Ironic Metallurgist ,
I have been involved in two systems of this type the first was made from copper tubing and ran at a regulated pressure of 25psi this was fed from a bank of compressed gas cylinders on a manifold outside the shop to outlets on the work benches with quick disconnect fittings for 8 Tig welders . The major malfuntion with this system was people not being careful to shut off the lines when changing tanks getting air in the lines requiring a purge. It would have helped if the regulator had been placed on the tank instead instead of the end of the manifold . Once the system was purged it would function well until the next screw up we were consuming about two tanks of argon per day That was 99.5% purity

The second system used anodized aluminum lines Transair by Parker Hannifin feeding approximately 9 welding stations. some Mig and some Tig. This system used a Dewar with Liquid argon into a boiler then gas to the welding stations 99.998% purity. I do not remember the service pressure for that system I seem to recall that it was regulated down from 250psi. I think the Dewar held some 3500 liters, it was about 3 feet in diameter and about 5 feet tall.
Anyway the main enemy is moisture in the lines if they are left open on a cold day when changing tanks or Dewars. You will need to purge the lines , You will consume less gas getting the lines purged if you can pull a vacuum on them first to remove any residual moisture.
B.E.

You are judged not by what you know, but by what you can do.

Our lines are welded stainless (since we make it).
We come in from the bulk cryo tanks at about 150psi, then regulate to 25psi for the house lines.
These run to each station and then through low pressure regulators near point of use.
Prior to use we pulled vacuum on the system for about 3 days, and did a He leak test.
We did some maintenance and had the system open. Rather than using vacuum we purged with high purity nitrogen (also from a bulk cryo tank) and watched oxygen and DP.
We manage to keep oxygen below 2ppm and DP<-80C.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

EdS and berk,
Thanks very much, that is useful information and very applicable to our situation.
I want know how you measured gas purity at the outlet, and whose instrument you recommend.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

We use fuel cell oxygen meters and solid state DP probes.
I hate the oxygen meters but they are not expensive and work fairly well at first.
For longer term use I would rather have a hot ceramic sensor unit or a paramagnetic one.
I have no experience with the optical units.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

We did not have a oxygen sensor , so we would get a rep from Praxair to come in and measure for us if we felt that we needed it. that was on the liquid system.

On the first system running off tanks we were only doing general welding of Stainless and Aluminum with 99.5 purity gas.

The only time we worried about purity was when we were welding Inconel, then we would put the high purity tank right on the welding machine not through the manifold.
B.E.

You are judged not by what you know, but by what you can do.

Our system did have some dual ferrule compression fittings in the system, but no pipe threads any place, and minimal amounts of hose (which is changed periodically as a maintenance item).
We have a DP sensor permanently in the lines, it helps trouble shooting.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

More good info guys.
Can you give the names of the sensor equipment, I've tried googling but there's a lot of weeds on the interweb.
I will talk to our bulk gas supplier very soon; they provide such systems. I want this to be best-in-class in every aspect.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."