sanitary welding...help.

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I am new to this site and very impressed by what I have seen over the last few days. I have an opportunity to do a job at a local winery replacing many old hose fittings with new; these will need to be welded to the existing (old) 4" stainless pipe. I have welded stainless, (mostly 16 ga.sheet) but very little experience with purge welding pipe.  Any help getting started as far as set up would be appreciated.
Reply:well from the info that i can gather...you'll need to fill the tubing with argon prior to weldingchances are that no filler will be needed if the joints are good and tight..fusing is just as good when you can do it...ACETONE THE CRAP out of the pipe and fittings INSIDE AND OUT!!you need to block off the joints and purge th insides with argon to keep the "crusting" from happening..you can put a "t" fitting on the argon line and use surgurcal tubing(1/8) will work fine for delivery to the tubing..cardboard and duct tape to seal the ends...when the tubing is full of argon (when you can "breathe" it in from the far end)..commence welding..straight argon..you may want to do sub assy's to keep it small...have funbeen there done that and its no picknicbut then again if it was easy everybody would be doing it now would'nt they?...zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Thanks Zapster.Any thoughts on what type of purge pressure? I am thinking if the pressure is too high, it would be like a plasma cutter going to town from inside the pipe.
Reply:4in stainless. Sounds like a fun job. Are they Butt, Branch Fitted, Y-ed ?Purge pressure depends on how long the run of pipe carries the argon. But not so high that it sucks in air behind. Is it posible to build a pipe purge dam at the welds? Could be a lot of variables.If it's HOT, Don't touch it
Reply:Originally Posted by jrweldThanks Zapster.Any thoughts on what type of purge pressure? I am thinking if the pressure is too high, it would be like a plasma cutter going to town from inside the pipe.
Reply:Root Dog,There are about 200 new fittings that are going to be butt welded. About 1/2 can be done in the shop, the others will have to be done in place out at the "tank farm". I am hoping there is some fun involved and at the least, there is a couple of bucks on the table.Zap,I will start at 1-2 psi on my practice pieces and go from there.Thanks,      J.R.