Hello guys,
A little question that has baffled me for years, hopefully someone can clear it up for me.
A pipeline comes into a compressor station, processing plant, refinery etc and it is a buried pipeline and usually it is designed,built and inspected to API 1104 and is welded with 6010/7010.
The first joint above the ground after the riser is usually designed, built and inspected to ASME B31.3 and welded with ER70S/E7018 or E7016/E7018.
Even if there is an isolating valve between the API 1104 section (after the weldneck flange)and the B31.3 section it is still basically the same pipe (I realise one might be API 5L and one may be A106 Gr B but it is the welding acceptance criteria I am concerned about) , and if the valve is opened then both sections are exposed to the same pressure of fluid.
I have always thought that the reason for the different acceptance criterias was that one was buried so could better absorb an explosion and the other was above ground so was more exposed.
Are my assumptions correct or is there another reason why they differ ?
Thanks and regards,
Shane