS, the Bureau of Mines initiated an effort to define the population
of mining equipment that would be affected by a regulation requiring the
installation of FOPS. This equipment population determination was pri-
marily concerned with self-propelled track-type (crawler mounted) or
wheeled (rubber-tired) front-end loaders; dozers; tractors, including
industrial and agricultural tractors but not including over-the-road type

tractors; motor graders; and prime movers.



and the equipment manufacturers have been involved in an increasing
number of liability lawsuits resulting from roll-over and falling object
accidents in the construction industry. Typically, the counsel repre-
senting the injured operator or the widow of the operator attempts to
show that the equipment manufacturer or the ROPS manufacturer con-
tributed to the accident through faulty design, faulty workmanship, or
faulty installation. If field modifications or field repair of ROPS and
FOPS are performed, the ROPS manufacturer feels that there must be
some method of insuring that the field work does not degrade the per-
formance. Welding standards for field work are a help but do not insure
that the mine operator's modifications are sound from an engineering
standpoint. Requiring a design approval by a registered professional
engineer is one way of placing the engineering responsibility, however,
the ''energy absorption" design approach used in SAE ROPS is not under-
stood by most non-structural registered professional engineers. It is
possible that the structural changes performed by the mine operator in
trying to meet the FOPS performance requirements may, in some way,
alter the energy absorption capability of the ROPS design. In any case,
ROPS manufacturers will take the position that any modifications to their

ROPS will invalidate the warranty and the SAE performance certification.

The requirement to install FOPS meeting a new performance
criteria on new machines manufactured after some date in the future
is an approach to upgrading the life-saving capability of FOPS without
invalidating the FOPS that are already in use. This approach was used
by MESA and OSHA in their existing ROPS regulations. Machines manu-
factured before a specified date can be fitted with ROPS that meet any one
of several approved ROPS standards (State of California, U.S. Army
Corps of Engineers, and Bureau of Reclamation). Machines manufactured

after the specified date must be fitted with ROPS meeting the SAE



distributed to concentrated within the middle ninth area. In either case,
the effective bending moment is one-half the length of the ROPS top
overhang. Two-post configurations must therefore withstand a static
yield load of 74,000 lb and can be applied as fully distributed or con-

centrated within the middle ninth of the top area.

Vehicles with gross weights under 30,000 lb must be covered
by special performance criteria. As shown in Table 4-4, all ROPS for
vehicles in this weight class can not withstand a 74,000 distributed top
load without yielding. The predicted yield loads for representative ROPS
for the 5000 1b and 20,000 lb industrial tractors are 13,000 lb and
47,000 lb, respectively. Since small vehicles are exposed to some rock
falls, it is recommended that they be equipped with "substantial" canopies.
The structural capability of these designs should be consistant with the

capability of the vehicle frame structure near the attachment location.

A summary of recommended static load criteria is shown in
Table 4-7. As depicted in the table, FOPS which can successfully with-
stand these static loads will be capable of absorbing 40,000 ft-lb of

kinetic energy from a rock fall.

Certification Procedures

A valid certification procedure must demonstrate the capability
of FOPS installed on vehicles with gross weights above 30,000 lb to
absorb 40,000 ft-lb of kinetic energy with a distributed force applied to
simulate a non-competent rock fall impacting the entire plan view area
of the FOPStop. Vehicles with gross weights less than 30,000 lb must
meet the same requirements or demonstrate that a ''substantial' canopy
has been provided with a capability consistant with the capability of the

vehicle frame.

4-40



~

respectively. The total was 67. Of this total, 21 were in surface mines.
Nine of the 21 surface mine fatal fall-of-ground accidents involved
machines of interest for the three year period. Therefore, there was

an average of 3 fatal fall-of-ground accidents in surface mines per year

which involved machines of interest.

Second, using the data from the WAI sample for comparison,
it is seen in Table A6-1 that information was gathered on 45 fatal fall-
of-ground accidents for the years 1972, 1973 and 1974. Sixteen of these
were in surface mines. Machines of interest were involved in 6 of the
16 surface mine fatal fall-of-ground accidents. The sample indicates
an average of 2 fatal fall-of-ground accidents annually which involved
machines of interest in surface mines. Using the number of total fall-
of-ground accidents (45) studied in the sample and the total known fall-
of-ground accidents (67) for the same period, an estimate of the fall-
of-ground accidents occurring in surface mines involving machines of

interest canbe made. The prediction is 3 fatals per year.

Three fatal accidents a year represent about 2% of the annual

total fatals in metal and nonmetal mines for the years 1972-1974.

Non-fatal fall-of-ground surface mine accidents involving machines
of interest can be estimated using similar techniques. The WAI estimate
is that there may be as many as 133 non-fatal accidents, approximately

6 of which produces some degree of injury.

In the underground portions of the sample (Table A6-3), machines
of primary interest were involved in less than 2% of the fall-of-ground
accidents, in about 3% of the fatal and disabling injury accidents, and
in 4% of the fatals. In fact, there are only 2 accidents in the sample

which involve machines of interest, and both were fatals.

A6-11





(—

Table 3-1.

Conclusions — Accident Analysis/Rock Fall Characteristics

Accident Analysis

Rock falls, or fall-of-ground accidents are responsible
for approximately 7 deaths and 150 injuries per year in
surface metal-nonmetal mines. Of these, approximately
3 deaths and 62 injuries occur to operators of the
machine types covered by this study.

Rock falls cause about 15 deaths and about 570 injuries
per year in underground mines. Machine types studied
on this program are involved in rock fall accidents
claiming less than one death and approximately

28 injuries per year.

Load-haul-dump units are involved in more underground
rock fall accidents than for the total of all ''machines of
interest.'' These units operate in potential rock fall
areas (forward of the supported roof) and have much
greater exposure than do ''machines of interest."

Rock Fall Characteristics

Rock falls experienced in both surface and underground
mines often involve large masses of material falling
from significant heights. It is impractical to attempt
to provide operator protection for every rock fall.

The material involved in many rock falls is often not
"competent" rock, that is, it does not have great
structural integrity. It may fracture and break up
upon impact or it may fall as a fractured layer. In
surface mine rock falls, the material may be loose or
unconsolidated. The actual kinetic energy transmitted
into the FOPS may be considerably lower than that cal-
culated using the total rock fall weight and the total
fall height.

Approximately one-half of the total rock falls in metal-
nonmetal mines will transmit less than 40,000 ft-lb of
kinetic energy into a FOPS structure.

~



assumptions are possible, but as discussed in Section 4.1, the majority

of rock falls more closely correspond to the distributed load assumption.
Therefore, the fully distributed loading model was used throughout the
report as the basis for establishing recommended certification procedures

and is repeated as the first loading condition shown in the table.

A review of the table shows that the distributed load condition
has the highest predicted energy absorption capability. However, the
predictions for other loading assumptions are probably somewhat con-
servative since as the canopy is overloaded and begins to collapse the

load starts to redistribute over a greater area of the canopy top.

The most severe condition is the concentrated loading on the
corner of the canopy over the support column as depicted by the joint
"E" loading condition. A competent rock striking the corner of the
canopy is simulated by this condition. The predicted energy absorption
capability is only 500 ft-lb. This value is derived by limiting the stress
in the column to the tensile yield allowable of the material. Significantly
higher loads would result in buckling of the column and some possible
load distribution. The energy absorption capability would therefore
increase. Also, it should be noted that this condition in most cases

represents a small rock fall.

The fall of a large competent rock that bridges between the
upright columns must be analyzed in a manner similar to that described
above. Four columns are available to react the load. A conservative
prediction of the energy absorption capability would be approximately
2000 ft-lb. The predicted level is very low since the center portion of
the canopy top does not deform appreciably. The columns must buckle
before significant energy will be absorbed. The distribution of load

and behavior of the canopy structure during a buckling failure is very

WA.



a = SLOPE OF THE FALLEN MATERIAL, 40°
p = "PROTECTION LEVEL" OR HEIGHT OF A PROTECTIVE

STRUCTURE ABOVE THE SURFACE ON WHICH THE
MACHINE OPERATES

f = TOTAL FALL DISTANCE

Figure A5-2. General Model of Rock Fall

The maximum volume of material, with a 40° angle of repose,
which can be retained entirely on the top area, will occur when the pro-
tective structure is directly under the fall and the material piles sym-
metrically with respect to the center line of the structure's top. The

shape of the material at rest is shown in the following sketch.

A5-22



.

Using the same reasoning as discussed above for surface mines,
an average frequency of fatals which involve machines of interest is

estimated at less than one per year.

One fatal accident a year represents 0.7% of the total annual

fatals in metal and nonmetal mines for the years 1972-1974.

The estimating technique indicates there may be as many as 44
non-fatal fall-of-ground underground mine accidents involving machines
of interest a year, approximately 28 of which produce some degree of
injury.

There are many more surface mines than underground mines in
the metal and nonmetal mining industry. The numbers used in this
study are 668 active underground mines and 13,321 active surface mines.
According to the MESA classifications, 1756 of the surface mines are
open pit, 4029 are crushed stone operations and 7536 are sand and

gravel operations.

There are more fall-of-ground accidents in underground mines
than in surface mines. There are approximately 329 such accidents
annually in surface mines, and approximately 877 in underground mines.
However, there are fewer fall-of-ground accidents involving machines
of interest in underground mines than in surface mines. The annual
rate for underground mines is approximately 44; for surface mines it
is approximately 133. Table A6-4 summarizes the WAI estimates of

fall-of-ground accidents involving machines of interest.

It may be estimated that the addition of a ''perfect''’ operator
protective structure on all machines of interest which do not already
have some form of falling object protection, presently working in metal

and nonmetal mines, might reduce the fatal fall-of-ground accidents by

WMA.

A6-12


TABLE

A5-18

A6-1

A6B-2

A6-3

A6-4

APPENDICES
LIST OF TABLES (CONT)

ROPS/FOPS-Related Accidents, Except
Fall-of-Ground, for Which Data Recorded

Accident Data Obtained by Mine Type and
Extent of Injury

Fall-of-Ground as Percentage of Total
Accidents

Summary Statistics — Samples of Mine
Fall-of-Ground Accidents Reported in
This Study

Estimates of Average Annual Fall-of-
Ground Accidents Which Involve Machines
of Interest

PAGE

A5-39

A6-3

A6-7

A6-10

A6-14

A-ix



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A4-3


critical buckling load would be determined for each beam element in the
model using the primary bending moment as predicted by CANOPY and
the secondary (axial load induced) bending moments computed within the

new routine.

The plate and buckling modifications should be included as a sub-
routine to the existing CANOPY program. These changes would not add
significantly to the complexity of the program since they would not affect
the stiffness matrix. The addition of the plate element would add slightly
to the input complexity. No additional input data would be required for
the buckling routine. The output should be structured to be directly

applicable to evaluating canopies.

Additional Considerations

The methods presented in this appendix are guidelines to help the
analyst in several of the important areas of FOPS design. It must be
emphasized that other methods based on sound engineering principles are
acceptable and in some cases more accurate than the methods outlined
here. Sound methods of analysis depend on the configuration of the FOPS.
A complete analysis performed by a competent engineer should be sub-
mitted for each design to be certified by analysis. In addition, the cri-

teria specified in Appendix Al must be met.

A2-20



80

70

fo
i=)

a
=)

as
°

PERCENT OF ACCIDENTS IN SAMPLE
w
o

20 H mms UNDERGROUND MINE SAMPLE — 138
H semee SURFACE MINE SAMPLE — 60
La
10
0 i i iT | J
0 50 100 150 200 250

KINETIC ENERGY (1000 FT-LB)

Figure 4-4. Rock Fall Kinetic Energy at FOPS Protection Level

XX MA.



