Cleaning 3 phase AC motors while still in service 1

[billy6139]

Am attempting to implement a motor cleaning maintenance program.Most motors are vertical hollow shaft WP1 and open dripproof enclosures.HP ranges from 25 to 300.Voltages are 480 and 2300 VAC 3 phase.I used to work for a refinery and I observed the maintenace techs. cleaning operating motors (running) with some kind of soapy looking substance in a bucket.They would apply it with a brush on the exterior and even splash it on the air intake so it would be forced over the windings while the motor was running.Any suggestions?

 

[powerjunx]

billy6139, trying to implement such maintenance would require good planning, consideration and factors that affects the machine while in operation. Please consider: safety.. Safety First! You should be open on pros and cons regarding to carrying out such maintenance.
Is there no other way to shutdown the machine to conduct such action? How critical the machine should be in operation?

 

[petronila]

Hello Billy,

For motor in services the following could help:

1.Stop the motor
2.Cut off the power
3.Log Out and Tag out
4.Verify the motor don´t start open the connection box and look for damage on leads and power wires.
5.Take an insulation reading(IR) at 500 V from the CCM and record the reading.
6.Uncouple the motor
7.Made a complete visual motor´s inspection looking for damage in motor parts,couplings or pulley, belts and foundations and for unusual services conditions.
8.Clean all motor´s surface with a dry wype
9.Apply new grease to the bearings.Take out the fan and fan cover.
10.Clean the grease excess
11.wash and clean the fan (If is made with plastic)
12.Clean the cover inside
13 Assembly the fan and cover fan.
14.Couple and align the motor
15.Restore the power conditions and start the motor.
16.Take a voltages, Line Current, frame and bearings temperature readings,and vibration levels.

Remember record all readings.

If you don´t have a good IR readings the motor could be sended to shop or could be dry out on site with a blower, the motor may need dissambled.

Regards
Petronila

 

[itsmoked]

petronila; That is a nice list but I wouldn't call that "still in service".

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[powerjunx]

petronila, it sounds good procedure but as Keith mentioned, it never answer the query when carrying out the procedure while the unit is "in service".

 

[itsmoked]

billybry; I suggest that most here will consider that:

1) Messing with motors that are running or can start at any moment to be flat out hazardous.

2) Generally this would be likely illegal by any local authority like OSHA or against corporate policies.

3) There is not a lot you can do with an active motor. You can do about four things.

A) You can measure the phase currents and compare them to previous readings that are always logged along with comments like the process load.

B) You can measure the vibration and sound at several specific points and log these.

C) You can use a contactless temperature gun on several specific spots and log these, (including the ambient temperature as measured contactlessly on a logical nearby surface).

D) You could measure the RPM with a contactless tachometer and note this in the log.

These various safe, (with the possible exception of the current measurement), aspects should alert you to any critical changes or aging processes going on.

Bearing areas may slowly start rising in temperature, current can increase, vibration increases, and noise increases as a motor ages.

All this falls short in my opinion with regard to "servicing" a motor and are rather "monitoring" the motor in a quantitative useful manner.

Other points anyone?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[petronila]

Dear All,

Yes you are right. The above List will be usefull for MOTOR MAINTENACE MATTERS and not for cleaning.My Appologies.

To clean motors in services is very important to be sure about the Technical data sheet of cleaning compounds, solvents or soaps you are using. This products most be dielectric and no corrosive, take account if you clean a motor runing the windings could be exposed to be in contact with the product, if this is not dielectric the winding coul fail. Also the mechanicall parts and grease can be in contact too with this solvent.The connection box,bushings and electrical pipes most be checked looking for wrong juntions.Also You can blow the fan with air.

I am agrree the protection is very important, for it you will need all personal protective elements like glasses and globes (The motor is warm and you will use liquid solvent) the other risk is the motor itself because is running, don´t use innapropiate cloth, the moving parts coul catch the maintenance personal.

Remember perform the job with trained people.

Regards

Petronila

 

[441441]

I worked at a depot where that used to happen ( used a degreaser type liquid) but we stopped the practise. Do it on a red hot motor and the chances are it may blow in your face. I agree with all, its dangerous.

 

[edison123]

Keith covered it all about the running motors "maintenance".

I would rather "maintain" myself than the motor.

