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Shot blast in transformer; IR good so ok to energize?

Shot blast in transformer; IR good so ok to energize?

Shot blast in transformer; IR good so ok to energize?

(OP)
Installing a new 5MVA ONAN  22-11kv transformer known to have 1-2kg of shot blast sitting in the bottom of the tank. IR between lv-hv was still good so manufacturer says ok to energize. Can anyone foresee any problems if energized.  

RE: Shot blast in transformer; IR good so ok to energize?

How did the shot get there?

RE: Shot blast in transformer; IR good so ok to energize?

Since it is not a forced oil cooled unit,it is safe to energise.But find out from where it is coming.If it is falling from top cover,what ever reason,it can be dangerous.But it is not good for the reputation of the manufacturer.

If it were a bigger transformer,you could have entered inside and cleaned the mess.

RE: Shot blast in transformer; IR good so ok to energize?

My concern is the possibility shot may be lodged in the coils. An insulation resistance test (I'm assuming that's what is meant by "IR") may not detect it.

RE: Shot blast in transformer; IR good so ok to energize?

Shot blasting is usually used to clean paint dirt and/or corrosion from surfaces. It is usually dirty. It may contaminate the oil.

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

RE: Shot blast in transformer; IR good so ok to energize?

(OP)
thank you for the replys so far. just to add; the shot blast was found by accident. The transformer was shipped full of oil less radiators. But all the butterfly valves were on back to front. so after draining and removing the valves the metal was found in the top headers  . removed aprox 5kg's  with the vac and magnet but i could hear it falling into the tank. So guessitimate bout 2kg's left. they must not of cleaned it out when they built it.

RE: Shot blast in transformer; IR good so ok to energize?

(OP)
anyways  the question is there any other test to check the integerty of the transformer

RE: Shot blast in transformer; IR good so ok to energize?

Call a NETA testing company to come run a full series of tests, they will do a TTR, PI, Pf, Winding resistance, and draw a DGA oil sample.

You can find one in your area at www.netaworld.org

RE: Shot blast in transformer; IR good so ok to energize?

Obvious question but have you contacted the manufacturer and asked them?  I would investigate strongly sending the unit back to the manufacturer, have it de-tanked, cleaned, re-tested and sent back all at the manufacturer's expense.

I would consider this a warranty type issue.

My concern would also be shot lodged in coils and moving around due to the natural core vibrations and thermal convection.  Conceivably, this can lead to errosion of coil insulation and an eventual fault.

What happens when the unit fails after the warranty expires after you knowingly accepted the transformer from the manufacturer and energized it in this condition?

RE: Shot blast in transformer; IR good so ok to energize?

If this is a new transformer and was delivered in this condition, you have a couple of options:

Tell the manufacturer to take it back and fix it.

Ask for an extended warranty (say 10 years) on the transformer - and get it in writing.

There is no way I'd accept a screw-up like this without some kind of compensation.  

RE: Shot blast in transformer; IR good so ok to energize?

the electric man

i can not agree more with wbd. i just can't understand why the manufacturer would go ahead in energizing the unit knowing fully well of the situation. this would be a warranty liability issue in the future. are you ready to take the risk?

capuchi

RE: Shot blast in transformer; IR good so ok to energize?

I 'third' that sentiment.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: Shot blast in transformer; IR good so ok to energize?

I "fourth" it.

* Women are like the police. They can have all the evidence in the world and yet they still want a confession - Chris Rock *

RE: Shot blast in transformer; IR good so ok to energize?

I'll get in here and "5th" it. This is a situation that has no excuses.

RE: Shot blast in transformer; IR good so ok to energize?

One of my sixth senses tells me that something's wrong.

RE: Shot blast in transformer; IR good so ok to energize?

OP must be in "seventh" heaven by now.

* Women are like the police. They can have all the evidence in the world and yet they still want a confession - Chris Rock *

RE: Shot blast in transformer; IR good so ok to energize?

TheElectricman

Are you "shocked" by the posts here ?

Seriously though, IR value is just one measure of winding health. These damned shot blast pellets could get in between the turns of the coils due to oil circulation and damaged the turn insulation due to the mechanical forces during load cycle.

If it is a new trafo, time to hold the manufacturer's toes to the fire on this. Blast them all !!!

* Women are like the police. They can have all the evidence in the world and yet they still want a confession - Chris Rock *

RE: Shot blast in transformer; IR good so ok to energize?

On my 1st post I missed the fact that this was a new transformer, so I "Eighth" that motion, the manufacture needs to replace this unit.

RE: Shot blast in transformer; IR good so ok to energize?

"Ninth" place to put "Eighth" instead of hate in you last reply, Zog

RE: Shot blast in transformer; IR good so ok to energize?

Huh?

RE: Shot blast in transformer; IR good so ok to energize?

LOL!

Big question to me is why do you need to shot-blast any part of a NEW transformer?  Are they using scrap metal to built it?  Did they leave the core out in the rain at some point?  Odd for me.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: Shot blast in transformer; IR good so ok to energize?

