Crack immediate welding 5

[MrPSK]

Dears,
I have a query,
Background:
During service 1" Line found leak, so we stopped the line and removed the spool to W/S to attend the repair.

Due to constraint we cannot fully cut and re-weld the joint, so planned to do weld on leaked section. During the welding it is noticed after done root, immediate weld crack was happening. Don't know why its happening (it happened 3 times). Need ur advice/suggestions to resolve this. Also needs to know why this happens?

Parent Metal : CS
Process : TIG
Filler Wire : ER70S-2

 

[MintJulep]

What's inside the pipe.

 

[david339933]

There is more weld than pipe in that spool....

 

[kingnero]

MintJulep's question will probably lead you straight to the answer. Also, I think I see porosity in the end crater. As there are no visible pores throughout the weld, I think that's due to welder error.

The history of this section will probably also contribute to the answer. Why all the previous repairs?

Due to constraint we cannot fully cut and re-weld the joint, so planned to do weld on leaked section.
I don't udnerstand, did you weld this on a welding table, so not constrained (part can shrink freely), or while still installed in the process piping?

 

[weldstan]

With all the previous repais, it would appear that you have the wrong material selection for the service. Welding over a crack is difficult enough but welding over a contaminated crack is almost an assured failure.

 

[MrPSK]

Dear kingnero,
Actually this is app 250mm length spool and the constraint was its Orifice type spool, so this the reason u can see more welds in that pipe spool. Weld was on welding table only. Also another constraint was due the Name plate (u can see in the pic) was in the other side of weld. so that we cannot able to cut the weld joint fully to make new weld.

 

[MrPSK]

Dear MintJulep
Inside of the Pipe is Orifice type set up.

 

[MintJulep]

I meant what is the process fluid that the pipe carries.

To me, this crack looks very much like a solidifcation crack (sometimes also called a shrink crack).

https://www.twi-global.com/technical-knowledge/job-knowledge/defects-solidification-cracking-044

 

[dik]

Excellent link... thanks

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

What line? What leak?

Here we go with another crowdsourcing failure investigation based on one picture...just remember, you get what you pay for.


"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[dik]

I find these wierd threads great... they are what makes Eng-Tips what it is. Some of the links posted are really interesting, as the one above. I don't think of it as crowdsourcing... it's informative and educational.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[MrPSK]

Dear MintJulep
Service that the pipe carries is Aquifer Water.
I agree with you, i also thought of Solidification crack due to its centreline and its appearance.

 

[weldstan]

It appears that there are 2 welds immediately adjacent on either side of the cracked weld repair. This indicates very high residual stress in tension acting on the weld being repaired. This may be the worst design from a welding standpont that I have seen. There are ways to make the welds involved but your way has proven an unmitigated failure.

 

[dik]

It might be time to replace a part of the pipe...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[r6155]

Ambient temperature?
Preheat temperature?, secuence before and after welding?, extension length of preheat at each side of weld?
Welder is qualified?.

Regards

 

[Interpreter888]

The name plate should not be a constraint, you take it off if needed and attach back on after completing the weld.

Try preheating if you didn't and make sure its the correct filler material.

I have a hard time believing any code would allow you to lay a weld against joint welds like that.

Edit: kingnero is correct, preheat is not the answer for what appears to be hot cracking.

 

[r6155]

"Not even a nuclear plant can be finished if you want to comply with all the rules" For that the non-conformity report was invented.

Regards

 

[dik]

Hehehehehe..

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[MrPSK]

Thank You for all for your valuable suggestions and feedback.

 

[saplanti]

Welded area colour tells you the story, I guess. You probably used high current, and burned the area. I agree with other comments which might be other causes for this kind of failure.
It seems that the crack comes from fast solidification. Same think can happen high carbon steel welding, the cracks may even happen during the welding. You really need to know what the base material is.

There is gold colour accumulation of material in line with the weld crack. Can you tell us what it is? There might be material contamination in the area as well.