Kiln Trunnion and Tire Seal Repair

The challenge

A rotary kiln rides on trunnion rollers that carry the tire and hold the shell on its running line. Over time the roller face and the bearing seats lose metal, the contact across the tire goes uneven, and the kiln starts to track off true. At the same time the seal area near the hot shell loses metal and opens up, letting air in around the kiln. When the contact is uneven and the seal leaks, the kiln runs rough, the bearings see uneven load, and the process loses the control that comes from a tight, true shell. The usual fix is to machine a new roller into place, which is slow and pulls the kiln out of service.

Our approach

We assess where the metal has been lost on the trunnion roller face and the bearing seats, and we look at the seal area to see how far it has worn. We clean and profile the worn surfaces so the repair bonds, then rebuild the roller face and the bearing seats cold with a machinable composite. Once it has cured we dress it back to the running line so the contact across the tire is even again. Around the seal area we apply a coating rated for the heat off the shell, so the steel is protected and the seal runs against a sound surface. The kiln goes back on a true running line without machining a new roller into place.

1. Assess and map wearWe inspect the trunnion roller face, the bearing seats, and the seal area to map where metal has been lost and confirm the running line.
2. Clean and profileWe bring the worn surfaces back to clean, profiled substrate so the composite and the coating bond.
3. Rebuild the roller and seats coldWe rebuild the worn roller face and bearing seats with a machinable composite, with no hot work on the shell.
4. Dress to line and coat the sealWe dress the rebuilt metal back to the running line for even contact across the tire, then coat the seal area with a system rated for the heat off the shell.
5. Return to serviceWe check the contact and the coating and hand the kiln back on a true running line.