When properly installed and maintained, the trunnion roller assembly on your kiln can last as long as the kiln drum holds up – and that’s a good thing because your trunnion rollers must be kept in good condition. Besides holding up the kiln, they are essential in ensuring it rolls smoothly and evenly, which is necessary to maintain the heat envelope within the kiln.
If they aren’t maintained, trunnion rollers will begin to break down. If they don’t roll smoothly, they can start to introduce harmful vibrations which can damage every part of the assembly. In addition, the quality of materials produced by the kiln will drop as it becomes less reliable.
So, if your trunnion roller assembly has begun to have problems, what’s the solution? Does it need to be replaced, or can it be repaired?
Repairing vs Replacing Your Trunnion Rollers
In some cases, repairing the trunnions is an option, particularly for mild damage or basic wear-and-tear from heavy use.
The most typical option is called trunnion grinding. This is a method of resurfacing which simply grinds away the outermost layer of the trunnion, to smooth out the surface again. This can potentially be done several times during the lifespan of a trunnion.
However, the issue is that trunnion grinding causes irreplaceable material loss. Every time your trunnions are repaired, they lose a bit of their original diameter. This is not sustainable. Eventually, the trunnion roller will reach a point that it’s lost too much of its diameter to function effectively.
Generally speaking, the rule of thumb is 5% surface loss. Once the trunnion roller has hit that point, further grinding will do more harm than good – and that’s when replacement becomes the only remaining option.
If it is necessary to replace one or more trunnion rollers, the optimal strategy is to replace all rollers simultaneously. This allows for them to be properly balanced and ensures the resulting trunnion roller assembly has the longest possible lifespan. Otherwise, if one set of rollers is new but the other is old, the old rollers will probably have to be replaced at some point down the line – necessitating another expensive shutdown.
Typically, a single trunnion will take an experienced kiln repair company 4-8 hours to replace. Replacing multiple rollers at once can be done with a large enough crew but replacing the full set will likely still take a couple of days.
Also, as we are frequently asked: no, it’s not usually necessary to replace the tires as well. Tires wear more slowly and need replacement less frequently than the trunnion rollers themselves. Also, the tires can stand up to more resurfacing, and typically only need to be replaced once they’ve lost 10% of their diameter.
If you’re having issues with your trunnion roller assembly, Kiln Technology Company Company is here to help! Contact us to discuss your repair options, and obtain a free estimate on the job.