A Case Study on Enhancing the Service Life of Rotary Dryers

摘要

ZIL is operating a dryer supplied by M/s TEC of Japan enclosed in their NPK plant for 30 years.The dryer having welded tyre construction failed prematurely and the same was changed over to loose ring type tyre support.Over the years due to corrosion and ageing,cracking of the dryer shell were encountered,predominantly at the centre and other locations.Initially,it was decided to replace the dryer with a new shell as the shell plate has thinned down drastically from 16mm to as low as 8mm at certain sections.However,due to high erection time of 60 to 65 days,it was decided to increase the service life of the dryer by another 3 to 5 years by reinforcement.Hence,in 1997 ZIL design modifications were carried out and other teething problems were sold.The modified dryer performed well till 2003.Meanwhile,various modifications were carried out to increase the capacity of the plant which put additional load on the dryer leading to bending stress on the middle of the dryer which caused periodic cracks in that zone .It was again decided to further reinforce the dryer so that the life can be extended by another 2 years,which will be adequate to replace the dryer with a new larger dryers to take care of the increased production.The reinforcement of the dryer was carried out in-house.The dryer has operated one year without any down time due to the shell cracking at the middle zone and still in operation and expected to be replaced by a new one in the first quarter of 2006.The article gives details of the modifications carried out to reinforce the dryer in 1997 and last year.