HP vs. LP Steel tanks. Whats the difference ?

[PerroneFord]

Got it. That is scary.

Not as much as you might think...

 

[BoltSnap]

You'll note that cave divers rarely use HP tanks. Once you come to understand why that is, you'll have the answer to the first question.

Can you give us a clue please?

 

[Diverdown269]

I work in the dive shop as part of my asst instructor class, and we are threatened with severe bodily harm (or worse, not going on the next dive trip) if we over fill tanks......

So cavers are getting 165cf out of an LP 108 by over filling them.... i aguree, that is scary.... i quite playing with explosives when i got out of the military

 

[T. Bix]

It looks like everybody was typing at the same time this thread went nuts all at once! I don't think overfilling was the answer as far as what my instructor was saying but it seemed that he was alluding to baselines..... That said my HP130s have a baseline of 3.7 (Cu Ft/100psi) So without "cave filling" how does this all work?

 

[scawt]

I have mostly high pressure tanks just because not all dive shops will over fill low pressure tanks. I do have some low pressure tanks that I use in fla or when I go to shops where I know the owners. Or when I can transfill them from other tanks I have.
As far as what works for what type of diving? It is all a matter of you and you preference. Take into account trim and buoyancy characteristics.
I speak from experience (cave and advanced trimix)
it all is about personal preference when it comes down to it.

Scott


The baseline number comes into play when you are gas planning and gas matching. You know your tanks are 130cuft when at 3442 psi ( pst tanks). But what if the shop you get it filled only fills it to 2900? Well you
Multiply the magic number by your fill pressure (0.037) and you get 107 cuft. Now you can use your sac (that is another discussion) and you can figure out your dive plan given the actual gas you have.

 

[VooDooGasMan]

Now if you fill your HP to 4500, you have alot of air for classes, most likely you will need a haskel pump and water tank for cooling and safety reasons. When I taught diving, my 102 HP's to 4500, and my al 50's 3900. I would do a friday pool, saturday morn pool, saturday dives 1&2, sunday dives 3&4. Four tanks and have 1000 left in all for reserve. Mind you I eat very little air.

But yes pump those baby's up, and diver down you are in michigan, and soon in your wreck diving you will have double burst disk, in all your tanks, cause thats what you do to have plenty of air on those wreck penetrations in the great lakes. (or you switch to a rebreather right now).


Happy Diving

 

[Doc Harry]

Thanks for the info guys. Perrone, how can an LP hold more gass than an HP. seams physicly impossible....

It is impossible, unless your over-pressurize.

 

[PerroneFord]

Can you give us a clue please?

Some divers overfill tanks. This is fairly common practice among cave divers.

At 3000psi a tank rated at 108cuft holds 122cuft of gas. This is a pretty common fill. Personally, when I do my tanks it's usually to 3200-3300psi.


Everyone makes their own choices about what they are willing to do.

 

[Rainer]

It is impossible, unless your over-pressurize.

If you over-pressurize both the LP and HP by the same percentage, the HP will still hold more gas.

 

[WetBoy101]

HP and LP tanks are constructed of different materials, they have different buoyancy characteristics, they don't weigh the same even empty.

And in some places (like where I live) the LP tanks can easily hold more gas or air than the HP130.[/QUOTE

Not if you overfill your HP130s too!?!?!?!?