When 80 does not equal 80

[paulwlee]

Welcome to Scubaboard, tivey!
Nice to have someone from Pressed Steel available to clear things up. I'm getting a couple of E7 100's to double up, and will be diving them as singles this weekend as the other components are still coming. Can't wait to try them out!

I have two questions for you.
Is the Pressed Steel website ever going to be updated with the new product information?
Also, are the tank specs, such as in http://www.lloydbaileysscuba.com/PST E Series Tanks.htm
accurate?

Thanks in advance.

 

[crispos]

Thought Catalina was bought by Luxfer been a few years now.
80's are rounded up for convenience, just like Honda 750's and lots of other things. Imagine if divers were shouting across the boat, can you grab my 77.456. What's the big mystery? I like water volumes. I am equally comfortable diving an 18L as a 138 (Canadian eh?). Oh yeah, PST, I would feel better if you said the tank gives exactly 80 cubic feet at a specific temperature and pressure. What's with this, at least stuff? Makes me wonder.....

 

[RichLockyer]

crispos once bubbled...
Thought Catalina was bought by Luxfer been a few years now....

Nope.
Luxfer picked up the scuba end of Kidde about 10 years ago, but Catalina and Luxfer are most certainly separate corporations.

 

[crispos]

Thanks for the correction. Catalina Cylinders alive and well, yes.
Owned by Aluminum Precision since 1992.

 

[pescador775]

"Standard" is a novel way to put it. Compromise is the word I would use. I suspect that the 'standard' part concerns the dimensions. Alcan designed an 11 liter tank with a round fill pressure of 3000 psi and called it "80" for marketing reasons. Like $20.00 sounds like more than $19.98, so "80" sounds like a whale of a lot more than 77.4.

 

[padiscubapro]

tivey once bubbled...
PST-Scuba

Cylinder Internal Volumes:
All rated volumes for PST-Scuba products are minimums. For example an E7-80 (replacement for the HP-80) holds a minimum of 80 cubic foot at 3442 psi at 70 degrees.

Best regards,

Thomas Ivey
PST-Scuba Product Mgr.
tivey@pressedsteel.com

Yes but what gas??? depending what you fill it with will alter how much it holds! Specifications are useless without being specific..


More oxygen gives you a greater capacity, add a little helium it reduces your capacity...


Also your calculation of 80 is that based on real, ideal or actual test data??
if its based on "ideal" calculations an 80 @3442 with AIR would only be about 76

Real and Ideal laws for "air" yield the same value at around 2050psi, in general "air" fills below this pressure have more than calculated by ideal laws, while higher than this pressure yield less than ideal laws state.

oxygen becomes more compressable until about 2300 psi then starts to become less compressable, but even at 400psi its still more compressable than at the surface..

I'm not sure how luxfer rates their cylinders but here is an example how ratings can be skewed a luxfer "80" rated at 77.4 in air (real) would yield about 81.7 if it was filled to 3000psi with 100% oxygen...
or 77.4 (ideal) to real would be 75(real) would yield 79.2 cu ft with 100% oxygen....