HP vs LP

[simbrooks]

No idea how this comment pertains to what I said. I didn't even mention plus ratings. My answer was general.

Should have stated my reply better. I meant to say that some LP tanks are positively buoyant when empty. Also that the rated volume quoted by the manufacturers is to the plus rating 2640 rather than the 2400 rating that you mentioned before. Just trying to clear a few things up and in the latter case double check if my thinking was straight regarding the rated volume/pressure quoted being the plus rating not the 2400psi rating.

 

[simbrooks]

I had my E8-119's on the brain.

That could hurt!

 

[RDP]

You said 2400, when most LP tanks are 2400+ or 2640. PST and Faber LP tanks are rated at 2640, not 2400.

It took me a minute to figure out what he meant too.

OK, I can understand that. I thought about that as I was typing. Just trying to get the idea across.

Thanks,

 

[The Kraken]

That could hurt!

Not when one is as dense and hard headed as I !!!

:bonk:

 

[RDP]

Should have stated my reply better. I meant to say that some LP tanks are positively buoyant when empty. Also that the rated volume quoted by the manufacturers is to the plus rating 2640 rather than the 2400 rating that you mentioned before. Just trying to clear a few things up and in the latter case double check if my thinking was straight regarding the rated volume/pressure quoted being the plus rating not the 2400psi rating.

At the risk of sounding stupid, who makes LP tanks that are positive when empty?

 

[simbrooks]

At the risk of sounding stupid, who makes LP tanks that are positive when empty?

The only tanks i could find were LP108 and LP120 (both behemoths of tanks) going positive, i thought had seen more around, particularly from someone like OMS/Faber, but cant find the info off hand beyond this site. No question is stupid (well almost no question), but it looks like maybe i made another slightly leading statement above, i might have to stop posting about tanks for a while

 

[DEW Diving]

Great math skills. You obvioulsy know the benifits of steel. Now KISS (keep it simple stupid) just tell the guy to dive STEEL!

Are you refering to the comparison between an aluminum low pressure tank and a steel high pressure tank?

If so, the significant difference falls in the displacement/capacity ratio.
For example, an aluminum 80 cu. ft. tank (Catalina), at nominal pressure, holds approximately 77.4 cubic feet of air. The tank itself is 7.25" in diameter and approximately 26" long.

A high pressure steel tank (PST E7-80), at nominal pressure, holds approximately 80 cu. ft. of air. This tank is 8.00" in diameter and approximately 20" long.

So, the aluminum tank, with a displacement of approximately 1073 cubic inches holds 77.4 cf of gas while the hp steel tank with a displacement of approximately 1005 cubic inches holds 80 cubic feet of gas.

Therefore the aluminum tank holds .0721 cf per cubic inch while the steel tank holds .079 cf per cubic inch.

Also the inherent densities of the tanks are different resulting in a more negatively buoyant characteristic for the steel tank.

All of these factors go into resultant areas of required weight with different equipment configurations.

 

[RDP]

The only tanks i could find were LP108 and LP120 (both behemoths of tanks) going positive, i thought had seen more around, particularly from someone like OMS/Faber, but cant find the info off hand beyond this site. No question is stupid (well almost no question), but it looks like maybe i made another slightly leading statement above, i might have to stop posting about tanks for a while

Learn something new every day.

 

[Leadking]

Yes they exist and the funny thing is that the steel tanks that are LP in the US are 300 bar in europe (actually just below). The Fabers are rated to 4K over there and 2640 here. That is why a lot of people don't have an issue with over filling the LP tanks.

I will tackle this issue again. Faber does not make a cylinder greater than 7" diameter that goes to 4000 psi for anyone in the world. The do make a version that resembles a steel 85. When you look at the manufacturers drawing and compare the weight the HP version weights 10 more pounds than our version.

Just because your getting away with it does not mean it is safe

 

[jonnythan]

Does anyone have any links to stories about overfilled LP steel tanks (Faber or PST) blowing? I've never heard of one.