REE for PST LP72

[Cyborg Pirate]

If you have your own compressor why worry about the plus just get a copy of the hydro results and figure it out yourself. That is what I do.

Because I just got the tanks.... want them hydroed with + stamp so I know that they r safe to be handling the additional psi

 

[rjack321]

Because I just got the tanks.... want them hydroed with + stamp so I know that they r safe to be handling the additional psi

The + does not make them "safer" in any way shape or form. They are built to the same 3AA standard using the same 5/3rds hydro test. There are have been a few lp72s which have failed, its always a corrosion issue. Be diligent about your VIPs and don't worry about the +s

 

[Cyborg Pirate]

The + does not make them "safer" in any way shape or form. They are built to the same 3AA standard using the same 5/3rds hydro test. There are have been a few lp72s which have failed, its always a corrosion issue. Be diligent about your VIPs and don't worry about the +s

Awww gotcha. I thought (my mistake) that with a + stamp when they did the hydro they also did an increase in the pressure/expansion test.

 

[Rred]

That's my impression too: That they put in 5/3 of the 110% pressure, instead of just 5/3 of the base rating, and the tank isn't supposed to expand more than the ##cc of the REE number during that higher pressure test. (Which is why shops don't want to bother doing + tests, because they'd have to change pressure settings as well as look up numbers.) No?

 

[captain]

The plus is determined by a simple calculation using the normal hydro test results.Somewhere in this tank section or the vintage scuba section there is a thread with the explanation of how it is done.

 

[captain]

That's my impression too: That they put in 5/3 of the 110% pressure, instead of just 5/3 of the base rating, and the tank isn't supposed to expand more than the ##cc of the REE number during that higher pressure test. (Which is why shops don't want to bother doing + tests, because they'd have to change pressure settings as well as look up numbers.) No?

Wrong.

 

[captain]

From another thread.

Testing for the + is NOT a huge amount of extra work. Here's how a standard hydro test is performed:

• The cylinder is pressurized to hydro pressure, and the displacement in mL is recorded. This is the Total Expansion.
• The pressure is released, and the amount of expansion left over is Permanent Expansion.
• Total Expansion - Permanent Expansion = Elastic Expansion (how much the tank expanded and contracted during the test).
• Was the permanent expansion 10% or less than total expansion? If so, then the cylinder passes hydro.
• Here is the "extra work:" -- Is Elastic Expansion < Rejection Elastic Expansion (REE)? If yes, then +. If no, then no + rating.

For a numeric example -- this is information from a hydro test on a PST LP80 I had awhile back:
Since this is an LP cylinder, the service pressure is 2400psi. 5/3 of 2400 = 4000. Thus, the hydro pressure is 4000psi.

• REE is 66.3mL as stamped into the side of the cylinder.
• Total expansion was 56.3mL.
• Elastic expansion was 56.0mL.
• Permanent expansion was 0.3mL.

First, did the cylinder pass hydro?
10% of 56.3mL = 5.63mL. Is 0.3mL < 5.63mL? Yes. Thus the cylinder passed hydro.

Does the cylinder get a + rating?
REE = 66.3mL
EE = 56.0mL
Is 56.0 < 66.3? Yes, thus the cylinder qualifies for the + rating.

 

[Rred]

Then it really is just the extra cost ($125) for the custom + stamp (that's not in standard die sets) and am inability to do simple mathematics that keeps the bulk of shops from being able to offer + hydros?

 

[ScubaBunga]

Let us know if you get the + on those (and what the hydro place says about it) - my hydro shop will only + a tank they can get the exact ree for that serial number. Which since PST doesn't have any docs (I had contacted them as well and got the same answer that they didn't have any old tank info). They won't even consider that old pst doc, but I have it in case I find a hydro shop that will take it. There was another thread on here somewhere where the guy (sorry I don't have the exact reference) had enough tanks and tools to measure the required number of tanks to generate the ree for pst, norris and I think others. A search may still find it.

 

[Cyborg Pirate]

From another thread.

Testing for the + is NOT a huge amount of extra work. Here's how a standard hydro test is performed:

• The cylinder is pressurized to hydro pressure, and the displacement in mL is recorded. This is the Total Expansion.
• The pressure is released, and the amount of expansion left over is Permanent Expansion.
• Total Expansion - Permanent Expansion = Elastic Expansion (how much the tank expanded and contracted during the test).
• Was the permanent expansion 10% or less than total expansion? If so, then the cylinder passes hydro.
• Here is the "extra work:" -- Is Elastic Expansion < Rejection Elastic Expansion (REE)? If yes, then +. If no, then no + rating.

For a numeric example -- this is information from a hydro test on a PST LP80 I had awhile back:
Since this is an LP cylinder, the service pressure is 2400psi. 5/3 of 2400 = 4000. Thus, the hydro pressure is 4000psi.

• REE is 66.3mL as stamped into the side of the cylinder.
• Total expansion was 56.3mL.
• Elastic expansion was 56.0mL.
• Permanent expansion was 0.3mL.

First, did the cylinder pass hydro?
10% of 56.3mL = 5.63mL. Is 0.3mL < 5.63mL? Yes. Thus the cylinder passed hydro.

Does the cylinder get a + rating?
REE = 66.3mL
EE = 56.0mL
Is 56.0 < 66.3? Yes, thus the cylinder qualifies for the + rating.

Nice! I learned a bunch of new information. Thank u. Guess a hydro will work. Save the extra cash and continue with my own VIP and fills.