SHD-GC and heavy-duty trailing cable from Ohio mines

How mine cable is put together

SHD-GC means shielded, with a ground check. Three power conductors sit inside a semiconductive screen and a metallic shield, alongside two grounding paths: the ground conductor that carries fault current and the smaller ground-check conductor that signals continuity back to the circuit breaker. Lose the ground check and the machine will not start, which is the point of it.

The jacket is a heavy-duty compound, usually chlorinated polyethylene or a comparable material, formulated for flame resistance, abrasion and resistance to the oils and hydraulic fluid that leak in a mine. Trailing cable is built even heavier, with extra reinforcement, because it is dragged behind equipment rather than fixed in place.

Voltages and the duties behind them

Two-kilovolt cable serves section equipment and small machines. Five and eight kilovolt cable feeds continuous miners, shuttle cars and the smaller longwall gear. Fifteen kilovolt cable goes to longwall systems and the large draglines and shovels at surface operations, where the run is long and the current is heavy.

Reeling cable and trailing cable are not interchangeable even at the same voltage. Reeling cable is built for repeated spooling under tension on a motorized reel; trailing cable is built for dragging and flexing on the ground. A reel of one used in the other duty fails early, and the jacket damage usually shows at the point where the cable was clamped.

The Appalachian context

Eastern and southeastern Ohio has a long coal history, and the equipment that came out of it is still in the state. Longwall sets, continuous miners, shuttle cars and surface draglines were sold, parked or abandoned as mines closed, and their cable went with them into trailers, conex boxes and equipment sheds.

Reclamation work moves that material again. A site being regraded and revegetated has to clear equipment and stores, and cable that was kept as spares gets pushed out on a schedule that has nothing to do with its condition. Athens County and the coal counties along the Ohio River generate most of what is reviewed, and the access is often the hardest part: steep ground, unpaved roads and a gate that has to be opened by someone who may no longer work there.

MSHA and what reuse requires

Cable used on face equipment underground has to be accepted for the purpose, and the acceptance is marked on the jacket along with the manufacturer and the construction. That marking does not expire when the mine closes. Reuse in another mine depends on the marking surviving, on the jacket being sound and on splicing being done to the rules that apply at the receiving mine.

Reuse above ground, or as a power feed in a plant, is a different question and often the practical answer for cable that no longer suits face duty. What disqualifies a lot is physical: jacket worn through to the shield, a ground-check conductor broken inside an otherwise sound cable, or a splice that cannot be documented. Those are found by inspection at the ends and by looking along the length, not by reading the tag.

• Jacket marking legible, including the acceptance marking
• Ground-check conductor continuity confirmed
• No jacket worn through to the metallic shield
• Splices identified and documented, not hidden
• Cable coiled on a reel or in a figure-eight, not dumped