RE: Blower Design

From: <Steve>
Date: Sat Oct 18 2003 - 17:57:00 EDT

Hi Thomas

one of my clients uses a lot of blowers for providing flotation air. They are normally fairly troublefree.

Your pressure is a bit low to justify the expense of a reciprocating compressor.
Same for a screw although you could probably find one The best selection for your application will most likely be either a multistage centrifugal or a lobe(Rootes) blower. If you google Gardner Denver you will see a good selection. There are many other good brands.

Things to watch out for:
Correction for altitude. 'nuff said, but it does get overlooked sometimes Surge. Many centrifugal blowers operate with a fairly small performance envelope. If the discharge is throttled too much, pressure fluctuation and unsteady delivery will occur.
Pulsations. Lobe blowers give a slightly pulsating flow. Normally this does not matter, sometimes it does.
The supplier should give you a pressure/flow "map" which shows the operating zone.
Noise. A lot of blowers are very noisy. You will almost certainly need at least an inlet silencer on a Rootes blower. Some centrifugals are fairly quiet.
Temperature rise. There will be appreciable difference between inlet and exhaust air temperatures.This can become excessive under throttled conditions if not designed correctly. Some Rootes blowers are installed with a pressure relief valve to prevent this. Flow regulation. If you need a variable flow then this needs to be thought about carefully. Normally its not that difficult but sometimes it can bite. Sufficient access to change lubricants and carry out routine servicing.

Appurtenances. As a minimum, consider the following.

Check valve - only required if flow reversal can really happen (e.g. standby unit fitted). Normally fitted as a matter of course. Blow off/divert/throttle valves as required Vibration mounts and flex joints
Air Filter. Most important with blowers having metal to metal contact. Silencer(s) if required
Pressure and temperature gauges
High temperature trip switch

Hopefully thats enough to get you started.

Cheers

Steve McKenzie

-----Original Message-----
From: Thomas Laupa [mailto:tlaupa@frii.com] Sent: Sunday, October 19, 2003 2:47 AM
To: PipingDesign@yahoogroups.com
Subject: [PipingDesign] Blower Design

Gents:

need some help selecting an air blower.

working on an air scour system for a large filter. air scour requirements are 150 cfm @ 5 psig. in effect, we are taking ambient air and blowing it thru a water filter during backwash to "stir it up". site is remote, and unattended. looking for a reasonably priced "air pump".

don't have much experience with blowers. and after a catalog search, it looks like there are several types (lobe, rotary screw, helical screw, reciprocating).

>at this operating condition, what types make sense?
>does one provide discharge check valve, block valve, and PRV like a water
pump? what other appurtanances are necessary?

thank you in advance for your help.

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Information presented on this list is given as helpful advice, nonsense, carefully-considered calulation or any combination of the above. The intent is to spark discussion and encourage knowledge-sharing amongst professionals. If you blow yourself up by doing stuff remotely described by info gleaned from reading this list, you are an idiot.

Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ Received on Sat Oct 18 17:57:00 2003