Attaching a 3/4" weldolet to a CS heavy wall Inconel lined pipe. 2

[Piping4me]

I have a substantial amount of Inconel clad CS piping ranging from 8" - 32". The average WT of the CS is 19mm, with a 3mm thick Inconel cladding. My problem is that I have numerous 3/4" instrument connections that require weldolet or weldoflange connections. I must ensure that the Inconel coats the inside of the instrument connection & the drilled out section of the CS piping. My Client states that oversize drilling and Inconel weld overlay is not acceptable as the 3/4" hole is too small for such actions. He feels that the welder will make a mess of the overlay in such a heavy walled pipe and small hole. Can anyone suggest a way to weld a 3/4" solid Inconel weldolet to 19mm thick CS piping (Inconel clad)? Many thanks.

 

[Metalguy]

If you have Inconel 600, the thermal expansion rates of the two metals are very similar, so you should be able to weld the Inconel nozzle to the pipe, even without cladding it first.

Are you aware of the general difficulties with welding any Inconel?

 

[Piping4me]

Thanks for the response, but I do not want to clad the weldolet as it is solid Inconel. I must drill a hole in the wall of the main process pipe to allow for the instrument connection. I must ensure that the CS outer section of the process pipe, which is now open to process gas as I have drilled through the Inconel inner layer, is weld overlaid with Inconel so not to allow corrosion etc. Any ideas how to weld overlay such small holes (1/2" & 3/4&quot? Is this procedure possible?

 

[Metalguy]

If I am reading this right, I think you may need to weld a thin Inconel sleeve into the hole in the steel pipe.

This way you avoid corrosion problems and welding is easily performed on the ID and OD only.

 

[GRoberts]

What about drilling a hole, and then plugging it with an inconel weld, then re-drilling a smaller sized hole. Depending on the ratio of pipe thickness to hole diameter, the hole drilled for plug welding may also have to have a bevel to provide adequate access for welding.

 

[Piping4me]

This was the answer I was looking for. Thank you very much. I presented my client with this solution before, but it was immediately rejected. I wanted further clarification before a second attempt into the lair.

Thanks again.

 

[GRoberts]

I forgot to mention, I would plug weld and drill before welding the soc-o-let to the pipe. Unless you customer, or someone else here comes up with a brilliant idea, they will either have to accept this method or live with the edge of the hole being exposed carbon steel.

 

[Hush]

I can think of one way to do it but it strikes me as excessive:

Shop weld the weldolet to a 4" long piece of 8" Inconel pipe. Cut a 4-1/2" section out of the clad pipe. Bevel the two ends back and overlay with a 1/4" of inconel. Butt weld the Inconel pipe in place.