Positioning of longitudinal welded pipe seams on a horizontal axis?

[SportPilot]

I was asked a question on where does it specify in a code or standard where the longitudinal seam weld in a section of pipe is to be positioned when fabricating a piping system where the axis of the piping system is in the horizontal plane. I remember being taught that it should be in the 9 O'Clock or 3 O'clock positions (horizontal plane and or 15 deg alternately from that axis) but I would like to see it in a Code or standard somewhere. I was also asked that when fabricating a piping system in accordance with ASME B31.3 (Normal Fluid Service), is it incorrect to attach a weldolet where the hole cut in the pipe for the weldolet was cut through the manufacture's longitudinal seam weld. What has happened in this instance is the orientation of the seam was fabricated in the piping system in the 12 O'Clock position and the weldolet needs to be installed on top in the 12 O'Clock position which of course involves cutting through the manufacture's longitudinal seam weld. Does anyone know of some reference material or a section in the ASME Code that would give me the information I'm looking for?

 

[bernoullies123]

These come down to good engineering practices. Neither are a specific requirement of the code.

It would be good practice to stagger the next long. joint which is a requirement of the BPV code.

As far as cutting through the seam, I have never done it on a pressure system but have on a tank which is covered in API 650 Section 5.7.3.4 (when all other options have been exhausted).

 

[BigInch]

In gas lines the 6 o'ck position is avoided to prevent possible corrosion from sustained contact with water and other liquids that might be running along in the stream.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/