Are unmarked J valves good for 3000 psi?

[Paul556]

I have a J valve with no pressure rating on it. It came off a steel 72 tank. Can I put it on a 3000 psi tank? I would think so, but I thought I would ask first.

 

[seafox69]

I have a J valve with no pressure rating on it. It came off a steel 72 tank. Can I put it on a 3000 psi tank? I would think so, but I thought I would ask first.

Change the burst disc. As long as the valve fits your 300PSI tank(ie. has a 3/4" valve width) you will be fine after you change the burst disc.


If your valve came off a steel 72, which would have a pressure rating of 2250 PSI(+ 10 % for 2475) the valve will have a burst disk that will blow between 3300 and 3500 psi depending upon how old the burst disc is. Go to your local dive shop and have them repalce the burst disc with one that would be used for a 3000 psi tank and not blow until 4500 psi or so, still below the hydrostatic pressure test rating.

The old burst disc could blow if the tank gets a hot fill or you leave it in a hot location, like your car, for a period of time. Burst discs weaken over time and will blow at a lower pressure rating the older they are.

A new burst disc will cost $8 to $12(and maybe labor) at a dive shop and needs to be put on with a torque wrench to a specific setting. Old valves never had a pressure rating on them, only the burst discs did and some of the older valves do not have today's new multi directional burst discs on them, only 1 way burst discs(air goes out of disc one way, tank moves in other direction) or lead plug burst discs(piece of lead that shoots out of valve like a small bullet) both of these are 15-40 years old and should have been replaced before now.

 

[Paul556]

Wow. Great info. Greatly appreciated. Thanks a bundle.