Table A6-1. Accident Data Obtained by
Mine Type and Extent of Injury

Under ground Surface Totals

F I N F I N F I N
1975 2 0 22 2 0 10 4 0 32
1974 11 8 26 6 2 8 17 10 34
1973 10 11 9 5 0 9 15 11 18
1972 8 3 3 5 4 2 13 7 5
Earlier 17 4 4 1 1 5 18 5 9
and
No Date
TOTALS 48 26 64 19 7 | 34 67 33 98

Total Underground 138
Total Surface 60
198

Key: F = Fatal
I = Injury
N = No Injury

The terms 'machines of primary interest", "machines of interest",
or "equipment of primary interest" refer to those machines specifically
identified in the Introduction of this report. To repeat their identification,
they are "self-propelled, track-type (crawler mounted) or wheeled
(rubber -tired) front-end loaders, dozers, tractors but not over-the-road

type tractors, motor graders, and prime movers with or without

A6-3



unpredictable and difficult to evaluate. As shown in the table, the load
in each column would reach 171,000 lb or more. It is very difficult to

design attachment structures to withstand loads of this magnitude.

Several examples of angular applied loads are included in the
table. A 29,000 ft-lb capability is predicted for a 45 degree load applied
to the two beams along the side of the canopy top. The canopy will absorb
22,000 ft-lb if a rock strikes the top corner at an angle of 45 degrees.
The energy absorbed for a distributed side load is 17,000 ft-lb at a

deflection limit of 4.0 inches.

Some of the different load inputs reviewed above are similar
to the conditions that might be expected in vehicle-object collisions,
vehicle-roof impacts, vehicle-rib impacts, and other side impact acci-
dents. If performance criteria for side impact capability of FOPS were

to be developed, these types of loads would have to be considered.

Development of Static Load Criteria

Establishing a static load criterion which gives confidence that
a ROPS/FOPS structure will absorb a specified kinetic impact energy is
an extremely difficult task requiring many assumptions. A rigorous
analytical method of establishing the analogy between static loading and
dynamic impact loading was not established. However, analyses were
conducted on several representative canopies to develop a reasonable
and practical static load criterion. The approach required determining
the energy absorption capability of representative ROPS/FOPS structures,
computing the yield strength under a distributed uniform top loading,
and comparing the latter value with the decreased yield allowable of the
structure when subjected to a distributed load over the middle ninth of

the plan view area of the canopy top. The results indicated that a



Sims Cabs, Inc.
Payne, Ohio 45880
(419) 263-2321

Manufactures ROPS and ROPS cabs for many indus-
trial tractors and front-end loaders. ROPS cab
models are available for David Brown, Ford, Inter-
national Harvester, Deere, and Massey Ferguson
vehicles.

Tube-Lok Products
Portland, Oregon 97202
(503) 234-9731

Manufactures ROPS and ROPS cabs for complete
Caterpillar vehicle line. ROPS and ROPS cabs

are also manufactured for GM-Terex, International
Harvester and Ray Go equipment. Both retrofit
ROPS and ROPS for new equipment are manufactured.

Young Corporation
Vancouver, Washington 98661

(206) 694-3313

Manufactures ROPS and ROPS cabs for Caterpillar,
International Harvester, Euclid, GM-Terex, Deere,
Massey Ferguson, Loraine, Allis-Chalmers, Wabco,
Michigan, Trojan, Case, Galion, Huber, Ingram,
Oliver, Scoopmobile, Ford, Austin Western, Buffalo
Springfield, and Wagner. Many different models
available; both retrofit ROPS and ROPS for new
equipment.



2) Elastic/Plastic SAP — A nonlinear general analysis

program.

Description of CANOPY

The computer program CANOPY was developed at the U.S.
Bureau of Mines Pittsburgh Technical Support Center. Information

Circular 8546 written by Stephen Gerard Sawyer describes the program.

The program permits rapid calculation of the elastic strength of
a canopy for a variety of static loading conditions. Stresses in, and
displacements of, each structural member are computed and printed out.
Additionally, identification of all members that have commenced yielding,
weight of the canopy, total loads on the canopy, and maximum loads that

the canopy can sustain elastically are output.

CANOPY is a space-frame program which uses the stiffness
method of analysis to determine a structures elastic response to static
loadings. Axial, bending, shearing, and torsional deformations are
considered in the solution routines. The program is divided into
five phases as follows: compilation of structure data, formation of
stiffness matrix, compilation of load data, calculation of joint displace-

ments, and calculation of member stresses.

Description of Elastic/Plastic SAP

The computer program SAP was developed at the University of
California at Berkeley by Dr. Edward Wilson. Plastic routines were
added by Woodward Associates personnel for the U.S. Army Mobility

Equipment Research and Development Center.

SAP is a general purpose finite element structural analysis pro-

gram for the static and dynamic response of linear three-dimensional

WMA.

A2-13



Figure 4-20.

aia

Figure 4-21.

Fleco ROPS on Caterpillar
Crawler Dozer

Sims Cabs, Inc. ROPS on

Massey Ferguson Industrial Tractor

4-74



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installed. The table separates the machines by type and age group.

The unit cost for retrofit of machines in each block in the type-age
matrix was developed in the manner discussed above through the use

of the ''type profile.'' It is a weighted average for machines in the type-
age block. Multiplying the weighted average by the number of machines
in the population to which it applies gives the retrofit cost estimates

shown.

A policy decision to retrofit FOPS with greater capability than
SAE J231 requires would raise a corollary question about the estimated
cost of modifying ROPS already installed to attain that same capability.
This question is fraught with a great many implications, technical,
financial and political, It is the kind of question which can be answered

fully if it can be answered at all, only through an extensive study.

Table 4-15 provides the estimates of costs, for retrofit of com-
mercial ROPS on all machines not presently ROPS-equipped, as a per-
centage of machine value. The estimates of machine market value were
developed from a ''type profile’ in the same manner as the ROPS retrofit

cost estimates were done.

For some of the machines in the population, the costs of ROPS
retrofit represent but a fraction of the financial implications of a ROPS
retrofit policy. These are the machines used in low back underground
mines, that is, mines with a roof height less than 12 feet. The point
to be emphasized here is that machines used in this kind of mine, although
few in number relative to the total population, represent a special kind
of financial problem. The retrofit of a commercial ROPS could, in many
cases, make the machines unusable in the mines unless the backs were

made higher. This would require extensive removal of additional material

4-106



sections before forming or welding for use in the canopy. Specimens
from tubular or structural sections are to be taken from the middle of

the side of greatest dimension, not to include welds.

Bolts and nuts used to attach the canopy to the vehicle frame and

to connect structural parts of the canopy shall be SAE Grade 5 or 8.

Welding Requirements

All welding on the canopy and attachment structure to the vehicle
must comply with the "Specification for Welding Rollover-Falling Object
Protective Structures (ROPS and FOPS)" currently being prepared by the
American Welding Society's D14h Subcommittee. Final publication is
scheduled for the first half of 1976. Adherence to this specification is
required during fabrication, installation and repair of the canopy and
attachment structure. This specification covers in detail requirements
for base metals; welding processes and consumables; joint and welder
qualification; joint preparation; workmanship and weld quality require-

ments; inspection; installation; and field repair and modification.

Canopy Top Design Requirements

The canopy top must be designed to protect the vehicle operator
from penetration of the falling object. Compliance with this requirement

shall be established by either of the following:
1) Meeting specified design guidelines.

2) Successfully passing a SAE J231 drop test.

Canopy Top Design Guidelines — The canopy top shall be covered

with a steelplate with a thickness of 0.1875 or greater; or it shall be
covered by steel mesh 0.50 inch minimum diameter with a 2.0 x 2.0 inch

maximum center-to-center grid spacing. An equivalent mesh fabricated

WA.

A1-3


FIGURE

4-28

4-29

4-30

4-31

4-33

4-34

LIST OF ILLUSTRATIONS (CONT)

Young Corporation ROPS Cab on Clark
Rubber-Tired Loader; ROPS on Wagner
LHD : . . . .

Young Corporation ROPS on Massey-
Ferguson Industrial Tractor; ROPS on
Massey-Ferguson Rubber-Tired Loader

Underground Mine Vent Bag Clearance
Problems

Underground Mine Canopy Clearance
Problems

Machine Value vs. ROPS Retrofit
Cost — Caterpillar D8 .

Machine Value vs. ROPS Retrofit
Cost — Light Industrial Tractor

Machine Value vs. ROPS Retrofit
Cost — General . . . . .

Fleet Size and Composition — Machines of
Interest

ROPS/FOPS Retrofit Costs vs. Percent of
Vehicle Population (January 1, 1976)
ROPS/FOPS Equipped .

PAGE

4-100

4-101

4-104

4-110

4-113



A second test is required when it is judged that the
vertical deflection due to a load applied within the
middle ninth of the plan view area is less than the
predicted deflection when a load is applied over the
operator. In this case the load will be centered over
the head of the operator while in the normal operating
position and can be distributed within an area equal to
one-ninth of the plan view area of the canopy top. It is
required that this test shall follow the center load test
and meet deflection criteria established for the first

test.

Instrumentation Accuracy Requirements

Force and deflection measurements are required. The
instrumentation used to measure force applied to the
canopy must have an accuracy of +5% of maximum force.
The vertical deflection of the centroid of the loaded area
must be measured to an accuracy of +5% of maximum
deflection. The above percentages are nominal ratings
of the accuracy of the instrumentation and should not be

taken to indicate that compensating overtest is required.

Measurement Requirements

As a minimum the following must be measured and

recorded:

1. The vertical deflection of the centroid of the pro-
tective structure's top which is caused by the

application of the total load.

2. The value of the maximum load.

A3-4



~

chassis by a welder certified to specific AWS criteria. The ROPS/FOPS
must then be attached (bolted or welded depending on the design) to the
mounting brackets. The machine can now be placed back in service.

The total elapsed time for this installation operation ranges from

2-3 hours for small industrial tractors to 10-12 hours for larger
machines. Two or three men may be required to complete the opera-
tion. There are ROPS/FOPS that take up to 80-100 manhours to install.
This cost is not insignificant, especially when the machine's non-

productive hours are charged against the ROPS/FOPS installation.

As with any safety device, the user (in this case the machine
operator) will have an opinion on the merits of the ROPS/FOPS. The
construction industry has been installing ROPS on machines for several
years and has met mixed response from machine operators. The lowered
visibility, the uncomfortable seat belts, and the reduced ability to jump
are frequent sources of complaint from construction industry machine
operators. Accident records in the construction industry indicate the
reduced risk of injury or death if an overturning machine has a ROPS
and the operator is using his seat belt. Many operators still prefer to
take their chances in trying to jump from an overturning machine. If
the machine has a ROPS installed and the operator tries to jump, he
may be crushed by the ROPS itself. The problem of operator acceptance
has been experienced in the construction industry and is to be expected

in the mining industry.

Certain minor work-function problems may be experienced after
a ROPS/FOPS is installed on a machine. A common problem involves
using a front-end loader to clean up the area under a loading bin or load-
ing hopper. The height of the ROPS/FOPS may prevent the front-end
loader from entering the area under the hopper. A smaller front-end

loader will have to be used to perform this task.



The question addressed here is: ''What are the costs to retrofit the
estimated 25,765 machines which do not have ROPS installed?" In
addition to answering this question, the financial impact on some of the
machine owners who have small fleets of only pre-1970 machines is
considered and the indirect financial implications of ROPS and FOPS

on machines of interest which are used underground are discussed.

Sources of Financial Information

It is appropriate to express the costs of retrofit not only in abso-
lute terms, but also in relative terms, specifically as a percentage of
the average market value of the machines considered for retrofit. To
do this, it is necessary to have data from a recognized source of market
information. In this study, the market value data were taken from latest
revisions of the Green Guide, published by the Equipment Guide — Book
Company, Palo Alto, California. The ''market value'' used in the compu-
tations was the ''average resale value" given in the Green Guide for

machines without "extras."

The total cost of installing a commercial ROPS on a machine was
calculated by adding to the ROPS manufacturer's FOB price an average
transportation cost of $7 per 100 pounds of ROPS weight and installation
costs varying from $125 to $250, depending on ROPS size. The trans-
portation and installation cost estimates were obtained through consulta-
tion with ROPS manufacturers. The transportation cost will vary, of
course, with the distance shipped and the mode employed. Installation
cost depends on a great many factors, not the least of which is in the
design of the ROPS mountings. Installation cost quotations for one
machine varied from $150 to $600. For the calculations, the median
values of estimates were used because they were consistently less than

the averages. The assumption implicit in this choice is that mines

WA.



