For seventeen years, the operation of the existing 40 massive coal pulverizer, weighing 110 tons each, has been plagued by an abnormal record of repairs and frequent replacements of the gear boxes, which were damaged by excessive vibrations. The cost of the replacement of the pulverizer was estimated at $200 million. The condition of the pulverizer foundation was suspected to be a possible cause. In spite of a number of extensive investigations, the findings were inconclusive and there was no consensus as to the cause of the problems and how to remedy them.

While with Ontario Hydro, Dr. Danay conducted a failure investigation program, which revealed that the condition of the pulverizer foundation is neither the cause of the excessive vibrations nor a factor in their aggravation.

The two most probable causes of the excessive vibrations were found to be the resonance of the grinding mechanisms with the coal grinding load, and the dynamic loading induced by adjacent pulverizer, which cause out-of-balance operation beyond the design limits.

Danay Engineering Ltd.