Single and doubles

[DA Aquamaster]

Under fills may still be an issue in some areas, but it is becoming less of a problem and those tend to be the same shops that under fill AL 80's to 2800 psi or so. The problem is often that the shops in question do not realize that you can exceed the rated pressure during the fill as long as it is at rated pressure when it cools to room temperature and if that occurs the tank is never "overfilled". When shops stop filling at the rated pressure at a normal fill rate, whether it is 2400 psi, 3000 psi, 3300 psi or 3442 psi, and underfill of about 200 psi is inevitable.

In that regard thre 3442 psi tank is no worse off. More importantly it does not matter as the diver with the under filled 3442 psi tank is still well ahead of the curve.

For example, an LP 95 filled to the "+" rated 2640 psi fill pressure holds 95.1 cu ft, but if filled to the 2400 psi service pressure it holds only 86.5 cu ft. The worthington LP 95 weighs 42 pounds is 8" in diameter and is 24" tall.

The worthington HP 130 is very similar at 43 lbs in weight, 8" in diameter and 25.5" in lenght. It is basically 1 pound heavier and 1.5" longer. But it holds 131.4 psi at 3442 psi. and still holds 95.4 cu ft at only 2500 psi, and 85.9 cu ft at 2250 psi.

So in effect the worthington HP 130 is nearly the same size and weight as a worthington LP 95 and you'd have to have the HP 130 under filled by more than 900 psi to have less gas than a plus filled LP 95. You would have to be under filled by nearly 1200 psi to have less gas than an LP 95 that is filled to the rated 2400 psi service pressure.

If you check the following links and play with the numbers, you will find the same is true in nearly all cases when you compare a low pressure tank to an HP tank of similar dimensions and weight. The HP tanks weigh maybe 1 pound more on average and have very similar volumes at identical fill pressures, so the diver is still way ahead with a very badly under filled HP tank compared to an LP tank with a 10% overfill.

XS Scuba Worthington Steel Cylinder Specifications

Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan

 

[rrweather]

Thanks for all the help. I lucked out. I fly in the Air Force and happened to be in Delaware for the night. I found the only dive shop in town and found their price on HP 100 tanks to be better than I have found anywhere else around California or online. I picked up two of them. Luckily Delaware has no sales tax so I saved $50 buying them here. I'll carry them on the plane with me tomorrow so I don't have to worry about shipping costs. Everything worked out! Thanks again for the help and the information.

 

[Van Isle]

Nice score on the new tanks! But to continue the debate - as I am pondering the same Q's right now - I am thinking HP 100's are also the thing for me.

Great single tanks with lots of air for recreational dives, and doubled they have lots of gas for the deco/technical dives I plan on doing, in the far future, one day when I grow up!. AND they are not absolute beasts doubled up. Although the HP 120's and 130's are the "be-all, end- all" doubles for hardcore tec diving, if I ever get to that stage, the extra $1K I'll need to spring for new tanks, bands, mainfold will certainly pale in comparison to the $$$ I'll spend on training, travel, and helium.

Thoughts?

VI

 

[DA Aquamaster]

That is pretty much it.

 

[rrweather]

Nice score on the new tanks! But to continue the debate - as I am pondering the same Q's right now - I am thinking HP 100's are also the thing for me.

Great single tanks with lots of air for recreational dives, and doubled they have lots of gas for the deco/technical dives I plan on doing, in the far future, one day when I grow up!. AND they are not absolute beasts doubled up. Although the HP 120's and 130's are the "be-all, end- all" doubles for hardcore tec diving, if I ever get to that stage, the extra $1K I'll need to spring for new tanks, bands, mainfold will certainly pale in comparison to the $$$ I'll spend on training, travel, and helium.

Thoughts?

VI

This is pretty much the conclusion I came up with. If I get to the point that I need doubled up 130s, I will accept the fact that I need to drop more money on new tanks. For now, the 100s will be more than adequate. Also, the two dive buddies I have here use 100s and 95s so I would be limited by their tank size if I went much larger.

 

[DA Aquamaster]

Your last sentence puts you ahead of the game compared to most people when it comes to deciding on tank size. If you do anything techical, your gas planning is limited by the person on the team with the smallest tanks, so consideration for what your buddies use is a major consideration.

One thing to consider is that if you ever start going to Florida to cave dive (admittedly unlikely for you to bring your own tanks from CA) an HP 100 and an LP 95 have vastly different real world capacities as the LP 95 will get filled to 3600 psi and hold 130 cu ft in north Florida.

Everywhere else, an LP 95 filled to only 2400 psi (ie; no plus rating) only holds 86 cu ft and an HP 100 filled to only 2950 (ie: 3000 psi fills only on a dive boat) holds the same 86 cu ft, so the two are pretty similar with the HP 100 being a little lighter.

Also, if you get to the point of needing more gas for deeper dives, a stage with bottom mix becomes an option. Adding an aluminum 80 as a stage that is used prior to starting on your back gas, gives you another 70 or so cu ft of useable gas and makes up for the smaller double 100's versus double 130's. Plus you only carry the extra weight of larger doubles on the dives where you need more than 200 cu ft of gas rather than on all of them.