MSHA conducted wire rope nondestructive testing (NDT) and inspections on hoisting ropes that had been determined safe for service as a result of a recent examination and found that these ropes had flaws and no longer met MSHA’s in-service standards
In its safety alert MSHA is recommending that mine operators use NDT when conducting required six-month inspections of wire ropes. NDT equipment utilizes magnetic or ultrasound waves to view the inner workings of the rope without cutting into it, much like a CT scan or MRI.
Loss of metallic area, flaws (broken wires and corrosion) and strength loss can be evaluated through NDT for the entire active length of a hoist rope.
The following are best practices for mine operators to maintain wire ropes, including conducting nondestructive testing and examinations:
- Conduct wire rope NDT at least once every six months to identify deterioration including: wear, corrosion, distortion, broken wires and loss of metallic area
- Review the wire rope NDT results to identify deteriorated portions of the wire rope that shall be visually examined more frequently
- Examine daily any portion of the wire rope where a reduction of rope strength is present
- Conduct wire rope examinations during daylight hours
- Perform visual examinations at a rope speed no more than 50 fpm
- Clean and remove old lubricant to conduct a thorough visual wire rope examination especially in high stress sections
- Follow the rope manufacturer’s guidance for proper lubrication. Use pressure lubricators to maintain proper lubrication at the core level.
- Correct mining conditions that cause corrosion to maximize hoist rope service life.
- Install and maintain wear blocks and rollers to minimize rope wear.