10

Forged wie rope Crosby ofp
Be deed. Vly at
wa 7 Ln ss Ge
2.540.em 7 Modified forged wire rope Crosby clip
aay. waco cp es =
wi//ianl ie | as ena ff fy
=p
Y) Top view Side view
Top view me Side view

Figure 13.—Design of flex-cabie load sensor for 3.8-cm (1-1/2-in) diam wire rope.

The flex-cable load cell is packaged to withstand the rigors of
long-term, unattended underground operation and to survive the
unusually hazardous conditions of underground hoisting operations.
Such conditions include limited access and cramped space; hot,
humid, and corrosive atmospheres; water and falling rock and
debris; and shock loads from blasting. It is immune to electro-
magnetic interference and repeated hoisting cycle temperature
extremes that may range between -47°C (-50 °F) and +53 °C
(+120 °F). It is simple and fast to install and relatively
maintenance free. Encapsulation provides electrical insulation,
high impact and mechanical shock resistance, and minimal
sensitivity to thermal extremes.

A custom-designed data acquisition and transmission package
(figure 15) used in conjunction with the HASCOMS includes a
battery-operated, microcomputer-controlled signal processing
board (SPB), a 2.4-GHz, spread-spectrum radio modem, and a
12-V battery. The SPB was custom designed to meet the
requirements of this specific application. The package

dynamically monitors and processes data from six analog
channels and one digital channel and provides optically isolated
serial data output. The SPB is linked to the 2,400-baud radio
modem for data telemetry from the moving conveyance to the
hoist machinery room. The data transmission rate is 100 m/s or
10 scans per second. For a conveyance traveling at 183 m/min
or 2.05 m/s (600 ft/min or 10 ft/s), this sampling rate provides
load and position data for every 300 cm (1 ft) of conveyance
travel.

A secondary RS232 serial port on the SPB transfers data to
a portable computer or terminal on the conveyance itself (figure
16). The 12-bit analog sensor input transmits information as
unsigned, four-character hexadecimal values ranging from
0000H to 1FFEH (0000 to 8190 decimal). An 8-bit analog
channel transmits information from the potentiometer, encoder,
and themnistors as unsigned, two-character hexadecimal values
over a range of OOH to FFH (000 to 512 decimal). The encoder
data represent the number of rotations of the encoder wheel


DEVELOPMENT OF A MINE HOIST AND ORE
PASS RESEARCH FACILITY

By Michael J. Beus’ and Todd M. Ruff

ABSTRACT

Research aimed at preventing injuries and fatalities related to vertical movement of personnel and
materials in mine shafts and ore passes is being conducted at the Spokane Research Center, a research
division of the National Institute for Occupational Safety and Health, in Spokane, WA. The goal of this
Tesearch is to improve monitoring, inspection, and operating procedures to increase awareness of the proper
functioning of mine hoists, ore passes, and chutes; develop means of warning of potentially dangerous
situations; and to improve the design of mine shaft and ore pass structures.

Current technology was assessed to determine what conditions and equipment should be monitored and
the availability of sensors. Components of various mine hoisting, elevator, and ore pass systems were
evaluated, including hoisting machinery and shaft and ore pass infrastructures. Progress to date has resulted
in the construction of a state-of-the-art hoisting and ore pass test facility, and the development of new sensors
and data acquisition interfaces to monitor hoisting and ore pass operations.

‘Mining engineer, National {nstitute for Occupational Safety and Health, Spokane Research Center, Spokane, WA.
"Electrical engineer.


An electric brake system manufactured by Warmer Electric
was installed on the motor shaft. While the regenerative
capabilities of the dc motor are sufficient to stop the full skip,
the brake system provides a positive and safer method of
stopping. Brake control is achieved through a Warner Electric
torque-adjustable brake controller. The brake provides a
maximum static torque at a input voltage of 90 V dc, which is
provided by the controller. When the stop button is activated,
the motor begins ramping down; however, the braking action is
delayed for the duration of the ramp-down before the brake is
set.

