July 23, 2008

The last few days have been busy but “sweet”. With a group of researchers from Peshawar University I went to the Premier sugar mills located just on the out skirts of Mardan town. Our visit was just at the right time because maintenance of the mill was under way and Mr Sarwar Jan, the mill engineer, explained the challenges on keeping a sugar mill running throughout the season without break down.

The Premier sugar mill is one of the oldest mills in Pakistan and was constructed in 1949 by the George Stewart Company in Derby, England. The mill has a 4000 tons per day sugar rushing capacity Sweet crop: Tahir Khan stands next to sugar cane being grown for next season at Pakistan's Premier sugar milland has seen very little technological upgrading since 1949! The corrosive and abrasive wear of the processing machinery is a severe problem and rollers shell surfaces must be rebuilt and repaired by “hardfacing” after the sugar season is over. Some of the severest wear is experienced by the thrashing hammer and cutting blades at the start of the processing mill.

After discussions with the Manager of the mill, Mr Abdul Qadir Khattak it was decide that some parts of the mill parts will be treated using micro and nanocrystalline cermet coatings developed at the University of Calgary and then installed in the mill to compare performance with untreated blades. There is still a lot of investigative work to do, for instance, why are the hardfaced weld deposits failing faster than the worn untreated surfaces? Could this material contribute to further chipping and wear of the roller shells deeper in the mill? There are no tribo-testing machines or ASTM standards for wear testing for this kind of processing machinery and I am helping to set up a wear testing rig at Peshawar University which will simulate the sugar mill service environment so that the mechanisms of surface wear can be investigated.