~

forms mailed. (See Appendix A4 for ''RS'" response performance.) There

Table A5-7 shows the response performance from the 113 "AH"

were 82 forms returned with the information requested in Section 1, or
with some statement expressing a reason for not providing answers to the
Section 1 questions. The most frequent reason was that the mine had been
closed or that ownership had changed. The next most frequent reason

was a statement to the effect that all known information was in the MESA
accident investigation report. The overall response rate was 82/113 =
0.726, or about 73%. Nearly 20% of the respondents provided Section 2
information on ''no injury" accidents. Many others reported that, although
such accidents had occurred, no records were kept and no data were

available.

Data Analysis Procedures

The fall-of-ground physical data available, whether from accident

investigation reports, from the questionnaires mailed, or from direct

Table A5-7. ''AH" Questionnaire Response Information
Total "AH" forms sent 113 100.0%
Full response provided 73
Response, but no data, Section 1 7
Response, data incomplete or unusable, 2
Section 1
Total responses to cutoff 82 72.6%
No response or undeliverable by USPS 31
Responses with data in both Section 1 22 19.5%
and Section 2

A5-13


—\

of machine value is not changed appreciably, but the estimates of dollar
costs to retrofit ROPS given in this study must be multiplied by some
value to obtain a good estimate for the time period in which retrofit
might actually be accomplished. The WAI estimate of the multiplier for
late 1976 retrofit is 1.24; the expected change in prices will be 24%
between early 1975 and late 1976.

Figure 4-33 pertains to a light wheeled tractor (6000 pound class)
illustration. The Massey Ferguson MF-302, 304 and earlier 303 models
are examples of this weight class. The average cost of retrofit of the
available commercial ROPS is $880 for machines manufactured during
the 17 years given on the graph. The market value of 1959 machines is
$900. For machines manufactured before 1959, the ROPS retrofit cost
exceeds the market value. The retrofit cost for a 1956 machine is 170%

of its market value.

To conclude the discussion of ROPS retrofit cost relative to
machine age, Figure 4-34 is a graph which illustrates the matter in
aggregate terms. The ROPS cost curve is flat over a large range of
machine ages, but it slopes downward slightly at the low age end and
upward at the high age end. The reason for the downward slope is that
newer machines are built with ROPS mountings installed. The reason
for the upward slope is that the unit ROPS cost is higher for some very
old machines which are very few in number. A ROPS is ''commercially
available" in the sense that one can be purchased from a ROPS manufac-
turer, but if it is related to a machine for which the manufacturer has
had no previous ROPS sales, the cost could be high. At some age, Ay)
the aggregate ROPS retrofit cost will equal the aggregate market value

of machines of that age.

Table 4-14 shows the estimates, from Section 4.3, of the numbers

of present machines of interest which do not have protective structures

WMA.

4-103


Table 3-3. Conclusions —- ROPS/FOPS Economic Area

There are approximately 49,000 ''machines of interest"
in use in metal-nonmetal mining operations.

Approximately 26,000 units of mining equipment could
be affected by a ROPS or FOPS retrofit policy for
metal-nonmetal mines.

The costs of ROPS/FOPS retrofit policies could vary
from about $11,000,000 to retrofit all "machines of
interest'’ manufactured after 1969 to about $45,000,000
to retrofit all ''machines of interest" regardless of date
of manufacture.

The cost of a ROPS/FOPS regulation for underground
"machines of interest" could be very high in low back
mines. Drastic changes in mine operation would be
necessary to accommodate the added height to the
machine.

The population of load-haul-dump units is estimated
at 600; about 240 do not have protective structures
installed.



>

of fallen material. Several models which would provide reasonable
estimates of impact weight and kinetic energy on the protective structures
were worked out and tested. It was finally decided to use, for this report,
avery basic one. Although the model requires several simplifying
assumptions regarding the geometry and kinematics of earth falls, it
produces satisfactory approximations which compare favorably with those
obtained through more refined models. Further, it satisfies the principal
objective, namely, to produce reasonable estimates with bias only in the
direction of larger values, as will be apparent in the discussion which

follows.

Assume that the material falls in a single, nearly cohesive mass,
that it falls vertically, and that the machine upon which it impacts is
directly under the fall, parallel to the face, and as near to the face as

its normal work allows.

In most of the accidents in the sample, the fall was indeed from
a nearly vertical face or wall. A few were from areas above undercuts.
Some, however, were slides no more than about 30° above horizontal.
The machines involved were usually not far from the wall, but within

machine working distance from it.

The "angle of repose" is usually defined in one of two ways. It
is the angle which the "natural slope'' makes with the horizontal when a
mass of earth has been exposed for a time to the elements. Or, it is
defined as the angle with the horizontal at which material will stand when
piled. The ''angle of slide'' is the angle at which material will flow.
Table A5-8 shows angle of repose values for several materials. Table A5-9
gives some angle of slide values. A fallen non-cohesive material will form
some angle with the horizontal after impact. The angle will be one between
its angle of repose and angle of slide. In the model, 40° was assumed for

all cases.

MA.

A5-15


highest position and must meet the acceptance
criteria of Step e. The second test will be con-

ducted with the canopy in the lowest position.

3. Hydraulic rams or cylinders may be replaced with

equivalently stiff structural members.

Option B

A static test of the canopy attached to a rigid platform in the same
manner as it is to be attached during actual use is specified. In addition,
engineering calculations must be prepared and several design and fabrica-
tion requirements must be met. The requirements of Option A and the

following items apply for Option B:

° Engineering calculations are required to establish the
adequacy of the attachment structure to the vehicle

frame.

° The attachment location of the canopy to the vehicle

frame must meet specified guidelines.

Step-by-Step Test Procedure (Option B)

a. Static Top Load Test

The requirements of Option A apply except for some
modifications to the specified test preparation, Option A,
Step a. Instead the canopy shall be attached directly to
a rigid platform in a manner which simulates the actual

attachment to the vehicle.

b. Attachment Structure Analysis Requirements

The structural components of the attachment structure

between the canopy which was tested in Step a and the

WA.

A3-6


of no machines, as mentioned above) were estimated using appropriate
sample proportions. These were then used with the total population
estimate to compute the estimated numbers of machines in each category.
The numbers used in Sections 4.4 and 4.7 were computed from mid-
points of 95% confidence intervals for population proportions. These

confidence intervals were calculated as:

or

where

p is the sample proportion
k is the confidence multiplier (1.96 in these cases)
n is the sample size

N is the population size

The confidence intervals vary greatly with different values of p. An
illustrative calculation for the proportion of the population of machines

of interest represented by machines with three attributes i, j, k is:

i is front-end loaders
j is post-1969 age group

k is ROPS-equipped

A4-17



LIST OF ILLUSTRATIONS (CONT)

FIGURE PAGE

4-16 Protective Structure Status — 1975

(Machines of Interest by Year of

Manufacture) . : : . : : . : 4-57
4-17 Egging ROPS Cab on Caterpillar Crawler

Dozer . . . . . . . . . 5-72
4-18 Industrial Cab Company ROPS Cab on

GM-Terex Crawler : . : . : . 4-72
4-19 Eimco ROPS on Eimco LHD Units . : : 4-73
4-20 Fleco ROPS on Caterpillar Crawler Dozer . 4-74
4-21 Sims Cabs, Inc. ROPS on Massey Ferguson

Industrial Tractor . . . : : . 4-74
4-22 Medford Steel ROPS on Komatsu Crawler

Loader; ROPS Cab on Komatsu Crawler

Dozer . : : : . . . . . 4-75
4-23 Palm Industries ROPS Cab on GM- Terex

Rubber- Tired Loader . : : . : 4-76
4-24 Sequoia ROPS Cab on Caterpillar Prime

Mover (Scraper) . : : : : . : 4-76
4-25 Saf-T-Cab ROPS on Euclid Off-Road

Dump Trucks; ROPS Cab on Ford Industrial

Tractor . . : . . . . . . 4-77
4-26 Saf-T-Cab ROPS Cabs on Caterpillar

Motor Grader and on Caterpillar Crawler

Loader . . : : : . : . : 4-78
4-27 Tube-Lok ROPS Cab on Caterpillar

Rubber-Tired Loader; ROPS on Caterpillar

Crawler Dozer . . : : : . : 4-79

ix



Table A5-2. Fall-of-Ground Accidents —
Identified from MESA Accident Investigation Reports

Year Fatal Non-Fatal Total
1975 5 6 11
1974 24 18 42
1973 21 15 36
1972 22 8 30
Prior to 1972 26 7 33
All Years 98 54 152
Table A5-3. Fall-of-Ground Accidents —
Physical Data Complete in MESA Reports
Year Fatal Non-Fatal Total Percent
1975 0 1 1 9.1
1974 8 1 9 21.4
1973 2 3 5 13.9
1972 2 3 5 16.7
Prior to 1972 1 1 2 6.1
All Years 13 8 22 14.5

A5-8



the life saving performance of a ROPS is dependent upon keeping the
machine operator contained within the ''safety zone"' of the operator's

compartment it is mandatory that seat belts be installed and worn.

During the formulation of a new ROPS/FOPS regulation, factors
in addition to increased safety must be evaluated. The economic impact
of a proposed regulation and potential effects on mining operation methods
must be studied. The operational effects on surface mining and in the

surface areas of underground mines are minimal.

In underground mines, the requirement to install ROPS/FOPS
could cause large changes in the use of mining equipment and the added
height due to ROPS/FOPS installation could render many pieces of equip-
ment unusable in the mine areas where they now work. The potential
economic effects are very large in underground mines. If the mine
height has to be increased to allow passage of ROPS/FOPS equipped
machines then a considerable amount of valueless material has to be
removed. This operation effectively lowers the value per ton of the ore
being mined. As a simple example, assume that a mine is currently
working a 3-4 foot thick mineralized zone, the back height is averaging
6 feet, and the ore is running $25 per ton (assume no upgrading). If
the back has to be raised to a 10-foot average height, then 67% more
material will have to be removed for the same amount of ore previously
mined with the 6-foot high back (10+ 6 = 1.67). Now 1.67 tons of material
will be mined to capture the $25 worth of ore that was previously captured
by mining one ton. The new worth per ton is $25 divided by 1.67 tons
or $15 per ton. The mine operation may be incurring costs of $20 per
ton to mine the ore, therefore this profitable operation would now be
unprofitable and mine management would have to consider new mining

methods or closing portions of the mine. Using smaller equipment and

3-4



Rome Industries
Cedartown, Georgia 30125
(404) 748-4450

Manufactures both retrofit ROPS and ROPS for new
vehicles. Models available for Caterpillar crawler
dozers, crawler loaders, scraper prime movers,
wheel loaders, wheel dozers, and motor graders.
Affiliated with Medford Steel.

Saf-T-Cab, Inc.
Fresno, California 93745

(209) 268-5541

Manufactures both retrofit ROPS amd ROPS for new
vehicles, Very large number of ROPS models
available. Units available for Fiat-.\llis, Austin
Western, Bros, Case, Caterpillar, Champion,
Clark- Michigan, Curtis Wright, Deere, Dvnahoe,
Fimco, Euclid, Ford, Galion, Gradall, Grove,
Hancock, Iluber, Hvster, Ingersoll Rand, Ingram,
International Harvester, Jacobsen, Koehring,
Komatsu, I.ima, I.ong, Loraine, \I-R-S, \Viassey
Ferguson, Multihoe, Oliver, Pactor, Ravgo-
Wagner, Tampo, G\l-Terex, Trojan, Vibro Plus,
Wabco, Scoopmobile, Waldon, and Worthington
vehicles. Both ROPS and ROPS cabs available

for many models.

Sequoia Manufacturing Company, Inc.
Fresno, California 93727

(209) 255-1611

Manufactures ROPS and ROPS cabs for machines
manufactured by Allis-Chalmers, Case, Caterpillar,
Ford, Galion, llyv-Dynamics, International Harvester,
Deere, Komatsu, \lassev Ferguson, Michigan,
Gi\I-Terex, Wabco and others.



