Confusion
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rstofer
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You asked specifically why Florida cave divers like LP tanks and NJ wreck divers like HP tanks and I gave you the exact answer: Florida cave divers pump a lot of air into their LP tanks based on the idea that the tank can be over filled. This is possible because almost every LDS has a compressor that can reach to 3000 psi or more. This is a decent overfill for a 2250 psi tank. Almost nobody can routinely produce the 5000 psi it would take to overpressure a 3442 psi tank.
You can read through the threads of this forum to find a LENGTHY discussion on overfilling LP tanks. It is not a concept I support. But absolutely nobody gives a darn about my opinions.
The ONLY other reason for LP tanks is the fact that you will almost never get a complete fill of an HP tank on a charter boat and rarely at fill stations that support a local dive site. They don't even take the time to properly fill a 3000 psi Al tank.
The implication is that your HP 100 will seldom have 100 cf of gas unless you can leave it at an LDS long enough for them to finally get it full. Depending on their compressor, they may not be able to make a pressure much higher than the 3442 psi of the tank and they need to let the tank cool to get a complete fill. It takes time...
But it's up to you to consider how and where you dive, what weight and buoyancy characteristics are important and, finally, how much gas you need to carry. You have been given a link to a tank characteristics table. You can also Google for one. They are all over the place.
The only LP tank I would consider is the old LP 72. That tank is absolutely perfect for diving in a pool w/o a BC or weight belt. Just strap it on, mount a double hose regulator and relax in the warm water.
Richard
The LP95 was one of the first tanks available to divers that was larger than an 80. Still not as much air as a cave diver wanted. The cave divers found that they could overfill them for more air. Since nobody has yet been killed by one of those tanks exploding, they still overfill them.
A hp120 will hold almost exactly the same amount of air at the same pressure as an lp95 but will be safer, more expensive and still legal at least at pressures up to 3442psi. It will also have about the same trim and buoyancy characteristics. The HP tanks are made from stronger steel so at a given pressure, they have a better safety margin.
A wreck diver in NY will prefer an hp120 because while it holds the same amount of air as an lp95 at 3442psi, he doesn't have to worry about NY lawyers.
Some cave divers are switching to HP tanks but they still tend to overfill them but just not to as high a percentage overfill.
I think I am one of the few cave divers that doesn't overfill tanks. I just select the most appropriate tanks in the first place.
adm3745
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My LP 108 is just about the same size as a HP 130 but I get a 144cf at 3500 in the LP tank. I pay $299 for brand new 108s, and the HP 130's are over $400. My girlfriend dives LP 77 that she buys for $200 and the comparable HP 100's are almost $350. Because I trust overfilling procedures in my area, and am readily capible of getting them, and also plan on switching our new tanks in 3-4 years, LP tanks are the better more economical solution for me.
If your doing most of your diving outside of Florida, buy a HP tank because the baselines are comparable to the same sized HP tanks, and that way you can still get 3000-3200 probably without an issue anywhere.
If your doing most of your diving outside of Florida, buy a HP tank because the baselines are comparable to the same sized HP tanks, and that way you can still get 3000-3200 probably without an issue anywhere.
adm3745
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By that I mean if you think 3500 fills are an issue, just buy a tank with a capacity at 3000psi that you will be satisfied with. A HP 120 will still give you 105 cf at 3000 psi and will be much smaller than the LP 108 filled to 2600. Then when you get a full fill, you can enjoy the "extra" air.
Heres a link to the Spec chart for the new XS tanks. I've used the LP 108, 85, and 77 and think all three are great tanks.
XS Scuba Worthington Steel Cylinder Specifications
Getting 3442psi fills is not as hard as it used to be. With many SCUBA shops now filling paintball tanks, even getting fills to 4,500psi is becoming common. Two of the three LDS's near me can fill to 4500psi and the third one can fill to 5000psi.
adm3745
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haha so are we gonna see Florida Cave divers start overfilling HP tanks to 5000 psi in the coming years? 130 cf penetrations? I know my LDS doesn't like to go over 4k because of the wear on the compressor. When you say 4500psi is becoming common-do you mean that people are actually starting to Overfill the HP tanks?
No, the shops that I have been at only fill to service pressure. 4500psi service pressure is common for paintball. A few paintball tanks are rated for 5000 psi service pressure. The shops also fill 4500psi firefighter tanks. They filled my 4400psi DOT SCUBA tanks (3AA4000 +10%).
An LP 95 will hold 130 cu ft at 3600 psi while an HP 130 will hold 137 cu ft at 3600 ps, an X7-120 will hold 126 cu ft at 3600 psi and an X8-119 will hold 128 cu ft at 3600 psi.A hp120 will hold almost exactly the same amount of air at the same pressure as an lp95 but will be safer, more expensive and still legal at least at pressures up to 3442psi. It will also have about the same trim and buoyancy characteristics. The HP tanks are made from stronger steel so at a given pressure, they have a better safety margin.
A wreck diver in NY will prefer an hp120 because while it holds the same amount of air as an lp95 at 3442psi, he doesn't have to worry about NY lawyers.
Some cave divers are switching to HP tanks but they still tend to overfill them but just not to as high a percentage overfill.
I think I am one of the few cave divers that doesn't overfill tanks. I just select the most appropriate tanks in the first place.
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Weight wise an X7-120 weighs 38 pounds, an X8-119 weighs 42 pounds, an X8-130 weighs 43 pounds and a Faber LP 95 weighs 37 pounds while a Worthintgton or PST LP 95 weighs 42 pounds.
So...a Faber LP 95 with a cave fill gives you 130 cu ft for a basic tank/valve weight of 37 pounds - basically the same capacity as an HP 120 at 3600 psi, but a lot shorter and for divers under 6 ft that usually means much better trim with the shorter LP 95.
The X8-119 and X8-130 are both noticeably heavier than a Faber 95 - especially when doubled - but it is a draw when the HP tanks are compared to the heavier Worthington and PST LP 95's.
The X8-130 is similar in size to the Faber, LP 95 just an inch taller and 5 lbs heavier. The Faber LP 95 will be preferred for the lighter weight in cave country while the HP 130 makes a lot more sense if cave fill s are not available.
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It is pretty common for 3442 psi tanks to get filled to 3600-3700 psi in cave country, but no one is filling them much over that. Most people understand that the test pressure is 3/2 rather than 5/3rds and that the safety margin on HP tanks is not as great (and they lack the service history of the LP tanks), so I don't forsee shops that cater to cave divers pushing them more than a few hundred psi over the 3442 psi service pressure.
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