XFMR Access 2

[AfricanAmber9]

I am looking at creating an access on a Sealed Transformer. Transformer is 2500kva rated, 24.9kv to 12.47kv. It is oil filled, approx 700 gallons. It is a special project, learning tool in hopes we find the cause for the accumulating Acetylene gas and the potential to repair locally. It is welded, so my question is, once we remove the oil, circulate Dry Air and or Nitrogen and then purge (not sure how long, since I cannot monitor the internal combustible gas while it is sealed) what tools does someone use in cutting the weld? Or just blast an opening? Cutting Torch or spade hammer chisel? Sounds like I've never done this? You are correct. I just need some guidelines to prevent any hazardous situations. I appreciate your time.

 

[prc]

How do you know acetylene gas is accumulating? Have you done any DGA tests on the oil sample? If not, please take an oil sample and arrange for DGA.
If there is appreciable acetylene (>5 ppm) in addition to other combustible gases, please take a shut down and send the transformer for repair. Please don't try to do any repair yourselves as it can be handled only by an expert. The presence of acetylene is a clear sign of arcing inside. If you leave it as such, it may lead to transformer failure and even tank explosion and consequent fire.

 

[AfricanAmber9]

Yes, we have done DGA's this year and see combustible gases rising in the 8 month time frame. I understand about shutdown, we are taking the unit offline (not our utility but an adjacent utility owns this transformer)we are scheduled to do more testing and potentially service this unit. There is another transformer to replace this one. Opening a transformer is nothing new, I am interested in accessing this and wondering if there was a person or company on here who has some knowledge in this area. I appreciate your time!

 

[waross]

Try one of these:
Metal Cutting Saw

Wear full PPE. Consider a hood.
A steel chip, ricocheting several times and hitting the back of your ear is painful.
Use the metal cutting blade with teeth, not an abrasive blade.
The toothed cutting blade cuts very much faster and will leave less debris inside the tank.


--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[AfricanAmber9]

Thanks Waross. I will look into that.

 

[3DDave]

How thick is that wall? Is there typically some clearance between the wall and the transformer? If so, power sheet metal shears or seat metal nibbler starting from a drilled hole will preclude the creation of metal chips and not generate high-velocity debris.

 

[stevenal]

I believe there is generally a gasket present between the interior and the weld. This avoids debris in the tank during assembly as well as disassembly. To be sure, you might check with the manufacturer.