Air leak in TIG system? Or???

First off, I'm just a hobby welder (mostly light stuff like bicycle frames)
and have used my machine very little in the last few years.
L-Tec Heliarc 250 HF Plus about 20 years old
Heliarc HW-17 gas cooled torch
Foot pedal control
I think I'm suddenly getting a lot of air in my argon flow. By suddenly I
mean one minute everything is fine and the next minute all I'm getting is s
puttering, a sort of corona between the cup and the work, a melted gas lens
screen and a blackened electrode.
This seems similar to what happened when I tried to weld after having to di
sconnect the hose from my flowmeter to the welder last year. It didn't occ
ur to me I'd have to purge air from the hose before welding again. This is
much worse than when I had a bad O-ring in the torch cap.
I was TIG welding some 0.065? wall rectangular steel tubing. I laid down
an inch of bead just fine. Then I skipped forward an inch and tried to sta
rt another bead. Nothing had been changed.
There is no leak between the flowmeter & the welder. When I blow into a ne
w cup there doesn't seem to be any leak between the torch and the machine.
I assume there is a valve inside the machine that has failed. Does that ma
ke sense? Can replacement parts be found or can the valve be repaired?
The welder is in my basement & I had to hire piano movers to get it there.
So bringing the machine in for service isn't Plan A.
I've been away from this forum for several years. Good to see Ernie's stil
l here.
Reply to
bikesmithdesign
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What has failed in the solenoid valve for your shielding gas. The exact part may be hard to get, but it is a pretty standard part and should be easily replaced.
Check your area for a welding machine repair shop. Every major city has at least 1. Call your welding supplier for ideas.
They can likely order the part from ESAB, and tell you how to put it in. The older machines are much easier to get into than the newer machines.
If they can't get that part, I am sure you can get a suitable replacement from Granger.
Reply to
Ernie Leimkuhler
Thank you Stagesmith. I think I remember you from when I was on the forum, years ago. Sometimes knowing what the part is called is half the battle.
I'm in Minneapolis and my supplier, Toll, carries ESAB. I'll make some calls in the morning.
Now my only concern is if they will just sell me the part instead of charging me for a service call.
Reply to
bikesmithdesign
I just googled "Gas Solenoid valve tig welder" The hits I got were cases when there was no argon flow. I get plenty of gas coming out of the cup, but I don't think it's all argon. Does that still sound like a faulty GSV?
Reply to
bikesmithdesign
The question I have is where is the air AT HIGHER THAN ATMOSPHERIC PRESSURE coming from ? Something has got to be pushing that air into the system ... have you recently changed bottles ? Could be a contaminated or mis-filled bottle .
Reply to
Snag
The venturi effect can pull air into the system. As the velocity of the gas or fluid increases the pressure drops and this pressure drop can pull air past a faulty seal. An example of a high pressure system using the venturi effect is a pressure washer with a soap pickup hose. The pressure is high coming out of the wand nozzle but upstream of the nozzle is a port connected to a tube that terminates in a container of liquid soap that is at atmospheric pressure. A sand blaster is another example. Air and sand are drawn into the air stream and ejected at higher than atmospheric pressure. Eric
Reply to
etpm
In theory that makes sense ... I am a bit familiar with venturi effects , but I don't know of anything that could act as one . -- Snag Learning keeps you young !
Reply to
Snag
All you need is a hole in the argon line or in the regulator.
Venturi has two inputs and one output. One is drawn in as the other pushes in. e.g. argon at psi pushes into the regulator and in that high pressure to low pressure draws in low pressure air.
You might be able to reverse the effect by stopping up the end and look for a gas leak - this time Argon backflows.
Martin
Reply to
Martin Eastburn
If your theory is correct then a water hose with a hole in it would flow air? Or an air hose with a hole in it would flow water if you used it in the water? Strange that nether seems to happen that way?
Reply to
John B.
Put a restriction in the water line, put a hole there, and watch it suck. Don't believe me though, look on the web for a cogent description of an experiment you can do yourself at home. You can also stop by a waterbed store or a pet store and buy for a few bucks a venturi made for draining waterbeds or fish tanks. Screws onto the end of the hose, has a side port at the constriction that sucks any fluid that's thin enough, like water or air. Cold molasses might be a problem. Eric
Reply to
etpm
That device is called an eductor , and is also used to increase water flow in shallow wells . The US Navy also uses them , I think to pull water out of compromised spaces . There's also a version meant to help drain basement spaces , it's hooked between 2 lengths of garden hose ; one from the faucet to supply working fluid , the other to drain it outside . That one might also be the one you referred to for draining aquariums .
