shielding gas piping

I think I'd run a fairly high pressure in the pipe, you can determine a minimum with some experience, and set a regulator/flowmeter at each station. That way you should be more sure to not get a pressure drop at the far end when everybody is pulling the trigger together for some length of time.

John

It has been a long time since I took a welding course where they had shielding gas piped to the cubicals. If I recall correctly, they had about 3/4 pipe and had 50 psig in the pipe. Then there was a flow meter at each station. With higher pressure and a smaller valve opening, the flow will be more constant CFM. The analogy is a constant current source made by a fairly high voltage and a high value dropping resistor.

With long pipe runs, I would want at least 50 psig. Don't think you will need much more than that, if any more. If possible, I would locate the gas bottles in a central location and run the pipe both directions to cover the area. Better than having the gas at one corner of the building and one long run to the far corner.

Please note I d> Has anyone any expereince at plumbing shielding gas around a shop?

It may be very good idea to run the pipe full circle; the second shop I was in had a recurring problem with the last guy not getting enough shielding gas. It only happened once in awhile making it hard to track down.

Worse part was he would end up with several feet of weld with subsurface porosity and the only anyone would notice is if there was a reason for gouging.

They kept looking to the regulator as the culprit as it would freeze up if all 25 guys were welding at the same time.

In the end the distributor recommended running some extra pipe to close the loop; which apparently fixed the problem. They also raised the pressure by five pounds so it would be difficult too know what was the main reason for the problem going away.

John

It may be very good idea to run the pipe full circle; the second shop I was in had a recurring problem with the last guy not getting enough shielding gas. It only happened once in awhile making it hard to track down.

Worse part was he would end up with several feet of weld with subsurface porosity and the only anyone would notice is if there was a reason for gouging.

They kept looking to the regulator as the culprit as it would freeze up if all 25 guys were welding at the same time.

In the end the distributor recommended running some extra pipe to close the loop; which apparently fixed the problem. They also raised the pressure by five pounds so it would be difficult too know what was the main reason for the problem going away.

John

Another thought would be to run 1 inch pipe from the gas bottles and go to 3/4 inch further down the way. Same idea as the way they layout pipes for lawn sprinklers.

If you gave us an idea of what the pipe layout is likely to be, I could see if I could find some data for gas flow thru pipes and see what kind of pressure drops are likely. That 12,000 sq feet gives some idea of the size, but is it roughly square? 120 by 100 ?

Dan

The Flowmeters are calibrated at a specific pressure. The ones I used were calibrated at 40 PSI. I have seen 30 and 50 PSI versions as well. If the pressure is fairly constant, you can calculate a new calibration for them if you want real accuracy. I am not sure it makes that much difference. If you want real accuracy, the other poster's suggestion of running

100PSI and have a regulator and flowmeter at each station is the surest way to get there.

Good Luck,

Bob

Thanks for the input and keep it coming. We got a line down one side of the shop above the crane railway today. Vertical drops will bring the lines to floor level. I never thought about the layout of the pipe but I guess since we are going from the center both ways in a tee and having a line running on a truss to the other side we should have good distribution. I was sorting out the flowmeters and regulators. They are labelled for fifty PSI. I think I will donate an extra pressure gauge to the shop. We can leave it at the far end of the lines. If the pressure starts to drop it will be visible.I am pretty sure that 3/4 line at fifty psi can feed ten machines. At maximum volume of 45 cubic feet per hour that gives a need for

450. That's only 7.5 cubic feet per minute at standard pressure. Next week we should have it running in some sort of arrangement even if it off a couple of bottles ganged together. A screwup at work gives us a bit of time. The steel supplier custom cut all the one inch plate. It turns out it all was A 36 plate supplied when 44W had been ordered. I spent over a day drilling holes and it all has to be done again. the guy selecting the plate from stock must be feeling pretty small .... if he still has a job. Randy

I'd like to add I'd likely cross link the 'loop' around the shop - making '8's' if you will - so one side doesn't starve and the other has a direct run to supply. It will lower pipe impedance and provide better service.

One could spend a mint on it - but I think a middle cross would be good. If a corner was really using up the gas there would be more than one route and more than a single flow. Everyone on the line can put a low impedance drop that taps from the main flow.

I don't think it is as important than water - look at the sprinklers - if you have them. Feeders are large then they neck down and down as branches sink flow.

Martin Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH, NRA Life NRA Second Amendment Task Force Charter Founder

MetalHead wrote:

| I was sorting out the flowmeters and regulators. They are labelled for | fifty PSI. I think I will donate an extra pressure gauge to the shop. We | can leave it at the far end of the lines. If the pressure starts to drop it | will be visible.

Nason makes a compact and inexpensive industrial pressure switches for damn near whatever pressure you want. Hook that up to a light and/or a buzzer that will give you a visible and/or audible warning that there's a flow problem, something a gauge can't do. It won't hurt to have the gauge of course, but I suspect an unmistakable alarm setup would be cheaper than grinding out a handful of bad welds because no one noticed.

I was thinking of having a single bottle with regulator set at ten psi below the banked cylinders. That way the single cylinder would pickup the pressure when the bank of tanks dropped below set pressure. The sound device would have to be pretty loud with the noise level in the shop. A strobe might work. Good idea anyway when there is some more money. Randy

| I was sorting out the flowmeters and regulators. They are labelled for | fifty PSI. I think I will donate an extra pressure gauge to the shop. We | can leave it at the far end of the lines. If the pressure starts to drop it | will be visible.

Nason makes a compact and inexpensive industrial pressure switches for damn near whatever pressure you want. Hook that up to a light and/or a buzzer that will give you a visible and/or audible warning that there's a flow problem, something a gauge can't do. It won't hurt to have the gauge of course, but I suspect an unmistakable alarm setup would be cheaper than grinding out a handful of bad welds because no one noticed.

The pressure switch sounds like a smart idea. You could probably use one that is sold for turning on a water pump when the tank pressure drops. They are usually set at about 30 psi, but are adjustable. It could turn on a auto horn, air horn and/or a strobe.

Dan