HP vs. LP / High Pressure versus Low Pressure steel tanks

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Originally posted by pescador775
The differences in partial pressure Nitrox filling a LP tank overfilled to 3000 psi and a HP tank @3500 are insignificant.

A 102 LP tank of 8 inch dia has 25% more drag than a comparable HP steel and 50% more drag than an older steel 72 or SP 3300 psi 72.
First statement.... apples to apples... the difference in PP mixing between a 2640 psi LP 104 and a 3500 psi HP 102 is very significant... you don't do much PP mixing do you? Or you are using a booster.... or you are sending a lot of gas back in the supply cylinders that was unusable because you used a hp tank.

Second statement.... Just how much drag is that compared to the total drag of the rig? The drag presented by the rounded end of any of these tanks is minimal compared to the total drag (and certainly that boot on the bottom of your tank is a bigger inducer of drag... not to mention the netting to keep your tank pretty.) 25% of a very minimal amount is a very minimal amount so get specific and quantify the drag for us.

You are right... the LP 104 is heavier to carry out of the water than a HP 102... but that isn't such a big deal to some of us. :D
 
Originally posted by pescador775 If you don't understand this, you are probably DIR .

What does that make you? DIW? If you understood DIR you would not have said that. So much for logic and civil discussions. You can still find double hose regs on ebay. Go for it.:confused: ;-0
 
Yo! Joe, how low can I go.... Double hose regulator? Funny you should say so. The Do-It-Retro guys should be right at home with a double hose. Let's see, they are already using 50's era tank harnesses with crotch straps, obsolete low pressure tanks sans boots, 60's type Turtle fins, dry suits copied from Cousteau's Constant Volume Frogman suit, bat bladders and wussy soft weight belts which coincidentally date to the NOW revolution. How old is Irvine anyway?

No matter, those old guys with the double hose scuba were diving the Andrea Doria before most of us were born. Sorta makes one humble, especially newbies who think that their leader invented the wheel.
 
Well I got up this morning to go out diving with a couple of friends. He has a HP 102 and she has a HP 80 and they are well matched because he uses more air. I took a single LP 104 but since the bank was low I could only fill it to 2100 psi without starting the compressor. So that gave me 83 cf for the dive.

Perfect I sez.

So we went out and had a great dive... astounding visibility for around here... 70'+ .... saw a giant Pacific octopus and all the rest of the usual stuff...

Finished the dive and still have 700 psi in the LP 104. So now I have to leave you fine folk and go out to the garage and start the compressor. I'll fill the bank as well as several LP 104s while I rinse my gear....

Shoot... maybe I won't even bother rinsing my gear since I am going out again tomorrow....

Shoot... maybe I won't even fill the bank since I can still get 2000 into a LP 104 for tomorrow's dive....

That's 79cf and....
That's the beauty of an LP 104 :D
 
Originally posted by Uncle Pug
LP tanks can be re-tested to the + rating
Additional information...
The above is theoretically true but at least around here practically impossible...

I checked with my hydro guy and he says that DOT has made it almost impossible to comply with the proceedures for + rating a cylinder and he won't even try...

Now if someone knows of a hydro tester that will + rate a steel cylinder post it on the board here...

I intend to get an answer from PST... though it is not an issue to me since I fill my own anyway...
 
My PSI instructor can & will do it... he is down in Ft Lauderdale, and I believe that my local Hydrostatic test guy can & will as well. I will get you definitive answers within a day.
 
Have mercy, I see what the problem is; Part 173.302 of the Federal Register requires some fancy footwork before the tester can legally plus rate a tank. The tester is required to calculate the maximum or average wall stress of the tank. The formula provided in the Register could be rather intimidating to most people. Basically, it would be necessary for someone with smarts to program a hand computer with the formula. Then, some data and specs for 3AA alloys would have to be researched from CGA 5. This, along with the hydro data would have to plugged into the equation.
 
Originally posted by NetDoc
My PSI instructor can & will do it... he is down in Ft Lauderdale, and I believe that my local Hydrostatic test guy can & will as well. I will get you definitive answers within a day.
Thanks Pete... I forgot about PSI... perhaps they can recommend some one near Seattle. Shipping is prohibitive.
 
https://www.shearwater.com/products/peregrine/

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