Figure 5. Hoist test facility at Spokane Research
Center.

also been fabricated. A 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. Output from these cells and loading gate posi-
tion sensors will control skip loading functions. A
similar approach is used for skip discharge at the top
of the headframe.

The hoist room components include a winding drum
and gearbox, a motor-gearbox interface, a braking
system, and a 50-hp de motor. A digital motor con-
troller allows sophisticated control of the de motor
through an interface to a PC. A ideal motor-velocity
profile can be input using numerous parameters; the
profile can be modified via feedback from sensors on
the motor, such as an optical encoder, a digital ta-
chometer, or armature current. The system is being
further modified with a Simplex model Lilly hoist con-
troller to back up the digital control system and dupli-
cate hoisting installations currently in use.

The testing approach is aided by development of con-
ceptual layouts in which all the features of a proposed
monitoring and testing system and preliminary con-
cepts for key sensor technology are delineated. A
computer simulation of the Spokane shaft test facility
was developed to allow researchers to visualize the
hoisting process. This permitted delineation of tar-
get areas that might be of special concern and that
would require additional sensors. An animated simul-
ation of the test tower allowed various scenarios to
be considered. The analysis also allowed computer
evaluations of key structural components of the test
frame and skip. Different skip and guide materials
may be analyzed and the computed results correlated
with the results of actual testing. For example, a

more flexible guide rail alignment wheel may allow
the skip to pass through tight spots with less resis-
tance, a major cause of tight rope conditions. The
computer visualization and simulation model of the
test frame continues to be updated and is being used
to simulate operation of the actual test hoist as fea-
tures are added.

CURRENT PROGRESS
Sensors

A new approach to conveyance load sensing incorpo-
rates a design that is independent of the conveyance
load path, and therefore does not compromise the in-
tegrity and safety of the wire rope. This concept is
called a “flexcable" load cell. The device imbeds a
slight curvature in the rope at the sensing point and
is totally independent of the load-carrying function of
the wire rope. A typical full bridge circuit measures
bending strains on the conforming cell body as the
rope is tensioned, providing the required output as
pounds of tension at the conveyance termination.

Pillow-block load cells at the sheave wheel are used
to verify loads from the flexcable load cell at the
conveyance. Figure 6 shows a layout of the labor-

Sheave
wheel
Pillow block Wire
load ceil / rope
NY (oO \ J Pins
Po 2 0
mh l |} Flex-Cable
at Sa load cell
doi tama
Vv
Tinius-Olson
test machine
Figure 6. Layout of laboratory test setup to evaluate
load cells.


and elevator operations. Real-time visualization of
hoisting processes will provide a hoist operator with
a desktop tool for control of hoisting operations in a
safe and efficient manner. By integrating this function
into a broader framework of hoisting process control,
the research will improve the health and safety of the
work place.

REFERENCES

Barkand, T.D. and Helfrich, W.J., 1988.
Application of dynamic braking to mine hoisting
systems. IEEE Trans. on Industry Applications.

Cseff, J., Forbes, W.J., Mills, A.W. III, Albert, L.

and Penning, F.A., 1981.
Procedures for hoist and shaft inspection and main-
tenance. Vol. I. Systems description and Vol. II.
Inspection and maintenance procedures (Contract
J0100035, V.B. Cook, Inc.), USBM OFR 196(1)-
82, 310 pp.; NTIS: PB 83-148049 and USBM OFR
196(2)-82, 140 pp.; NTIS: PB 83-148056.

Dames and Moore, 1977.
Safety analysis of United States shaft-sinking oper-
ations (Contract JO155174). USBM OFR 45-78,
289 pp.; NTIS: PB 282 289.

Farley, H.L., Fish, R.B., Jeffcoat, R.L., and
Hoadley, D.L., 1983.
Slack and overload rope protection system (Contract
J0199008, Foster-Miller Assoc., Inc.). USBM
OFR 213-83, 327 pp.; NTIS: PB 84-143460.

Loynes, E., 1976.
Safe manriding in mines. Mining Technology,
December, pp. 12-21.

Mine Health and Safety Administration, Health and
Safety Analysis Center, 1989.
Shaft accidents in metal/nonmetal 1989, ADA
(Accident data analysis).