Motor speed feedback is achieved with a Rotopulser encoder
and a Dynapar frequency-to-voltage converter. These units
function as a tachometer at a greatly reduced cost when
compared to purchasing a conventional tachometer generator.
‘The encoder consists of induction proximity sensors that sense
the teeth of a shaft-mounted gear. The resulting output signal
is a square wave with variable frequency. This signal is
converted to analog voltage by the frequency-to-voltage
converter, which provides +10 to -10 V proportional to motor
shaft speed and direction. This signal can then be used by the
motor controller for speed feedback control.

Further automation concepts are being studied using
Windows-based human-machine interface (HMI) software and
programmable controller technology. This expands the amount
of automatic control functions possible for the hoist. A GE
Fanuc series 90-30 programmable logic controller (PLC) runs
the logic for both manual and automatic operation.
‘Wonderware’s Intouch HMI software is used to provide the
operator interface. This software runs under Windows 3.11 on

an industrial 486 DX touch-screen computer (figure 9). A
control panel is currently set up to provide the operator interface
for operating the hoist manually. The panel consists of speed-
control potentiometers, hoist motor controls, valve controls for
the loading gates, and a flat-panel, touch-screen computer to run
the HMI software.

Figure 10 shows the main control screen for the hoisting
system. All sensor inputs and PLC outputs can be monitored
from this screen. Hoist operation can also be controlled from
the screen; however, the hardwired buttons on the control panel
override any.command given from the touch-screen computer.
Real-time graphs are used to monitor and record values such as
rope load and skip position, as shown in the upper right of the
screen in figure 10. These graphs are easily set up and are
especially useful for evaluating the most effective sensor types
and configurations. For example, optical encoders are mounted
on the hoisting drum and on the skip to determine the position
of the skip in the shaft. These sensor values are recorded to aid
in determining the effects of rope stretch and other errors that
may occur in sensing the skip’s position.

Detailed views of the hoisting and ore-loading process can
be accessed from the main control screen. For example,
pressing “Show Ore Pocket” brings up the ore pocket screen, as
shown in figure 11. Operation of the loading chutes and gates,
ore levels and loads in the bin, and conveyance net weight loads
can all be viewed from this screen.

Automatic operation of the hoisting, dumping, and loading
processes is controlled by a ladder-logic program in the PLC.
In automatic mode, the status of the process can be viewed on
the left side of the main control screen. Automatic operation
allows the system to cycle through the loading, hoisting, and
dumping processes without manual intervention. In the future,
this research will focus on a safety assessment of the sensor
systems and control system design.

A back-up Lilly controller is also installed on the hoist
system (figure 12). Lilly controllers have been the standard
mechanical contro! devices for mine hoist installations since the
early 1900's. They operate as skip position indicators and stop
the winding drums and apply brakes in the event of overspeed
and overtravel. A centrifugal governor is driven in
synchronization with the hoist drum to track the speed of the
skip. A pair of cams moves in proportion to skip position and
tips a limit switch to turn the motor off automatically and set
the brake if an overtravel condition is reached. The Simplex
model Lilly control system was installed at the facility to study
possible interaction and retrofitting of automated electronic
controls on systems typically seen at mining operations.


An evaluation of safety features for hoists and ore passes,
existing safety standards, and current monitoring and control
systems and sensors was conducted (Barkand and Helfrich,
1988; Cseff and others, 1981; Farley and others, 1983; Loynes,
1976). It was concluded that current technology should be
assessed, and sensors for determining conveyance loads, slack
and tight rope, conveyance position, and ore pass and chute
monitoring needed to be developed. For example, existing
commercially available systems for slack rope detection range
in price from $50,000 to $250,000 and are largely customized
to be site specific. Therefore, less expensive systems are
needed.

Research tasks now being conducted include—

1. Development of computer models to analyze design and
muck flow in ore passes to identify potential safety problems
and additional targets for research.

2. Identification of hoisting parameters to be monitored
and modification or development of new sensors and data
acquisition and transmission capabilities.

