hmm... LP or HP steel tanks?

[Black-Gorrilla]

im looking at possibly picking up a set of steel tanks... whats better to have? LP or HP? on an LP it's full fill at (less than 3000 right) and HP is full fill at like 3400?

[ScaredSilly]

I like LP85s (2400+) the wife has MP 72 (3000+) both doubled.

LP easy fills, epsecially with PP nitrox fills.

HP smaller package, can be harder to get full fills.

[cummings66]

I like HP tanks. They weigh a lot less than a LP tank of the same volume and like scaredsilly said, the fills are harder to get full.

The pressure is either 3442 or 3500 psi commonly, there are some rated to 4350 but not in common usage.

[Flatliner]

I haven't bought any yet but my research would indicate that HP is the way to go. Look at it this way, pick the tank that is the size (as in height/diameter) you want and then figure the volume at different pressures. Just because it is an HP120 doesn't mean you couldn't occasionally use it as an LP90.

[Black-Gorrilla]

well, im 6'4 so any size tank can be strapped onto me... and i can handle some weight too... so i guess some HP steel 100's, even when filled to like 3000 should be enough for a simple fun dive...

[in_cavediver]

When I want to choose a tank, here is what I do:

1) Decide on the min capacity I want/need
2) Determine the optimal buoyancy characteristics (positive or negative when empty and how much of each)
3) Trim issues - Which tank is easier to carry horizontally when diving

For instance, I'm 5'10' and I want a tank with more than 100cft. I Plan to dive dry so I want a negative tank when empty. That leaves a couple choices. Here's a few. LP120, LP112, HP120, HP119, and HP130. (Al gives + when empty)

Of those, the LP120 is roughly a small water heater which may not be very comfortable to lug around. The HP 120 is extremely long but only 7.25" inches (or 7" can't remember), again to long to be comfortable. The LP112 is just a bit taller than the HP119 (think LP95) and the HP130. They are still quite close in height. One of those tanks would be my choice depending on the specifics of the buoyancy characteristics and what I wanted.

Now, for HP or LP. It doesn't make much of difference. The HP130 is roughly an LP104, the HP149 is an LP120. If you can't get 'full' fills then remember what the 'lp' equivalent is and plan around that number.

I have LP104's and when I get another set, it will either be the HP130's, HP119's or LP112's but most likely the 130's.

[cummings66]

I like my HP120's, but to be honest the HP100 is a sweet tank. It's almost the perfect tank for diving IMO.

[Black-Gorrilla]

is there a tank pres. calculator online somewhere? (to figuere out hp 100's at 3000, lp tanks at overfills etc.?)

[in_cavediver]

Originally Posted by Black-Gorrilla

is there a tank pres. calculator online somewhere? (to figuere out hp 100's at 3000, lp tanks at overfills etc.?)

The math is easy: here the formula:

Cft rated
---------- * Actual Fill pressure = Actual Cft
Full pressure

OR for an HP 100 at 2600psi:

100/3482 * 2600 = 74.6 cft

[Jamesmb]

{100/3482 * 2600 = 74.6 cft}

Should that be 3442 instead of 3482?