0
ime (sec) Rope vaad

Figure 3. Control screen layout of deep mine hoist-
ing process.

mined that existing software packages were still either
too comprehensive or too expensive to be compatible
with the requirements of the project. It was decided
to develop in-house a public-domain data acquisition
and process control software package customized for
hoisting. Windows-based software appeared to offer
the greatest potential for reducing cost and enhancing
the user-friendly aspects of the interface between an
operator and a PC screen. Powerful and comprehen-
sive Windows-based data acquisition and process con-
trol software and hardware tools are available.

Sensor development has focused on determining con-
veyance position and load. Various sensors for moni-
toring skip or cage position and hoist velocity and
acceleration have been evaluated. For example, on-
board ultrasonic and a radar-based speed and distance
detectors developed for the agricultural industry has
been evaluated for determining the position of a skip
in a shaft. A position sensor located on the convey-
ance eliminates the need to correct the position of the
conveyance because of rope stretch. However, pre-
liminary results indicate that these devices are not
sensitive enough for accurate positioning, and the re-
sponse time is insufficient for proper control.

Shaft conveyance load is identified as the other key
element for enhancing hoist safety. Conveyance load
monitoring in real time will detect slack or tight rope
conditions resulting from shaft obstructions, rock
movement, and misalignment. In addition, it will
serve as a production monitor and warn of ore hangup
in the skip or loading pocket. Current approaches
favor inline load cells in the load path of the convey-

Figure 4. Simulation of loading packet with off-the-
shelf software.

ance or load cells in the sheave wheel pillow blocks at
the headframe. Both of these approaches have major
disadvantages. Inline load cells may compromise the
integrity of a wire rope, and they are costly and diffi-
cult to install, requiring a significant modification to
the conveyance termination point. Pillow-block load
cells weigh the total downshaft load, including the
wire rope and acceleration loads. This makes deter-
mination of the net weight of the conveyance, and
therefore overload conditions, difficult to determine,
particularly in deep shafts where the weight of the
wire rope becomes a significant part of the total load.
This situation requires a very high-capacity load cell,
the use of which would reduce sensitivity so that small
but significant changes in the conveyance load could
not be determined.

HOIST TEST FACILITIES

It was determined early on in the project that testing
of new technology would be difficult to undertake in
operating hoist installations. For this reason, a deep
mine hoisting test facility was constructed at Spokane
and a three-level elevator test facility was modified
for research at the Pittsburgh Research Center. These
test facilities are being used to evaluate position and
load-indicator sensors, data acquisition systems, and
software. The test facility in Spokane utilizes a 60-ft
hoist tower to simulate the headframe and shaft, an
18-ft-deep "shaft" lined with concrete sections, a
winding drum, sheave wheel assembly, and shaft skip
conveyance (figure 5). A loading-unloading circuit to
investigate skip loading and unloading operations has


Rope Load (oe
7 3 ;
rh

7
i i
wr

129021 120200 12:00:00 120800 120800 120800 1207-00
‘Toe (termes

Figure 7. Comparison of results of pillow-block and
flexcable load ceil.

atory test setup. Results of this work show an excel-
lent correlation between the pillow-block load cells
and the flexcable ceil. Figure 7 shows the results of
the comparison using a laboratory test setup.

The design for conveyance position favors the use of
an optical encoder mounted on a conveyance guide
wheel. In addition, an encoder mounted on the wind-
ing drum and hoist motor monitors shaft revolutions
and provides backup data for determining the same
operating parameters. These devices provide suffi-
cient data to establish conveyance position, and there-
by velocity, and acceleration. These data are needed
to develop the hoist speed curve, a shaft-hoisting
parameter essential for monitoring and testing hoist
safety features. This is considered a critical need by
MSHA inspectors.

Data Acquisition

Data acquisition consists of a hybrid scheme incorpo-
rating both a "desktop’ system for monitoring hoist-
room functions coupled with an “onboard” system for
downshaft monitoring.

The desktop data acquisition system utilized at the
Pittsburgh Research Center consists of a 486 PC
equipped with two ISA expansion cards and the ap-
propriate signal conditioning. One expansion card
provides A/D capability for 16 single-ended or 8 dif-
ferential analog inputs at 12-bit resolution. The card
can sustain a sampling rate of up to 100 thousand
samples per second. The second expansion card is a
counter-timer card that has five 16-bit counters that
can be configured for frequency measurements and
event count accumulations. Both cards have multiple

digital 1/O port capabilities. A eight-channel commer-
cially available signal conditioner is used to make the
sensor signal readable by the A/D board as well as to
provide electrical protection.

