New Macey EARTH TEST Plugs
A major safety challenge has been to test the electrical integrity of earth wires in mining cables.
The three earth wires are closest to the outside sheath of a cable, making them vulnerable to physical damage or breaking as cables are bent.
If one earth wire ruptures, the electrical field in the cable becomes asymmetric. Differences of up to 50 volts can be measured between machines, sufficient to cause sparks which can have serious consequences in explosive environments.
Although the risks from earth failure are well known, it is not easy to pinpoint earth faults. Plugs have to be fully disassembled, which is time consuming, expensive and earths have to be separated to locate any faults.
New Macey has introduced a patented way of testing earth wires without dismantling plugs. Incorporated into the New Macey range of waterproof plugs, this innovation is a valuable aid for safer operations in hazardous atmospheres.
Earth wires are permanently isolated from the plug body by insulating liners at the earth terminals. Stainless steel screws give full electrical continuity under normal operating conditions. For testing, these screws are removed from outside the plug and replaced by insulating test connectors. Each wire can then be independently tested. EARTH TEST plugs can be tested accurately, without manual disassembly, in just a few minutes.
EARTH TEST Plugs
These plugs can be placed at one or both ends of the mining cable. Testing the integrity of each earth can then be a routine part of normal inspection regimes.