Bulletins

Quench Fan Integrity

Ref: 05
Rev. Date: Oct-31-1996

Quench fans are designed to operate for years. However, a quench fan impeller failure can be catastrophic with the risk of personnel injury, property damage, and extended downtime while repairs are completed and/or replacement parts are being procured.

A fan in continuous duty can rotate more than 200 million times in just three months. Heavy duty impellers used in cyclic ramping service with variable speed drives are under the heaviest loads. The fluctuating centrifugal stresses induced under those conditions can create fatigue loading.

All fans should be checked at least quarterly, regardless of type of drive or usage. The following procedures can ensure safe and continuous operation with a minimum level of maintenance. Please recheck your manufacturer's manual for specific recommendations for your fan units.

Glasstech recommends the use of vibration and/or bearing temperature instrumentation systems to provide an early warning of potential trouble. Sophisticated systems can actually shut down the fan at preset threshold limits.

As a safety precaution, fan rooms should have limited access, with signs posted stating that both noise and equipment hazards are present.
Inspect all rotating parts on a scheduled basis.
Fan bearing and coupling alignment should be checked regularly. Misalignment can cause overheating, wear to bearing dust seals, imbalance, and bearing failure.
Lubricate fan bearings regularly with a lubricant recommended by the manufacturer. Lubricate to about one-third of the volume of the housing. Do not over-lubricate, as this could cause overheating.
Inspect fans for wear and dirt buildup. The impeller wheel may require cleaning with steam or a water jet. If so, cover the bearings to keep them dry. Also, check impeller welds, hub-to-shaft tightness, and set screws.
Do not permit vibration or high bearing temperatures. Typical causes can be: imbalance, misalignment, loose belts, over or under lubrication, or dirt buildup on the wheel, etc.
Check inlet vanes (where applicable) for loose linkages and amount of lubrication. Check the inlet air scroll position and verify the correct interface.
Make sure all housing and foundation bolts are tight.