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| Welcome to the Centrifugal Blower Maintenance Minute,
the 60 second newsletter designed specifically for centrifugal air & gas blower operators. Each month we will feature a different aspect of service and maintenance to centrifugal blowers. We will review operation, troubleshooting, actual case histories, and answer reader questions. |
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| Not enough flow? --- Why?
 There are more than a dozen reasons why your centrifugal blower will not give you enough flow, but 90% of the time, it is simply a restriction on either the inlet, or the outlet. It either can't get enough air, or gas, or there is a blockage in the outlet piping preventing it from getting out! "Not enough suction", or "not enough pressure", also means low/restricted flow. The most common cause: dirty inlet filters, clogged water separator tanks, or just a closed inlet valve.
If all is OK on the inlet end, then you look at the outlet piping to be sure all valves(including check valves) are physically opening(not just indicating open). Diffusers will clog up over time. They are also not leakproof. If no air pressure is present in the diffuser piping, water will leak through the rubber diffusers filling the piping with water that will take time for the blower to push out, if it can! The flare flame arrestor filters are also notorious for clogging & restricting flow.
 If the inlet and outlet piping appears to be unrestricted, then you start looking at some other common causes: incorrect machine rotation; gauge not reading accurately; improper design, or assembly, of piping system; and decreased motor speed. All multistage centrifugals are originally designed to operate at 3600 rpm(60 Hz.) A decrease in blower speed will dramatically decrease the blower performance, much faster than any mechanical butterfly valve. Incorrect voltage or incorrect phasing could decrease the motor speed, but the more common VFD's can reduce performance very easily. A simple, hand held, optical speed tach can easily tell you how fast the shaft is rotating.
Foreign material, of any kind, will reduce flow. Gaskets, plastic bags, wire, & dirt are all easily "sucked" into the blower inlets. Removing the inlet piping and looking into the inlet head can tell you how much dirt is being sucked into the blower. You can always see the inlet vanes of the first impeller to determine how much clogging you may have.
Not so common, but entirely possible, causes of low flow could be incorrect re-assembly of the blower, worn out impellers, or increased inlet temperatures and/or pressures. The factory, 99.9% of the time, does not incorrectly build a blower. Blower rebuilders, however, have been known to do it regularly.  Impellers will wear out, especially if subjected to abrasive materials. A spark plug manufacturer used a blower to vacuum up the porcelain "dust". After a couple of years, you could put your finger through the aluminum impellers, it was so thin. Decreased performance, whether flow or pressure, is not mysterious! It can easily be determined with a logical approach to troubleshooting.
© Copyright 2009 Snyder Technical Services, LLC. All Rights Reserved
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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.
Bill Snyder
Founder - Snyder Technical Services, LLC |
| Next Month:
Blower Design & Assembly |
| Thought for Today:
"Failure,
is the opportunity to begin again
..............more intelligently."
---Henry Ford
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