Broken wire ropes can lead to serious incidents in a mine, cautions the Mine Safety and Health Administration. Wire ropes often break due to shock loading – when a load is applied to a rope that has developed slack as the result of a stopped or slowed load. When the slack runs out, a shock load will occur, generating extremely high force on the rope.
To avoid slack rope and other situations that might shock load a wire rope, MSHA recommends:
- If an obstruction stops a mantrip on the way down a slope, always bring the trip up the slope – never try to continue down.
- Maintain and periodically test overspeed switches and slack rope safety mechanisms. Never defeat an overspeed switch or slack rope stop.
- Hoists and elevators should all be equipped with overtravel protection, as unintended overtravel can shock load a rope.
- Never remove blocking, release a brake or otherwise release a load attached to a wire rope without checking the entire length of the rope to make sure it is not slack or snagged on anything.