3. Development of graphical user interfaces to visualize the
hoisting process.

4. Laboratory and field evaluations and transfer of
technology to industry and MSHA.

SHAFT AND ORE PASS FACILITY

A computer simulation of the research facility was de-
veloped to conceptualize layouts in which all the features of the
test facility and preliminary concepts of key sensor technology

could be assessed. The computer simulation (figure 2) provided
a tool to allow researchers to visualize the hoisting process by
animating the hoist components and the sequence of operations.

mee senna oe

Figure 2—Computer simulation of testing facility.


INTRODUCTION

Some of the deepest mines on the North American continent
continue to be important sources of precious and base metals,
such as silver, gold, antimony, copper, lead, and zinc. Most
important to safety and production is uninterrupted operation
of the shaft and ore pass systems. A shaft, as shown in figure
1, provides access to the network of openings used to recover
the underground resource, serves as an escapeway in case of
emergency, and allows vertical movement of miners and
materials. Ore passes provide for movement of ore and waste
rock from one level to another. Shaft and ore pass structures
must be well designed and maintained for safe and reliable
service.

Researchers at the Spokane Research Center (SRC) of the
former U.S. Bureau of Mines (USBM) concluded that a
research facility and improved technology were required to
assess and improve the safety of mine hoisting and ore pass
Operations. This work is continuing under the administration
of the National Institute for Occupational Safety and Health
(NIOSH). The present Report of Investigations (RI)
describes construction of this facility, retrofitting of the hoist
motor with state-of-the-art components, and development of
a new device for mine hoist conveyance monitoring. The goal
of the research is to improve monitoring, inspection, and
control systems to imcrease awareness of the proper
functioning of mine hoists, ore passes, and chutes; to develop
means of warning of potentially dangerous situations; and to
improve the design of mine shaft and ore pass structures.
Monitoring hoist and ore pass operations will allow operators,
inspectors, and maintenance personnel to increase their
awareness of potentially dangerous situations. Improved ore
to be controlled in and around ore passes in hard-rock mines

Silver shaft

Bottom at 2,067 m
Figure 1.—Typical deep mine shaft system.

and lead to improvements in detection of and remediation
measures for ore pass blockages.

STATEMENT OF THE PROBLEM

According to Mine Safety and Health Administration
(MSHA) data, many of the shaft- and ore-pass-related ac-
cidents in the United States are associated with the hoisting and
loading-unloading cycle. Using MSHA accident reports
(1989), SRC researchers determined that personnel located in
areas related to muck and materials loading and unloading
were particularly susceptible to injury or death. For example,
a common occurrence is water inundation or muck hang-up in
a loading pocket or ore pass. Several fatalities have occurred
recently in the United States and Canada because of the sudden
inrush of water and muck into these structures. In addition,

recent structural failures of ore passes have underlined the lack
of ore pass design capabilities and standards available to both
mine engineers and MSHA enforcement staff.

Hoist and elevator machinery must meet the requirements
specified in the Code of Federal Regulations (CFR), Parts 57
and 75. MSHA has been reluctant to require new safeguards
and accept new design criteria for hoists and ore passes
without fully developed technology. Hoist equipment manu-
facturing companies cannot justify expenditures to develop new
technology. The mining industry cannot interrupt production
to conduct research in vertical haulageways.


HOIST CONTROL

A state-of-the-art, computer-based system controls the
hoisting motor, ore chute gates, and related hoisting functions.
Hoisting and loading operations can either be controlled
manually or the system can be allowed to cycle automatically
through the loading, hoisting, and dumping process. Motor
control is achieved with a Saftronics DCM-series motor
controller (figure 7). The control functions are performed by a

16-bit microprocessor. Control parameters are entered on a
keypad and stored in electrically erasable, programmable, read-
only memory (EEPROM). An RS485 serial interface is also
available for inputing control parameters and monitoring
outputs with a personal computer (PC). An automatic tuning
procedure is run with no load during setup and provides
feedback parameters for precise motor control.

