Motor Air Filter cleaning schedule 5

[electricpete]

Our large motors have metal screen (viscous impingement) air filters. They are not cleaned regularly... instead we
clean them if we see abnormal temperatures. This is based
on our historical assumption that these filters act similarly to disposable household filters which decrease air flow as they clog up.

I just read in Nailen where these types of filters may not decrease air flow when they are saturated with dirt... they just stop removing dirt. Our motor repair vendors have often
remarked how dirty our motors are (particuarly outdoor motors). I have in the past attributed this to excessive bugs etc in our environment but am now changing my opinion to consider that it may simply be our misguided filter replacement practices.

I will contact the filter manufacturers for recommendations.

In the meantime, I'm interested to hear how other plants manage their filter cleaning... on a periodic time basis or based on motor temperature?

 

[don01]

Hi electric pete
I can't say as how i've had this situation too often on the motors them selves
But I have on air duct inlet systems.
The general solution is too put a low range (pa) or "water guage pressure switch.
I have found even better is a differential pressure guage like magnehelic make to to read the dp across the filter. use this as an indicator of need to clean.

If you mean cintered bronze type fiters you should see some rise in dp
but I could (as usual) be wrong.

I really think monitoring the dp will give you an indicator but what the bench mark should be I don't know. Its usually application specific. eg bag house but if you don,t get much of a response I'll ask around some of my suppliers.

Regards
Don

 

[THooper]

Hi electricpete,
One of the most reliable options is to install a pressure gauge to sense the pressure drop across the filters. When that reches 1/4 to 1/2 inch of water, it's time for filter cleaning. We perform on site service motor maintenance and part of this is filter cleaning and setting scheduling for several different types of plants and industry. Each one we have found varies considerably due to the environment the motors and filters are subjected to. The most effective plan our facility has found is to check conditions frequently until a reasonable cleaning schedule can be established through experience. Their is a complete chapter on this subject in Richard L. Nailen, P.E. book called Managing Motors. Maybe this is where you have already received the information you have thus far?

I would like to add and make a suggestion for any open drip AC motors in harsh, dirty, abrasive debri, or moisture exposed environment. We have instituted since 1995 the application of Dow Corning 1890 protective compound, which is designed for abrasion resistance in open motor windings. The coating causes these abrasives to actually "bounce off" rather than "skid through" the motor slot sticks and coil insulation coating. Moisture can't seep through, abrasives can't wear in. In one cement plant, we extended the winding life of a 5000 hp 4160 vac finish mill synchronous motor for 6 years with an annual application of the coating.

NOTE: Would not recommend this in any DC motor application due to the silicone additives in this product.

Kind Regards,
motorhead1

 

[jbartos]

Suggestion: Visit

http://www.exnet.iastate.edu/Information/Flood/Leave_Cleaning_Motors_to_Specialists.html

http://www.ag.ndsu.nodak.edu/flood/wetmotor.htm

etc. for more info. However, the manufacturer instructions and tech support shall not be underestimated since the manufacturer may have the most detail information, hard to reproduce or imitate.

 

[GordS]

electricpete...We change filters in our motors every 3 months. This number is based on our experience in our plant over about the last 20 yrs. We cange the filter while the motor is running so there is no production impact.

 

[dynogod]

Dear Electricpete -
I work with 2 large (600 hp) GE DC electric dynos. I think I've taken filtration to the next level. Ours just had a piece of expanded metal over the cooling air inlets, and they somehow survived for many years with occasional rebuilds.

After the last set of funky brushes were removed, I bought a set of K&N filters and installed them. These are the type used on Baja race trucks, and are available in a number of configurations, both flat and circular. You can get them at your local race car parts store, or contact K&N online - I don't recall the site address, but found them easily using Google. Our set-up needed 12" diameter, and we picked the tallest ones they had - about 8" high. A simple stud and they bolted right up.

Currently, I am cleaning them once a year, but the idea of a pressure sensor is a good one. The K&Ns will definately increase pressure drop with loading, so this would work well for us. By the way, these filters have a 1,000,000 mile warranty, and can be cleaned indefinately. In our test cells, we found that you have to pre-clean them in the parts washer before using the K&N cleaning kit.

Hope this helps

 

[THooper]

I ran an average on service reports of numerous filtered motor applications from the past 10 years and came out right around 90 days also.

I would like to respond for the readers that: Manufacture tech support should not be underestimated!! But strongly believe that it would be very unlikely for any manufacture to have a field test study of 20 years history like Gords post, which would be hard for the manufacture to reproduce or imitate...

I know of numerous incidents when several MAJOR manufactures have consulted with our facility and repair methods for corrections we have made improving some of their motor products and performance.

We all have heard that saying: We don't make the products they make, we make the products they make better! "that statement should not be underestimated in many cases or applications with proven performance and substantial backing of course!!!!

No shots intended, just making an honest statement.

Kind Regards,
motorhead

 

[jbartos]

Suggestion: If the motor air-filter replacement is posing any inconvenience, one may consider other forms of cooling, e.g. liquid, gas, or installation of the motor and load in a cool room (perhaps refrigerated).