Surface damage of tire is very important symptom of failure. The metal failure that can appear on running surface could be a spalling. There is always some metal shape deviation especially in contact point between tire and roller. On the microscopic point of view this can be analyzed as flat contact area. When the axial run-out is getting higher or for any other reason the load on the contact line changes the stress is higher than elastic limit of rotating components. The crack appearance is possible between them. In an extreme case spalling and the reason of it can lead to tire crack (and even to crack in half).
Chair pads wear and broken welds.
Worn out chair pads (or damaged) and as a result loose tire causing high ovality readings. To assess how flexible kiln shell is measurement of ovality in necessary. This parameter is significant when we are consider refractory lining condition.
High ovality, tire migration and excessive axial force causing the stop-blocks damage. Visual inspection should include checking of area between working parts. It gives a lot of useful information to experienced diagnostician.
Also heavy side loading of the tire against retainers will cause the damage – the welds can break, the bolts may shear. Base on this kind of symptoms we can tell that something is wrong. Most of problems of this kind is caused by not correct skewing of rollers or crank formation in the shell. There are many other reason as well. Repairing, or replacing broken parts not always resolve the existing problems. Important is to fond the reason of symptoms.
If the problems with tire condition is serious the user may have to one thing to do – replace the component (tire or roller). If it is possible to identify the problem earlier the correcting work would be to grind the surfaces. The Important is to grind both rollers and tires surfaces at once. Also if there in not serious reasons (only normal mechanical wear) of chair pads and stop-blocks wear the replacement may be enough. Also by re-shimming we can bring tire migration to operation tolerance zone.
Another failure possible – shell segment collapsed under the tire. To resolve this problem replacement of shell segment must to be performed. As we know shell segment replacement is very expensive that is why resolving the problems on the beginning (based on the first symptoms, deviations) is so important. Proper preventive maintenance procedure allow to save money.
Procedure for chair pads replacing:
- Determine that bars are excessively worn
- Check for collapsed shell
- Take measurements of existing bars
- Determine the design of the new bars
- Make notes on condition of components (temperature, damage, noise, position etc.).