In the case where the rotary kiln is running for a long time in one axial position some wear pattern can occur. If the axial position changes a new sign of metal consumption will appear and add to the previous. When the mechanical wear will be severe as a result the contact between working components will be worst and also the pressure will be much higher.
Another point is lubrication. Due to high operation pressure the oil is squeezed and very often not effective. It causes a continuous and incremental consumption. Mechanical wear becoming faster and faster.
The user/operator of the kiln can even see on motor amperage chart. When the pressure and operation load is higher the amps increase. Too high pressure on the teeth can lead to failure (spalling, cracking) and forced, not planned kiln stoppage.
When teeth are gradually destroyed metal parts/fragments comes to lubricant causing father destruction affecting other components as well.
One of the serious sign of serious mesh damage is “false bottoming” This issue should be checked during each gear inspection. “False bottoming” kind of wear creating additional step on working teeth (both gear and pinion) and very often when root clearance changes create high vibration on drive station.
Different mechanical wear of teeth creates different wear pattern on working components surface.
Below some example:
- Heel and toe – this kind of pattern coming from the girth gear axial run-out. Higher wear will be observed on downhill part of teeth. The wear will be uneven.
- Cross – this pattern means that root clearance parameter is over tolerance – too low value. The reason of that wear shape can be also angular non-alignment of pinion and gear.
- Low and high – to low or too high value of root clearance.
- Short – the reason of this pattern very often is uneven and hard part of pinion teeth surface.
- Bridge – the root clearance can be too low and alignment of pinion is not correct.
- Wedge – main reason of this wear pattern is angular non-alignment between pinion and girth gear. The axis of this components is not parallel to each other. This situation means that is horizontal position of pinion is not correct or its inclination is different then kiln slope.
The correct wear and operation patters can be observed as even, full length and most of the surface contact mark in the area up to pitch line.