motor burnout from pressure washing

[Airsmybag]

While servicing industrial air compressors it is frequently necessary to use a pressure washer with cold water to clean oil coolers and aftercoolers. Some water can enter ODP motors. We would normally use compressed air to "blow dry" visible water from electrical components before rrestoring power.

I have used this procedure fort many years without event. Recently we had a 23 year old 30HP ODP motor fry windings after cleaning. MY position is that if the insulation of the motor windings had not suffered age related failure, the small amount of moisture would not have caused a problem. My customer feels otherwise, saying "It ran before you worked on it, there was no problem with the motor." I am interested in other opinions.

 

[waross]

Most of us would avoid allowing water in the vicinity of an ODP motor. Have you thought of bagging the motors before cleaning the compressors?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[wayne440]

IMHO, Waross has it right - it is prudent to keep water out of motors, generators and similar devices. To me, ODP does not mean "spray water inside", even indirectly.

Also, my experience has been that the last person to work on a device prior to catastrophic failure will usually be blamed for same, generally with the prevailing attitude of "prove that you didn't break it". You will not like this, but if that were my motor, I would ask you to pay for repair or replacement.

 

[itsmoked]

I suspect you are a victim of wrong-place-at-wrong-time syndrome. But all that's said above is still valid.

30hp... ouch. Since that motor is decades old you might give a shot to a partial replacement like half the cost. Also take a good clear picture of it and ask a motor shop what the re-wind would cost. 30hp is financially rewindable.

You might also find a used replacement at a local used equipment supply. You have an excellent argument that it's unreasonable for you to provide a new replacement for an ancient motor. Same as an insurance company that doesn't replace your 8 year old wrecked car with a new one.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[rhatcher]

I'm sorry to say that, in my opinion, even if this motor was new then you are liable for the failure. With the exception of special insulation systems, no manufacturer rates their insulation for operation when wet. If you have been doing this for years without a problem that you are lucky that this has not happened before now.

The good new is that, as stated by itsmoked (how ironic), you have a chance to argue that the motor was near the end of its' service life and therefore you should only pay a portion of the rewind cost. This is not to say that age caused the failure; it is to suggest that your liability is not to provide a new motor to replace the old one in much the same way that a car insurance company would not provide a new car to replace an old one that was 'totalled'. Your total liability should not exceed the value of the 27 year old motor.

 

[mikekilroy]

in case you need more quantity of sources saying it is your responsibility, I add mine. Bagging sounds like a great idea for future jobs. I hope your customer is reasonable and accepts your offer to pay for say 1/2 of the repair. They could argue that you're liability is more than just the motor, such as cost of their down time. Altho I would not think this would be fair since you used normal 30 yr practices without mal forethought, but they still could try.

 

[wayne440]

When estimating fair liability it is easy to overlook the value of continued business from this customer. Even if you find some way to "win" this argument, you may consequently lose this customer and others that he/she has influence with.

 

[electricpete]

In terms of the actual mechanism for failure, it is just a guess. Nevertheless, I’ll suggest some “most likely” scenarios.

First some discussion: The enamel insulation on the magnet wire is never perfect. The NEMA specs allows so many defects per 100 feet. What you bank on in that in the end-turns that the likelihood of defect from one strand ending up exactly next to and contacting the defect from another strand is minute (and in the slot section there is slot liner to prevent ground contact). If you have conductive contamination, then it can tend to a short distance to complete the circuit between two defects which are nearby.

Therefore the most likely scenarios imo are:
* your washing introduced conductive contaminants in the washing solution. (What kind of solution?)
or
* your washing solution worked together with contaminants already in the motor to dissolve them and/or move them around.
In either case I envision the end result was shorting between pre-existing enamel magnet wire defects in the end turn region.

Again, just a guess, no-one knows for sure.
I agree with the others, the practicality of furthering your interests by making an argument is a different question.


=====================================
(2B)+(2B)' ?

 

[Airsmybag]

When the smoke clears (no pun intended) Wayne440 has it right. Winning the battle is less important than winning the war. Protecting the relationship with the customer is more important than being right or saving a few bucks. Electricpete's comment about the NEMA spec is as heart warming as the the FDA limit of insect perts per pound of peanut butter... Lesson learned!

Aloha,

Bob

 

[biggeorgetechnical]

Dear Airsmybag,

If you are already meggering these motors after your cleaning work, disregard this post.

For the future - as you still intend on staying in this line of work, right? I suggest you might want to megger the motors before restart. Its possible/even likely this liquid contamination could have been detected, and maybe dried/driven out. A basic, used 250V/500V/1000V megger can be got used from ebay for well under $200.

Meggers bad= don't restart until some drying/correction steps are tried. Could be as simple as waiting a few hours for it to dry, or it could be steps including heaters, etc, etc.

I presume the motors on these compressors are locked out during your services at the local disconnect (at least) before you do this work? - Meggering from the disconnect is a few minute simple "insurance" step.

George

"When you go looking for problems, you will find them... But they may not be the problems you went looking for!"

 

[Airsmybag]

George

Great idea. Megging beforehand would most likely told me to avoid cleaning. Megging before starting to assure no moisture/insulation issues would have been prudent.

Yes, we lock out. That is why I am still alive at 76! Megging at disconnect would not work since motor is isolated through starter contactor.

Thanks

Bob

 

[waross]

There are not many safety codes left in North America which recognize a starter contactor as a safe lock-out device. When I was taking some of my training in the 60's our instructors shared several accident reports where a motor starter was locked out by the control circuit and someone died. Our code was in the process of being changed to require a visible disconnect of all three phases and provision to lock the device in the off position.
Isolation at the contactor may be adequate for washing but you may want to reconsider using the disconnect for meggering.

Bill
--------------------
"Why not the best?"
Jimmy Carter