At this time, the data acquisition system is being used
to monitor dc hoist motor voltages and currents as
well as signals from speed- and position-measuring
sensors on the elevator. The sensors are hard wired
into the signal conditioners. This system will be vali-
dated against the current monitoring system now used
by MSHA inspectors.

Obtaining accurate and reliable data from a moving
hoist conveyance in a deep shaft remains a key
element of future efforts. A commercially available
transmitter-receiver set was procured and installed at
the Spokane Research Center for wireless transmis-
sion of load cell and encoder data from the test hoist.
This unit provided a standard for evaluating prototype
transmitter-receiver sets. The receiver, located at the
headframe or in the hoist room, has been tested both
as stand-alone equipment and with a “leaky feeder"
antenna that extends the receiver’s effective range.
The leaky feeder antenna allows signals to be received
around corners underground, such as around a rope
raise and into an underground hoistroom.

A battery-operated, microcomputer-controlled signal
processing board has been designed jointly by the
USBM and McCoy Engineering Co., both of Spokane,
WA. Functionally, this board processes data from
various hoist sensor inputs and provides serial data
output for a radio uplink from the conveyance to the
hoist control room computer. Inputs are—

1. An analog load-cell input channel for monitoring
loading of the hoist wire rope by the conveyance.

2. An analog input channel configurable for use with
another load cell or with other sensors, such as
accelerometers, linear potentiometers, or ultrasonic
transducers.

3. A digital optical encoder input channel for moni-
toring the location of the conveyance in the shaft.

Analog sensor input data are sampled by the monitor-
ing system at 100 ms intervals. This sampling rate
allows data to be acquired about 10 times per second,
which is adequate for evaluating satisfactory hoist
operation and affecting timely control at a speed of
600 m/min or 10 m/s (1,800 ft/min or 30 ft/s). At


A PC-Based Monitoring System for Mine Hoisting

Michael J. Beus
Spokane Research Center, U.S. Bureau of Mines, Spokane, Washington USA

Frank T. Duda, Jr.
Pittsburgh Research Center, U.S. Bureau of Mines, Pittsburgh, Pennsylvania USA

Timothy J. Orr
Spokane Research Center, U.S. Bureau of Mines, Spokane, Washington USA

ABSTRACT

The technology to enhance safety and control features for mine shaft hoists is being investigated by researchers at
the U.S. Bureau of Mines (USBM). The objective of the research is to prevent injuries and fatalities related to
hoist and elevator operations. Monitoring and controlling mine hoisting operations will allow hoist operators,
inspectors, and maintenance personnel to increase their awareness of potentially dangerous situations and provide
controls for safer operations. Process simulation and visualization software, real-time data sensing, and advanced
programming techniques are being applied to this problem. Development of reliable and cost-effective sensors and
data acquisition interfaces to monitor hoist loads and detect slack rope conditions is underway. Three-dimensional
design software was used to visualize mine hoisting to enhance understanding of hoist operations. Quick Basic and
Visual Basic (an object-oriented Windows interface) are being used for acquiring and processing hoisting data.
Testing and evaluation of components are underway at USBM testing facilities. The resulting system will allow
hoist personnel to assess critical operating parameters, such as hoist position, speed, acceleration, conveyance
load, and rope tension.

RESUME

La technologie, pour réhausser la streté et traits controllés des hissages de puits dans les mines, est sous recherche
par les ingénieurs du Bureau des Mines aux Etats-Unis. L’objectif des recherches est de prévenir les altérations
de santé et dégats mortels au rapport des hissages et élévateurs en mines. Les observations et le controllement des
activitées de hissage en mine permettra !es ouvriers, inspecteurs et le personnel de maintien, d’augmenter leur
perception en situations potentielles et dangereuses, et fournir des mesures de control pour des travaux de meilleure
sireté. Un procédé simulateur et programme de visualisation, sensorisation de données en temps-actuel et
techniques avancées de programmatique sur ordinateur sont appliqués 4 ce problem. Le développement des
censeurs exacts et coit-éffectifs est entrepris, ainsi que |’interface d’acquisition de données, pour observer l’éffet
du chargement des hissages et de détecter 1’état du cable en détente, pendant l’abaissement. Un programme de
dessin proportionné trois-dimensionel a été utilisé pour etablir une réalisation visuelle de hissage en mines et pour
réaliser la compréhension des hissages eux-méme. Quick Basic et Visual Basic (an object oriented Windows
Interface sur ordinateur) sont utilisés pour acquir les données sur hissages. La tenue des épreuves et les évaluations
des éléments constitutifs sont commencées dans les établissements d’évaluation des U.S. Bureau des Mines. Le
résultat permettra le personnel du hissage d’imposer les paramétres des procédures délicates; tel sont l'état du
huissage, la vitesse, l’accélération, le transport et la tension du cable.


