Air leak in TIG system? Or???

Yes, I know what a venturi is.

You are grasping at straws.

Yes a venturi causes a decrease in pressure but that is not necessarily evidence that the pressure drops to below atmospheric pressure which would be necessary for outside air to flow into the hose.

Example: Scuba bottle at 3,000 psi. First stage regulator drops pressure to ~150 psi however no outside air flows into the system (when used above water) as the pressure inside the hose is 150 psi greater then that outside the hose.

If the pressure in an argon system never drops below atmospheric then no outside air can possibly contaminate the system.

By the way, there isn't any such thing as "suction" it is simply a difference in pressure causing flow from the high pressure toward the low pressure.

There isn't really a question of how a venturi works and if you connect a pressure gauge in a flow line then you will certainly discover a drop in pressure at various points along the line - some of which is due to friction at the pipe walls :-) - but you seem to be missing the critical fact. That while a venturi causes a decrease in pressure it does not automatically mean that a connection to the venturi will have "suction", as you call it.

(actually there is no such thing as suction, rather it is simply a difference in pressure causing flow from the higher to the lower pressure area)

A venturi is simply a configuration of a flow line that reduces the cross sectional area of the line. Depending on the size of the restriction and the flow rate there will be a certain reduction in pressure and temperature at that point.

However, for outside flow into the line the pressure reduction in the venturi necessarily must be to a lower then the outside pressure so merely inserting a "venturi" does not mean that there will be flow into the line.

In another post I use the example of the scuba regulator that reduces pressure from 3,000 psi to 150 psi with no possibility of contamination by outside air. Why? Because although there is a venturi effect the pressure is always at least 150 psi higher then the outside air and any flow is from the higher to the lower pressure.

Is your regulator sucking air ? - diaphragm seal cracked ? And are you measuring static pressure or dynamic!

It only adds air on dynamic - flow conditions.

Mart> >

What I have is a simple flow meter.

If there is a diaphragm in the silver bit I don't think it's cracked. If I shut the valve on the tank, there is still pressure at the gauge a week la ter. The valve on the tank isn't leaking, I've had that tank hooked up for over a year.

I guess I have refined my problem down to 3 questions;

1. Could a faulty Gas Solenoid Valve flow argon, but also allow air to ente r the flow through the venturi effect?

1. Is there any explanation for a blackened electrode other than air in the flow?

2. Will air in the shielding flow cause the arc to be weak and ?thready ?

I work for a company that makes automated welding equipment. Over the past 20 years I have seen conclusively, many Torch, Trailing, and Backing Gas l eaks that introduce air into the gas line. Customers will begin to notice discoloration in their welds. I rely on products like Swagelok's "snoop" b ottle, to find and repair the leaks.

I have seen leaks that did not discolor the welds, but cannot tell you the exact mechanism of why certain leaks pull in air and others do not.

I have seen leaks that did not discolor the welds, but cannot tell you the exact mechanism of why certain leaks pull in air and others do not.

Perhaps there is a venturi effect at the downstream side of a connection that is leaking? phil k.

replying to Snag, Randsl wrote: Peri jet inductor

replying to Snag, Randsl wrote: Peri jet inductor