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.

 

[alehman]

How did the shot get there?

 

[prc]

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.

 

[alehman]

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.

 

[waross]

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

 

[TheElectricMan]

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.

 

[TheElectricMan]

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

 

[Zogzog]

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

http://www.netaworld.org

 

[wbd]

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?

 

[dpc]

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.

 

[capuchi]

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

 

[itsmoked]

I 'third' that sentiment.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[edison123]

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 *

 

[LionelHutz]

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

 

[unclebob]

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

 

[edison123]

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 *

 

[edison123]

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 *

 

[Zogzog]

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.

 

[unclebob]

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

 

[Zogzog]

Huh?