How thick of material can you weld with a Tig?

My question is how thick of metal can you weld with a Tig weld? I have a guy telling me that he can weld pipe from 2-5" thick with a tig. Why would somebody do this? He says it is for high pressure oil and it must be tigged because it is the best application. I dont understand why most pipeline guys use ARC but he says they use TIG.

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It is possible to weld very thick metal with tig using multiple passes.

It is not necessarily better. Certainly is slow....and can be detrimental with large grain size.

I can understand the root and first couple of passes using tig for higher quality root.

After that, more productive processes take over.

on the other hand, for something like 6 inch schedule 80, sometimes its faster and better to just tig all the way because it only takes a few more passes and you avoid all the chipping and brushing for final inspection.

regards,

Jody