Purging Long Runs of Stainless Pipe

How about pulling a vacuum on it and then introducing the argon?

Actually we have already tried that in a crude sort of way shop vac, we haven't pulled it down to north of 29" can't imagine how long that might take.

Interesting question. It would depend on how big a vacuum pump, but at least a gauge would tell when the line was sufficiently empty.

When purging with nitrogen, do you measure the gas composition emerging at the other end to be sure the oxygen is low enough? I wonder how long that would take in comparison.

Yes we would check the exit purge port for gas composition, we would run it at a very high CFM, we have actually been pressure checking all systems with Nitrogen this is above and beyond the NDE already required. This line gets buried and part of it is under a live railroad, the outer shell will have a monitoring charge on it. Thanks for your interest your serve. :)

The process you adopt is OK. Blowing With high CFM nitrogen will definetely drive out oxygen sufficient enough to the requirement. If you consider evacuation by a vacuum pump, I suggest to do it after nitrogen purging (to drive out the moist air) and before introducing argon.

A possible alternative, which would require qualifying a welding procedure, would be Solar Flux. A paste with water or methanol forms an excellent interior purge. If the specifications allow, the quality might well be better than the purge achievable on 2000 feet of pipe with ~ 50 open butt joints, any or all of which can leak air. From an old retired Steamfitter weldor.

Has the pipe already been used for JP8, giving an explosion risk if it's welded? If it's a new installation, why do you need to purge, can't you just pump the fuel through? Gas suppliers don't use inert gas on a new pipe, they purge the air out with gas.

I did a job where a biogas pipe needed aditional welded fittings. We blew the biogas out using the installed biogas booster, admitting air to the suction. After completing the job, we purged with biogas, and checked when it burnt. Took the discharged air/biogas via a hose under water in a bucket, to prevent flashback, but not much risk of that as could smell the gas before we tried lighting it. Worked fine, but most of the plant operators kept well away!

Cheers........Codey

This is a new line and all described method/procedures are required by end user, Thanks for your input and interest.

Regards,

PI

We routinely use nitrogen to purge fuel lines. You don't have to use extremely high flow rates. Nitrogen will mix with the existing air, decreasing the O2 content as it does so. Purge for an hour and sample. You should be below 100 ppm O2. Any residual O2 will be absorbed & diluted by the JP.