Improving condition of worn gearbox

CHALLENGE

A gear reducer was running rough and was very noisy. Visual inspection showed early signs of aggressive wear on a recently installed high speed pinion gear. There was also significant wear evident on the intermediate spiral bevel gear and some destructive pitting in the loading zone that appeared to be due to misalignment. Pitting was also present on both the intermediate pinion and final drive. Pictures below.

Stamler Crusher 072, Double Reduction Gear drive right angle Input: 1750 RPM Output: 188 RPM, running on 20 Gallon Mobilgear 85W/140 in splash Lubrication

OUTCOME

Before the treatment on May 2nd measurements were taken. Follow-up measurements were taken on June 19th. The results are as follows:

		Before	After
Amperage draw:	Under load	140	150
	No load	70	70
Temperature:	Final drive	153	135
	Intermediate drive	152	142
	Pinion	122	110
	Bottom of Box	152	136
	Top of Box	142	124

Most noticeable improvement is in the overall operating temperature. An average decrease of 10% was documented. Generally, in a continuous operating gear reducer, lower temperatures are good indicators of reduced frictional forces, and an improvement in the tribologic system.

Vibration readings may not be the most reliable measurements in this type of application since there is excessive and variable vibration. Due to existing wear patterns and misalignment the gear mesh noise and roughness was unlikely to be diminished significantly.

RESULTS

We met the Reliability Manager of the mine who commented that while the crusher described above coated with Rewitec was operating much better, a similar crusher in the same condition was damaged a month later. The replacement cost was above $80,000.

Given these results, the customer applied Rewitec Surface Treatment in all crushers′ transmission gearboxes. Under pressure to lower maintenance cost in the 7 digits, this technology will avoid damages to equipment and unscheduled downtime.

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