Aluminum tanks High Pressure 74 vs 80

[jsado]

I have a Catalina aluminum 80 and I just bought a Catalina High Pressure aluminum 74. The 80 is rated for 3000 and the 74 is rated for 3442..... Assuming both tanks are filled to their rating and are used on exactly the same dives under the exact same conditions, which tank will potentially allow for a longer dive?

Also, a tank may be rated at 3000 and after the fill, it might have 3200 or 3300 in it. With that being the case, is it ok to fill the 3442 up to 3600 or 3700?

 

[wannabedivin]

IF the tank is filled to the working pressure, the gas in the tank is what the volume of the tank is rated at. So in your scenario the 80 has more gas. Another example is my 19CF Pony has a working pressure of 3000, but it is still only 19CF. Regarding you question about overfilling, I would highly recommend NOT overfilling. Some scuba cylinders have a plus rating on them, but I am almost positive that high pressures do not have this rating and I am also almost positive that aluminum tanks don't have this rating. (It has been several years since I researched this)

 

[mkutyna]

When you take your Scuba class, your instructor will explain to you how the pressure in a tank relates to how much air you have and what the Aluminum 80 and Aluminum 63 ratings mean.

Dive stores will sometimes fill tanks beyond their rated pressure because during the fill process they heat up. Once the tank cools down the pressure will decrease by a couple hundred psi. So, in order to counter the decrease in pressure, the tank is initially overfilled by a few hundred psi so in the end you will have a usable 3000 psi after it cools.

 

[Spimon]

Don't mind me

(Once again, the subtle differences between the metric system and imperial have bitten me in the rump and I proceeded to confuse myself.)

 

[Nemrod]

I have a Catalina aluminum 80 and I just bought a Catalina High Pressure aluminum 74. The 80 is rated for 3000 and the 74 is rated for 3442..... Assuming both tanks are filled to their rating and are used on exactly the same dives under the exact same conditions, which tank will potentially allow for a longer dive?

Also, a tank may be rated at 3000 and after the fill, it might have 3200 or 3300 in it. With that being the case, is it ok to fill the 3442 up to 3600 or 3700?

The 80 cubic feet @ 3,000 psi is more than 74 cubic feet @ 3,442 psi. The compressed gas becomes 80 or 74 cf at atmospheric pressure, at the rated pressure it exactly occupies the water volume of the tank in question.

NO, it is not OK to overfill aluminum tanks of any cubic foot or pressure capacity.

N

 

[WarrenZ]

If memory serves the Aluminum 80 is really a misnomer as the 80 is really 76-78 CF rounded up so both tanks are about equal I think.

If it was my tanks I wouldn’t try to push the limits of the tank; it could rupture. I personally haven’t seen a tank rupture but I have heard it can be a life changing experience.

Besides if you really need that extra 5 CF you can always dive LP 95s overpressured about 600-1000 PSI about giving you about 108CF (Not recommended but I survived my brush with da bends) We were on the hairy edge of the computers, off the deep end of the tables and still had air.

 

[Nemrod]

If memory serves the Aluminum 80 is really a misnomer as the 80 is really 76-78 CF rounded up so both tanks are about equal I think.

If it was my tanks I wouldn’t try to push the limits of the tank; it could rupture. I personally haven’t seen a tank rupture but I have heard it can be a life changing experience.

Besides if you really need that extra 5 CF you can always dive LP 95s overpressured about 600-1000 PSI about giving you about 108CF (Not recommended but I survived my brush with da bends) We were on the hairy edge of the computers, off the deep end of the tables and still had air.

You are correct, the typcial aluminum 80 is actually only 77 cf at it's rated 3,000 psi.

http://www.huronscuba.com/equipment/scubaCylinderSpecification.html

And while we are at it I am not familiar with any 3,442 psi aluminum tanks by Catalina?

http://www.catalinacylinders.com/

So I am curious exactly what you have?

N

 

[jsado]

And while we are at it I am not familiar with any 3,442 psi aluminum tanks by Catalina?

Catalina Cylinders

So I am curious exactly what you have?

N

The dive shop told me they were brand new from Catalina. I just went to their site and the tanks not there..... Here are the numbers on the tank:

DOT-3AL3442 FN00000004 M4002 11C07 CATALINA C74 SP12 TC-3ALM237

Don't know if that tells you what you wanted to know but....

 

[ronbeau]

You are correct, the typcial aluminum 80 is actually only 77 cf at it's rated 3,000 psi.

Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan

And while we are at it I am not familiar with any 3,442 psi aluminum tanks by Catalina?

Catalina Cylinders

So I am curious exactly what you have?

N

I wan't aware that HP aluminum tanks exist.

 

[spectrum]

I wan't aware that HP aluminum tanks exist.

Same here. Apparently his was produced last November.

What are the buoyancy properties? It may be a downsized version of the 3300 PSI Neutral 80.

Pete