Which brand of steel cylinder / tank should I buy?

[Thomas Ivey]

Originally posted by Tavi
Hey Thomas,

I was going to e-mail you but you have it turned off.

Other than the sticker on the tank, Is there any difference between the Aqua-Aire Sport and the Genesis HP Tanks ?

Thanks, Tavi

Good question, the answer is yes and no.

In 1986 we originated the first HP 3500 psi scuba tank. This design (DOT-3500 E9791), which today is the AquaAire Sport series, was sold exclusively sold to Sherwood Co, they labeled it in their "Genesis" line of scuba gear and they sold it for about 6-8 years. Lately there is a new company now called Genesis, they sale a HP pressure tank and it is not a PST product. Some stores will say it is ours but is not. To verify that it is ours look for the E-9791 mark on the tank.

This other tank come from Japan and is heavier, longer, and bigger in diameter, is not hot dipped galvanized. Plus it is a made from tubing which is not the preferred way to make a scuba tank.

ti

 

[scubakat]

Hi Dane... yup I had mostly settled on the LP cylinder for that reason, but then I saw the Genesis HP's at Leisurepro for $209 ea. & was tempted. Now that I know they are not made by PST (thanks TI!) I'm not gonna go there. I'm doing 30-40 minutes on an AL80 w/ 1000 psi left over. My LDS is going to let me try a Faber LP85 which I think will put me into the 50+ minute category. The only reason I am tempted by the HP80's is size. I'm only 5'4" I seem to pitch & roll more with the LP95's. I haven't paid attention to the size of the 104's you have. Nope, I have not met Dave yet.

-kate

ps
Are you gonna let me try out those Jets one of these days?

 

[Thomas Ivey]

Originally posted by WetDane
Hey Kate,

I have another consideration for you...
Here's the scoop the way I see it - to get your 100 cf in a HP, you need to have a 3500 psi fill - which most shops are incapable of giving - so you end up with about 3000, by the time the tank is cooled you may be down to 2800 - without doing the math - I'd say you now have about 80cf or less in your tank...

As you know I dive LP104's - I need 2400 psi to get my 104 cf - our favorite mix master usually boost me alittle and I end up closer to 2800 in the water - you wanna guess who has more air? David (have you met?) and I consistently have 50+ minutes dives and plenty of air to spare...

Anyway - there was some other metaphysical subnuclear explanation that the mixmaster could not remember last time we talked about it...

Short of the long - I'm a happy camper - but maybe that's just because I can see in the dark murhy waters here...
<VBG>
Dane

You actually need 2640 psi for internal capacity of 104 cf.

ti

 

[dsquid]

This is probably a stupid question but....

My dive shop fills my PST HP120's to 3500psi by filling them, letting them cool, and giving them another shot to top them off.

Someone said earlier in this thread that most dive shops
are unable to fill HP to 3500. Is this a matter of
a shortcoming of their hardware or patience?

Bill

 

[Thomas Ivey]

Originally posted by scubakat
Hi Dane... yup I had mostly settled on the LP cylinder for that reason, but then I saw the Genesis HP's at Leisurepro for $209 ea. & was tempted. Now that I know they are not made by PST (thanks TI!) I'm not gonna go there. I'm doing 30-40 minutes on an AL80 w/ 1000 psi left over. My LDS is going to let me try a Faber LP85 which I think will put me into the 50+ minute category. The only reason I am tempted by the HP80's is size. I'm only 5'4" I seem to pitch & roll more with the LP95's. I haven't paid attention to the size of the 104's you have. Nope, I have not met Dave yet.

-kate

ps
Are you gonna let me try out those Jets one of these days?

If you are going the LP route. Two things, one the OMS 85 (82cf) is a 7 inch diameter and is the same length as your alum 80 (26 in), two look at the PST LP-80 (82cf) it has a 7.25 diameter and a length of 24 inches length.

The HP-80 at 2640 psi holds 64.5 cf.

ti

 

[WetDane]

dsquid,
it is my impression that some shops systems simply are setup to run to 3000 psi and not to 3500 - I think it is an equipment deficincy more than an issue of being lacy - however - I have no hard facts on the number of shops/compressors - Sounds like I would like to get my tanks filled at your shop - are you anywhere near the puget sound?!?! ;-)

ti
I just want to say thanks - I really appreciate you taking the time to answer these questions - it is obvious that you know what you are talking about and it is nice that you are informing rather than pushing PST - personally, I will never buy any other brand - I love my tanks.

