Inspection and repair service on ZPMC gearbox

This client from THE NETHERLANDS came to us with this ZPMC. We inspected the gearbox and performed a repair. After a successful test run we shipped the gearbox back to the client.

GBS has been instructed to find the cause of abnormal vibrations and strange noises from gearboxes. The complaints are described as follows:

"Gearbox gives great vibration which is easily felt in the floor"
"2nd cat hoist has a separate sound, possibly with input shaft or first stage"

The complaint descriptions have been partially confirmed on location, but there is no reason for action. Both the vibration measurements and the visual inspection on both gearboxes have yielded no observations of tooth or bearing damage. Both cabinets are in good condition apart from some small leaks and imbalance on the chain sprockets.

The raised position of the oil in the gearbox of the top work is worrying. The complete immersion of a gear transmission will cause resistance during the intervention of the toothing, similar to the operation of an oil pump, this will amplify the existing vibrations.

The most likely cause for the observed vibration is a combination of factors: imbalance in the sprocket and a 1st-stage gripper frequency enhanced by the increased oil level. It can therefore be concluded that the vibration is not the result of damage. ECT staff explained that this vibration in the cabin was much more prominent. It is plausible that the relatively low-frequency vibration is reinforced by the construction of the cab.

The noise described in the introduction to this document was not observed during the inspection. Both the vibration measurements and the visual inspection did not reveal any tooth or bearing damage. The case is in good condition apart from some slight imbalance on the chain sprocket.

Should the noise occur again and give cause for concern then it is recommended to perform a vibration measurement again this time unloaded, at full speed, 1800 revolutions.

We recommended:

- Ensure that the gear units are filled with the correct amount of oil, for example by fitting new oil level glasses
- To be able to detect the development of a damage on time every three months to perform a vibration measurement
- Carry out a yearly visual inspection (and increase the vibration levels or detection of error frequencies).