Cascade cylinders: watch out for CGA346 fittings

[2airishuman]

I had leaking valves on my four cascade cylinders, and the valve repair mushroomed into a $400, six-week project. It is difficult to purchase repair parts for cascade cylinder valves, and they cannot be replaced with ordinary hand tools due to the enormous amount of torque required and the difficulty of holding the cylinder in place without special tools. I had arranged with a local welding gas company to revalve the cylinders. They sent the work out to a hydro shop that insisted on replacing the CGA 346 valves with CGA 347 valves because of the pressure rating of the cylinders. This is much like the 232 bar vs. 300 bar DIN connection -- the CGA347 has a few more threads to make it incompatible with CGA346 regulators but isn't physically stronger. So I had to change up my cascade plumbing with new connectors, and, well, anything involving high-pressure air is expensive.

I did come across valve parts for sale at August Industries after I already had the cylinders revalved. There's no way of knowing whether a repair would have been successful. The valves had been in use in a dive shop for many years and were badly worn.

The CGA346 specification states that the connection is for use up to 3000 PSI. CGA346 valves are widely used on cascade cylinders, because the CGA347 connection was not in widespread use for any purpose until fire departments started switching out to HP cylinders for their SCBAs after 2001.

One more thing to watch if you're trying to save some time and money by doing your own fills.

 

[Wookie]

I had leaking valves on my four cascade cylinders, and the valve repair mushroomed into a $400, six-week project. It is difficult to purchase repair parts for cascade cylinder valves, and they cannot be replaced with ordinary hand tools due to the enormous amount of torque required and the difficulty of holding the cylinder in place without special tools. I had arranged with a local welding gas company to revalve the cylinders. They sent the work out to a hydro shop that insisted on replacing the CGA 346 valves with CGA 347 valves because of the pressure rating of the cylinders. This is much like the 232 bar vs. 300 bar DIN connection -- the CGA347 has a few more threads to make it incompatible with CGA346 regulators but isn't physically stronger. So I had to change up my cascade plumbing with new connectors, and, well, anything involving high-pressure air is expensive.

I did come across valve parts for sale at August Industries after I already had the cylinders revalved. There's no way of knowing whether a repair would have been successful. The valves had been in use in a dive shop for many years and were badly worn.

The CGA346 specification states that the connection is for use up to 3000 PSI. CGA346 valves are widely used on cascade cylinders, because the CGA347 connection was not in widespread use for any purpose until fire departments started switching out to HP cylinders for their SCBAs after 2001.

One more thing to watch if you're trying to save some time and money by doing your own fills.

Wish you'd called. I have probably 100 used nuts and nipples.

 

[tbone1004]

@2airishuman that blows dude. Can you explain where they were leaking? They are usually standard cheap Sherwood valves and rebuild is very much the same as a standard scuba valve. I have new ones in mine, but I'm surprised the hydro shop wouldn't put CGA346's back on there, that's strange.

 

[2airishuman]

Two had seat leaks and all of them had minor stem leaks.

I didn't realize the welding place I was using would be sending them out -- I thought they did their own cylinder work. They ended up going to a hydro place that I've had problems with before. They refuse to follow the PST round-out procedure, and they condemned a cylinder of mine because some of the galvanizing had flaked off the outside and they called that a "pit." This is just one more extremely narrow reading of the regs.

 

[2airishuman]

Wish you'd called. I have probably 100 used nuts and nipples.

That ended up being half of it -- I made adapters out of CGA347 nuts and nipples and a CGA346 adapter fitting.

My manifold is set up with CGA346 T fittings and silver-soldered copper CGA346 pigtails between them. The modern way, I guess, is to use stainless steel tube pigtails with double-compression fittings, and NPT-to-compression Ts with CGA347 nuts and nipples. Or NPT-to-JIC T fittings with short hoses. I am at something of a loss to explain why either of these are progress.

 

[Wookie]

I detest the soldered fittings and would never use them. I am old school.