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A4-5


Figure 1-9. ROPS Canopy (Rome Manufacturing Co.)

Figure 1-10. ROPS Cab (Young Corporation)

1-10



Figure 1-1, Rubber-Tired Front-End Loader

Figure 1-2. Crawler Tractor
(Dozer if equipped with blade;

Loader if equipped with bucket)





\

In summary, it appears that ROPS that meet the ROPS structural
performance given in SAE J1040a ''Performance Criteria for Roll-over
Protective Structures (ROPS) for Earthmoving, Construction, Logging,
and Industrial Vehicles", dated February 1975, or the ROPS performance
required in the Corps of Engineers Safety Manual EM-385-1-1, Change
1, Paragraph 18.A.20, dated March 27, 1972, are available for almost
all post-1959 models of the ''machines of interest!’ covered by this
study. Likewise FOPS that meet the performance standards given in
SAE J231 ''Minimum Performance Criteria for Falling Object Protec-
tive Structure (FOPS)", dated May 1971 are an integral part of most
ROPS systems or can easily be added to those that do not now have
FOPS capability.

The only qualification in the area of ROPS/FOPS availability
concerns the light industrial tractors sometimes used to tow small ore
trailers or as personnel carriers (boss buggies). While ROPS are
generally available and can be readily installed on the post-1964 models,
there are some structural problems associated with mounting ROPS on
some pre-1965 models. Also, the FOPS routinely provided with the
ROPS on light industrial tractors are designed to meet SAE J167
"Protective Frame with Overhead Protection- Test Procedures and

Performance Requirements."

This FOPS performance standard does
not provide the same level of operator protection as do the FOPS that

meet SAE J231.



’
4.4 COMMERCIAL AVAILABILITY OF ROPS/FOPS

The availability of ROPS/FOPS units for the types of mining
equipment studied on this program has been determined. The yearly
ROPS/FOPS production capacity exceeds 300,000 - 350,000 units per
year. Three primary sources of information were used to develop the
status of ROPS/FOPS production capability and to determine the avail-
ability of ROPS designs for the various models of equipment in the field.

Information Sources

A report prepared by Woodward Associates for the Occupational
Safety and Health Administration in 1974 entitled "Study to Determine
the Engineering and Economic Feasibility of Retrofitting ROPS on pre-
July 1, 1969 Construction Equipment" (DOL Contract L-73-158) contains
information on the ROPS Production capacity inthe U.S. in 1973. This
material has been reviewed and up-dated to reflect the industry capa-
bility in 1975. This report has also been used as a basis to determine

the availability of ROPS/FOPS for different models of equipment.

Direct contacts with major ROPS manufacturers have provided
additional information on the availability of ROPS designs for the many
models of equipment. Information on production capability changes
was also received. Several of these ROPS/FOPS manufacturers pro-
vided photographs of ROPS/FOPS installed on mining equipment. These
photographs are included later with text describing some of the ROPS/

FOPS manufacturers.

Additional information on ROPS/FOPS availability was received
during visits to ROPS manufacturers, equipment manufacturers, and

mining operations.



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4-19


3. The residual vertical deflection of the centroid
of the protective structure's top after the load is
removed. This represents the permanent vertical

deflection of the canopy top.

4. If atest with the load applied over the operator is
required, measurements 1 and 3 will be taken at

the centroid of the load application.

Additional deflection measurements may be recorded at
various load increments to more accurately characterize

the behavior of the FOPS.

Test Acceptance Criteria

The following criteria must be met to successfully pass

the static top load test:

1. The recorded residual deformation as measured in
Steps d.3 or d.4 must be less than 10% of the recorded
maximum vertical deflection as measured in Steps d.1

or d.4.

2. Visible failure of welds or any structural member is

not permitted.
Special Considerations

1. Should the residual deflection be greater than 10%,
the canopy cannot be certified nor retested because
damaging permanent deformation of some of the

structure's members has probably occurred.

2. Two tests are required for adjustable canopies. The

first test should be conducted with the canopy in the

WA.

A3-5



~\

The equipment population information, together with FOPS cost
data, could be used to estimate the economic implications of any proposed
FOPS regulation. The equipment population information could also be
used to estimate the mining industry costs of complying with proposed
ROPS regulations. In June 1975 the Bureau of Mines awarded USBM
Contract No. J0357710, ''Design Criteria and Guidelines for Falling
Object Protective Structures (FOPS)", to Woodward Associates, Inc.,
Redlands, California, to prepare information that would allow
MESA to determine the possible approaches to implementing a FOPS

regulation in metal-nonmetal mines.
The primary tasks of this program were as follows:

1) Characterize rock falls in surface and underground

metal-nonmetal mines.

2) Determine the required structural performance of
FOPS to provide operator protection from rock falls

in surface and underground metal-nonmetal mines.

3) Gather information on the equipment population that

might be affected by future FOPS and ROPS regulations.

4) Assess the industry costs of complying with future

FOPS and ROPS regulations.

These tasks were accomplished during the period between June 13, 1975
and January 31, 1976. In performing these tasks, Woodward Associates,
Inc. relied heavily on the results of a USBM Fall-of-Ground and Equip-
ment Survey that supplied information from over 600 mining operations,
on work conducted previously for the Department of Labor's Occupational
Safety and Health Administration, and on falling object protective struc-
ture and roll-over protective structure design efforts previously conducted

for the U.S. Army and commercial customers.

WMA.



Figure 4-31. Underground Mine
Canopy Clearance Problems



Table A5-1. MESA Accident Investigation Reports
(Pre-Survey Review)

Fatal Accident Reports

Denver, HSAC

Year 1972 139
1973 168
1974 146
1975 57

Fatal and Non-Fatal Accident Reports

Arlington, MESA

All Years 191
Reno, MESA

All Years 304
TOTAL 1005

reports in which needed data were complete, by year and type of accident.
The overall percentage of accidents of interest which had all required

data in the reports was 14.5%. One hundred thirty of the 152 identified

in Table A5-2 had insufficient information for the data requirement of

this study. The 130 accidents were those about which mail inquiries were
made, using the Bureau of Mines Fall-of-Ground and Equipment Survey
form discussed below. Table A5-4 is a summary of the 130 accidents by
mine type (underground or surface) and type of accident (fatal or non-fatal).
The table also shows, in the first column, the numbers of questionnaires

which were mailed to obtain data not available in the accident investigation

A5-7



SECTION 1.0

INTRODUCTION

Several federal and state agencies have promulgated regulations
that require the installation of operator protective structures on mobile
equipment used in mining, construction, agriculture and logging indus-
tries. These regulations cover many different types of vehicles, from
small farm tractors to large rubber-tired front-end loaders, and require
structures that help protect the operator from death or injury from vehicle
overturns, from falling tree tops and logs, from falling rocks, and from

tree limbs in clearing operations.

Two general types of vehicle operator protective structures have
evolved over the past twenty years. The first of these is the ''Roll-Over

‘or "roll

Protective Structure" or ''ROPS" that is essentially a "roll bar'
cage"' that provides a relatively safe area for the vehicle operator if the
vehicle should tip over and roll. The second protective structure is the
"Falling Object Protective Structure" or 'FOPS" that provides overhead
protection against falling material. The terms ''ROPS" and ''FOPS" are
often used interchangeably (sometimes inaccurately) with ''cabs",

"canopies", "roll bars"

, protective structures" and other such descrip-
tive names. Inthis report, 'ROPS" describes the function of the struc-
ture; ''FOPS" also describes a particular function. Thus a ROPS/FOPS
could describe a cab or a canopy that provides both roll-over protection

and falling object protection.

"MESA" is used as an abbreviation for the Mining Enforcement and
Safety Administration; ''USBM" is used to abbreviate the U.S, Bureau of

Mines,

WMA.



5 cubic yard capacity load-haul-dump unit is more productive and more
cost-effective than three 2 cubic yard load-haul-dump units. These

larger machines tend to ''crowd" the back or the roof.

If canopies are required on equipment used in underground mines
that have low backs, the mine operator must either raise the height of
the mine back (a very expensive and non-productive operation) or sub-
stitute smaller mining equipment (another very expensive alternative

that doesn't increase production).

This type of problem is not experienced in underground mines
with high backs. Large underground salt mines are good examples of

mines where the back or roof may be 30-100 feet high.

The clearance problem is not always solved by having mine back
high enough to allow a FOPS-equipped machine to travel. It is common
practice to hang water lines, compressed air lines, and vent lines from
the mine back. These can cause clearance problems for the FOPS-

equipped machine. Figures 4-30 and 4-31 illustrate this problem.

Another potential problem could develop for surface or underground
mine operators if a FOPS performance criteria different than SAE J231
is used in a FOPS retrofit regulation. If the new FOPS criteria requires
structural capabilities greater than SAE J231, many of the ROPS/FOPS
units that have been previously supplied and installed must be strengthened
in some manner. The mine operator is faced with modifying the ROPS/
FOPS-equipped machines he already owns in addition to acquiring new

FOPS for his machines that do not presently have FOPS or ROPS.

The possibility of FOPS regulation that would allow in-the-field
modification of an existing ROPS or FOPS is of concern to the ROPS

manufacturers. In the past several years, both ROPS manufacturers



conditions for static equilibrium. A rigorous solution for a structure
with multiple redundancy is quite complex and usually best approached

with a computer method.

What alternate approaches are feasible for the analyst that does
not have a computer or computer program available? The answer to this
question depends somewhat on the configuration of the canopy and attach-

ment structure.

Some four-post canopies can be analyzed by the methods presented
in Bureau of Mines Report of Investigations, RI7799, ''Elastic Plane
Frame Analysis of Semisymmetric Cabs and Canopies Used on Under-
ground Electric Face Equipment.'' This report describes methods by
which some three-dimensional space frame protective canopies can be
analyzed by employing the theory of plane frame analysis. Certain geo-
metric arrangements must be present to enable reasonably accurate

approximation of three-dimensional behavior:
1) The canopy must be symmetric about at least one plane.

2) Structures with one or more top members in the long
direction that do not frame into the columns should be
approximately twice as long as they are wide and have

two or more internal top members in the short direction.

3) Canopies with symmetric tops that have sets of legs that
do not vary in length more than 10% may be treated as

symmetric about one plane.

Even when the required geometrical configurations are present
approximations must be made to reduce the structure to a series of
interconnected plane frames. All members in the loaded plane of the

structure that do not frame into columns are modeled as simply supported

WA.

A2-2


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14) Substantial Underground Cabs and Canopies Provide
Needed Protection for Equipment Operators, by
Dr. Stephen Sawyer and John McCormick, article

published in Coal Mining and Processing Magazine

15) A Testing Procedure for the Certification of Under-
ground Protection Cabs and Canopies, MESA
Informational Report IR 1002, by Dr. Stephen Sawyer
and Darryl Brogan

ROPS/FOPS REGULATIONS

1) Bureau of Reclamation, Safety and Health Regulations
for Construction, Part II — paragraphs 9.6 thru 9.9
(ROPS, FOPS)

2) Corps of Engineers, Safety Manual, General Safety
Requirements, EM 385-1-1 including Change 1,
March 27, 1972 — paragraph 18.4.20 (ROPS, FOPS)

3) Mining Enforcement and Safety Administration,
Part 75, Coal Mine Health and Safety — para-
graph 75.1710-1 (FOPS)

4) Mining Enforcement and Safety Administration,
Part 77, Coal Mine Health and Safety — para-
graphs 77.403, 77.403a (ROPS, FOPS)

5) Occupational Safety and Health Administration,
Part 1928, Occupational Safety and Health Standards
for Agriculture; Subpart C, Roll-Over Protective
Structures — paragraph 1928.51 (ROPS)



~

the identification of any machines involved. Of the 152 fall-of-ground
accidents identified through MESA fatal or non-fatal accident investigation
reports, only 22 had all of the physical data needed. A questionnaire

was employed to acquire the physical data about the accidents which was
not available in the reports. Questionnaires were sent to 113 mines,
inquiring about specific physical details of 130 accidents. Thirty-seven
questionnaires, relating to 37 accidents, were sent to surface mines.
Seventy-six questionnaires, relating to 93 accidents, were sent to under-
ground mines. Response rates and related information concerning the
questionnaires appear in Appendix A5. Data concerning 198 fall-of-ground
accidents was received through the questionnaires and through responses
to the Fall-of-Ground and Equipment Survey. These accidents are
summarized by type of mine, extent of injury to persons and time periods

of occurrence in Table A6-1.