Cheers all - back in the water,
Dane

 

[dsquid]

WD,
Heh, no My shop is nowhere near the Puget sound... I live in Southern New Jersey. HP tanks are the norm here, and every shop I've ever visited (in NJ) can fill 'em to 3500.
Admittedly I've only been to a handful of shops.

We get out to Seattle every other year or so... looking forward to diving that area soon.

Bill

 

[scubakat]

Originally posted by Thomas Ivey
The HP-80 at 2640 psi holds 64.5 cf.
ti [/B]

Thanks TI, that's all I needed to know to know that I don't want an HP tank.

So now it's dumb question time. How do you do the math to calculate that? I get just wacked trying to do the unit conversions...

I have been diving the PST LP-80's (rentals) I like them very much. I think I want just a little more air though. Can you paint the PST's?

-kate

 

[Warhammer]

Scubakat.....For a small guy like yourself, I think you should strongly consider HP tanks over LPs. Here's the reason:

• 
  Catalina S80 (Aluminum)
• Height________________25.8"
• Diameter______________7.25
• PSI___________________3000
• Weight(empty)_________31.6 Lbs
• Weight(full)__________37.8 Lbs
• Bouyancy(empty)_______+4.1 Lbs
• Bouyancy (full)_______-2.1 Lbs
  [red]
• Real Weight______35.7 Lbs[/red]
• Amount of air @3000___77.4cf
  
  Pressed Steel HP100
• Height________________23.9"
• Diameter______________7.25
• PSI___________________3500
• Weight(empty)_________31.0 Lbs
• Weight(full)__________39.0 Lbs
• Bouyancy(empty)_______-9.4 Lbs
• Bouyancy (full)_______-1.4 Lbs
  [red]
• Real Weight______29.6 Lbs[/red]
• Amount of air @3000___85.7cf
  
  Pressed Steel HP120
• Height________________27.9"
• Diameter______________7.25
• PSI___________________3500
• Weight(empty)_________36 Lbs
• Weight(full)__________45.6 Lbs
• Bouyancy(empty)_______-10 Lbs
• Bouyancy (full)_______-0.4 Lbs
  [red]
• Real Weight______35.6 Lbs[/red]
• Amount of air @3000___102.9cf
  
  Faber LP95
• Height________________23.8
• Diameter______________7.25"
• PSI___________________2640
• Weight(empty)_________37.3 Lbs
• Weight(full)__________44.9 Lbs
• Bouyancy(empty)_______-5.2 Lbs
• Bouyancy (full)_______+2.4 Lbs
  [red]
• Real Weight______39.7 Lbs[/red]
• Amount of air @3000___108cf(overfilled)

Look at the [red]Real Weights[/red], if you'll notice the same "real" weight your carrying with your AL80, you can go to a PST HP120 and have the same weight but gain almost 26cf of air @ 3000PSI, and the potential for 43cf more air if you filled it to 3500PSI. With a PST HP100, you'd loose 6Lbs off your back and still gain 8cf of air, with the potential of a 23cf air when full. Plus due to the negative buoyancy of the HPs, you'd loose weight off your belt.

A tanks "real" weight is the actual empty weight + it's bouyancy when empty.

To figure out how much air any given tank has at any given pressure, you take the tanks rated capacity and divide by it's rated pressure, then multiply that number by the pressure you're wanting to determine the amount of air for. So to find out how much air a PST HP 120 has at 3000PSI:

(120/3500) * 3000 = ?
(0.03429) * 3000 = ?
0.03429 * 3000 = 102.87 cf

 

[rcohn]

Scubakat,

If you're happy with the extra weight go for it. My wife would kill me if I tried to get her to use LP tanks and I have no desire to lug them around either.

Wetdane, your math isn't improving. Here in Massachusetts all the shops I know can pump to 3500 psi. On a typical fill you get 3200 to 3300 psi after cooling. If you cool the tanks and top them off you'll get a full 3500 psi. I've never had a 2800 (or even a 3000) psi fill.

Ralph