how do i back purge pipes that im tig welding,could someone give me an idea how to set up and tel me what i need,and how to regulate it thanks
im trying to make myself a turbo exhaust manifoldthe pipe size is 1 1/4,what sort of flow rate would i need?do you haveany idea were i can get the bits to make myself a purge systemSimple really, you require a Y branch which attaches after gauge and, after flow meter, then attach another flow meter, it is from the second flow meter that you will control purge flow rate (I may have the setup slightly wrong, been a while?)
As for gas purge flow rate, this will depend on pipe dia, good blast to start with to eliminate air, then back well off while welding, more so when closing up weld.
Dams you can make yourself, held in place with non combustible tape, same tape around outside pipe dia, peeling back as you progress. Check out the link below for further details.
http://www.airproducts.com/NR/rdonlyres/6AC2C3E9-40E1-4E21-8BBC-57CA2F3E27CE/0/stainless_pipe.pdf
Out of curiosity, are you working to a WPS or experimenting?
Cheers.............
thanks for your advise,so the gas runs in the pipe with a small exit?I can take a pic of my set up if you want but all you need is one of these on the regulator output to give two gas lines from one cylinder. Flowmeter(s) fit straight on, one to the welder t'other is your purge line. Any decent welding supplier will sell y-splitters. Doing it this way the flow from one outlet has a small effect on the other so set your welders flowrate with the purge line running
As said you can get away without a flow meter for the purge line but for what they cost it makes life easier. Exhaust work... all you need is to reduce the O2 content in the pipe to eliminate coking, very little flow rate will be sufficient. 3 or 4 L/min will purge something the size of a manifold primary in a minute or so, when the exiting gas puts out a lighter the O2 will be low enough (for this sort of work) and the purge can be turned down to 1 or 2L/min if pipe fit up is good and you're taping up joints until you weld 'em. Higher flow rates will give a cleaner result (too much can cause problems) and can help the root profile too but a bit of blueing is hardly an issue for an exhaust manifold
Argon is denser than air so O2 can become trapped in some situations- purge entry at a lowish point and the exit at a high point will fix that for odd shaped things