Welding Sockolets in 304

[Stefan2211]

Dear All,

our contractor looks for a common way how to weld a 3/4" pipe (304) into a 3/4 "sockolet (304). The gap between sockolet and inserted pipe is to small (~0.1mm) to purge the oxygen completely with forming gas. There will be a risk of crevice corrosion. The pipe (3") uses many sockolets so it is not possiple to purge from the 3" pipe due to all the holes of the sockolets. It is very time consuming.
Any practical solution like drilling a small hole on the side of the sockolet to easier purge?
I guess there is a common used way to do it.
Thanks

 

[FacEngrPE]

Tug Fig 2 looks like a make due. Not compliant with code intent.
Better to grind out the weld and start over.
My experience has been no gap often results in a cracked weld before the welder is finished with the joint, in which case the defect is self correcting as welders should inspect their work before calling for the NDE inspector.

Alloy 304 is subject to stress corrosion cracking particularly in the presence of chlorides. This tendency to crack is aggravated by the geometry of the socket weld.

 

[TugboatEng]

Fig 2 was from a study on repairing socket weld fittings used where butt weld fittings should have been specified in power generation applications (condensate drains a gauge taps). This is supposed to give the same strength/fatigue resistance of a butt weld fitting.

 

[r6155]

The crack is not repaired and remains in the same place. The crack runs through the entire thickness of the pipe. This bad work is never allowed in any code.

Regards

 

[TugboatEng]

This was from a study suggesting a solution that did not require removal of the crack. Here is the link to the study.

https://restservice.epri.com/publicdownload/000000003002004873/0/Product

And it did get approval under ASME Code Case N-666

https://www.nrc.gov/docs/ML0816/ML081610816.pdf

 

[r6155]

@ TugboatEng
Thank you !
I worked in Nuclear with the Reactor, but I never saw a socket-weld near it.

Regards

 

[Rex Hang]

One common solution is to drill a small hole (about 1/16") near the weld on the side of the socket. The hole can be used to purge the oxygen with an inert gas, such as argon. Once the oxygen has been purged, the hole can be plugged with a weldable plug or capped with a small piece of pipe.

Another option is to use a special type of purging gas that is designed to penetrate tight spaces. These gases, such as argon-hydrogen mixtures, may be more effective at removing oxygen from small gaps than traditional forming gases.

It is critical to understand that drilling a hole in a pipe or fitting weakens it.As a result, it is critical to ensure that the hole is as small as possible and that it is located in a location where it will not affect the joint's strength.

 

[kingnero]

Do hydrogen mixtures really help in/for tight spaces? Seeing as the mixture generally consists of only a small % of H2, and balance is nitrogen (I have no experience using argon/hydrogen mixture as backing gas).