 

[powerjunx]

itsmoked, you're right.
That's what a preventive is, but wasn't the case when "cleaning the machine's winding while running" , hence petronila is right. All you suggest will then converge to SAFETY - as i said safety first. The procedure eventually against the corporate agenda on safety likewise to safety agencies enforcing or advocating it at workplace as a set of standard(OSHA, NESC, NEC, IEEE, etc).

Petronila:
"Remember perform the job with trained people." I prefer to say; Perform the job with qualified personnel only. "Qualified personnel" refers to a person who are trained for the specific job and trained with safety issues pertaining the its know trade.

 

[stardelta]

From my experience cleaning windings whilst the motor is still asseambled is a very hit and miss affair and not something I would reccomend. The negatives outweigh the positives. You cant access all the winding, the liquid often has nowhere to drain to, it pools and tends to mist and find its way into bearings and dissolve the lubricant as a result. In most cases it just moves the dirt from one place to another without actually removing it from the winding, usually to the lowest point where it builds up. If we were to find ourselves in the position where a customer requested us to carry out such an operation we would not even contemplate doing it with the motor running and would certainly not be giving any guarantees.

 

[electricpete]

Yes, there are a of things that can go wrong cleaning a motor while running as detailed above. The rotating hazard and the electrical hazard top on the list.

I will add one to the list that has happened twice at our plant. If you get a rag anywhere near the inlet of a TEFC fan, it can get sucked right out of your hand and into the fan where it can damage the fan (cheap plastic fans) or just make the vibration go through the roof. I think maybe newer motors have some kind of fine mesh grille to prevent this but ours don't.

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[electricpete]

And the main question: why is it so important to have motors which are sparking on the outside? Surely clearning every year or two during shutdown availability is enough, isn't it? Do you have some unique contaminant in this plant like coal dust?

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[petronila]

The Dry Ice is a preactical alternative,some advantages are: Is not Abrassive and can eliminate grit and dirt.

The external parts could be cleanned wiyh out any interruption of service.

Regards

Petronila

 

[waross]

When I was young, the old electricians talked about how well carbon-tetra-chloride worked for cleaning running motors. Thios was shortly after carbon-tet was banned from use. All those electricians are now dead. At least one of them died from the cumulative effects of carbon-tet exposure.
Compressed air was used regularly to clean dry sawdust from open drip proof motors without incident. One motor was inadvertantly missed from the cleaning schedule and eventually caught fire. Compared to that, I can't remember any incidents related to cleaning the other motors when they were running.
Some were not accessible when running for safety concerns and were blown down when they were stationary. Blowing them out when running worked better.
One day someone cleaned a stopped, open drip proof motor with a steam cleaner. It never ran again.
respectfully

 

[electricpete]

Wow - we're not just talking about cleaning the motors while running but cleaning the windings while running?

That is something that is out of my experience. We rarely have a need to clean any windings on new VPI windings and when we do, the motor is sent to a repair shop where it can be steam-cleaned afterwards.

For cleaning windings on site while shutdown, the only options I know of are: 1 - vacuum for dust, 2 - spray lightly and wipe with a solvent which will evaporate (choose carefully) and 3 - dry ice which will sublimate.

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[electricpete]

Let me repost that with correction in bold:

Wow - we're not just talking about cleaning the motors while running but cleaning the windings while running?

That is something that is out of my experience. We rarely have a need to clean any windings on new VPI windings and when we do, the motor is sent to a repair shop where it the stator can be baked afterwards.

For cleaning windings on site while shutdown, the only options I know of are: 1 - vacuum for dust, 2 - spray lightly and wipe with a solvent which will evaporate (choose carefully) and 3 - dry ice which will sublimate.

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Eng-tips forums: The best place on the web for engineering discussions.

 

[oldfieldguy]

I've heard of cleaning motors internally while they were running, but I personally think the risks are too great. You'll talking about spraying a winding which is at some temperature quite above ambient with a solvent or a cleaning medium like dry ice. There's a thermal shock in that action. Add that to the possibly deteriorated condition of the winding which you're preparing to attack mechanically, well, I'm thinking that I'd definitely want to do this offline.



old field guy

 

[powerjunx]

"but I personally think the risks are too great"
Oldfieldguy,..is right. This would require a special attention regarding to unsafe acts. There would be a Hazard/risk analysis, a MSDS of solvents, and other safety provisions.