New Couplings Stop The Hunt
A change from gear couplings to rubber-in-compression couplings has completely cured a problem with motor hunting on a huge inclined conveyor at a drift mine in Wollogong, Australia. The metre-wide conveyor is nearly half a mile long and transports coal downhill at a rate of approximately 900 tonnes an hour. The 750kW electric motor was hunting during DC injection braking as a result of backlash in the gear coupling.
To solve the problem Renold Hi-Tec Couplings, of Halifax, supplied a rubber-in-compression coupling with pre-compressed rubber blocks. This type of coupling offers zero backlash operation and in this application was fitted to the head shaft of the conveyor and is driven by the motor through a 15:1 reduction gearbox. The new coupling has completely cured the problem of hunting and the motor control system is able to drive and stop the conveyor smoothly.
An added bonus to the plant operator is the fact that the rubber-in-compression coupling Renold Hi-Tec supplied is maintenance free and offers a significantly lower lifetime cost than the previous gear coupling. Gear couplings require regular lubrication and needed changing every two-and-a-half years. The new rubber-in-compression coupling requires no lubrication and is unlikely to require any attention for at least ten years.