Shot blast in transformer; IR good so ok to energize? 1

[TheElectricMan]

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.

 

[itsmoked]

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

 

[ScottyUK]

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.


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

 

[TheElectricMan]

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.

 

[ScottyUK]

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.


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

 

[edison123]

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 *

 

[BJC]

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.

 

[itsmoked]

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

 

[edison123]

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 *

 

[itsmoked]

Keith Cress
kcress -

http://www.flaminsystems.com

 

[edison123]

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 *

 

[Zogzog]

"IR beetwen LV and HV" wont tell you much. If you really want it tested go to

http://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.

 

[waross]

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

 

[ScottyUK]

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?



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

 

[TheElectricMan]

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