Minimum distance between welds in piping 2

[MicroEng]

Hi
There is a problem in piping of my project. the distance between weld(related to pad of branches)and circumferential weld line is very low and the inspector has not accepted them. The material of piping are both CS and SS. Please let me know what the related standards and common practice of this matter are?
Thanks in advance.

 

[Frank1344]

Each weld creates a Heat Affected Zone or HAZ, the ideal case is not to have the two HAZ intefered. Determining the HAZ is not an easy task. I think (but not sure) that you should have at least 2 inch or 50 mm space between the two welds.
Take care.

 

[DekDee]

MicroEng,
It is not something that is addressed in the piping codes - it is generally always noted in the project specifications.
If you cannot find it yourself in the specifications ask the inspector to provide reference to where it is unacceptable.
Just remember - if it isn't documented, it cannot be enforced.
Regards,
DD

 

[Shmulik]

Former discussion at same subject:
thread378-242240

 

[XL83NL]

There are dozens of topic on this at eng-tips; this topic comes up a few times a year at least. Do a search to find other recommendations.
Refer to Shmulik reference as an example.

I think (but not sure) that you should have at least 2 inch or 50 mm space between the two welds.

I think that's a pretty common method, Ive other reference this rule of thumb also.

The material of piping are both CS and SS.

The requirements for CS may differ from SS (in that CS may be more strict), since SS is not a hardenable material.

Just remember - if it isn't documented, it cannot be enforced.

Correct, but that doesn't take away that sound engineering practice should always be applied, which may still require the manufacturer to apply a minimum spacing, even if it's not required. Remember the Code sets out minimum requirements.

 

[DekDee]

XL83NL,
My comment was not code specific - it relates to anything documented, be it codes, project specifications, procedures, purchase orders, contract documents etc.
If it is not documented it cannot be enforced.
An inspector cannot reject something based on his opinion or the fact he has verbally been told there has to be a minimum spacing requirement.
Regards,
DD

 

[XL83NL]

DekDee, if you let it come so far you take it co court, I think you'd be right, but in practice I wouldn't let it come that far.
Furthermore, it should be basic understanding of engineers that for some materials a minimum distance should be kept, regardless if it's enforced or not, to assure sound material properties after fabrication.

 

[DSB123]

One of the British Standards for pipe welding used to have "40mm between toes of welds" .

 

[moltenmetal]

Welds which intersect are commonly encountered in vessel construction. I'm sure the issue could be solved by reference to ASME VIII, which does set out rules on how such intersecting welds are to be inspected and in what order.

Obviously an issue best avoided by design of course. But sometimes you can't.

In the case of the intersection between long seams and circ seams, that happens on every circ seam when you use welded seam pipe. The pipe is annealed after welding so in theory there is no HAZ in the long seam weld to concern yourself with.

 

[Frank1344]

Sorry XL83NL,
it won't happen again.

 

[DekDee]

Guys,
You are straying from the issue.
The OP has noted piping so ASME VIII has nothing to do with it.
If there is nothing noted in MicroEngs contract documents and it is not noted in the applicable code how can the inspector reject it ?
I am currently supervising 10 x welding inspectors on a multi billion dollar subsea project and if I found them rejecting things because they read about it on an internet forum they would be out the gate so fast their heads would be spinning.

This is an excerpt from a previous project (major US EPCM)

4.3.2 The minimum distance between adjacent welds shall be the greater of 75mm or five
times the thickest pipe/fitting wall thickness.
4.3.3 Non-pressure attachment welds such as welded pipe supports shall be a minimum of
50mm from each other or from any other pipe welds.
4.3.4 The minimum distances between welds defined above shall be measured from weld toe
to weld toe and not between weld centrelines.

The OP has noted that the problem is branch pads being too close to circ welds so the piping has obviously been designed that way - therefore a TQ to the design engineer would be the best option (pass it back to the person who created the problem)

Cheers,
DD