stainless back purge
- Thread starter that-guy
- Start date
shocwav3
Well-known member
Just enough to fill the area and keep it purged. I usually set it at 5-7 with a small hole for relief at the end of the line. you will have to set it higher the more leaks you have.
if you are using a damn and not a closed set up start at 12-15 and work from there.
if you are using a damn and not a closed set up start at 12-15 and work from there.
steel 35
Well-known member
5 cfh is a good place to start, I use very close to a 1/4" hole and if it can be felt on the bottom of your wrist after you lick it should be enough. + fill time and the purge hole should be the highest point.
(Don't inhale Argon)
(Don't inhale Argon)
dr_clyde
Well-known member
It honestly depends on what you're purging. The settings for 6" sanitary pipe will be different than 2" sched. 40.
Whatever you do, be consistent in your settings. Choose a CFM, hole size, welding current for a given wall thickness, and so on. By doing this you ensure consistent results in welds you can't check. Find what works for you and stick to it. Learn to walk the cup, and tail out without a foot pedal. I assume you're welding pipe of some sort, you didn't specify.
On 16 GA wall sanitary pipe I run an 1/8" hole, 10 CFM and 35 amps, usually walking a #6 cup with a 1/8" tungsten sharpened 1:1 taper, fairly recessed for the appropriate angle.
Here are a couple of shots of a weld I did with the settings described.
Whatever you do, be consistent in your settings. Choose a CFM, hole size, welding current for a given wall thickness, and so on. By doing this you ensure consistent results in welds you can't check. Find what works for you and stick to it. Learn to walk the cup, and tail out without a foot pedal. I assume you're welding pipe of some sort, you didn't specify.
On 16 GA wall sanitary pipe I run an 1/8" hole, 10 CFM and 35 amps, usually walking a #6 cup with a 1/8" tungsten sharpened 1:1 taper, fairly recessed for the appropriate angle.
Here are a couple of shots of a weld I did with the settings described.
Guster
Well-known member
Pure argon is heavier than air so account for that as it displaces air from what ever you are purging. It will dam and collect in low areas which can be handy but also dangerous for yourself as it replaces breathable air. Large volumes will also need a little time to purge and good to make room for air to displace in order to be replaced by argon. It may help to turn up the flow initially to speed up displacement then turn it down just to maintain positive pressure. Just be wary of the venturi effect with high flow rates without a cap or baffle near the outlet as it can actually draw fresh air in with it as will a small hole in the supply hose.
You are actually inhaling argon right now... a lot of it in fact as it is on of the more prevalent freely available gasses. Though as it can displace free air it acts as an asphyxiant - like drowning.
You are actually inhaling argon right now... a lot of it in fact as it is on of the more prevalent freely available gasses. Though as it can displace free air it acts as an asphyxiant - like drowning.
JDon99
Well-known member
Just as Guster said, it is heavier than the atmospheric air, so treat it as if you were purging it with water. When doing exhausts, I simply used wide masking tape/heavy duty aluminum foil to block off the ends of the pipe securely and run my hose in and poke a vent at a high point above the joint to be welded. If you are too close to the end of the pipe to use any tape, use the foil and a hose clamp to seal it off.
yes, I will mostly be doing 16 gauge stainless tubing, from as small as 1.5" to 4"
Clyde, the inside of yours looks great and has excellent penetration, but I think the gas coverage on the outside is low. I'm also curious as to why you used such a small cup size. I usually run minimum of a 10 on stainless with a gas lens
I see you say 10cfm, was that for inner or outer? I really just need to know the inner
is there a formula to say that "if you have "X" amount of volume on the inside of your work piece, use "Y" CFM???
Clyde, the inside of yours looks great and has excellent penetration, but I think the gas coverage on the outside is low. I'm also curious as to why you used such a small cup size. I usually run minimum of a 10 on stainless with a gas lens
I see you say 10cfm, was that for inner or outer? I really just need to know the inner
is there a formula to say that "if you have "X" amount of volume on the inside of your work piece, use "Y" CFM???
steel 35
Well-known member
CFH = HOUR on mine 
Try 5 CF_ less on the inside.
Try 5 CF_ less on the inside.
dr_clyde
Well-known member
I meant CFH. Whoops.
I used 10 CFH on the inside. As long as you give it positive pressure and enough time to completley purge, anything will work, within reason. On the outside I just leave the welder set to 15 CFH, unless there's a breeze.
I was not terribly concerned with the outer appearance, as it gets buffed.
I change cup size to change the length of step when walking the cup. A smaller cup will give a more tight weave and smaller weld. Use what you're comfortable with. I find a gas lens is too short for my big paws to walk the cup best. I usually prefer a gas lens, but on my air cooled #9 torch it's not very practical. I would run a larger cup on like 4" schedule 40 for instance.
I used 10 CFH on the inside. As long as you give it positive pressure and enough time to completley purge, anything will work, within reason. On the outside I just leave the welder set to 15 CFH, unless there's a breeze.
I was not terribly concerned with the outer appearance, as it gets buffed.
I change cup size to change the length of step when walking the cup. A smaller cup will give a more tight weave and smaller weld. Use what you're comfortable with. I find a gas lens is too short for my big paws to walk the cup best. I usually prefer a gas lens, but on my air cooled #9 torch it's not very practical. I would run a larger cup on like 4" schedule 40 for instance.