Tank Pressure and Volume

[RAD Diver]

I know when we did our Nitrox check out dives with Discovery in Beaufort the instructor was curious to know what pressure was left in our tanks after a 40min dive to 70 fsw. When I told him just over 2000psi in my lp121 he was amazed til I told him I started with 3000. Thats when he pointed to the Max pressure on the tank 2450psi & stated that was the highest they would fill them.
Ive had them to 3300 before & since.Our LDS said they pressure check them at the factory much higher than that. I personally like to have as much gas as possible.

 

[wreckchick]

The big thing to remember is that the cylinders are designed to withstand X number of filled to their rated pressure without overstressing the metal/composite (for scba tanks). It's not that the tank can't be filled to that pressure, but with repeated overfills you reduce the life of the tank and subject it to premature stress and cracking.

By the way, the 2400 psi tanks that are being filled to 3700 are exceeding hydro pressure, so no they aren't tested to that pressure.

Happy Filling!

Rachel

 

[spectrum]

I know when we did our Nitrox check out dives with Discovery in Beaufort the instructor was curious to know what pressure was left in our tanks after a 40min dive to 70 fsw. When I told him just over 2000psi in my lp121 he was amazed til I told him I started with 3000. Thats when he pointed to the Max pressure on the tank 2450psi & stated that was the highest they would fill them.
Ive had them to 3300 before & since.Our LDS said they pressure check them at the factory much higher than that. I personally like to have as much gas as possible.

I sure hope you have a greater respect for the other limits involved in diving. Got DAN?

 

[brianstclair]

Can someone tell me what the difference is between the old PST LP 104s and the new PST HP 130s (ditto for the 95s and 119s)? The LPs are rated to 2640, the HPs are rated to 3500, but I've been told they're the same tank and that just the rating was changed. Is it really the exact same tank? If so, what's the problem with filling a 104 to 3500 PSI and getting 130 cubic feet, or filling a 95 to 3500 PSI and getting 119 cubic feet?

Brian

 

[brianstclair]

By the way, the 2400 psi tanks that are being filled to 3700 are exceeding hydro pressure, so no they aren't tested to that pressure.

I thought they were tested to something like 10,000 PSI or something crazy like that. Or was that valves? Or am I smoking crack?

Brian

 

[Dan Gibson]

I believe that was on the OMS website in the past and listed as 4000 psi at 10,000 cycles.

I thought they were tested to something like 10,000 PSI or something crazy like that. Or was that valves? Or am I smoking crack?

Brian

 

[Dan Gibson]

Correct me if I'm wrong, but aren't cylinders tested to 5/3rds working pressure? Maybe steel and AL are different. That would mean all those cavers filling their LP104s to 3600-3700 are not reaching hydro pressure.

The big thing to remember is that the cylinders are designed to withstand X number of filled to their rated pressure without overstressing the metal/composite (for scba tanks). It's not that the tank can't be filled to that pressure, but with repeated overfills you reduce the life of the tank and subject it to premature stress and cracking.

By the way, the 2400 psi tanks that are being filled to 3700 are exceeding hydro pressure, so no they aren't tested to that pressure.

Happy Filling!

Rachel

 

[Lead_carrier]

Don't you know that in Fl we are very safety minded when it comes to filling tanks. Hey some guys do a Hydro every time the tank is topped off

:confused1 Is they why it is getting impossible to get an Al80 filled but in the same breathe they will look at you and tell you that they can filled you 2400 tank to 3200psi?

 

[Tony "D"]

Greetings Dale,
I too have been looking at all these posts on the math. Your right they are correct. There are many ways of getting the calculation. However I have a question on the laws. I took a cyclinder inspection course many years ago, I also use the Visual plus at my shop. I to this date haven't seen anything on laws other then the DOT standards for transporting cylinders and fill pressures during transport. Is this the law your thinking of? Or is there another one written I don't know about? I know on the high volume L.P. tanks I'll go to 3200 max pressure because they'll take it. On 3500 H.P. tanks I'll go to about 4000 thats it. I do know people that really pump them up. However it is hard on the compressors to work that hard on the storage system for such a long period of time to get that kind of pressure.

 

[tlawler]

Shhhh...I don't want anyone finding out my secret to long bottom times with my steel 72's.