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[July 2002]
Kiln Tyre Grinding Restoration Eliminates Risk of Shell Cracking
In order to eliminate the risk of a cracked casing on one of its china clay drying kilns, Imerys Minerals (St Austell, Cornwall, England) called upon Metalock Engineering UK (Exhall, Coventry, England) to in-situ machine one of the tyres on a 41 year-old kiln to remove the effects of wear. Vibration caused by tyre wear can result in cracks in the hot metal shell of a kiln and also the internal refractory lining can become detached and break away, contaminating the product.Kilns used for china clay drying operate at 1080°C at the hot end down to 600°C and revolve on circumferential tyres running on support rollers. A typical 15 metre-long drying kiln used by Imerys has two tyres and the kiln is rotated by a rack and pinion system.
Tyres tend to wear unevenly as moisture removal while the china clay progresses down the kiln reduces the weight supported by the rollers. The tyre in question had reached a stage where it could no longer be tolerated due to the degree of vibration it was causing.
Metalock Engineering undertook to regrind the most badly worn 300mm wide, 4m diameter steel tyre. The kiln needed to be stationary while Metalock set up its purpose designed equipment but as the tyre needed to be revolved to grind it, normal production was resumed thus reducing downtime to a minimum. Normally, a kiln will run continuously 24 hours a day all year round.
Although Metalock had originally planned to restore only one tyre at St Austell, such was the success that it was asked by Imerys to repeat the operation on a second identical tyre on the same kiln while on the premises. Metalock was on the site for five days for the set-up and dismantling and the regrinding of two tyres to clean up and restore roundness. During three of those days, production continued as normal.
ENDS