Important Definitions

There are three definitions employed consistently in this study
which are very important to a correct understanding of the data discussed

in this and subsequent sections.

The definition of the term "accident" was taken from the Bureau
of Mines, Miners' Circular 51, ‘Injury Statistics as an Aid in Preventing
Accidents in Metal and Nonmetallic Mines," namely, ''an unplanned or
unforeseen event that may or may not result in occupational injury."

This definition was chosen because, as was discussed in Section 4.1,
it was primarily the physical characteristics of fall-of-ground phenomena

with which the accident analysis part of the study was concerned.

The term "fall-of-ground'' was defined to mean the fall of any
material related to mining operations from any mine surface, or from

any machine or structure.

WMA.

A6-2


Compute the total load applied to the canopy,

TL = (p)(L)(W)

‘where

p = Distributed force

ra
"

Length of canopy top

4

Width of canopy top

The support columns should be analyzed according to the specified

' The conservative

buckling procedure in the section entitled ''Buckling.'
approximation of the applied simple beam bending moment for each

member is:

m? = (0.50)(TL)(L/2)

The applied compressive load,
P = (0.50)(TL)

After computing mt and P the factor of safety can be determined by com-

pleting the buckling analysis procedure.

The roof reinforcement beam members can usually be analyzed
by making conservative load distribution estimates to reduce the degree
of redundancy. As an example, consider member BE which must transfer

a portion of the bending loads due to the roof overhang to the support

WMA.

A2-4


Table A5-18 is a summary of the accidents other than fall-of-ground for

which data were recorded. The total number is 68. Of these, 58 were

fatals. This number is approximately comparable to 38 fatals involving

fall-of- ground and machines of interest plus LHD types (see Table A6-3).

Again, the sample in Table A5-18 is not a random sample, but several

general observations seem valid:

1)

2)

3)

The need for protective structures on machines of

interest used in mining operations is greater with

respect to roll-over and other machine accidents than

with respect to fall-of-ground accidents. In Table A5-18,
all of the roll-over and machine fall categories are surface
mine accidents. The other categories include both under-
ground and surface accidents. The underground accidents

include some involving LHD types of machines.

To require a ROPS without simultaneously requiring

that a seat belt be installed and used in conditions where
roll-over or machine fall is a danger is extremely poor
policy. Without a seat belt in use, the ROPS may actually
increase the hazard to the machine operator in roll-over
or machine fall situations. ROPS and seat belts, when
properly used, do not assure absolute safety in roll-over
accidents, but they greatly reduce the probability of

fatal injury.

Properly designed FOPS on machines used underground
will also provide some high degree of operator pro-
tection for other than fall-of-ground accidents. In
particular, for those in which the operator struck, or

was struck by, an object (roof support, overhang,

A5-38



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A5-35


form also asked for information on no-injury accidents, to obtain a
larger sample from underground mines than using k = 8 for all mines

would produce.

The survey response rates varied from 45% for crushed stone
mines to 73% for underground mines. (The details of responses,
follow-up actions and final response rates are in Appendix A4.) The
size of the survey response in relation to the total number of mines,
rather than to the number sampled, is shown in Table 4-10. The overall
percentage of responses relative to the mines on the HSAC list was
7.5%; relative to Mine Reference File, it was 4%. That is, the infer-
ences drawn concerning machine population are based on a modified
random sample of 4% of the total active metal-nonmetal mines in the

U.S.

The inferences drawn concerning machine population in underground
mines are based on a modified random sample of about 12% of those

mines.

Every state is represented in the total sample.. To assure that
this would be so was one of the several reasons for using systematic
sampling. (In Appendix A4 there is a table which shows the sample and
response numbers for all states and for the four mine type classifica-
tions.) In addition to the responses from the survey sample, there were
81 machine data responses received with the accident history (AH)
questionnaires. These were recorded separately from the survey
sample. They were not used directly in making inferences about the
machine population and sub-populations, but they were employed in
various statistical comparisons. In short, they were treated as results

of an entirely separate convenience sample.

The estimate of the total population of machines of interest in

metal-nonmetal mines is shown in Figure 4-11. The number 49,293 is

WA.



~\

On the positive side, an enclosed ROPS/FOPS provides operator
protection from adverse weather conditions and permits the operator
to effectively work his machine during periods when an open machine
could not be operated. Protective enclosures are available that have
heaters, air conditioners, positive pressure systems, air filters and
noise control packages, These units are more expensive than the standard
open ROPS/FOPS but may pay for themselves in increased productivity,

Even the open ROPS/FOPS provides increased operator comfort during

drizzles and light rains.

The use of ROPS/FOPS in underground mines presents the same
installation and operator acceptance problems experienced in surface
mines plus added problems in the area of work-function limitations.
Since machine roll-overs in underground mines are very rare, there
is little need for ROPS on equipment used underground. Fall-of-ground
is a serious accident cause in certain areas of underground mines. If
FOPS are required on equipment working forward of the unsupported
roof or in any area of an underground mine, a problem of ''clearance"
is encountered. The machine that previously worked in a particular
mine area may not be able to continue that work if a FOPS is installed.
The present practice of some underground mine operators is to try to
mine the mineralized zone with as low a mine back as possible and with
the largest load capacity machines as possible consistent with the low
height of the back. A simple example is a mine with a horizontal 3 foot
thick mineralized zone. The height of the back may vary between 4 and
7 feet in different areas of the mine. This height is determined by the
equipment used in the mine. If it were possible, the mine operator would
like to mine only the 3 foot mineralized zone but this isn't practical for
existing personnel and equipment reasons. The mine operator will use

the largest capacity ore moving machines possible in his mine. One

WMA.



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4-41


~

Figure A4-3 is the cover letter which was mailed with the survey
form, less address and salutation. The fact that the Government Technical
Project Officer permitted, in fact encouraged, the use of such a letter
accounts largely for the relatively high survey response rates achieved.
The initial mailings were made in Bureau of Mines franked envelopes,
which also improved the response by decreasing the number of forms
discarded by secretaries and so forth. The GTPO cooperated in many
other ways to make the survey successful. His effective answers to
mine inquiries and his prompt handling of undelivered letters made the
survey problems small compared to those experienced in similar work

in the past.

Some of the survey administration problems on this survey,
typical of all surveys of this kind, are summarized in Table A4-4.
Each of these cases was treated as a problem situation and in most
cases an individual letter was written to attempt to produce a usable
response. The exception to the individual letter follow-up was the
three respondents who said that they refused to provide any data. One
of these was a large '"'RS-S'' company; one was a large ''RS-U"' mine;
the third was a small 'RS-O" mine. Table A4-5 shows the effect of
follow-up actions, both the individual actions and routine actions for
mines that had not responded within six weeks of receiving the initial
survey mailing. A form follow-up letter was sent to the non-respondents,
enclosing a new survey form and a copy of the cover letter. Only a single
stage mail follow-up was used, with some telephone supplements.
Table A4-5 shows results which are slightly above the expectations from
past experience. There was about 37% response to the RS mailings
before the follow-up and about 57% after. This response is considered

excellent. The survey was structured to be valid if only 28% of the

A4-10



The resulting safety factor is,

1 1

R_+R_ 0.312 + 0.791

= 0.907

SF

Compute the allowable axial load,

P = (SF)(P) = (0.907)(25,000) = 22,675 lb
allow.

These results show that the example beam cannot withstand the
applied compressive load of 25,000 pounds and the 40,000 in. -lb end
moment. The maximum allowable axial compression load is 22,675 pounds,

approximately 10% under the applied value.

For purposes of illustrating the need for requiring a buckling
check in the analysis procedure, recompute the safety factor for the
example without considering buckling. Compute the applied bending

stress,

. Mc _ (40,000)(1.75) _ .
fb == “p07, =~ +23 ,202 psi

The stress ratio is determined as,

f
_ _b _ 23,202 _
Ry = Fry = 36,000 — 0-844

A2-11



This report addresses several engineering and economic facets

of possible ROPS/FOPS requirements in the metal-nonmetal mining

industry.

1)

2)

.

Specifically, the following areas are addressed.

It has been proposed by MESA that regulations be pro-
mulgated to require the installation of ROPS on certain
types of mobile mining equipment manufactured after
1969 and used in the surface areas of metal-nonmetal
mines. This proposed MESA ROPS regulation would
require the installation of ROPS on many thousands of
vehicles throughout the metal-nonmetal mining industry.
The vehicle types that would be affected by this regulation
include ''all self-propelled track-type (crawler mounted)
or wheeled (rubber-tired) front-end loaders; dozers;
tractors, including industrial and agricultural tractors
but not including over-the-road type tractors; and motor
graders; and all wheeled prime movers, all as used in
metal and nonmetal mining operations, with or without

attachments."

This report describes the population of these vehicles
in use in metal-nonmetal mining operations by type and
date of manufacture. The economic effects of the pro-

posed regulation are also defined.

The promulgation of a ROPS regulation would require

the installation of ROPS on mining equipment per a set
acquisition schedule. The commercial availability of
ROPS, both in terms of production capability and in terms
of the ROPS manufacturers' ability to provide ROPS for
the many different models of equipment affected by this

proposed regulation, is reviewed in this report,

WMA.



.

Appendix A4.) The total number of active mines in the mine reference

file was 13,969.

Table 4-9 shows the number of mines from the HSAC list which
were selected for the survey sample. The HSAC list was arranged by
state. The sample selection method used was systematic sampling,
that is, every kth item was selected with a random start. In the case
of underground mines, the value used was k = 4. For surface mines, the
value was k= 8. A greater proportion of underground mines was selected
because review of the MESA accident investigation reports showed that
fall-of-ground accidents were much more frequent in underground mines.
Accordingly, it was desirable to obtain a more precise estimate of the

machines of interest used in underground mines and, because the survey

Table 4-9. Composition of Survey Sample
(Equipment Survey)

— oo ~~ a ae |
|
Number of Number of :
Mines on Mines Selected Sampling |
Mine Class HSAC List for Sample Ratio
_—_.- | —____|
| Underground (RS-U) 444 111 1/4 |
|
; Open Pit (RS-O) 1441 182 1/8
| Crushed Stone (RS-C) 2320 291 1/8
Sand and Gravel (RS-S) 3164 396 1/8
TOTAL 7369 980 13/100



posts. An unconservative estimate would be that members BE, GK and
DF each carry 1/3 of the applied overhang load. Member GK would not
carry an equal share of the load since it does not attach directly toa
support column. Therefore overlapping assumptions should be made to
assure conservative results. Member BE will be assumed to react

1/2 of the total load and member GK will react 1/3 of the total load.

This example is included to illustrate the type of analysis which
can be performed quickly and economically while still obtaining results
leading to a safe design. Other more rigorous techniques based on
stiffness considerations are acceptable and result in lighter weight

structures.

Top Plate

The canopy top plate must be designed to protect the vehicle
operator from penetration of the falling object and to distribute the applied
uniform loads to the roof support members. The problem of local pene-
tration is addressed in the FOPS Certification Procedure with specified
design guidelines and testing requirements. The procedure for verifying
the structural adequacy of the top plate to distribute loads to the roof

support members is presented in the following paragraphs.

The canopy roof plate must support a uniformly distributed load
of 74,000 pounds divided by the plan view area of the roof applied over
the plan view area of the roof. The top plate is effectively divided into
several smaller plates by roof reinforcement beam members. The
length and width of the plates is determined by the spacing of these beam
members. The edge fixity of the plates is dependent upon the bending

stiffness of the beam on which the plate rests.

Methods for determining edge fixity conditions and plate stresses

are presented in the Bureau of Mines Report of Investigations, RI7799,

WMA.