It's usually to get a good mechanical key on virgin metal for the paint system to bond to. Transformer paint has to last a long time, often with very little maintenance to the paintwork so the manufacturers (should) follow the application techniques recommended by the coating suppliers.
 

----------------------------------
  
If we learn from our mistakes I'm getting a great education!

RE: Shot blast in transformer; IR good so ok to energize?

(OP)
so many replies     but the question remains so pls reply if you have some  experience in transformer test. My background is mv switchgear, so abit stuck here. Transformer was built in a developing nation so i guess it's a case of, you get what you pay for. However it can not be sent back or detanked if there are no failed test results. Only IR beetwen LV and HV has been done since it was shipped from maunfacturer.   

RE: Shot blast in transformer; IR good so ok to energize?

Quote:

However it can not be sent back or detanked if there are no failed test results.

Why? It is indicative of poor QA and is likely to constitute a latent defect which will cause a problem after a period in service. The shot is not something which is designed to be in the transformer and is therefore a contaminant. If the manufacturer expects you to keep this transformer then it should at their risk, so if it fails and causes an outage or blows up and kills somebody then the manufacturer carries all liability. It seems you're looking for reasons to keep it, and I can't really see any. It is poor workmanship and should be corrected.
 

----------------------------------
  
If we learn from our mistakes I'm getting a great education!

RE: Shot blast in transformer; IR good so ok to energize?

TheElectricMan

You seem to take the sincere advice given by many experts here lightly. Yes, I am transformer/motor/generator repair man in a "third world" and I wouldn't have allowed this trafo leave my shop.

You don't seem to get that the normal tests and routine tests will not detect this problem. This will develop into a failure at a later date due to reasons given above and I have seen serious trafo failures turn fatal.

If you are looking for some justification to keep this trafo, this would not be the right place, IMO.

Good luck.

* Women are like the police. They can have all the evidence in the world and yet they still want a confession - Chris Rock *

RE: Shot blast in transformer; IR good so ok to energize?

You can hire someone to inspect and fix the transformer.  Cutler Hammer, ABB etc and even some independant shops will do it.  It only takes money.  They can do what it takes to assure it is safe and reliable up to and including detanking.
 I would backcharge the original manufacturing for all the cost.

You might want to check with your insurance company.  The thing is a time bomb.  The cost of keeping it may be very high.  You are potentilaay looking at a fire and maby some expensive down time.  
The thing was poorly or delibertly sabatoged.

RE: Shot blast in transformer; IR good so ok to energize?

Furthermore why do you need a "test"?  Your eyes are a form of test.  A visual test.  It failed that test the moment you saw steel shot littered about.

Would you insist on some form of 'testing' if you looked in there and saw 300 gallons of dirty water with dead rats floating on the surface?  Or cut windings?  No! You would not bother.  Same with the steel shot...

Keith Cress
kcress - http://www.flaminsystems.com

RE: Shot blast in transformer; IR good so ok to energize?

Keith

Dead rats ? Probably shot by them damned pellets ?

* Women are like the police. They can have all the evidence in the world and yet they still want a confession - Chris Rock *

RE: Shot blast in transformer; IR good so ok to energize?

LOL

(Damn.. Just when I thought I had mastered TGML code for color, I find them smileys are still out there to conquer, sigh)

* Women are like the police. They can have all the evidence in the world and yet they still want a confession - Chris Rock *

RE: Shot blast in transformer; IR good so ok to energize?

"IR beetwen LV and HV" wont tell you much. If you really want it tested go to www.netaworld.org to find a NETA certified testing company to come out and perform all required NETA Acceptance tests, including the PF test, that may be optional depending on the specifics of the unit, do the PF test regardless.

I highly doubt it will pass.

RE: Shot blast in transformer; IR good so ok to energize?

The steel plates that the transformer are built from often arrive with a coating of mill scale on them. Mill scale is not a good thing to have in a transformer. Shot blasting is used to remove the scale and leave a clean steel surface. I imagine that the shot becomes contaminated with the scale.
Notwithstanding, if there is still shot in the transformer (contaminated or not), how can you be sure that the scale has been removed, rather than left lying in the bottom of the tank?
I would suggest that the test that will detect this will be oil quality tests over a period of years. The transformer may very well last for enough years before failure that a warranty claim is impossible.
The safe action may be to de-tank and de-grease.

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

RE: Shot blast in transformer; IR good so ok to energize?

Quote:

I highly doubt it will pass.
Did you mean you would be surprised if it failed? PF tests are not usually done at a very high voltage, only 10kV or so. The contamination would have to be at an outrageous level to provoke failure, especially on a new transformer with the insulation in good condition. Why do you think it would fail?
 

----------------------------------
  
If we learn from our mistakes I'm getting a great education!

RE: Shot blast in transformer; IR good so ok to energize?

(OP)
just a follow up ...  contacted the manufacturer and job has been put on hold pending further investigation . Thank you to all who responded   I'l post a follow up with the outcome when it gets sorted
 cheers    

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