Mining Cable Basics
ConstructionMining cable has a unique construction that allows it to be somewhat flexible while carrying all three conductors, a ground and a ground check wire all under one jacket. The owner of a wire and cable company I worked at used to teach us about wire and cable by starting with the inside out, beginning with the conductor and ending with the jacket. We use this approach to look at three of the more common types of mining cable which are G-GC, SHD-GC and MP-GC Mining cable conductors are made from flexible tinned copper that is stranded. Stranding aids in flexibility as it allows the conductors to move independently within the insulation. This is common to all types of mining cable.
G-GC Mining Cable
G-GC is typically used to power equipment in mining tunnels. The G-GC stands for ground with a ground check, and like the name implies it contains grounding wires and something that is unique to mining cable, a ground check wire. The ground check wire sends a signal that let’s the operator know the ground wire is in tact. The individual conductors are twisted to help reduce internal circulating currents. Covering the individual conductors is the insulation, which protects the conductors and keeps people and objects from touching the conductors. The insulation is typically made of a material called ethylene-propylene rubber (EPR) and is good for 90 degrees c, just short of the boiling point of water. Covering the insulation is the jacket of the cable, which serves the purposes of containing the conductors, additional insulation protection and to act as protection for the conductors. The jacketing material in G-GC mining cable can be either mold-cured thermoset chlorinated polyethylene, or CPE, or continuous vulcanized rubber (CV) which is a way to turn rubber compounds into a usable jacket. Mold-cured, or as it was previously called, lead-cured, jackets are produced by taking standard vulcanized rubber jackets and compressing them with a lead mold shortly after extrusion. The finished product is a denser and much more durable jacket that lasts longer and is resistant to scrapes and cuts. The mold-curing process is more expensive since it takes an extra step, however mold-cured jackets have been proven to last longer than CV cured jackets. G-GC mining cable comes rated at 2000V.
SHD-GC also known as shovel or dragline cable, is used for continuous mining electric shovels, conveyors, loaders and other mobile mining equipment. SHD-GC cable construction is similar to G-GC construction with a few differences. SHD-GC construction contains a separator tape around each conductor that allows for more flexibility, and an extra layer of insulation underneath the outer jacket. SHD-GC cable also comes with mold-cured or CV cured options. SHD-GC mining cable can come in 2000V and 4160V ratings. SHD-GC cable at the 4160 volt rating contains a tinned copper color coded braid around each conductor.
MP-GC cable, otherwise known as mine power feed cable is used to connect medium voltage distribution systems. As the name implies, it contains a ground and ground check cable, The conductors are stranded for flexibility and contains an insulating copper tape shield over each conductor which shields the conductors from the kinetic energy produced by high voltage. The insulation is ethylene-propylene rubber and the jacket can be either mold-cured or CV.
-Optional jacket configuration
Another compound used in jackets beside rubber is a material called thermoplastic polyurethane, or TPU. TPU uses “virtual crosslinking” polymers that enhance the strength and durability of the jacket. TPU jackets have been proven to have 5 times more abrasion resistance and twice as much tensile strength and tear resistance as compared to Chlorinated Polyethylene (CPE) jackets. TPU jackets are not meant to be stored for long periods on reels, as the jacket tends to create a chemical reaction that flattens the touching sides due to the heat generated.
Nexans, whose brand name for mining cable is Tiger Brand, has developed a reflective stripe than can be applied to the outer jacket of mining cable. These “Tiger Stripes” allow the cable to be seen at night when the lights of a vehicle such as a mining truck or loader are shined on it. I have even heard of applications where the reflective striped cable are used to line the roads leading to a pit at a mine site.
ATI Electrical Supply is a distributor of General Cable, Nexans, Southwire and Telefonika mining cable. Call one of our mining experts at 800-597-9311 today. We can help specify and provide pricing and availability for all your mining needs.