Double joint weld definition 1

[zacharialamsyah]

Sorry, my question might be basic knowledge. I try to find searching by google..but still getting any confuse

My question is about double joint welding , which commonly used in offshore pipeline installation.
1.What the definition of double joint, can someone to give brief explanation?
2. Is the double joint weld means the weld is only can be done by done internal weld and external weld of the pipe or also can be done by external weld over external weld?
3.Is this joint can eliminate the requirement of field joint coating? Why?

Hope Your answer can enlighten me..

Thank you
Regards,
Zachari Alamsyah

 

[desertfox]

Hi

Have a look at this link and see figure 6.7

http://www.g-w.com/pdf/sampchap/9781590708668_ch06.pdf

 

[racookpe1978]

That's a good quick summary. Thanks, desertfox

 

[brimmer]

Seems like you are refering to pipeline joints? Double joints refer to two joints joined in the factory, so they will be shipped out twice as long as a normal joint. The pipe is then sent for coating, so the entire section is coated at the factory, thus eliminating the need for a field joint coating at that weld. If you build a pipeline with "double joints" it will only have half the number of field welds / field coated welds. Has nothing to do with welding process, not sure what you meant by external weld over external weld, or external weld over internal? But normally would use automated welding machine to compete all these welds, then every other weld is completed in the field, rather than every girth weld.

 

[zacharialamsyah]

Thanks desertfox and brimmer...Your explanation solve my question..

Regards,
ZA