Inspection and overhaul on ZPMC gearbox

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

The state of the gearbox can be described as good. The complaint description has been confirmed on location, the singing sound has been observed. During the downward movement of the boom, the vibration measurement was performed. As a result of the vibration measurement and visual inspection, it can be stated that there is no reason for direct action.

The gears and pinions are in good condition. On the pinion of the 1st stage, slight markings of the first stage gear are visible on both the loaded and unloaded side

The oil sight glass showed a minimum oil level for turning the gearbox. After the boom has been lifted up and down, a lot of foam has been detected in the oil, which may indicate water in the oil. The combination of a low oil level and a lot of air in the oil can cause insufficient lubrication. This can cause both the visible impressions on the pinion 1st stage and the perceived noise. At the same time, the indentation on the pinion 1st stage may indicate a too small flank clearance which may partially cause the singing sound.

No indications for bearing damage were observed in the measurements on the gearbox and the electric motor. An increase of GMF1 has been measured on both the gearbox and the electric motor, which indicates a non-ideal toothed ripening. Since no damage has been observed, this increased GMF1 may be the sole cause of the perceived noise.

Recommendations:

- A oil analysis
- Provide the correct quantity and quality of oil with the gear unit
- Carry out a new vibration measurement after correcting the oil level or replacing the oil
- Measure the flank clearance of the 1st stage and carry out further inspection if the complaint continues
- Perform an annual vibration measurement and visual inspection.