95cu.ft. steel LP, 3000-3500psi?

[BORG]

I have a 95cu. ft. LP steel tank I've had about 8-9 years, current V.I. P. and hydro., like new interior.
I talked to my LDS recently and he said I could probably fill it(overfill) to 3000-3500 psi with no adverse effects.
What would be my cu. ft. of gas with 3000 and 3500 psi, respectively?

Also approx. how much would the filled weight increase on the tank at 3000 and 3500 psi. I'm wanting to know this for buoyancy reasons, of course.
Should I have the burst disk changed to safely handle the higher PSI on a regular basis.


THANKS!

[cummings66]

.0807 lbs per cf of air is the magic number you need to know how to answer your question.

You do not need to know this for buoyancy because it doesn't matter what your tank weighs when full, only when it's empty, the full one just weighs more at the start of a dive is all you'd notice.

So, figure up how many cf your tank holds and then you can figure out how much more it weighs overfilled by using the above figure to get it. ie if your 95 cf tank holds 95 cf at 3000 psi you can guess that you've got about 15 cf more gas. Now that would weigh about 1.21 lbs. To figure that and this applies to any tank, it's AOW knowledge that you should hopefully learn when you take your course, you take your tank capacity in cf and divide it by the tank pressure. This gives you a number that you can then use to tell you how many cf of air you have at any psi reading. You need to know this if you dive multiple tanks and want to know how much gas a dive would use, obviously your tank would have more gas than an AL80 and if all you know is your SAC in cf then you've got to know how to convert between tanks and pressures to make them equal.

So, I should note that not all tanks carry the amount of gas the tank label would seem to indicate, for example an AL80 does not contain 80 cf of gas. Without knowing what your tank is I don't know for sure how much it has, but I'm sure the final weight addition is still pretty close to 1 and a quarter lbs.

PS, good luck on the drysuit course and the AOW course you want to take. Drysuit is the most fun course I think, it's got it's ups and downs...

[Matt P]

My LDS regularly rents out LP 95's and over fills them, Generally to about 3200. In rare cases they'll take it to 3400.

[BORG]

Thank you for the info. I really appreciate it!

[BORG]

Thanks!!!!

[awap]

And the volume question: Your 95 cu ft tank is rated for 2640 psi so that works out to .036 cu ft per 1 psi (95 divided by 2640). Multiply time 3000 and you get 108 cu ft. Time 3500 and you get 126 cu ft.

[in_cavediver]

The only other point added is that if you plan to 'cave' fill them, you will need to change out the burst disc. I'll leave out any reference to moral or ethical implications. If you don't do it, you'll likely blow a disc.

[BORG]

I checked my original burst disc and it is stamped with 4000psi. on it.

[BORG]

Thanks for the info. I didn't what a versatile tank I had with my 95 LP.

[in_cavediver]

Originally Posted by BORG

I checked my original burst disc and it is stamped with 4000psi. on it.

Yep, that's correct for the 2640 rated tanks. 3000 psi al 80's get the 5000psi burst disc. The 5000psi disk is what I'd use if I overfilled my LP 104's, That of course I never do. I let the dive shop do it for me!