What is "Working Pressure" ?

[tschmitt]

New diver here. Did a search on SB for this and didn't find an immediate answer after some reasonable milling around.

I just starting using the Suunto Dive Manager for my Cobra and it asks for the working pressure of my tank. I use AL80s, is it 3000 ? Is it what ever the shop fills it to ? What is it ??

Thanks.

 

[TSandM]

The "working pressure" is the pressure at which the tanks hold the rated volume of gas. For LP steel tanks, it's the +10 pressure; in other words, a 2400 psi tank holds the rated volume at 2640. I believe this is also true of an Al80; at 3000 psi, it's actually 77 cubic feet.

 

[vicdiver656]

Lynne, isn't working pressure just tank pressure> in other words 200 BAR or 3442 PSI?? Maybe I'm confused. At least that's what my tanks say on them

 

[Kern]

The tank will have WP or PW (working pressure) in the case of my tank which is 23.2 MPa (Mega Pascal) or 232 bar. The tank will also have TP or in my case PT (test pressure) which is about 5/3 of WP.

Don't know about your Cobra & I'v never bothered to log a dive to PC but mine knows what pressure I start & finish a dive with. Does the software ask for the WP for every dive or just once in the preferences section.

 

[spectrum]

TS&M has it right. That and the rated volume need to be cylinder property inputs to your software so it can make sense of your pressure drop profile. All it can sense is pressure values. With the cylinder specs it can determine actual remaining volume and consumed volume for any interval and from there provide SAC data.

Do not use an actual pressure gauge reading.

For the common AL80, yes the value is 3000

Pete

 

[Walter]

Working pressure is the pressure stamped on the tank. That does not include the 10% overfill allowed on some low pressure steel tanks. Yes, the 10% overfill does need to be included to get the stated volume of low pressure steel tanks, but that is not working pressure.

A steel 72 holds approximately (my slim 72s hold 71.4) 72 cu ft when overfilled by 10%. When filled to their working pressure, they hold approximately 65 cu ft.