Sensors Warn of Hazards During Mine Hoisting

Objective

Develop a method to warn of hazardous conditions and enhance
safety during operation and inspection of vertical mine shafts and
hoists.

Background

Mine hoisting is the most critical and potentially the most dan-
gerous operation in underground mining. Many hazards are related
to falls of miners and materials, ground instability, and malfunction
or lack of safety devices. All have the potential to cause a cata-
strophic accident. A condition known as “slack rope” is particulary
dangerous, expecially if it occurs without the operator's awareness.
The most common occurrence of slack rope is in metal or nonmetal
mines that have a history of ground control problems near the
shaft.

Approach

Studies of hoist safety features and Mine Safety and Heath
Administration (MSHA) ident statistics suggests a need to
measure wire rope tension, conveyance speed and position, and
shaft guide misalignment. The most accurate data are obtained
directly from the conveyance. Such data could warn of potentially
dangerous situations during hoisting operations, as well as during
inspections, maintenance, and lowering of large equipment. Figure
1 shows the concept for monitoring wire rope tension, conveyance
position, and guide displacement.

Progress to Date

A conveyance-mounted system has been developed that monitors
rope tension; hoist conveyance position, speed, and load; and shaft
guide misalignment. A “flex-beam” load sensor mounted just
above the conveyance protects against slack and tight rope. The
measurements are transmitted 60 times a second via wireless
equipment from the conveyance to the hoist room. An encoder
mounted on the conveyance eliminates the need to correct the
position because of rope stretch. Figure 2 shows the encoder
wheel and guide displacement sensors being mounted on a cage in-
spection deck. A potentiometer monitors misalignment of the shaft
guides during inspections. Information about the cage or skip can
be acquired by the shaft inspector using a hand-held indicator.
Inspection can also be conducted remotely from a station or hoist
room using the wireless link to a laptop computer. Figure 3 shows
test results from a simulated slack rope condition.

Patent Status

NIOSH has a patent pending on this device entitled “Cable-Load-
Sensing Device.”

For More Information

NIOSH is seeking cooperators to assist in further tests of this
technology to improve hoisting safety. Additional information can
be obtained by contacting Michael J, Beus, Steven Iverson, or
Elaine Cullen, Technology Transfer Officer, NIOSH, Spokane
Research Laboratory, Spokane, WA 99207 at (509) 354-8000.

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U.S. Department of Health and Human Services
Public Health Service
Centers for Disease Control and Prevention
National Institute for Occupational Safety and Health

CDC

‘CENTERS FOR DISEASE CONTROL


Mention of any company name or product does not constitute
endorsement by the National Institute for Occupational Safety and
Health.

To receive additional information about mining issues or
other occupational safety and health problems, call 1-800-
35-NIOSH (1-800-356-4674), or visit the NIOSH
Home Page on the World Wide Web at http:/www.cde.
gov/niosh/homepage.htm!

As of October 1996 the safety and health research functions
of the former U.S, Bureau of Mines are now located in the
National Institute for Occupational Safety and Health
(NIOSH).

=~ Antenna

Hoist rope

Flex-beam Protective cover

load sensor Transmitter
inal processing
ard (SPB)

Crosby clips

Shaft
guide

Encoder, charger

Figure 1.—Slack rope detection system.

90
TIME, s

Figure 3.—Results of tests simulating a slack rope condition.