Pipe crack after welding 1

[newbeehere]

Good day everyone,
May I ask about our pipe that after welding it cracks.
-pipe is a106 GRB.
-Size 2inches schedule 20
-distance between two welds is 150 MM
-pre heating is 10 degree celcius
-no pwht


What could be the possible reason for this?
This is the first time i saw like this.
Our past experiences in middle east,
welding 2 inches even in closer distance apart
the pipe did not crack.

Please see the attached photo.
Thanks every one.

 

[metengr]

Cracking in carbon steel base material weldments can be caused by several factors; poor cleanliness resulting in hydrogen pick-up, poor weld rod control, poor welding technique and last, poor fit-up or alignment.

A photograph you mentioned was not attached to your post so without any further information you can sort out each of the possibilities I mentioned.

 

[newbeehere]

Thank you for your comment Sir,
due to slow connection i was not able to attached the file.
the photo is now available, please re access my thread. thanks

 

[metengr]

Sorry but no photograph or file was attached in my view. Is the crack transverse to the circumferential but weld or parallel with it?

 

[newbeehere]

The crack is actually not on weld but on pipe horizontal formation (or going to the length of pipe) almost 2 inches in length. the crack is in the middle between two welded joints.
the length between two joints is approx 15mm.

Thanks in advance

 

[XL83NL]

Please upload a photo, it did not end up on the site for users to download. So its a longitudinal crack?

 

[weldstan]

Where is the crack relative to the termination of the weld? Was the weld made in the 5G position from 6:00 to 12:00?

 

[metengr]

Sounds to me like you overstressed the pipe material from welding sequence for the butt welds or poor alignment of the pup piece.

 

[racookpe1978]

Only 10 degree C preheat?

 

[newbeehere]

Thanks for the reply.

It is a longitudinal crack.
and have a 10degree C preheat.

Is there any factory defect can be considered also in determining the cause of the crack?

 

[DekDee]

Are you sure that is Sch 20 ?
Lot of weld on that Olet for very thin pipe.

 

[metengr]

Based on review of the photograph, you had a section of pipe containing a fabrication flaw.

 

I concur with metengr - such defects do not arise in healthy pipe during normal fabrication processes.
Recommend you scrap all pipe from the same lot.

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

 

[racookpe1978]

Your "preheat" requirement is dead wrong. You should NEVER plan on welding that cold. Get it up to at least room temperature (20-25 degree C)

 

[weldstan]

Concur with metengr. Pipe has a linear flaw of some sort. I would suggest cutting it out and determine the nature of the flaw. In any event it needs to be cut out and replaced. And that is a rather large amount of welding on the o'let.