Large motor air filters - "poly" pre-filter

[electricpete]

Our large ODP/WP motors 4kv and above have standard removable metal filters ("viscous impingement" filters) internal to the motor housing. These filters can be removed for cleaning or changeout from outside the motor, but only while the motor is shut down due to safety reasons (what if some rust/debris gets sucked into the motor while changing the filter resulting in failure while someone is standing right next to the motor changing filters). Due to long extended runs required for some of these motors, we can't change filters as often as we'd like and we end up with problems - a lot of bugs drawn into the motors.... the metal filters no longer block once they are full.

Our motor repair shop mentioned that some customers add some kind of temporary disposable "poly" air filter accross the external air inlet in series with the metal filters (provided there is some thermal margin available to cope with slight decrease in air flow). The advantages:
1 - the poly filter is external and provides visual indication when it is full (debris all over the front)
2 - the poly filter is in series with the internal viscous impingmenet filter, so the poly filter can be safely changed while the motor is running without concern about anything getting into the motor.

Has anyone used these types of externally-visible poly filters?
Any link or more specific name of the poly material?
Has your experience with these been good?
Thanks


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[mlhspike]

I have used Scott Foam before during overhaul, heavy dust conditions to protect running motors from the dust and dirt. That might just be what your looking for.

 

[edison123]

"lot of bugs drawn into the motors.... the metal filters no longer block once they are full. "

You mean they block completely any air flow because of the "motor kill" ?


The idea of two series filters sound like a good one to me.

Questions I would ask

Are the poly filters mechanically strong enough to withstand suction forces of the fans, especially when the other metal filter is removed ?

What happens to the air flow (and cooling) when another filter is added in series ?

 

[Adalius]

I did PM work at a large batch facility and every single electric motor had a polyfilter cut to size so it could be wrapped around the metal canister intake filters and they were held in place with zip ties. Every 3 months we'd cut the ties and replace the filters, and then every year during shutdown we'd blow out the canister filters. After adding the polyfilters, it was noticed that the metal filters had very little if any particulate during their blowout.

As long as you're not impeding the airflow and cooling too much, they're a wonderful solution.