Fans are more similar to centrifugal blowers than to positive displacement blowers. In fact, fans can be further classified into 2 types: axial fans, or centrifugal fans. The floor mounted fan in your house, or the more common ceiling fan in your living room are both types of axial fans. The air flow is directed axially(in line with the shaft) to usually cool thinks off.

 

Centrifugal fans can be designed with many different types of impellers, or with squirrel cages, or other special designs. They usually draw their air, or gas, from a center inlet, and discharge to the radial side(perimeter) of the spinning rotor. As with centrifugal blowers, they would be considered vacuum exhausters if the work is on the inlet(sucking).  

 

When I compared PD performance to Centrifugal performance last month, more than one of my readers were quick to correct me. PD blowers can't produce 80 lbs of pressure. Most of them will max out at 15 - 20 lbs/in² same as centrifugals. Fans will compare equally with the centrifugal blowers in performance, but they will generally produce greater volume with lower(even fractional) pressures/suction.

 

Fans are not cast iron blowers. They are usually made of less expensive rolled steel, with welded frames. Fans are used in a much wider variety of applications, from laptops, to furnaces, to cooling towers, to large factory induction fans. They are not used in most of the applications as PD and centrifugals.   They are usually providing air to feed something: boiler, furnace, ventilation system.

 

Fans do compete with centrifugals in vacuum system applications, especially landfill gas extraction. They may not be as efficient as centrifugals, but their low cost and variability make them viable alternative.

 

As far as maintenance and durability is concerned, fans may require a little more PM due to their being v-belt driven, but almost all PD's and many centrifugals can also be belt driven. Fans can become "out of balance" with heavy dirt build-up, or damage to the fan blades, but they are relatively easy to correct for imbalance(with the right tools). Centrifugals and PD's are only balanced during manufacture, or reconditioning.  

 

Although there are some crossover similarities, fan blowers are totally different animals than centrifugal blowers. The mechanic/technician won't see much difference in the maintenance mechanic/technician mechanic/technician mechanic/technician, but the application engineer could not very easily substitute a fan for a centrifugal blower application.

 

The common thread between these 2 types of equipment continues to be the bearings. Often the same type-single roll ball bearing with grease or oil lube. So the preventative maintenance is the same to keep your equipment operational. Invest in PM, it will save you money!

 

 

Copyright © 2015   Snyder Technical Services, LLC.  All Rights Reserved

Maintenance Minute is published each month by Snyder Technical Services, LLC and is based on the work of former Lamson National Service Manager, Bill Snyder.   Should you have any questions, or problems to discuss, please contact me.

Sincerely,