A2-5



FRONT END LOADERS
750
61.7%

DOZERS
80
6.6%

TRACTORS
277
22.8%

GRADERS
72

PRIME
MOVERS
36

3.0%

Figure 4-12. Machines of Interest Used in Underground Work Areas

4-52



Table A4-6. Survey Problem
Situations — Second Mailings Required

Problem Area Number of Cases

Initial letter and form declared 16
undeliverable by Postal Service

Follow-up letter and form declared
undeliverable by Postal Service 14

TOTAL 30

responses were received. An even more puzzling problem occurred with
14 follow-up letters. These were sent to mine owners who had not
responded to the initial mailings and whose initial mailings had not been
returned by the USPS. The same addresses were used on the follow-up
letters, but the 14 were returned as undeliverable. It does not seem
likely that 14 mines did an administrative vanishing act within a six-week
period. It is left to the reader of this report to explain this matter to his

satisfaction.

There were two types of responses which reflected that the

respondents had no machines of interest:
1) Mine closed.

2) Mine operational but machine fleet does not include

any machines of interest.

These were represented as a proportion of the mines sampled which had
no machines. The sample proportion was used as the estimator of the
number of "active mines'' in the Mine Reference File which had no

machines of interest.

A4-14



\

average canopy configuration using the program CANOPY would be $200,

comprised of $5 machine time and 10 labor hours. As a direct compari-
son, the same analysis using SAP would cost about $500, including $30 of
machine time and 20 labor hours. A more extensive plastic analysis

using Elastic/Plastic SAP would cost approximately $800.

In summary, it appears that since a plastic analysis is not required
as part of the certification criteria the use of Elastic/Plastic SAP is not
warranted. The elastic program SAP is technically acceptable as a
certification method. However, the estimated cost for performing a
complete analysis of a canopy is 2.5 times that of using the program
CANOPY. The lack of a plate element in the current version of CANOPY
presents a technical deficiency. CANOPY appears to be the best com-
puter program for a certification tool if the changes recommended in the

following section are incorporated.

Recommended Computer Program Changes

Two modifications should be added to the computer program
CANOPY to make it a technically acceptable method for certifying pro-

tective canopies. The two recommended additions are:
1) Plate element
2) Beam buckling prediction

As a minimum, the plate element should handle in-plane membrane
loads and out-of-plane bending loads. Stresses should be printed for both

surfaces at the center of the plate.

The recommended buckling routine should be based on general
beam column theory. Lateral deflections which change the moment arms

of the axial compression forces would be considered. Therefore, the

A2-19


Compute the Euler buckling load,

2 2 6
Po _2 a . ir )\(29 x 1g Gin = 134,925 Ib
L (80)
The bending moment in the beam column,
mM 40,000
M = = 2 = 49,097 in. -lb

T-(P/P_.) © 1 (25,000/134,925)

Compute the applied beam column bending stress,

_ Me _ (49,097)(1.75) _ .
f - 7 —“p>o17 * 428,478 psi

Compute the axial compressive stress,

P -25,000 .
es 2 = oe = 11
f, 2.228 11,220 psi

Therefore stress ratios can be determined as follows:

- 2 . 11,220 _
Ra = F_ * 36,000 — 0-3"?
ty
* 28,478
Ry 7 F_ * 36,000 > 0-791
ty

A2-10


ROPS/FOPS Manufacturers

As mentioned earlier in this section, there are 50-60 ROPS
manufacturers in the United States. Woodward Associates, Inc. con-
tacted several of these companies during the course of this study to
gather information and to solicit opinions of various aspects of poten-
tial ROPS/FOPS retrofit regulations. Several ROPS manufacturers
are already supplying ROPS to mining companies and some are working

directly with the manufacturers of specialized mining equipment.

The following paragraphs give brief descriptions of several
ROPS/FOPS manufacturers that supplied information in support of this
U.S. Bureau of Mines program. This listing of specific companies is
not meant to imply endorsement of their products by the U.S. Bureau

of Mines or by Woodward Associates, Inc.

It is of interest to note that sources for ROPS are available in
all parts of the United States. Several ROPS manufacturers provided
photographs of typical mining machines with ROPS/FOPS installed.
These are presented in Figures 4-17 through 4-29.

The Egging Company
Gurley, Nebraska 69141
(308) 884-2233

Manufactures an environmentally controlled protective
enclosure for the Caterpillar D8 crawler tractor and
for Caterpillar 660B prime mover. Also manufactures
ROPS cabs for industrial tractors such as John Deere,
Case, Allis-Chalmers, and International-Harvester.



values and related percentages may be more easily read. Upper limits

of the two curve bands from Figure 4-5 were then replotted and the
region between them was shaded. The shaded area thus represents the
WAI estimates of the distribution of kinetic energy levels in fall-of-
ground accidents in any year. The area is bounded on the lower edge
by the predicted kinetic energy curve for surface mines and on the upper
by the predicted kinetic energy curve for underground mines. The graph
may be used as illustrated in the following example (see dashed vertical
lines on Figure 4-6):

If all of the machines of interest were equipped with pro-

tective structures capable of transforming 8500 ft-lb of

kinetic energy (read 8500 on horizontal axis), protection

of the operator in the operator's normal position would be

provided for 21% to 33% (read on vertical axis) of the fall-

of-ground accidents which occur each year. Likewise, if

FOPS capable of transforming 40,000 ft-lb of kinetic energy

were installed, protection would be provided in 47% to 66%
of the fall-of-ground accidents.

It has been noted by WAI personnel that in many of the MESA accident

reports and in many discussions with mine personnel that the rock fall

is usually not a single solid section of competent rock that falls. It is
often rock that is laced with fissures, cracks, fractures, etc. When it
falls this "bad ground", as it is called, is not as a single mass. It drops
in pieces or it breaks up immediately upon contact with a resisting force.
The energy that is actually transmitted into a FOPS structure may be a
small fraction of the expected value based on weight and height measure-
ments. Machines and men have survived rock falls that would seem to
possess energy values high enough to destroy anything caught beneath
them. It is important that the test procedures prepared for validating

the performance of FOPS correctly simulate the characteristics of rock



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A5-10


it could be expected to provide satisfactory operator protection in
approximately 50% of the surface mine rock falls and about 70% of the
underground rock falls. The large difference in kinetic energy absorp-
tion capability between ROPS designed for small machines and those
ROPS designed for large machines presents a serious problem when
considering methods of upgrading the FOPS capability of ROPS that are

already installed on machines.

The MESA standard for canopies in underground coal mines is
the only regulation that uses a non-destructive static test to demonstrate
compliance with the standard. The MESA engineering personnel have
devised static test and static analytical analogs of the dynamic perform-
ance requirements. The SAE FOPS test procedures use destructive
dynamic tests to demonstrate the capability of the FOPS. The SAE ROPS
test procedures include both destructive static tests and destructive
dynamic tests. Generally, the dynamic tests that expose the FOPS to
impact conditions similar to those expected in an actual rock fall are
thought to be the best approach to verifying the structural performance
of the FOPS. The disadvantage of these dynamic tests is that the FOPS
unit and sometimes the vehicle frame are damaged. The cost of the
FOPS unit and the vehicle frame must be included in the test cost. A
ROPS certification test on a large machine can be very expensive. Costs
to certify a ROPS design have been estimated by several equipment
manufacturers as shown in Table 4-3. A non-destructive static test
would be attractive if a clear derivation from the dynamic situation is

advanced.

Development of a New FOPS Performance Criteria

The information presented in Figure 4-6 of Section 4.1 indicates
that a FOPS system that could absorb about 50,000 ft-lb of kinetic energy

would provide operator protection in about 70% of the rock falls

WMA.



The data input requirements for CANOPY are straightforward
and easily interpreted. An analyst should be able to input a simple
canopy problem in approximately six hours. The input for SAP is more
complex and would require an estimated 16-20 manhours. A more

experienced analyst is needed since the input requires more interpretation.

As discussed previously, the output from CANOPY includes most
of the information necessary to adequately evaluate a protective canopy.
The output of SAP includes only bending moments and forces. Stresses
and associated safety factors must be determined by the analyst. Elastic/
Plastic SAP computes and prints out all stress data for beams, but it

does not evaluate safety factors or load capability of the canopy.

The accuracy of CANOPY and SAP was established by inputting
identical problems and comparing the solutions. The results correlated
closely for problems falling within the limitation bounds of CANOPY.
No attempt was made to evaluate CANOPY for configurations with plates

since the accuracy would depend largely on input model simulation.

The program CANOPY could be used by any general engineering
graduate or person experienced in structural analysis to conduct analyses
of protective structures. Elastic/Plastic SAP requires a Structural
Engineer with a background in plastic analysis. The analyst must pre-
judge points of high stress and input plastic beam elements. If his judg-
ment is incorrect, and an elastic beam exceeds the proportional limit of
the material, the computer solution must be repeated at additional overall

cost.

Overall cost is an important consideration in selecting a computer
program. The total cost includes computer machine time costs and labor
costs associated with the analyst preparing the input data and interpreting

the output results. The estimated cost for a computer analysis of an

WA.

A2-18


Figure 1-5. Motor Grader

Figure 1-6. Prime Mover Pulling Scraper



% OF TOTAL MACHINES OF INTEREST

60

50

40

30

20

50.7

C] ONLY PRE-1970 MACHINES

MIXED PRE-1970 AND
POST-1969 MACHINES

ONLY POST-1969 MACHINES

36.2

10 -
7 :
OWNERS OWNERS OWNERS
OF 1-5 OF 6-15 OF >15
Figure 4-35. Fleet Size and Composition — Machines of Interest

4-110



% OF TOTAL MACHINES OF INTEREST

60 r

ONLY PRE-1970 MACHINES

MIXED PRE-1970 AND

50F POST-1969 MACHINES
ONLY POST-1969 MACHINES

40h

30b

20b

10 b

0 Uf YW

OWNERS OWNERS OWNERS
OF 1-5 OF 6-15 OF >15

Figure A4-7. Open Pit M-NM Mines — Distribution of Machines of
Interest by Owner Fleet Size and Composition

A4-23



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4-49


(-

study shop-built FOPS, and to investigate other aspects related to the
use of FOPS. The following mines provided much needed information

during field visits. We thank them for their excellent cooperation.

Allied Product Co.,
Montevallo, Alabama

Anaconda Co.,
Butte, Montana

ASARCO,
Wallace, Idaho

Bing Materials Co.,
Gardnerville, Nevada

Bunker Hill Co.,
Kellogg, Idaho

Citadel Cement Corp.,
Birmingham, Alabama

Cortez Mining Co.,
Cortez, Nevada

Domtar Chemicals, Inc.,
Louisa, Louisiana

Duval Corp. ,
Carlsbad, New Mexico

Georgia Marble,
Tate, Georgia

Homestake Mining Co.,
Lead, South Dakota

Kennecott Copper Corp.,
Bingham Canyon, Utah

MacGuire Farm,
Mosinee, Wisconsin

Mobile City Road and Bridge
Department,
Irvington, Alabama

Montevallo Quarry

Berkeley Mine
Continental East Mine
Kelley Mine

Steward Mine

Coeur Project Mine
Galena Mine

Bing Mine

Bunker Hill Mine
Crescent Mine

Birmingham Quarry
and Mill

Cortez Mine

Cote Blanche Mine

Nash-Draw Mine

Cove Mountain Mine
New York Mine
Tate Quarry
Whitestone No. 1

Homestake Mine
Bingham Canyon Mine

Salzman Pit

Boe Pit

1-12



Table 3-4, Recommendations (Cont)

USBM should continue efforts toward increasing the validity
and usefulness of the CANOPY computer program, The addi-
tion of a buckling subroutine and a plate-element subroutine

should be considered,

Efforts to educate machine operators on roll-over, falling
object, and collision hazards should be initiated by MESA as
a part of existing training programs,



\

Maximum predicted stresses at critical points in the structure must not
exceed the material yield stress allowable. Calculations based on sound
engineering principles are acceptable. Guidelines are included in the
Appendix A2 to aid the analyst. Approaches for analyzing the canopy

top plate, checking for buckling of the support columns, analyzing two
post configurations and evaluating combined stresses to determine safety

factors are included.

