Summary: When hoisting, a skip trip in the head frame occurred. The skip tipped and the cylinder pushed the skip back into bridle, then the skip descended to the guides. The skip became caught and the winder tripped out. The winder driver heard a bang and stopped to look at what happened. Upon inspection, the cylinder didn’t finish pushing the skip into bridle before the bridle descended.
The skip wear plates (herring bone liners) allowed rocks and material to build up to the point where rocks jammed the skip door. The push plate became caught on the lip of the chute, jamming the conveyance.
The site modified the liners and repositioned the retract cylinder and proximity switch to ensure the skip was pushed and monitored into the bridle once tipped.
Recommendations to industry: Mines with winders should consider the type and adequacy of shaft and winder inspections, including:
- ropes and attachments
- guides to identify damage or areas where a conveyance may bind or become stuck
- maintenance requirements in accordance with the original equipment manufacturer recommendations
- testing of safety-related functions in a manner and frequency as required by the designer.