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After two years study and analysis of the operating behaviour of the rotary dryer at the Malaysian fertiliser plant, it was decided to renew the thrust tyre.

This is one of two cast steel tyres which rotate on support rollers and hug the shell of the dryer. It was not like changing a car tyre; everything is on the grand scale. The dryer is a 14ft diameter x 112ft long vessel, while the thrust tyre is a 17ft diameter unit, weighing 15 tonnes. Space was constrained, the building having been put up around the equipment at the time of initial installation back in 1965. But careful planning led to the job being done safely and successfully in 12 days in December 1993, working 24 hours a day. The dryer was commissioned and test run to great satisfaction the day after the work was completed.

The surface of the thrust tyre, which is around the inlet section of the shell, had been steadily deteriorating ever since 1985. Heavy pitting and flaking had caused the tyre to be 'out of round' at certain areas. This meant eccentric rotation of the shell which resulted in heavy impacting and damage to the foundations and the drive gear. Back in 1989, the tyre was linished on-site to remove all the flats on the surface, this was done in collaboration with Dresser Rand (UK) and HW Technical Services Ltd (UK), consultants on the technical operation of the dryer. Two years later however, the tyre began again to show signs of deterioration on its surface - this time more rapidly. Within 1-2 years it was as bad as before.

Such rapid deterioration was unusual as linished tyres had been known to remain in good condition for 5-10 years at least. So a thorough analysis was carried out to determine its cause. After a study and discussion with ICI Australia Engineering Ltd and HW Technical Services Ltd, the diagnosis was that large numbers of cluster porosities in the original castings were being exposed by wear and tear, and then collapsing and forming flat spots when impacted. Prior to the renewal, the old tyre had eight areas which had become flat (the tyre was octagonal) with the severest depression being almost 1/2" from the true circumference.

HW Technical Services Ltd were appointed to supply the new tyre because of their proven expertise over the past 28 years and being the lowest bidder in their competition with leading companies from UK, Australia and India. They were also the technical consultants for the job. The total project cost Malaysian $900k (237k).

In face of the 'acute space constraints' engineering expertise in conceptualization was stretched to the limit in planning the renewal. After two months of detailed study of the building structures, drawings and beam designs, a safe, cost effective and easy route and method of removal were determined. Modifications and additions to steel structures were carried out after detailed design study with the appointed civil consultant. The same care led to speedy installation of the new tyre, making it overall a tremendous project, 'a once in 28 years' experience!

'Reprinted from "The ICI Engineer", This production facility is now owned by CCM Fertilizers Sdn Bhd'