the completion of each sampling period, this informa-
tion is combined with an updated optical encoder pulse
count and transmitted as asynchronous serial data over
the radio modem. A secondary RS-232 serial port
output of the processing board can provide the same
information to a portable computer or terminal on the
conveyance itself. The conceptual data acquisition and
sensor package is shown integrated into a hoist and
shaft conveyance monitoring system (figure 8).

Figure 8. Hoist and shaft conveyance monitoring
system.

Software

A user-friendly software interface to collect, save,
analyze, and provide hoist control from sensor data in-
put has also been developed. Visual Basic, an event-
driven programming language, was selected. Instead
of lengthy instructions taking weeks to write, this
program is drawn. Subroutines are embedded in tool
boxes of requisite functions by simple “point, click,
and drag" programming. Subroutines are carried out
in reaction to an event caused by either user input or
internal actions. For example, events could be entered
with a mouse click on a start button on the screen or
input to a text box from a communications port on a
PC.

Initial programming efforts resulted in a series of
screens displaying hoisting data. The main menu in-
cludes eight buttons for displaying different data:
“hoisting,” “loading/unloading," "data-save," “cali-
bration," "shaft inspection,” "set operating limits,"
"set password," and “exit.” The user can move any-
where in the system from either the main menu or the
pull-down menus that exist in each window. For ex-
ample, in figure 9, the "hoisting" window is shown
with a mine shaft and conveyance represented, along
with various operating parameters. The conveyance
moves in accordance with position data input into the
text box. Speed, acceleration, and conveyance weight
are displayed as input into the text boxes. Another
icon on this screen represents conveyance contents
tied to warning conditions set in the operating limits
window.

Figure 9. Computer screen showing shaft and con-
veyance simulation.

Updates and new capabilities are being incorporated
as needed. For example, a menu bar is currently be-
ing incorporated into each process screen with a repre-
sentative icon for different screens. Algorithms for
time trends of rope load and conveyance speed with
the effects of tight compartments from ground squeeze
are also being considered. Coupled rock mass and set
distortion data with slack and tight rope sensing can
define potentially hazardous sections in the shaft.

SUMMARY

The major benefit arising from this research will be
a reduction of injuries and fatalities related to hoist


INTRODUCTION

Mine shafts are the "lifeline" of underground mining
operations. A shaft (figure 1) provides access to the
network of openings used to recover the underground
resource and serves as an escapeway in case of
emergency. As such, a shaft must be well designed
and maintained for a long and reliable service life.
Hoist and elevator systems for underground metal/
nonmetal mines and coal mines must meet the require-
ments specified in the Code of Federal Regulations
(CFR), Parts 57 and 75. The Mine Safety and Health
Administration (MSHA) has been reluctant to require
new safeguards for elevators and hoists without fully
developed technology. However, in many cases, the
mining industry and hoist equipment manufacturing
companies cannot justify research and development
expenditures.

Researchers at the U.S. Bureau of Mines (USBM) are
conducting research to develop a PC-based monitor-
ing, inspection, and control system that will increase
awareness of proper functioning of mine hoists, warn

Silver shaft

Bottom at 2,067 m

Figure 1. Typical shaft layout in deep metal mine.

of potentially dangerous situations, and provide con-
trols for safer operations. According to MSHA data,
many of the shaft-related accidents in the United States
are associated with the hoisting cycle and maintenance
operations (figure 2). For example, about 10% of all
injuries in U.S, metal/nonmetal mines in the period
between 1985 and 1992 were related to hoisting. Of
these, almost all (>90%) were related to errors by
operating (i.e., hoistman or cagetender) and mainte-
nance personnel, as opposed to injuries caused by
faulty or poorly maintained equipment.

