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Edition #11 Sept 2011 
Expert Cooling Tower Repair Newsletter
Tower Topics
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Cooling Tower Bearings

 

Bearings are an important cooling tower component.

 

Gear boxes and fan motors use bearings installed by their respective manufacturers.

 

Cooling tower manufacturers occasionally use flange mount designs but most are pillow block type. [Flange mounting bolts are parallel to the shaft while pillow block bolts are perpendicular.]

 

Ball Bearings are used on the drive end of virtually all V belt applications because of their ability to withstand high radial loads from belt tension. They are also found elsewhere on larger towers and are used for their ability to handle the dead weight of  large components. They are grease lubricated via zerk fittings. On vertical shafts, the bearing most distant from a V-belt must be locked to the shaft first. This way it is purely thrust loaded while the bearing near the belt becomes exclusively radially loaded. An improper locking sequence could have only one bearing handling both the thrust (dead weight) load and the radial (belt tension) load simultaneously leading to shortened bearing life.

 

Sleeve bearings are found on small towers away from the v-belts. The sleeve is machined from cast bronze with graphite filled grooves. Lubrication is by oil introduced via oil cups.

 

It is essential that fan shafts rotate in place. If the fan shaft moves longitudinally, fans will begin to scrape stationary components- not to mention having problems with belt misalignment. Since current designs always have at least one ball bearing, the fan shaft can be secured in place by locking the inner race of any ball bearing to the shaft with an eccentric locking collar. All ball bearings must be locked this way to prevent relative motion between the inner race and the shaft. If the inner race 'spins' on the shaft, quick failure will result.

 

Always use manufacturer recommended lubricants. It is particularly important that conventional motor oil be avoided with sleeve type bearings. For more info, see www.expertctr.com/ch_8.php


Don Davis
Expert Cooling Tower Repair, LLC