Control functions possible with the motor controller include
Tun, stop, motor direction, and motor speed. The run and stop
controls are defined by adjustable velocity profiles, as shown in
figure 8. Two separate maximum motor speeds are used,
depending on the skip’s position in the shaft. Figure 8 shows
the first velocity profile with the maximum motor speed of 400
rpm. This speed is used while the skip is traveling between
stations. As the skip approaches the loading or dumping
station, a second maximum speed reference, or creep speed, is
used. A maximum motor speed of 50 rpm is used in these areas
to position the skip at the station. Two limit switches are
mounted near the top of the shaft and two near the bottom. The
limit switches are momentarily closed as the skip passes, which
activates the appropriate maximum motor speed (400 or 50
rpm) or stops the skip at the station.

400
Shaft
velocity.
‘pm
Cy
Run Stop Set brake
20 096

TIME s
Figure 8.—Speed curve for winder motor.


Report of Investigations 9637

Development of a Mine Hoist and Ore Pass
Research Facility

Michael J.Beus and Todd M. Ruff

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES
Public Health Service
Centers for Disease Control and Prevention
National Institute for Occupational Safety and Health
‘Spokane Research Center
Spokane, WA

February 1997




Figure 10.—Main hoist control screen.


‘This permitted delineation of target areas that might be of
special concem and allowed various test scenarios to be con-
sidered by altering designs and operating parameters.
Figure 3 shows components of the closed-loop mine shaft
and ore pass testing facility. The ore pass is simulated by 30.5-

12m

15.6m

by 30.5-cm by 15.6-m (12- by 12-in by 51.3-ft) long
steel sections. It contains two 45° dogliegs and is constructed in
3-m (10-ft) long removable sections. The removable sections
will allow researchers to change configuration and inclination.
A bypass on the lower section allows ore to be cleaned out of
the pass and discharged on the ground. Ore is initially loaded
through a ground-level grizzly into a gated, below-ground
discharge chute and loading cartridge, and then into the skip.
The loading cartridge is equipped with balancing load cells to
monitor the net weight of material in the cartridge prior to its
discharge into the skip. Weight detected by these cells in
relation to loading gate position controls skip loading functions.
‘The skip hoists the ore to the top of the headframe, where it is
dumped into a hopper connected to the top of the ore pass. The
ore is gravity-fed down the ore pass into the below-ground
discharge chute, completing the closed loop.

The hoist room components (figure 4) include a winding
drum and gearbox, a motor-gearbox interface, a braking system,
and a 37-kW (SO-hp) dc motor. The electric motor is used to
drive the hoist drum. A 6-to-1 gear reduction is achieved with
a Rex planet gear speed reducer. An additional speed reduction
of 2-to-1 is achieved through a chain drive at the drum. The
hoist drum is 76 cm (30 in) in diameter and has a capacity of
152 m (500 ft) of 9.5-mm (3/8-in) diam wire rope. The total
system was designed for 227- to 254-kg (500- to 1,000-Ib)
hoisting capability over 24 m (80 ft). The 18.3-m (60-ft) hoist
tower (figure 5) and 20-cm (8-in) diam sheave wheel assembly
includes a shaft skip conveyance. The shaft is 5.5 m (18 ft)
deep (figure 6) and is lined with concrete sections.

Figure 4.—Hoist room components, including de motor, gearbox,
and winding drum.


UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT

cm

GHz

kw

fUmin

hp

Metric Units

foot
foot per minute
foot per second

horsepower

ov/min

°C

in

Ib

°F

meter per minute
millisecond

meter per second

volt

degree Celsius

inch
pound
degree Fahrenheit



Tension on
wire rope

E

Normal force

component
at wire rope
oifset at
midpoint causes
beam to flex
= Strain gauges in
> | So Wheatstone bridge
Normal force configuration
component measures
of wire rope beam bending
tension

Figure 14.—Operating principles for flex-cable load cell.

since transmission of the last encoder count. The SPB, the flex-
cable load cell, and the remaining sensors on the hoist cable and
the hoist conveyance or elevator car are designed for ease of
installation and maintenance and minimal interference with
hoisting functions. Also being tested is a new concept to
charge batteries with an on-board wind-charging system driven
from the mine ventilation air stream.

