hp vs lp tanks

[CJ-62]

There are several sites that list tank specs, i.e.;
http://www.nitroxdiver.com/Library/tanks.html
http://www.huronscuba.com/equipment/scubaCylinderSpecification.html

As an example:
Luxfer AL80 @3000psi has volume 77.4 ci, Dia 7.25 in, Length 26.06 in, weight 31.38 lbs, bouyancy empty +4.4 lbs, bouyancy full -1.4 lbs.
PST Steel LP-80 @2400psi has volume 80 ci, Dia 7.25 in, Length 24 in, weight 34 lbs, bouyancy empty -1 lbs, bouyancy full -7 lbs.
PST Steel HP 80 @3500psi has volume 82 ci, Dia 7.25 in, Length 19.75 in, weight 28.6 lbs, bouyancy empty -3.3 lbs, bouyancy full -9.3 lbs.
so let's start with the scenario that you are perfectly weighted with an AL80 and 25lbs of lead, surface neutral with ~300psi in tank.
Changing nothing else but tanks/lead, you shed 5.4 lbs of lead, perfect at 19.6 lbs, when using a PST steel LP-80. Your dry weight drops 2.8 lbs.
You are perfect at 17.3 lbs lead, drop 7.7 lbs, when using a PST Steel HP 80. And your total dry weight is 10.5 lbs less. That's enough to feel over a long walk to the entry point.
When I ran these numbers by my wife, who is a rather petite diver, she immediately asked me why I had not procurred a HP80 for her a year earlier. She now has 3 of the PST HP80's.
Good luck and good diving.

 

[lamont]

PST Steel LP-80 @2400psi has volume 80 ci, Dia 7.25 in, Length 24 in, weight 34 lbs, bouyancy empty -1 lbs, bouyancy full -7 lbs.
[...]
so let's start with the scenario that you are perfectly weighted with an AL80 and 25lbs of lead, surface neutral with ~300psi in tank.
Changing nothing else but tanks/lead, you shed 5.4 lbs of lead, perfect at 19.6 lbs, when using a PST steel LP-80. Your dry weight drops 2.8 lbs.

and lets compare LP-80 to E7-100 in order to hold water volume constant, instead of gas supply:

E7-100: volume 100 cu ft, 32 lbs dry, -1.3 empty, -8.8 full.

add #0.3 lbs to 19.9 lbs of lead. lose 1.7# dry weight, gain 0.1# when full.

basically same tank, same size, same weight all around generally, but 20 cu ft more of gas. so if you're okay with the weight of the LP tank, there's no reason not to get the HP version of the same water volume to get more gas.

LP80 -> HP100
LP95 -> HP119
LP96 -> HP120
LP104 -> HP130

 

[AZ_Zoner]

One other thing to consider is topping off using 3000psi tanks. The dive boats that I was on a few weeks ago had alum 80's at 3000psi. Topping of my lp 108's using the 80s was nice. The hp 120 tanks that were on board were not able to be topped off completely. Meaning thier 2nd and 3rd dives of the day they were lacking back gas. How much less, I don't know. We didn't spend the time to figure it out then.

CB