From MSHA accident reports, personnel located in
areas related to muck and material loading and unload-
ing were particularly susceptible to injury or death.
A relatively common occurrence was water inundation
or muck hangup in the loading pocket or ore pass.
Several fatalities have occurred recently in the United
States and Canada from the sudden inrush of water
and muck, washing loading-pocket operators into the
shaft (MSHA, 1989). Another problem occurs when
spillage or equipment falls to the shaft bottom, often
severely damaging shaft hardware and requiring ex-
pensive downtime and hazardous repair work. Down-
time for inspection, maintenance, and repair also
significantly decreases the time available for muck
hoisting.

In the past 10 years, several documented mine hoist
and elevator accidents (Dames and Moore, 1977) have

1S i596,
1908 1909 1590)
tm wa

Figure 2. Shaft-related accidents in metal and non-
metal mines in the United States—1988-92.


also resulted from electrical, mechanical, and struc-
tural failures, despite MSHA requirements for periodic
testing of hoist systems. All these accidents had the
potential for injuring or killing miners, as did the acci-
dent at the Markham Colliery in the United Kingdom
on July 30, 1973. With advances in computer tech-
nology, including process visualization, real-time data
acquisition, sensors, and microcomputers, safer, more
cost-effective inspection, monitoring, and control sys-
tems are possible. This paper will present some appli-
cations of computer methods and sensor development
approaches to the mine hoist monitoring and inspec-
tion problem.

APPROACH

This research is being conducted at the Pittsburgh
and Spokane Research Centers, in cooperation with
the MSHA Technical Support Group in Pittsburgh.
Components of various mine hoisting and elevator
systems were assessed, including hoisting machinery,
such as hoistroom controls, motors and gearboxes,
and winders, and shaft infrastructure, such as support
frameworks, guides, wire ropes, and skips and cages.
Current technology was assessed to determine what
conditions and equipment should be monitored, avail-
ability of adequate sensors, and how to process and
act on the information.

Specific research tasks were defined as follows:

© Evaluate the complete shaft hoisting and materials
handling process and facilities, including stations,
loading pockets, and safety and control features.

* Develop a working computer model to simulate the
hoisting process and delineate potential safety
problems and targets for condition sensing.

© Assess currently available sensors and monitoring
and process-control technology for hoisting person-
nel and materials in mines.

© Identify parameters to be monitored and modify
or develop new sensors and data acquisition
capabilities.

© Develop laboratory test facilities to conduct proof-
of-concept testing.

© Develop software with hoisting process and sub-
process graphics screens and collect, save, and
evaluate sensor data.

* Conduct field evaluations and transfer technology
to industry and MSHA.

TECHNOLOGY ASSESSMENT

Shaft hoisting technology, safety features, and stand-
ards have been assessed. Such work includes an eval-
uation of all safety features for hoists and elevators,
existing safety standards for both hoists and elevators
as well as current hoist and elevator monitoring sys-
tems and sensors (Farley et al., 1983; Barkland and
Helfrich, 1988; Loynes, 1976; Cseff et al., 1981).
Most monitoring and control systems have been devel-
oped and introduced in Canadian, British, and South
African mines. However, indications are that cost-
effective hoist monitoring systems are not widely used
in the United States, particularly for smaller oper-
ations and for use with older hoisting equipment.
Existing commercially available systems range in price
from $50,000 to $250,000 and are largely customized
to be site specific. Major cost items are sensors, data
acquisition, and associated monitoring and control
software.

It was concluded that research to improve sensor tech-
nology and increase information flow on operational
status of the hoisting function is important. More
cost-effective methods and software for automated
inspection operations and sensors for determining
conveyance loads, slack and tight rope, and convey-
ance position must be developed.

Software kits for developing personal-computer- (PC-)
based data acquisition systems for enhancement and
customization of current software were evaluated.
State-of-the-art, factory-floor process control technol-
ogy for monitoring and controlling schemes for mine
hoisting operations were evaluated.

Figure 3 shows an example of a control screen layout
of a deep-mine hoisting process using currently avail-
able technology. This screen incorporates cage or
skip position, speed, and acceleration using various
layouts of in-shaft processes. Figure 4 shows how the
loading pocket may be set up and simulated, again
using off-the-shelf software. However, it was deter-