Chemical manufacturer saves £18,000 on recurring drive problem

Thermphos UK is a manufacturer of special chemicals used in pharmaceuticals, hygiene, industrial cleaning, household cleaning, food additives and feed additives. The company's six main products are produced in a rotating kiln, each operating at its own temperature. The different characteristics of the products mean the kiln must operate in a wide temperature range and the highest temperatures can produce a 40 mm expansion of the kiln. This expansion caused problems because the kiln was originally driven by a girth gear around its circumference. Thermal expansion meant that the gears were threshing, leading to high wear and frequent replacement. Mike Organ, works engineer for Thermphos, says: "The gears cost £18,000 to replace and we needed to replace them on average every two years. It was also becoming increasingly difficult to source companies with the expertise to make these large gear assemblies." Another difficulty was reversing the kiln to remove the product at the end of the process. The increased forces caused by the unloading mechanism threatened to throw the kiln off its supporting trunnion rollers. Thermphos asked ABB distributor Halcyon Drives to design a solution. "Halcyon is our preferred supplier," says Organ, "and we knew that with the support of ABB, they would know how to do it. We have a number of ABB drives on site and we have a good relationship with Halcyon." The power transmission rotating the kiln was updated and redesigned using two motorised gear units which drive friction rollers to rotate the kiln drum. They are controlled by two ABB industrial drives in master/follower control, allowing load sharing. Using two driven rollers ensures that movement due to heat can be tolerated, allowing a wider range of production temperatures. Employing a master/follower arrangement also cuts the need for a feedback encoder, which could be affected by the dusty conditions. Another advantage is the ability to reverse the kiln direction more easily, allowing it to be emptied much more quickly, increasing productivity. "With the new system, we don't have to worry about gears, "says Organ. "We no longer have the major replacement costs and we can run the kiln at any speed we need, using less power."