Several other requirements must be met with each of the three
recommended certification procedures. As specified in Appendix Al,
the FOPS must meet material, welding, and impact resistance require-
ments in addition to static load/deflection criteria. The material in
the canopy must meet ductibility requirements as specified by Charpy
V-notch impact strength standards, The Charpy impact test measures
the energy absorbed in fracturing a notch specimen that has been prepared
according to definite standard dimensions and is supported at both ends in
a standard manner. All bolts used in structural applications must be SAE
Grade 5 or 8, All welding on the canopy and attachment structure to the
vehicle must be in accordance with the ''Specification for Welding Rollover -
Falling Object Protective Structures (ROPS and FOPS)"' currently being
prepared by the American Welding Society's D14h Subcommittee,

4-45


Kinetic energy data are needed and, in addition, information about the
shape of the falling object, especially the impact area. The manner of

handling the data in this respect is discussed later.

Data Acquisition

The initial action at the beginning of this study was to arrange,
through MESA officials, to review MESA accident investigation reports.
The first reviews were made in the MESA Reno Field Office. When work
on all of the reports available at that location had been completed,
additional reviews were arranged at the Health and Safety Analysis Center,
Denver, where a central repository of fatal accident investigation reports
is maintained, and at MESA headquarters in Arlington, where a large file
of nonfatal accident investigation reports is maintained. At Denver,
accident investigation reports for every fatal metal and nonmetal mine
accident since January 1, 1972, were reviewed and data were extracted
and recorded for every accident of possible interest in this study which
had not been previously reviewed in Reno. Similarly, in Arlington, data
were recorded for every accident report which had not been reviewed in
Reno or Denver. Some reports of special interest for the years 1970 and
1971 were reviewed in Reno. Table A5-1 shows the number of MESA
accident reports reviewed by year and type. The total is 1005. Most
of the accidents which involved some fall-of-ground were so designated
by the MESA officials who were responsible for the investigations. A few,
however, were under other designations, apparently because fall-of-ground
was not the primary accident cause. The numbers of fall-of-ground
accidents which were considered to be of interest to this study are given
in Table A5-2 by year and type. The total is 152. Sufficient information
to satisfy the data requirements discussed above was available in only a

fraction of the investigation reports. Table A5-3 shows the numbers of

WA.

A5-6


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2-11


SAE J397a

SAE J320b

SAE J394a

SAE J395a

SAE J396a

Deflection Limiting Volume for Laboratory
Evaluation of Roll-Over Protective Structures
(ROPS) and Falling Object Protective Struc-
tures (FOPS) of Construction and Industrial

Vehicles

Minimum Performance Criteria for Roll-Over
Protective Structures (ROPS) for Prime

Movers

Minimum Performance Criteria for Roll-
Over Protective Structures for Wheeled

Front-End Loaders and Wheeled Dozers

Minimum Performance Criteria for Roll-Over
Protective Structures for Track-Type

Tractors and Track-Type Front-End Loaders

Minimum Performance Criteria for Roll-Over

Protective Structures for Motor Graders

Note: The SAE Recommended Practice SAE J1040a incorporates
material formerly published as SAE J320, J394, J395, and J396.

PLASTIC DESIGN PRINCIPLES

Applied Plastic Design in Steel, by R. Disque

Plastic Analysis of Structures, by P. Hodge

Plastic Analysis and Design, by C. Massonnet

Plastic Design of Steel Frames, by L. Beedle

Plastic Methods of Structural Analysis, by B. Neal

Plastic Methods of Structural Analysis, by B. Neal

Strength of Materials, by F. Shanley



4.5 ROPS/FOPS RETROFIT CONSIDERATIONS

This section reviews the primary engineering and operational
factors that must be considered in formulating a ROPS/FOPS regulation
that accomplishes the primary goal of increased operator safety without
undue adverse effects on the individual mining operation or on the mining
industry as a whole. The interrelation of the various considerations is
complex and must include an economic evaluation. This section addresses
the issues independent of the economic factors. Section 4.7, ''Economic
Effects of Possible ROPS/FOPS Retrofit Policies ,'' addresses the eco-

nomic implications of the material discussed in this section.

Engineering Viewpoint

The current ROPS regulations promulgated by MESA for the sur-
face areas of coal mines and by OSHA for the construction industry require
ROPS on specific equipment manufactured after July 1, 1969. One reason
given for this cutoff date was that equipment manufactured earlier than
July 1, 1969 did not have chassis strengths sufficient to accept the struc-
tural loads that might be experienced during a roll-over. Subsequent to
promulgation of the OSHA ROPS regulation, the Office of Standards of
OSHA contracted with Woodward Associates to, among other tasks,
investigate the problems associated with retrofitting ROPS on pre-1970
equipment. The following information was derived in part from that

study.

A significant and valid concern exists relative to the structural
capability of mining and construction equipment of the types studied on
this program to accept the loads that will be transmitted into the vehicle
chassis during a roll-over or during a rock fall. The question of vehicle
chassis structural capability centers around the thesis that the original

equipment manufacturers designed and produced equipment for many

VA.


Figure 1-7. Wagner Load-Haul- Dump (LHD)

Figure 1-8. Eimco Load-Haul-Dump (LHD)

1-8



PERCENT OF ACCIDENTS IN SAMPLE

70

60

50

40

30

20 seeen SURFACE MINE SAMPLE — 60
10
0 — | i J
100 150 200 250
KINETIC ENERGY (1000 FT-LB)
Figure 4-3. Total Rock Fall Kinetic Energy
RA.

aus UNDERGROUND MINE SAMPLE — 138



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A4-8


Figure 4-28. Young Corporation ROPS Cab on
Clark Rubber-Tired Loader;
ROPS on Wagner LHD



Table 4-12. ROPS/FOPS Model Availability
(Furnished by Saf-T-Cab, Inc. , Fresno, California)

Piat-Allis (Att

falmers)

Caterpillar
Crawler Tractors Crawler Tractors
-3 6 2G HDs
HD HD- HD-12G 0 HD-41 D-2 D-4 ps D-8
7 <7 HD:
HD-4 HD: HD-16 pea pe p-9
HD-5 HDL -HD-21

Crawler Loaders
Wheel Loader

933 oa 951 955
p-10 pat Theta TLs4s on 083
pt 16000 TE-200 T1645
D-15 Th-10 0 Th-3000 TH745 Scrapers
Day The12 0 TL-40 pw-10 618 621 623
scrapers pws 627 620 631
pw-20 633 6a 650
2608 TS-380 pw-21 651 657 560
480 TS-562 613

Motor Graders Motor Graders

wer M15
48 ° 1150 a2 12 120 2
5 M
pp wt 1-200 140 4 6 126
Agricultural Tractors 1G
150 185 200 7050 Wheel Loaders
170 190 6040
920 922 8: oa
180 190xr 7030 %0
950 966 eno 988
Western Wheel Dozers & Compactors
ata ais a4 825,
Motor Graders 30 baa aan
88 200 Pacer 300Super 500 Pacer
99 200Super 400 Pacer 500Super Champion.
100 100 Pacer 400 Super,
Motor Graders
Mobile Cranes
)-560 1-582 HBH DBO
110 220
p-640 1-650 -680 886
210 410
Clarks Wiehsgan
Bros —e
Wheel Loaders
Rollers “
SP 54R SPV 735 SP-3000 SP 10000 a SAWS
S511
SP\ 370 SPY 845 SP 3500
spy SP 2800 SP 6000 mniy
as arn as Ht
125 1A
Case

HA

OTA
Crawler Tractors
a0 350 450 750 Wheel Dozers
#50 1150 180 re0 1 2801 2801
2RO IA 3801 38011 380 111
Wheel Loaders 380.4 SAOIA 480
w woe
ws 8 Scrapers.
ws wen wes
MO-HT 110-11 110-12 TO-4
we: Weta 20
10-15 210 20-310
Wheel Tractors 310-1 ano-t 10-11 tO
480 500 510 580 410
680 isgon 1797 Loader = Rackhoe
140 <00
Rollers
RW RWB



~

from reported dimensions. A corollary decision was to take all weights
as reported, based principally on two considerations: no satisfactory
basis for correcting them could be found, and it was judged that miners

were likely to estimate weight more accurately than any other value.

Table A5-13 gives the study data, from accident reports or survey
questionnaires, for the 60 surface mine fall-of-ground accidents in the
sample. The W, and V, columns give the values of weight and volume
as reported. Wg and Vg columns give the values adjusted as discussed
above. When Wy was not given, Wg was computed from V1, with correc-
tions. V9 is V1 with correction constants and ROPS area limits applied.
Table A5-13 also shows the results of calculations of kinetic energy at
the protection level. The machines involved in the accidents are indicated,
the degree of injury noted, and the operation being conducted at the time

of the fall is given when known.

Model for Underground Ground Falls

A model similar to that for the surface mine accidents was used
for underground accidents. One principal difference is that the protection
level was taken to be 6 feet (rather than 8 as in the surface model), or
1 foot less than the fall distance, whichever was smaller. Another is
that, rather than using a 10 foot vertical dimension limit on fall volume,
an 8 foot limit was used unless the reported fall thickness was available.
In that case, the reported fall thickness was used with the 43.75 square
foot ROPS top area to compute the limiting volume, that is, the maximum

volume which would impact on the protective structure.

Table A5-14 gives the data, from accident reports or survey
questionnaires, for the 138 underground fall-of-ground accidents in the

sample. The table also shows the kinetic energy calculations for the

MA.

A5-28


Ne

extracted from those reports in which it was given. Several of the
accidents had more than one victim. There was a total of 106 fatalities
in the 98 fatal accidents and, in addition, there were several disabling
injuries. Age information was recorded for 94 persons fatally injured.
In this sample of 94, the age range was 18 to 63. The medianage was
37 and the mean 38.3. Surviving dependent information was recorded
for 90 of the fatalities. The 90 victims left 270 surviving dependents.
These data affirm once more a fact that really needs no affirmation:
the costs of a fatal accident are high. The pertinent question in this
study is how much of the total cost of metal and nonmetal mine accidents
relates to fall-of-ground and the machines of interest. Some estimates

in this regard may be made from the data collected.

It is important to treat the data concerning underground mine
accidents separately from that concerning surface mine accidents, for
the reason that the machines of interest are generally more prominent
in surface mining than in underground operations. The samples in
Table A6-1 are small in both categories, too small in fact to permit the
construction of confidence limits, using the normal approximation, for
population proportion estimates. Table A6-3 gives a summary of the
data from the samples. Inthe surface mine portion of the sample,
machines of primary interest were involved in one-third of the fall-of-
ground accidents, in 38.5% of the fatal and disabling injury accidents,
and in 36.8% of the fatals. These figures do not permit a good deter-
mination of how many accidents per year involve machines of interest
because the sample, in addition to being small, is not accurately time-
bounded. However, there are ways to get rate figures for fatals and

simultaneously to judge how representative is the sample.

First, it is known that the fatal fall-of-ground accidents for the

years 1972-1974, as they are defined for this study, were 22, 2l and 24,

MRA.

A6-9



Table 4-12. ROPS/FOPS Model Availability (Cont)
(Furnished by Saf-T-Cab, Inc. , Fresno, California)

ternational Harvester (cont

Crawler Loader

T3490 590-¢
150 175 RAC
r-6 rp-8
Tp-20

Sorapers
TD-75 F200
F270 298
495

Payhaulers

100
340
Wheel Tractors
400
606
aa
2608
344
3800
Pavloaders
mr
ima
W307,
H-60
Hes,

1-99

1-500

140
450

4a
706

2500
2636
ass
4109

mac
fins
1-40
H-60R,
n-70
1-100

b-100n

Agnioultural Tractors

Super I!

