Stress-Wave Investigation Reveals Damaged Gear in Tunnelling Machine
Reliable Road Tunnelling machines are fundamental to the efficient operation of the mining industry and a key element within these machines is the cutting boom, which undergoes regular on-site maintenance and periodic overhauls in the workshop. After one such overhaul, a small knock, believed to be coming from the coupling, was identified and PCMS were asked to investigate and certify the gearbox was fit to be returned to operational service.
At selected points on the boom, readings were taken using Stress-wave and Standard Vibration Analysis. Whilst the standard vibration spectrum and wave form showed no unusual cause for concern the stress-wave readings at point G5, (Fig 1) and comparisons with readings from other points, indicated to PCMS Engineers a broken or damaged tooth on the third motion shaft (see Fig 2).
Closer examination revealed the existence of a cracked tooth on the gear (Fig 3).
As a result of the investigation, the boom was completely rebuilt with new gears and a further set of readings taken. These confirmed that no impacting was taking place and the boom could be safely returned to operational service.
If the boom had been returned to service with a cracked gear, further deterioration to the gear would have been rapid. If the tooth had sheared and become embedded between the gears, secondary damage could have been extensive, leading to considerable loss of production as well as the high costs of
major repair or full gearbox replacement.