Transformer Lid Welding Repairs?

There is too much unknown to help you.

Hire a welder, who can see the transformer.

He will:

Learn the material by looking, understand what process and electrodes to use, cleaning/surface prep, if it is oil filler, etc.

No one can tell you how to do this if you have know knowledge or experience in welding.

Hire someone. It will save you time and money.

1. Why does it need to be welded?
2. If the top is attached with screws, there may be a reason?
3. Maintenance?

Like Lyn said, Hire a QUALIFIED welder and pay them to do the work you do not know how to do!

Usually, the open top is used not only to insert the coils, but to do the oil fill as well. Welding the lid shut precludes repairs and inspections. It will become a throw away unit, not a bad thing if it is small and cheap to replace, but larger ones can become very expensive to replace.

No. As I have no knowledge why you want to deviate from the manufactures design.

I've seen a few that have fused secondaries for protection of the windings. How does welding it shut allow access. Or the wiring.

You state it was bolted on. What happened to the bolts? Why not just replace the bolts?

I am concerned also as I have never heard of someone doing this. Welding the lid to the transformer reduces if not eliminates the ability to maintain the transformer and depending on the design there is a good chance the oil could become polluted by the welding causing transformer failure. What about pressure relief?

Why the bizarre request and not just replace the lid and seal? How old is the transformer and how big is it? Has a cost benefit analysis been done regarding just replacing the transformer?

Yes, and it eliminates those pesky costs associated with testing and maintenance of said transformer.

You mean, you haven't talked it through over the phone with the manufacturer? Ye gods!

Whose requirement to weld it shut is it?

Assuming that this is an oil filled transformer then the correct answer is "don't even think about it". You want to heat thin metal to 2,000ºC which just happens to be in contact with oil that may have a flashpoint as low as 140ºC, or worse you want to pull a partial vacuum on an empty tank that may have said oil film/vapors inside.

You're question indicates that you're not qualified to do this work, let someone who is take the risk.

A client of mine told me the other day that although her husband is a great guy sometimes he needs to hire a professional. I hope she was talking about me.