Heat input for welding in pipelines in service 1

[tfdavid]

What shell be the maximum heat input for welding fittings to pipelines in service? Is it the ones specified in the qualification welding procedure?

 

[JStephen]

I can't really answer your question, and hopefully, you're not depending on anonymous internet advice to go weld on a pipeline. However, I would point out that the heat input specified in a qualified weld procedure is not intended to be a "safe" heat input for any particular application.

In looking at the tank hot-tap procedures, I notice they limit the tank stress when welding is done and prohibit hot tapping tanks under various conditions. I would assume there are similar restrictions in pipe or maintenance codes or company procedures for pipeline work.

 

[11echo]

I'm not a welding expert but I've seen a number of hot taps been done. I don't believe there is any limit on the amount of heat used in welding these connections. It requires "X" amount of heat to do the job no "if ands or buts"! The only limitation I'm aware of is company limitations and this is dictated by the commodity. In my location oil companies don't hot tap on steam lines above 600# or fuel lines, just too much potential for major problems and lost of life.

 

[SJones]

You shouldn't exceed the stated heat input of the WPS anyway. There may also be a need for a minimum heat input in order to avoid hydrogen cracking. Heat input restrictions then become a balance of the mechanical effects of elevated temperature against the metallurgical effects of insufficient temperature. You may also not want the product within the pipeline reaching a specific temperature. Try to find the Welding Journal article: A Simple Approach To Hot Tap And Sleeve Repair Welding by W A Bruce of Edison Welding Institute. If your wall thickness is above 6.4 mm, there are no identified defects in the proposed weld zone, and the WPS was qualified correctly, blow out shouldn't be an issue but 'blow up' of the transported fluid could be!

Steve Jones
Materials & Corrosion Engineer

http://www.oilandgaspeople.com/cv/11499664

http://www.linkedin.com/pub/8/83b/b04

 

[tfdavid]

In the DEP 32.38.60.10 from Shell there is an appendix which allow us to calculate the maximum heat input that can be generated in welding pipeline in service for the butterings and for the first and second fillet weld. What about the other beads after these? Welding a fitting in a pipeline involves much more than 3 beads. We don´t have to worry about heat inputs further the first three welds?

 

[SJones]

It's DEP 31.38.60.10-Gen and, if you are following it, you should be asking the owner who is using it as a specification.

Steve Jones
Materials & Corrosion Engineer

http://www.oilandgaspeople.com/cv/11499664

http://www.linkedin.com/pub/8/83b/b04

 

[tfdavid]

Thank you.