When the kiln tyre stops turning, the safety margin is gone. The alarm now sounded suggests the need for understanding the reason for this condition. Quantifying the magnitude of the problem will give us the options of what to do.

Two possible reasons:

A second reason is that the kiln tyre is simply jammed on the shell. It may not be free to rotate due to the introduction of a foreign object or a broken piece of one of its support elements into the gap. A wedged piece of steel like this will slowly rip its way along between the bore of the kiln tyre and the shell, stopping normal kiln tyre migration for the time being. This then is not temperature related but en kiln tyrely mechanical in nature.

Careful visual inspection may give evidence of which situation is at hand. But nothing is better than knowing what the usual range of kiln tyre-to-shell temperature difference is. Most kilns now have shell temperature monitors, like the "T-Scanner", from which a history of temperature differences can provide immediate assessment of the present condition. Foresight suggests that the preparation of a table of temperature differences vs. creep values will give a warning of incipient problems.

The mechanical condition is of less immediate concern. Ample and appropriate lubrication is the immediate "fix". When a shut down permits, the mechanical deficiencies can be addressed.

 Loss of clearance, on the other hand, may need immediate intervention. If due to a rapid warm-up schedule, slow it down. If due to partial loss of coating, changing the location burning zone by moving it back or forward, may be possible. Loss of coating, along with partial refractory loss, may be creating a "hot spot" underneath the kiln tyre which is reason enough for an immediate kiln shut-down.

A possible third and most difficult problem.

Sometimes insufficient clearance for normal operation exists. This often happens on an older kiln with a section replacement or filler bar (chair pads, or shell pads) repair, when the work has resulted in a fit that's too tight. Such a repair is expensive to reverse. It may be possible to cope with this for awhile, maybe even long enough for natural wear to create a passable situation.

  A snug kiln tyre, as long as it does not pinch the shell, has its benefits. A migrating kiln tyre unavoidably causes a lot of wear. A kiln tyre which doesn’t migrate would eliminate this wear, extending the service life of the parts considerably. Doing this by simple thermal expansion is risky, as explained, but if temperatures are monitored and controlled, it is no reason for immediate panic. New kiln tyre mounting designs using splined kiln tyres are available. They may be costly, but they certainly eliminate the problems surrounding this enkiln tyre issue. They should be considered when shell section replacements involving kiln tyres are required.

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