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

 

[r6155]

Socket weld for SS is a very incorrect design. Use butt weld.

Regards

 

[Stefan2211]

r6155. Yes I agree but now we have to find a solution. Thanks for your input.

 

[r6155]

How do you ensure that the hole is completely filled with weld at the end of welding the pipe?.
Try plastic wrap to cover all the holes.

Regards

 

[Stefan2211]

Yes it could be done but very time consuming.Weldolet would have been the right choice. But the project is in Czech and will be done for US so it is difficult to get ASME fittings from stock.

 

[DVWE]

There is absolutely no reason to purge a socket weld, even if it is stainless steel. You are only wasting purge gas doing this.

The practical solution is to stop purging all together.

The devil is in the details; she also wears prada.

 

[Stefan2211]

Why is that DVWE. I am neither a welding engineer nor a welder. Thanks

 

[DVWE]

Because of the inability to get an adequate purge; just like the problem you’re having.

The devil is in the details; she also wears prada.

 

[r6155]

I agree with DVWE, but my reason is different.
If socket welding is a wrong design (as I said before) why use a backup gas that is for a good design (butt welding)?
Has no sense.

Regards

 

[EdStainless]

You use inflatable bladders on the inside to isolate the area being worked on for purge.
And the correct gas is pure Ar.
You will end up with crevice corrosion.
You need to make sure that the pipe does not bottom out in the socket.
There is a required gap after welding.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[DVWE]

You will end up with crevice corrosion.

If there is concern of crevice corrosion, then a socket welded joint is a poor choice, as indicated by r6155. By design, socket welds always have crevice.

There is a required gap after welding.

That depends on the customer requirements. Most codes state that the gap has to be present prior to welding only. Recently, B31.3 went as far as stating directly that gap is not required to be present or verified after welding. I’ve seen the “after welding” requirement in some customer specifications.

The devil is in the details; she also wears prada.

 

[DVWE]

https://www.eng-tips.com/viewthread.cfm?qid=504652

The devil is in the details; she also wears prada.

 

[TugboatEng]

Socket wels fittings are for externally corrosive environment. An appropriate example for SS socket weld is hydraulic fluid in piping exposed to fresh water.

An import requirement for socket weld is that the pipe MUST NOT bottom out in the fitting. Leave a 1/16th inch gap. This is difficult to control in the field. Welding without a gap leaves residual stress in the weld which will cause it to crack if it is exposed to cyclic stresses.

 

[Stefan2211]

Thank you everyone, was helpful

 

[r6155]

@ TugboatEng

"Socket welds fittings are for externally corrosive environment": WHAT??

"This is difficult to control in the field" - it's the same as butt welding, with RT

".....if exposed to cyclic stresses.": socket weld is not permitted for cyclic service.

Regards

 

[TugboatEng]

Pssh... you just need to add more weld beads.

 

[DVWE]

"Socket welds fittings are for externally corrosive environment": WHAT??

I agree with what Tug wrote. The key word is “externally”

The devil is in the details; she also wears prada.

 

[gtaw]

Weld-o-let, sock-o-let, and thread-o-let are trade names. They are not list as suck by ASME pressure piping codes. However, if one looks at the provisions for "socket welds" or "socket fittings", one should find the limitations and requirements in the applicable ASME pressure piping code, B31.1, B31.3, B31.9, etc.

Best regards - Al

 

[r6155]

See ASME B16.11, mentioned in ASME B31.3
Weld-o-let, sock-o-let ... are included as "socket fittings"

Regards

 

[FacEngrPE]

Tug
F