Signat
processing
board (SPB)

Figure 15.—Signal processing board, battery pack, and radio
modem.

Flex-cable

toad cell

SPB and

transmitter

Encoder and
potentiometer

Figure 16.—HASCOMS showing use of laptop
computer for direct data acquisition trom con-
veyance system.


Abstract ..
Introduction
Statement of problem .
Shaft and ore pass facility . .
Hoist control ......-.
Conveyance monitoring -
Summary ........
Acknowledgments -
References

ILLUSTRATIONS

Typical deep mine shaft system ...... 0... 26. e eee eee eect ee tenet ete ete ete eee ents
Computer simulation of testing facility . .. .
Closed-loop hoisting system ..........-
Hoist room components, including dc motor, gearbox, and winding drum .
Hoist tower and headframe ...........-
Downshaft portion with loading pocket .
Motor controller ...........--
Speed curve for winder motor .
Control panel ..........
10. Main hoist control screen .
11. Ore pocket monitoring screen .
12. Lilly controller
13. Design of flex-cable load sensor for 3.8-cm (1-1/2-in) diam wire rope
14. Operating principles for flex-cable load cell
15. Signal processing board, battery pack, and radio modem
16. HAZCOMS showing use of laptop computer for direct data acquisition from conveyance system . . .

CRENAWAYNE



Intemational Standard Serial Number
ISSN 1066-5552


Electric contact points

Overspeed

Normal operation ——

x
J Normal! operation

it ——

Slowing

siowing

Stop at travel fimit

Stopped

CONVEYANCE MONITORING

The development of improved shaft conveyance monitoring
systems has focused on the determination of conveyance
position, velocity, acceleration, load, wire rope tension, and
guide displacement. A position sensor on the conveyance
eliminates the need to correct the position of the conveyance
because of rope stretch. Conveyance load monitoring protects
against slack and tight rope conditions. Measurement of guide
displacement can war of possible slack and tight rope
conditions.

Various sensors for monitoring skip or cage position and
hoist velocity and acceleration have been tested. For example,
on-board ultrasonic and radar-based speed and distance
detectors developed for the agricultural industry have been
evaluated for determining the position of a skip in a shaft.
However, preliminary results indicate that these devices are not
sensitive enough to allow accurate positioning, and their
Tesponse time is insufficient to allow proper control.

An innovative concept called a hoist and shaft conveyance
monitoring system (HASCOMS) was developed. This system
detects wire rope tension, slack and tight rope, conveyance load,
hoist and elevator position, and hoistway guide rail mis-
alignment. It consists of two components: the sensor package
and the data acquisition and transmission package. The sensor
package includes an optical encoder, a rotary potentiometer,
thermistor temperature detectors, and a conveyance load Sensor.

The key component is the newly developed conveyance load
sensor, termed a “flex-cable”? load cell (figure 13). A unique
design feature allows conveyance weight to be determined
independently of the wire rope load path by measuring beam-
bending strains resulting from the normal load component of
hoist cable tension. The flex-cable load cell is designed to
develop a slight curvature in the wire rope at a null load. As the
wire rope is tensioned, normal force components develop,
resulting in corresponding bending strains at the midpoint of the
cell body. The curvature at either end is realigned with the initial
unflexed alignment of the wire rope to eliminate wire rope stress
concentrations that may develop at entry and exit points. The
design principle is based on the theory of elasticity for a
distributed line load across and normal to the transverse center of
a beam supported at each end. Crosby clips, which are
commonly used for wire rope terminations, clamp the load cell to
the wire rope at one end, provide the required offset at midpoint,
and allow slip at the other end. The design minimizes flexural
strain in the wire rope during loading and unloading cycles so as
Rot to compromise its ultimate strength and working life, and yet
generates enough flex to provide the required output. Figure 14
illustrates the operating principles.

*Patent applied for as “Cable Load-Sensing Device,” MIN/PGH-9603.