Reply to
Snag
Sounds more like the waterbed drain. Eductors arenot just used in shallow wells. Well, I guess it depends on what you call shallow. Since you can't suck water more than 30 feet or so on planet Earth wells that are deeper are sometimes equipped with a jet pump. This is a pump that mounts at ground level and uses the eductor, provided with water from the jet pump, to bring water up from wells deeper than about 20 feet. Though not as effecient as a pump 60 feet down that only pushes water up they are easier to service. Cheaper too. I personally have a nice stainless steel top of the line Grundfoss pump that will last a long time. In fact, the projected lifetime means it will fail on the hottest day of the summer, which will be Friday, at 5:00, on my 80th birthday, and all the well service folks will be busy replacing pumps for a week and I'll be too old and frail to want to deal with the damn thing and what does this have to do with welding anyway? Eric
Reply to
etpm
If, as you seem to assert, the argon flow line acts as a venturi then why does one need a special venturi to drain the water bed?
You might try explaining how, if you have an argon line with a metered inlet flow of X and an outlet flow of the same, a lower then atmospheric pressure (necessary to allow flow from the outside into the line) is generated.
Reply to
John B.
Think of it this way. Angle of attack. If the flow is rushing by in the tube and you direct a stream of air in the same direction - not making a Y but an upside down Y so two flows come in and compress into the bottom leg. At a lower flow you might get some back flow until the pressure is higher.
We had some silicon wafer probe machines that needed both vac and air. And 220. What a pain. I talked to the tech and explained that only a single hose was needed that the pressure hose could provide the vacuum with a venturi tap. The air flow was in the range that the unit needed close to the standard value. Didn't need much vac.
Google venturi - Wiki page has some info.
Martin
Reply to
Martin Eastburn
It might be called whatever. The "Effect" is the venturi effect.
Trade names and the like always get into the way. Like coke and Kleenex. I use both name brands, but hear the brand used as a class.
Martin
Reply to
Martin Eastburn
Inlet isn't equal to output if you have air in the mixture.
If the line is at pressure and flowing you might have the effect working. If you turn off the torch - and the gas - flow stops and the sucking of air stops - gas leaks out - needs flow for the effect.
Martin
Reply to
Martin Eastburn
Nope, I'm not going to think of it any way. Flow through a hose does not produce a lower pressure. If you don't believe me try connecting a gauge to the outlet of the air hose. 100 psi at the tank and 100 psi at the end. No drop in pressure what so ever.
Reply to
John B.
The venturi effect comes from increasing the velocity of the fluid (gas). Anywhere in the system where the velocity is increased will cause a pressure drop. A restriction, such as decreasing the diameter, will cause a velocity increase. This restriction can happen in the valve mechanism controlled by the gas solenoid. If a leak happens to be in the same area, such as from a failed seal, then fluid(gas) can be drawn into the stream. After the restriction the velocity drops and the pressure increases again. Take a look at the Wikipedia page about the venturi effect. I don't even know why I keep trying to explain it. And I guess I shouldn't care if you can see it or not. I have personally seen a leaky valve draw air into a system. Eric
Reply to
etpm
Disclaimer: I am no scholar on this subject, just a lurking hobby weldor, motorhead and pilot.
In your example, if you introduce a restriction in the hose (venturi) the speed of the gas (fluid) will increase along with an associated pressure drop. If you connect your gauge in the middle of the venturi, you will see a pressure drop there. If this were not true, a carburetor (venturi) would not draw in fuel from the float bowl which is at atmospheric pressure.
The same is true of an airfoil, which is simply half a "venturi". As the air flow must travel over a longer distance along the top (curved) surface, its velocity increases and exerts less pressure along the top of the wing than is present along the lower surface, hence "lift". In reality, there is much more going on with the wing during flight, but the venturi effect is still present and part of the total equation.
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"The Venturi effect is a jet effect; as with a funnel the velocity of the fluid increases as the cross sectional area decreases, with the static pressure correspondingly decreasing. According to the laws governing fluid dynamics, a fluid's velocity must increase as it passes through a constriction to satisfy the principle of continuity, while its pressure must decrease to satisfy the principle of conservation of mechanical energy. Thus any gain in kinetic energy a fluid may accrue due to its increased velocity through a constriction is negated by a drop in pressure. An equation for the drop in pressure due to the Venturi effect may be derived from a combination of Bernoulli's principle and the continuity equation."
DJ
Reply to
IdaSpode
What was snarky or condenscending about my answers? Really. Eric
Reply to
etpm

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