Swagelok Ball Valve performance

[SCUBA_Phil]

Question for the group. I have bought some Swagelok SS-43GS4 ball valves for my panel. They are rated for 3000 PSI. I have disassembled them, O2 cleaned them (ultrasonic) and then used a little Christo Lube MCG 111 during reassemble. After reassembly, I integrated them into my new panel. When leak checking, I had the pressure at 3000 psi, opened and closed them a few times. Now if I close the ball valve and then close the whip valve and wait for ~ 5 minutes, I find that the about ~5 psi of pressure when I reopen the whip valve. Is this normal behavior? One other question, how high can these valves go?

Thanks

 

[tech_diver]

I'm sure SB air systems experts will chime in but I don't think you want to use ball valves for handling hyperoxic mixtures. Most people are aware that an oxygen service systems need to be o2 clean and o2 compatible but a there is a third element, oxygen compatible design. Ball valves are fast acting valves. When you open them, a 3000 psi wall of gas travels at the speed of sound down the line to the next obstruction or restriction and impinges with force (energy). You may notice pure oxygen systems usually have seat/orifice type valves and the piping has gentle bends instead of sharp curves.
Systems handling hyperoxic mixes should handle their gases gently.


DISCLAIMER:This post is for entertainment purposes only. It is not a substitute for actual qualifications to design gas systems. If anyone reads this and hurts themselves with compressed o2, pipes, valves or pointy objects, I did what I could to warn them so don't blame me.

 

[steveharriss]

3000 psi at room temperature (100 deg Fahrenheit), 2500 psi at 300 deg Fahrenheit. They shouldn't be leaking like that. The manufacturer specifications are that seat tests have a maximum allowable leak rate of 0.1 std cm3/min. You can adjust the packing to cope with high pressure as they are factory set for 1000 psi as standard.

From MS-INS-40.pdf "Adjust the packing by turning the packing bolt clockwise in 1/16‑turn increments until leak-tight performance is achieved."

 

[SCUBA_Phil]

Tech_diver,
I did put a needle valve after the ball valve to control flow.

Steve,
I will start tighten down the valve.

Thanks

Here is a picture of my setup

 

[steveharriss]

Phil, that's a great looking job there. Only one question springs to mind. Why have the ball valve in the O2 line at all? The trouble with them is there is no fine control over flow so you open it and the gas then slams into the shut needle valve. If it were me I'd take it out of the line completely and just have that needle valve. I know it will spoil the visual appearance but you'll make things a lot safer. I'd love to see the rest of the job you've done there.

 

[Akimbo]

Tech_diver,
I did put a needle valve after the ball valve to control flow…

That doesn’t help much. Ball valves are great for lean mixes in complex systems like saturation complexes, but a poor choice for simple systems with rich mixes. The problem is the ball valve’s virtually instant-open characteristic can result in very high velocity and heat of compression when upstream of a restriction like a regulator or needle valve. I saw NASA high-speed films in the 1970s that showed tiny particles picked up by a gas stream that reached some phenomenal speed and glowed red... which I understand is the source of “no ball valves in O2 systems” dictum.

We rarely used O2 mixes above 21%, other than pure oxygen, so I don’t have any experience with where the cut-off point for rich mixes and ball valves is.

Regarding Swagelok ball valves: For ¼" and smaller, many of us in the sat industry have found the Hoke Flomite 71 Series ball valves to be much more reliable, especially with pure and Helium-rich mixtures. Hoke’s version of the compression fitting, Gyrolok, is compatible with Swagelok and was originally manufactured under license.

 

[frogman62]

It's really hard to beat the Sherwood 6000PSI line valves (panel mount) because the seats are the same for many of their valves and replacement is quick and easy. Very easy to control flow also because of the softer seats Easy to O2 clean
Jim Shelden

 

[SCUBA_Phil]

Steve,
To close off needle valves, you really need to crank on them. The Sherwood inline valves were also on the list but I got a better deal on these. 5 new ball valves on ebay for $120 and the needle valve was $20. The other issue with needle valves is that a quick look will not verify all valves are closed, one quick look at this panel, and you know the state. Note: after cranking down the valve seat, everything is working as expected. The one on my bank is running at 3500 PSI.

For safety sake, I could close off the needle valve first, then the ball valve. Then to open, open ball valve, then needle valve. Hence, minimal pressure difference between them, and visually, I know the state of the system. Wonder about the long term wear on the needle valve?

Thanks

 

[Wookie]

Lessons learned with ball and sherwood line valves in the same system.

My Masterline booster which is equipped for O2 service has a Sherwood line valve in the back to shutoff flow through the booster. I never use it. It is always open. When I used Swagelok ball valves to shutoff the flow of Oxygen to and from the booster, I would get the teflon seats of the line valve burning up because of the fast flow of Oxygen through the valve, past the booster through the check valves into the cylinder I was filling. I also burned up more than one cylinder valve during the process. The cylinder valve and the line valve use the same seat.

So, the lesson is, close the sherwood line valve and leave the ball valve open. The combustion products of teflon are nasty tasting and toxic to divers. Rebreather divers don't get the nasty taste, but O/C divers do.

 

[steveharriss]

Phil, it's the on/off nature of the ball valve rather than the gradual opening of a needle valve that is concerning everyone. Your shut off procedure isn't an issue but your opening procedure lets high pressure O2 slam into a dead end. There will be plenty of times it won't be an issue but why take the risk?