12

SUMMARY

Hoist and elevator systems for underground metal/nonmetal
mines and coal mines must meet the requirements specified in
the Code of Federal Regulations. Nonetheless, MSHA
inspections and accident reports show that many mine hoist and
ore pass accidents have occurred because of electrical,
mechanical, and structural failures, despite the requirement for
periodic testing of the equipment.

Current technology to enhance safety and control features for
mine hoists was assessed and new approaches for ore pass
design are being developed. Various components of mine
hoisting and elevator systems were evaluated, including
hoisting machinery (hoise room controls, motors and gearboxes,
and winders) and shaft infrastructrue (support frameworks,
guides, wire ropes, and skips and cages). Progress to date has
resulted in completion of a state-of-the-art hoisting and ore pass
research facility. Sensors and real-time data acquisition

interfaces to monitor hoisting operations have been developed.
The hoisting test facility and the monitoring system allow
Personnel to assess critical hoist operating parameters such as
conveyance position, conveyance speed and acceleration, load,
Tope tension, and shaft guide misalignment. In addition, efforts
are focused on investigating the causes of ore pass blockages
and ensuring safer operations by detecting the locations of
blockages and improving hang-up removal methods.

The major benefit arising from this research will be the
prevention of numerous injuries and fatalities related to hoisting
and ore pass operations. With improved monitoring and control
technology and the integration of this function into a broader
framework of hoisting and ore pass process control, research
will enable miners to be removed from hazardous locations
within the hoisting and ore pass infrastructure and improve the
safety of the workplace.

ACKNOWLEDGMENTS

The authors appreciate the technical assistance of Peter
Kovalchik, electrical engineer at the Pittsburgh Research

Cewer, Pittsburgh, PA, for his assistance in procuring and
installing the dc hoist motor and motor control systems.

REFERENCES

Barkand, T. D., and W. J. Helfrich. Application of Dynamic Braking to
Mine Hoisting Systems. IEEE Trans. on Industry Applications, 1988.

Beus, M. J., F. T. Duda, Jr., and T. J. Orr. A PC-Based Monitoring
‘System for Mine Hoisting. Paper in Computer Applications in the Mineral
Industry, ed. by H. S. Mitri (Proc., 3rd Can. Conf. on Computer Appli. in
Miner. Ind., Montreal, PQ, Oct. 22-25, 1995). Dept. Min. and Metall. Eng...
McGill Univ., 1995, pp.

Beus, M. J., and W.G. McCoy. Mine Shaft Conveyance Load-
Monitoring System. Paper in Conference Record of the 1995 IEEE Industry

‘Application Conference, 30th IAS Annual Meeting (Orlando, FL, Oct. 8-12,
195), Va Vol. 3, Instit. Elect. Electron. Eng., 1995. pp. 2048-2053.

Coeff, J., W. J. Forbes, A. W. Mills, UI, L. Albert, and F. A. Penning.
Procedures for Hoist and Shaft Inspection and Maintenance. Vol. 1, Systems
Description; Vol. 2, Inspection and Maintenance Procedures (Contract

40100035, V.B. Cook, Inc.). USBM OFR 196(1)-82, 310 pp.; NTIS: PB &3-
148049 and USBM OFR 196(2)-82, 1981, 140 pp.; NTIS: PB 83-148056.

Dames and Moore. Safety Analysis of United States Shaft-Sinking
Operations (Contract 30155174). USBM OFR 45-78, 1977, 289 pp.; NTIS:
PB 282 289.

Farley, H. L., R. B. Fish, R. L. Jeffcoat, and D. L. Hoadley. Slack and
‘Overload Rope Protection System (Contract JO199008, Foster-Miller Assoc.,
Inc.). USBM OFR 213-83, 1983, 327 pp.; NTIS: PB 84-143460.

Loynes, E. Safe Manriding in Mines. Min. Technol., Dec. 1976, pp. 12-
a.

Mine Health and Safety Administration, Health and Safety Analysis
Center. Shaft Accidents in Metal/Nonmetal 1989, ADA (Accident Data
Analysis). 1989.