Keeping water out of bearings on a TEFC motor

[twidgett2]

When the motors, in a dirty atmosphere are cleaned with high pressure water, water gets into the bearings, causing them to fail.
I think the bearings are the weak link, rather than the motor frame joints.
I am looking for a bearing configuration which will prevent water contamination and damage.

 

[electricpete]

We have a similar problem but I haven't looked at available solutions too closely yet.

There are a variety of sealing configurations offered. Sealing of the bearing itself as well as sealing of the enclosure.

Ex-member jOmega sent me an e-mail on this exact subject. I'll try to forward the info when I get home.

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[SteveKW]

If it is the bearings, the bearing grease will have water in them.

Have you looked at labyrinth seals or motors equiped that way?

 

[edison123]

pete,

Ex-member jOmega ? Why ?

kumar

 

[jbartos]

Suggestion: Visit

http://www.ryko.com/Italy/contour manual.pdf

for:
Waterproof bearings

http://www.smbbearings.com/smbapplications.htm

for:
Waterproof lubricants

 

[electricpete]

I have corresponded with jOmega by email.

He left for some personal reasons.

He has a web page at:

http://www.ticon.net/~jomega

The e-mail address at that web-page is a little different than the one he uses to correspond with me. I have e-mailed his address to you kumar. It probably wouldn't be a good idea for me to post it here on the board.

His advice to me when I asked a similar question:

"For motors in outdoor service, DC, Squirrel-Cage, WR, Synchronous, etc; I've always spec'd sealed bearings or IMPRO seals for the bearings. I don't like WP class enclosures..and prefer TEFC or TENV with thermostatically controlled space heaters. The extra cost is well justified in downtime and maintenance savings."

So mostly I think it amounts to specing sealed bearings. If it's an existing motor, with some effort the bearings can be replaced with sealed bearings (with a little evaluation to ensure they won't overheat).

I have seen writeup of many other features used for sealing the clearance between shaft and housing. Forsheda V-ring etc. Sorry I don't have much more info. For new motor I'm sure distributor would be helpful.

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[jbartos]

Suggestion: After visiting the JOmega website, I would recommend an additional reference, for example:
Bimal K. Bose "Modern Power Electronics and AC Drives," Prentice Hall PTR, 2002
to continue with the topic.

 

[SteveKW]

Reading your post I begin to wonder if putting a band-aid on the "effect" is the answer.

Take a closer look at the "cause"!

RTV the joints where the end-bells mate to the stator.

Don't pressure clean the shaft area.

Considered using a stiff brush instead?

 

[BJC]

twidget12

IF your hosing down the motors when there hot the rapid cooling is going suck water into the motor. You can wait untill there cool.
One solution I have seen for this is to pressurize the water case with dry air (better nitrogen if available). Pressurization in the case means a couple of inches of water. It can be expensive to do and weather it's worth it or not depends on the cost of the problems your having now.

 

[aolalde]

IMPRO seals will help a lot.

 

[jbartos]

Suggestion: Submersible motor bearings arrangement might be considered.
Visit

http://www.reliance.com/pdf_elements/b507.pdf

for:
Shaft Seal
3.2.1 Two independently-mounted mechanical face type seals shall be provided. The inner and outer seal shall be separated by an oil filled chamber. Double seal (back to back) configurations are not acceptable due to the potential for failure of both seals as a result of lodged solids. Similarly bellows-type and jacketed seal construction is also prohibited.
The oil chamber shall act as a barrier to trap moisture and provide sufficient time for a planned shutdown. The oil shall also provide lubrication to the internal seal.
Standard John Crane Type 2 or equal seals shall be provided. Carbon rotating faces and ceramic stationary faces shall be considered standard. Optional seal construction including Tungsten Carbide, Silicon Carbide
faces and use of Viton elastomers are acceptable alternatives. Viton elastomers are recommended for ambient of 61
C and higher.
The outer seal construction shall be designed for easy replacement.
The outer seal assembly will be designed to allow solids and particles to be thrown away from the seal face. Optional stainless steel seal shroud is recommended for slurry applications.

 

[jraef]

IMPRO is the way to go.

"Venditori de oleum-vipera non vigere excordis populi"

 

[macmckim]

I would suggest a bearing isolator that I have been using
made by a company called JM Clipper in Texas. Product called PROTECH Sea, type LS - its rated for IP56 & 66 atmospheres.
Made of Teflon/Graphite material. Works great.
web site is

http://www.jmclipper.com

 

[jbartos]

Suggestion: Alternately, a special housing over the motor can be built, which will keep the motor in a clean environment.

 

[kassad]

Any seal designed for IP55 degree of protection would work. It would be better to go back to the manufacturer and ask them for a field conversion set of these seals.

Using sealed bearings would cause the water to go into the windings rather than onto the bearings like they have been doing upto now. And you know what will happen when that happens.

Secondly it is never a good idea to clean a motor with high pressure water, especially when that motor does not have that extra protection. Next time you want one of these motors and want to clean the same way , make sure that you ask for an IP55 degree of protection.

If the manufacturer does not have field conversion sets of seals (which will most probably be the case), then try to use sealed bearings and stuff something to seal the opening between the shaft and the end shield, so that water does not penetrate into the motor (remember to take it out when you again start the motor).

 

[electricpete]

"Using sealed bearings would cause the water to go into the windings rather than onto the bearings like they have been doing upto now....

If the manufacturer does not have field conversion sets of seals (which will most probably be the case), then try to use sealed bearings and stuff something to seal the opening between the shaft and the end shield, so that water does not penetrate into the motor (remember to take it out when you again start the motor)."

Can you please describe the path for water to enter the windings. I am particularly interested in why it gets worse when you add sealed bearings.

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[jbartos]

Suggestion: If a high pressure water stream is applied to an electrical motor, the motor should be "submersible type," since the water pressure equals to the motor submersion into water. Then, my suggested motor special waterproof cover may be less expensive and more practical for the cleaning purposes.

 

[kassad]

Well electricpete, that sure beats me too except that i have seen that happening.
Maybe when you use sealed bearings, the presurized water has nowhere to go except between the clearances between the bearings and the end shields of the motor. The sealed bearings might add up to the pressure causing the water to pass around the bearings and reach the overhung of the windings. Remember that the leakage of the water is very small, and if that is accomodated by the bearings then there is not much left to reach the windings.

This is my idea and i have nothing to back it up.

 

[electricpete]

Thanks for answering, kassad. From my thinking I can't see how switching to sealed bearings allows more water to windings but you never know.

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