Mortor Starter rust removal on the Iron. 3

[54494060]

I am currently involved in performing corrective/preventive maintenance on several (68) Size 5 GE Motor Starters for a Cooling Tower Fan project. The MCC's are in enclosed outdoor Motor Control Centers, but the environment and the lack of preventive maintenance has provided quit a challenge. The contacts I can replace and/or burnish but several of the contactor's have quite a bit of rust on the iron (contactor armatures) laminations which is the cause (hysterisis) of motor failures at the towers. The contactors are not sealing in as they should (much noise) and probably resulting in contact defects. My question is, since we (past) used CRC and other electrical solvents which are no longer EPA approved, is there suggestion for another type of electrical cleaning solvent or method of cleaning the iron, "besides wire brushing and air".

Thanks ahead for any suggestions.
12 Fish
As Iron sharpens Iron so does a man sharpen the countenance of his friends.

 

[itsmoked]

I would think you would want no liquids touching that part of the contactor. I would limit it to say... a wire brush in a Dremel tool to remove any scale or rust. Paying close attention to the armature parts that make physical contact so they can seal correctly and prevent the buzzing....burn out.

Keith Cress
Flamin Systems, Inc.- <

http://www.flaminsystems.com>

 

[jraef]

CRC would never have cleaned the rust anyway.

There is no easy way out and to be honest, wire brushing may not do it either. Those old GE contactors with the spring clips holding down the coil and armature were somewhat notorious for that problem. Depending on how bad the rust is, once the pole faces are pitted it will be difficult to get the same performance out of them, the air gaps left by the rust pitting will result in more eddy currents in the pole faces and increased reluctance in the magnet. The faces are supposed to be a machined polished fit. You might get lucky though, it's certainly worth a try. You should also be able to buy new components for the contactor without replacing the entire thing. The good part about GE's design is that the same thing that made them prone to problems makes them easy to access for parts replacement.

Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[54494060]

Thanks itsmoked for your response.

CRC and other electrical cleaning solvents had/have the ability to evaporate immediatly after contact so there was no liquid left on contacts or other electrical surfaces. I wasn't looking for a solvent that would leave "liquid or conductive residue" in the contactor. These contactors disassemble down to the line/load contacts which allows the removal and replacement of the armature, coil, and contacts.

Clearification to the EPA comment. I'm thinking that the cleaning solvents that we used "in the past", were found to be more of a human health issue than environmental.

When I had inquired with my original question requesting what is available at present, I was at work and didn't have time to search other resources "the web" so I thought I'd leave it up to the vast experience of Eng. Tips experts to help me out. I'll try the web and see what is available and safe at present.

Thanks,
12fish
As Iron sharpens Iron so does a man sharpen the countenance of his friends.

 

[waross]

The parts will probably cost quite a bit. Consider changing out the complete contactors and go for bid prices for the starters. Let the GE distributor know that you are not bound to use GE and want a competive quote, not a replacement price.
I have seen a "Replacement" price of $20,000 drop to a "Competitive" price of $5,000. (One section of an MCC.)
You may be better off to replace the starters and you may have the chance to pick the manufacturer.
Consider space heaters in the MCC to prevent condensation.
Sealing refers to the closing of the auxilliary contacts so that the contactor maintains itself energised, sealing does not refer to good contact of the iron parts. Dirty magnet faces and the growling and vibration that result will not affect the motors. It may cause slighly higher coil current and in particularly bad cases can lead to coil burnout.
I strongly suspect that just as you have a corrosion problem in the MCC you also have a moisture/corrosion problem in the motors.
Consider heaters for the motors also.
respectfully.

 

[54494060]

Just wanted to thank you "itsmoked, jraef, waross, for your many valuable comments. I always see your handles leading comments for various posts in the Forums, and am ever learning. I have worked in an antiquated industry "Nuclear Pwr. Generation" for 27 years now and the technology is mostly late 60 early 70 design. A lot of plants are trying to retrofit and update technology as they can but as we move into the future the component replacements are going to get worse, (ie.) Size 5 motor contactors. (One of the reasons I chose to try cleaning and contact replacement verses trying to buy 68 new ones). Industry doesn't stock parts like they used to because technology is ever changing.

Thanks again,
12fish
As Iron sharpens Iron so does a man sharpen the countenance of his friends.

 

[itsmoked]

You bet "60" we appreciate your appreciation. Really.

Glad we can help.


I totally see where you are going with the referb and certainly believe in giving it a shot. If it lets them all work for another few years. Good on you. If you end up cannibalizing a few to feed the rest so-be-it, you'll still save some bucks.

Keith Cress
Flamin Systems, Inc.- <

http://www.flaminsystems.com>

 

[waross]

Thanks for the feed back.
For your information I have a couple of transfer switches with bad pole faces.
One had both coils burn out due to the wrong voltage.
They then installed a manual transfer switch and someone beat one of the coils off the contactor in the automatic switch with a hammer. The coils have a tendancy to swell and haveT to be cut off with a hack saw. Then the transfer switch spent 6 or seven years in a shed. I got a call about two years ago from the Hotel manager.
"I'm tired of getting up in the middle of the night to start the generator. Can you get the old automatic switch working again?"
It's back in service. The patina of rust on one of the contactors responded to a light application of abrasive cloth. The contactor with all the hammer marks in the pole face roars and growls. It's used when the standby generator is running. Fortunately the generator is in the next room and mostly drowns it out. They had some extensive generator time after a series of lightning hits on their transformers, and the contactor is still doing it's job.
I have another transfer switch in a department store. It's about 800 amps. The standby section gets a coating of rust on the face when it's not in use. It growls and roars but does it's job. We lost a coil about a year ago, but it was the quiet one not the noisy one.
Suggestion, don't worry about the noise, and try to get some heat on the MCCs and Motors.
respectfully

 

[candu6]

If you are still looking for a solvent that will leave no residue on electrical components then google PF solvents. We use PF to clean and wipe down ceramic insulators.

 

[itsmoked]

Oh and "Three cheers for nuke power!" The clean energy.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com