Shane, maybe just the differences in time zones, lol... but I'm sure you meant to say 5G instead of 4G? If the axis of the pipe is running horizontal and the joint running vertical we call that 5G, turn the pipe vertical with the joint running horizontal and we call that 2G. Also, there aren't any 3G in the piping world (at least here in the USA). There are of course 1G and 6G positions but I'm probably spending too much time correcting what may be just an editorial error!
If welding in a 5G, I would still allow sufficient time for the purge to be complete even though argon is heavier than air. I am not laughing as there may be some merit to the scenario you pose, but why risk it? As Chuck points out a molten puddle is easily contaminated as I'm sure you're aware. Also, in my own experience, I've seldom seen the purge line a dead bottom, I know I haven't seen it all but just relating to what I have... in a shop fabrication they would probably poke the purge line through a plastic end cap or similar closure device.
In any case, the original posting was discussing the fabrication of pipe from plate material and I would nearly bet my bottom dollar that they were welding with the longitudinal seam in the flat position, if they weren't then they probably need more help than can be offered in the Forum.... ;-)
Thanks for everyone’s comments. I feel that we have come to a conclusion with this problem the O2 meter is the way to go. All
Longitudinal seam were welded in the 1G position, circ seams in the 5G.:)
Good job, gsi! Lot's of luck for future fabs!
Gidday Jon,
No I meant to say 4G. The original post was dealing with circ and longtitudinal welds and the time to purge the pipe.I didn't even mention the circ welds as they are pretty basic and you would obviously use purge dams or "rice"paper.
The problem appeared to be the long seams, that is why I suggested the 4G position.I probably should have suggested welding between 3 o'clock and 6 o'clock and not 3G and 4G (should have been 2G and 4G)but the general idea was to be welding in the bottom half of pipe.
One would think that welding in the 1G position would be the worse scenario for purging as the top of the pipe is the very last area the oxygen inhabits prior to being pushed out by the argon.
I probably didn't explain myself properly in the post.
Regarding the 3G on pipe I have to respectfully disagree. I realise there is no officially recognised 3G position in pipe!
However I have welded hundreds of pipe root runs with either STT pulsed GMAW or 6010 cellulose in the 3 o'clock position using electric rotaters.
This cannot be classed as 5G rotated, would it not be classed as 3G rotated.?
Regards,
Shane
Hi Shane; I do agree the 1G is the worst scenario with regard to purge; i.e., last place purge becomes effective, but suggested 1G being the best position because of ease for the welder. Most longitudinal seams I am familiar with have pretty strict NDE requirements so my thoughts were purely regarding volumetric weld quality. As for the positions, my focusing on the definitions in your previous message was probably inappropriate and I apologise for that. As you clarified, even though the positions mentioned aren't officially recognised, your logic in explaining them makes sense.
Shane,
Just to be a little more specific on the actual area or position the weld was deposited. We rotated the long seam down around the side of the pipe. And all welding in the 5G was deposited around 2 to 3 o'clock position. It’s nice to see other people thinking the same thing. Thanks Shane !
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