Easy back purge

[Paul Moir]

I have a bunch of welds to do that need back purge gas only while actually welding. So I figured now's the time to setup my LX225 with an electrical connector to run an auxiliary gas solenoid. I thought about it a bit. There is no serious problem with any sort of plan, since the relay that runs the existing solenoid is rated for 5A/250VAC and the solenoid consumes about 100ma. But then I had to run 240VAC to the aux solenoid, or setup a 240VAC coil relay in the welder, obviously drill out a hole for a connector, mount all that up, etc, etc, then get on to plumbing in a solenoid valve.

It all seemed like a lot of work, and then it occured to me that I could do it all up at the regulator. All I'm using is a 3 way spring return single pilot valve. Sounds complicated, but this is simply a valve which sends it's input out one port or another depending on whether it sees pressure on a control port. (Actually, this was an old pilot solenoid valve that was kicking around, but I disabled that by blocking off the solenoid ports. It just so happened to be easy to set up for air operation.) The "normally shut" output port is plugged, and the "normally open" port goes into the back purge flowmeter. The input comes from the manifold after the main pressure regulator. The control signal comes off from after the torch flow control.

When you press the pedal and the torch gas solenoid opens, the pressure after it's flow control drops to practically zero. This turns the the valve to the "normally open" position, allowing gas to flow through the purge flow control. When you stop and the gas solenoid closes, some pressure builds up after the flow meter (~15 psi?) which directs it's input into the "normally shut" port, which is blocked off.

When I want to get a continuous flow through the back purge, I simply remove the control line from the valve and plug it. When I don't need the back purge, I wind the flow control all the way in.

I'm sure I'm not the first to do this, but I haven't seen it out there. At least I don't think I have.


Sorry about the crappy cell phone pictures. It's a little tight back there. Oh, the brass flow control on the left is the torch one, and the silver Everlast one is the back purge.


(PS - by "normally open" I mean normally connected to the input port. Unfortunately the opposite of an electrical switch!)

[zoama]

Here's my simple solution. works well.

[Rambozo]

I'm sure I'm not the first to do this, but I haven't seen it out there. At least I don't think I have.

Nice setup. I bet it really saves on gas, when the back purge area is not very gas tight. Especially if you have to start and stop a lot to position or move around.

[Paul Moir]

Zoama - that's exactly what I had before. The valve is an addition to automatically turn it on when I key the torch. Even with a valve at the end, you end up wasting a lot of gas: crack open the valve, blow off the pressure in the line, get ready to weld, weld, turn off the valve. It doesn't help that I'm paying the small bottle tax.

Rambozo - The task is to weld a bunch of pins to some sheet metal. I'm using a gas lens to hold the pins and purge the porcupine side, and then fuse down the back side (leaving a bit of rod sticking up for material to work with). But there are lots of times I find I want to purge the back side, but wouldn't bother because of the waste of gas & put up with dealing with popcorn. No more popcorn for me!

[scootarida1]

Here's my simple solution. works well.

He just wondering a little about this setup. Are the fittings 1/4 npt or 1/8 npt. Also did you buy a tee for high pressure rating or is that not needed?

[Rambozo]

He just wondering a little about this setup. Are the fittings 1/4 npt or 1/8 npt. Also did you buy a tee for high pressure rating or is that not needed?

That tee is 1/4"NPT and since it's after the regulator the pressure is low (under 100 psi).

[zoama]

He just wondering a little about this setup. Are the fittings 1/4 npt or 1/8 npt. Also did you buy a tee for high pressure rating or is that not needed?

It's as Rambozo said. If you make one of these be careful not to overtighten the fitting going into the regulator, too much force could crack it.

[Vinhtec]

Here's my simple solution. works well.

Hey where did you get those little regulators on the left from ? I need to back purge and this would be a quick way for me to get a set up.

[zoama]

Hey where did you get those little regulators on the left from ? I need to back purge and this would be a quick way for me to get a set up.

It's the standard regulator/flow meter that comes with the welder plus a tee, a 1/4" npt close nipple and the flow meter from another everlast regulator.

[Vinhtec]

It's the standard regulator/flow meter that comes with the welder plus a tee, a 1/4" npt close nipple and the flow meter from another everlast regulator.

Ohhh that was a dumb question for me to ask. I see now Ill try to make something like that too !

[zoama]

Ohhh that was a dumb question for me to ask. I see now Ill try to make something like that too !

There's no such thing as a dumb question... ask me anything.

[Vinhtec]

Zoama Thanks man your a cool guy forums need more of you ! I cant wait to get my machine back and weld more !!!!!!

[Markcuda]

There's no such thing as a dumb question... ask me anything.

Ok, here goes
On one picture of the guage, it shows female threads, then another picture, it shows male threads?
I know male threads are what goes into the tanks.

[Rambozo]

Ok, here goes
On one picture of the guage, it shows female threads, then another picture, it shows male threads?
I know male threads are what goes into the tanks.

The Everlast Flowmeters are male so they screw into the female Tee, then use a close nipple to screw the Tee into the regulator. Different makers use a mix of male and female so you might need a slightly different setup. You might also want different length nipples to make it easier to screw things together or to have them point the same direction. There are fittings for whatever you need.

[zoama]

Ok, here goes
On one picture of the guage, it shows female threads, then another picture, it shows male threads?
I know male threads are what goes into the tanks.

I just noticed that I grabbed the wrong pic. All the regulators that come with everlast welders are male into the tank. I just used two standard regulators plus a tee to make a purge setup.

[Markcuda]

All the regulators that come with everlast welders are male into the tank.

Ok great, I was worried a tad bit

[Jason]

Now everlast needs to sell just the flow meter parts if they don't already...