F300
434

Peoa

“658

2400

r10 “10
Roehring

Roller- Compactors:

50 100

100-¢
250
Ths

190

504
2400
2508
3200
ass

125-¢

0 FAC

Th-18

a0

sean

asta
ana
aai6

Haw
Hon
1-50
11-600
1-700

W120

b-129¢

F906

F-1966
156

2500

1-500
H-606,

1-500

b-400

K-530

Komatsu
bess b-60 p65, 7s
bens Des 155
Loaders
R69 ao
ain so 125 400
“nes
Prime \iowers
150 200 “0. 190s
1955 A190.
Massex Ferguson
Crawler Tractors
os 3166 190 500
Wheel Tractors
n 20 a0 8
40 0 5
10 202 ong
180 2138 00 =)
a165
grieuiural Trai
29 “5 0 :
40 135 an 0
r 202 203 20s
401 too 1105
1150 1155 214

Comwter

pas) bey

Pac

4-66



Table A6-2. Fall-of-Ground as Percentage of Total Accidents

FOG as
Year Total FOG Percentage of Total
MESA Fatal Accident Reports
1972 139 20* 14.4%
1973 168 20* 11.9%
1974 146 21* 14.4%
1975 (Partial) 57 5 8.8%

Secretary of Interior, Report on PL 89-577, Fatals

1971-73 568 90 15.8%

All MESA Reports Reviewed by WAI

1970-75 1005 152 15.1%
(Partial)

«Includes only categories ''fall of roof or back'' and ''fall of face
or side."

FOG = Fall-of Ground

fall-of-ground accidents as percentages of various totals. WAI believes
that a random sample of all accidents since January 1970 would produce
a 95% confidence interval for the proportion of fall-of-ground accidents
of 0.12 to 0.18. Of course, this would apply only to metal and nonmetal
mines in the aggregate, not to individual segments of the industry, nor
to individual years. For example, the MESA Safety Review covering
injury experience for the sand and gravel industry in 1970 shows that

only about 3% of the non-fatal injuries and about 16% of the fatal injuries

A6-7

WA.


Table A5-8. Angle of Repose, Some Common Materials

Material Angle (Deg.) Source

Clay, Dry, Loose 37 1
Clay, Dry, Bank 45 1
Gravel, Clean, Loose 37 1
Rock (Riprap) 45 1
Sand, Wet 22 1
Sand, Clean, Loose 34 1
Screened Iron and 37 2
Copper Ore

Source: 1. Mining Engineer's Handbook; Peele, Robert (ed.),
John Wiley and Sons, N. Y., 1961.
2. Marks! Standard Handbook for Mechanical
Engineers; Baumeister, Theodore (ed.); 7th Edition;
McGraw-Hill Book Company, N. Y., 1967.

Table A5-9. Angle of Slide

Material Angle (Deg. )
Mine-Run Ore 35-40
Ore, Fine Removed 30

Source: Marks!’ Standard Handbook for Mechanical Engineers;
Baumeister, Theodore (ed.); 7th Edition; McGraw-Hill
Book Company, N. Y., 1967.

A5-16



FIGURE

1-4

1-5

1-6

1-7

1-8

1-9

1-10

1-11

LIST OF ILLUSTRATIONS

Rubber-Tired Front-End Loader
Crawler Tractor

Rubber-Tired Dozer

Industrial Tractor

Motor Grader

Prime Mover Pulling Scraper

Wagner Load-Haul- Dump (LHD)

Eimco Load-Haul-Dump (LHD) .

ROPS Canopy (Rome Manufacturing Co.)
ROPS Cab (Young Corporation) .

Falling Object Protective Structures
(FOPS)

Rock Fall Kinetic Energy vs. Percent of
Total Rock Falls

Energy Absorption Capability of ROPS/
Vehicle Systems . . :

Protective Structures .
Fall Distance Frequency

Fall Weight Frequency

1-5

1-6

1-6

2-4



Table 4-8.

Certification Procedure Alternatives

Certification Method Description Advantages Disadvantages
Drop Test ‘o Weight dropped on FOPS top ‘0 Excellent simulation of actual rockfall | 0 Destructive
(moncompetent material) © Product of weight and height equal to © Minimum instrumentation required | 0 High hardware and test cost
40,000 15 (0 Test simple to perform © Difficult to obtain drop weight which
(© Weight must cover entire plan view meets requirements
area of top
© Weight comprised of noncompetent
material which simulates a uniform
load application
© Maximum deflection of 4.0 in.
permitted during test
Drop Test © Same as above except weight is of (© Test simple to perform © Destructive
(competent material) competent material which does not
Sree diving tet © Minimum instrumentation required | o High hardware and test cost
© Not always a realistic simulation of
actual rockfall, overloads support
columns, underloads roof members
Pendulum Test 0 FOPS top struck with pendulum weight © Better control of weight during test | 0 Destructive
‘0 Energy input of 40,000 ft-Ib required © Minimum instrumentation required © Migh hardware and test cost
© Weight must cover entire plan view © Not always a realistic simulation of
area of top actual rockfalt, overloads support
0 Weight is of competent material columns, underloads roof members
(© Maximum deflection of 4.0 in. permitted © Requires complex tie-down configuration
during test with vehicle on aide
Static Test © Load applied over center ninth of © Analogous to SAE J1040a aide load © Destructive
(energy absorption) FOPS top energy test © High hardware cost
© Area under force-deflection curve (© Demonstrates energy absorption '
(energy) must reach 40,000 ft-Ib before capability @ Not a realistic simolation of
eee a in of deflection actual rockfall, overloads roof
© Petter control than with dynamic test members
since test can be stopped if problem
develops
Static Test © Loadot 36 000 tb applied over center © Non-destructive © Does not simulate actual rocktall
(elastic tonal ninth of POPS top © Low test hardware costs © Requires force and deflection
© Permanent deflection can not exceed ke measurements
Ton er detlcction taeasured during test © Analogous to MESA test for canopies
on electric face equipment
Computer Analvsis| © Product of force and deflection must © Good simulation of drop test with © High computer and analyst cost
(elastic/plastic! equal te noncompetent materi
Tastic/Plast squat 40.000 f-1p pa © Requires experienced analyst
9 Plastic deflection can not exceed 4.0 in © No hardware or test cost > Possibility of erronenus results
© Large computer core requirements
© Requires large computer which 1s nat
widely available
Computer Snalvais 9 Loa of 74,000 1 uniformly distributed © No hardware or test cost © Does not simulate actual rocktall
telasticy over entire plan view area of FOPS to
" , P © Analogous to MESA analysis method
© Stresses can not exceed vield allowable for canopies on electric face equip
of material ment
© Canuse simple computer program
such as CANOPY
(©. Can be run on many types
puters
‘Relatively easy to input
Engineering Analysis © Load of 74,000 th uniformly distributed © No hardware oF test cost © Does not simulate actual rocktall
inon-computer! over entire plan view area of FOPS top s
© Analogous to MESA analysis method | o Validity of results are sensitive to
0F 36,000 Ib over center ninth of top for canopies on electric face equipment | experience of analyst
© Stresses can not exceed vield allowable
9 No computer required

of material

4-43



ground" by the miners. It is rock that is fractured, unconsolidated,
loose or in some other state to cause the miners to consider it abnormal
or different than the rest of the ground in the area. Some rock falls are
of "competent" or "solid" rock or of large pieces of competent rock.

In the case of the "bad ground" type of a rock fall, the total energy
transmitted into the FOPS is far below that expected by calculating the
energy from the weight of the fall and the height of the fall. The rock
fall section breaks up as it falls and only portions of the total fall impact

the FOPS.

The figures in Sections 2.0 and 4.1 representing rock fall kinetic
energy in surface and underground rock falls have been adjusted to reflect

the lower expected energy transfer in large rock falls and rock slides.

Designing and installing ROPS/FOPS on the front-end loaders,
dozers, graders, large tractors, and prime movers studied presents
no unusual problems. The vehicle frames of these machines are gen-
erally quite strong in order to withstand the rigors of their work function;
strong attachment areas are available. A different situation is evident
when the small industrial and agricultural type of tractor is examined,
These machines are used to transport personnel throughout mine areas
and are used to tow small ore-carrying trailers in some mines, These
tractors do not have the strong frames necessary to react the loads
transmitted through the FOPS. The attachment of the FOPS to the
tractor frame is also of marginal load carrying capability. The FOPS
designed to meet the WAI FOPS performance criteria are overdesigned
for the structural capability of these small tractors. The WAI FOPS

performance criteria is valid on machines with gross vehicle weights

3-2



\

at great expense or, alternatively, discontinuing the use of the machines
and replacing them with "low profile" types or smaller capacity units,
also at great expense. Clearly, a detailed analysis of alternatives for
all mines which would be affected is beyond the scope of this study.
However, through mine visits, discussions, and correspondence during
the course of this study it became evident that some underground mine
people vigorously oppose any thought of ROPS/FOPS retrofit of all
machines of interest. Their reasons are clear and persuasive. It is
true that a commercial ROPS increases the height of the machine. This
is a problem even in the construction industry. When machines are
moved from site to site under overpasses, it is sometimes necessary
to remove the ROPS. The low back mines would have a problem for

which no low cost solution seems possible.

The ROPS could be reduced somewhat in height, but not without
sacrificing a significant degree of protection capability as well as
restricting operator vision and freedom of movement and egress. The
low back mine operators point out, correctly according to the MESA
data, that there are very few fall-of-ground accidents which involve the
machines of interest and that underground roll-overs involving the

machines of interest are extremely rare.

Table 4-16 shows the estimate of the machines of interest oper-
ated by underground mines and the estimates of those which are actually
used underground either full-time or part-time. It does not show how
many are used in low back underground mines. The survey did not seek
this information and WAI cannot provide a confident estimate of the
number. The information in Table 4-16 is presented here because a
possible ROPS retrofit policy might be one which required retrofit of

machines of interest manufactured after a selected date, except those

4-108


Figure 4-22. Medford Steel ROPS on
Komatsu Crawler Loader;
ROPS Cab on Komatsu Crawler Dozer



Table A6-3. Summary Statistics - Samples of
Mine Fall-of-Ground Accidents Reported in This Study

Under -

Surface | ground Total

Mines Mines M-NM Mines
Fatal Accidents 19 48 67
Non- Fatal Injury 7 26 33
Accidents
No Injury Accidents 34 64 98
Total FOG Accidents 60 138 198

LHD Type

Fatal Accidents, 7 2 3 12
Machines of
Interest (MI)
Non- Fatal Injury 3 0 2 5
Accidents, MI
No Injury Accidents, 10 0 3 13
MI
Total FOG 20 2 8 30
Accidents Involving
MI
Percent of Fatal 36.8% 4.2% 16.7% 17.9%
FOG Accidents
Involving MI
Percent of all 33.3% 1.4% 5.8% 15.2%
FOG Accidents
Involving MI
FOG = Fall-of-Ground

A6-10



MACHINES USED ON SURFACE
48,078
97.5%

MACHINES USED
UNDERGROUND
1,215

2.5%

Figure 4-11. Metal-Nonmetal Mines
Estimates of Population,
Machines of Interest
Total: 49,293



keeping the back height at 6 feet is another alternative. Smaller
equipment is less productive than larger equipment (three 2-yard bucket
front-end loaders will not move as much ore as one 6-yard bucket
machine) and the cost per ore volume moved is greater with small
machines than with larger machines. This alternative also has negative

economic effects.

While the above example is over simplified, it does illustrate a
problem encountered when considering ROPS/FOPS installation on under-
ground machines. The accident history of underground machines does
not support the need for roll-over protection. Since falling objects and
side impacts are the primary reasons for providing operator protection
for underground machine operators, the accident record for ''machines
of interest'' used underground should be examined. In the three years
of MESA accident records reviewed by WAI, ‘machines of interest'' were
involved in only two fall-of-ground accidents that resulted in death or

injury.

In many of these rock fall accidents a FOPS would not have pro-
tected the operator since he was not in the operator station but was
attending to some other activity nearby and would not have been under
the protection of the FOPS. Operator protection from side impacts,
roof impacts, collision with other objects, etc., is important in under-
ground mines. No accident statistics were developed on this study to
quantify the deaths and injuries due to machine accidents that did not
involve fall-of-ground or roll-over but accidents that could be termed
"tramming accidents'' seem to occur with sufficient frequency to cause
concern to many mine operators. Some mines have installed 'low brow

protection structures"; some have installed low profile canopies in an