The rollers, which are exposed on some brands of units and are meant to prevent trailing cable from coming into contact with the machine frame, are normally located between the car's sheave wheel carrier and the cable reel housing/spooling device.
The roller portion is isolated electrically, separated from the frame by bearing assemblies, MSHA noted, so most rollers are not made from or covered with a flame-resistant insulating material.
“If an exposed conductor, in a damaged section of an energised cable, comes into contact with this roller, the roller will become energized,” MSHA said.
“Since the roller is readily accessible and shuttle car operators routinely clean the area around the roller, if the roller becomes energised, miners could become exposed to a shock hazard."
The agency noted that not all units are equipped with this metal roller, but mines should contact the shuttle car's original equipment manufacturer for an MSHA-accepted trailing cable roller replacement.
In the meantime, OEMs have been made aware of the issue as well as MSHA's revision of policy on cable reels. Those wishing to view or print the amendments to Program Policy Manual Volume II, Section 18.45 can do so at http://www.msha.gov/regs/complian/ppls/2007/PPL07-V-4.asp.
