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