*HEPA Blower Lifespan Test*
Attwood Bilge Blower
By: Spitfire
08 August 2005

After I re-engineered our shelters positive pressure air filtration system to HEPA level ( New HEPA Filter )I thought it would be prudent to see just how long the blower motor would run before it died. The old system was designed to filter out Anthrax, and run for a few days to a week, but with the H5N1 virus on the horizon there is a very real possibility that weíll have to stay inside with filtered air for several weeks. Would the existing blower run that long? I didnít know.

I have always used an Attwood 3" bilge blower for filtration tasks like this. Itís an inexpensive unit that runs on 12VDC, puts out lots of air and just happens to fit nicely into 3" PVC drain pipe. The motor inside the blower is one of those cheap metal cans with plastic end caps. The motor bearings are simply molded into the plastic ends and the motor brushes are just pieces of beryllium copper pressing against the commutator. How long could something like this run anyway?

Since the old filter box wasnít up to HEPA levels and I was going to throw it out anyway, I decided to do a life span test on the blower motor. I bolted the old filter box back together and plugged the bilge blower into the 12VDC battery bank determined to let it run until it died. After a week, Wifee was beginning to get annoyed with the noise down there, but after 2 weeks we were both used to it ;)

To make a long story short, the blower lasted one month running 24/7. The failure mode was the beryllium copper brushes carving slots in the commutator until it shorted out. In my mind one month isnít nearly long enough and I will be getting a better squirrel cage type blower with sealed ball bearings for a permanent solution.
Spitfire



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