I got a PST 'mid pressure' tank recently that needs hydro. I remember reading somewhere that the 3442 tanks did not use the 5/3s hydro of other high pressure tanks. A lot of googling later found this from PST:

PST high-pressure (3442 psi) cylinders must be retested in accordance with DOT –E9791 or TC-SU4349-230 and have special test requirements based on
their design and the DOT/TC requirements. This bulletin provides the necessary information.
1. The retester must have a current copy either DOT-E9791 or TC-SU4349-230.
2. The test pressure is 5250 psi.
3. The wall calculations of CGA-C6 are not applicable to these high-strength steel cylinders. For the purpose of inspection criteria, the minimum
wall for a new E7 cylinder is .179 inch, and E8 is .197.
4. Almost all PST high-pressure scuba cylinders are hot dip...

5/3rds would be 5700 PSI. So, it is actually 3/2s. I'm thinking of writing on the tank the correct hydro pressure to test. The PDF from PST is here (http://www.vintagedoublehose.com/downloads/PST-D-100.pdf). In that also describes the difference in how to perform the test (it has to be pre-pressurized).

Damn glad you posted this..I have 4 compact 80 3442's...Thanks

I dont get the 5/2's or the 3/2's pleez splain it to me

Damn glad you posted this..I have 4 compact 80 3442's...Thanks

I dont get the 5/2's or the 3/2's pleez splain it to me

So how were you "damn glad" since you have no idea what it means? :D

:rofl::lol::rofl::lol:So how were you "damn glad" since you have no idea what it means? :D

Sure- standard tests for hydro involve increasing the pressure in the tank to 5/3rds its rated capacity. For a 3000psi AL80, that would be 5000. For 'high pressure' steels, it is also 5/3rds- to 5700 on a 3500 psi tank. But the 'mid pressure' steels (the 3442) have an exemption because they are really relabeled LP tanks and should only be tested to 3/2s of the rated pressure.

I suspect most hydro places don't know this. Two things bad when they do it- they 'age' the tank faster because of stress is outside the rated range, and tanks were failing more often than they should.

So how were you "damn glad" since you have no idea what it means? :D

Cuz i deeent wanna do it incurectally

Sure- standard tests for hydro involve increasing the pressure in the tank to 5/3rds its rated capacity. For a 3000psi AL80, that would be 5000. For 'high pressure' steels, it is also 5/3rds- to 5700 on a 3500 psi tank. But the 'mid pressure' steels (the 3442) have an exemption because they are really relabeled LP tanks and should only be tested to 3/2s of the rated pressure.

I suspect most hydro places don't know this. Two things bad when they do it- they 'age' the tank faster because of stress is outside the rated range, and tanks were failing more often than they should.

They are really LP tanks ?? WOW! so an LP 120 is effectively the same as a HP 120?? Thanks for the education.. :D

How does the new E8-Series compare to the LP series?
The 3AA specification, which is a 50+ year old specification, will be replaced with the E-9791 specification. The length, and diameter will remain the same. The tare weight will be reduced by two pounds and the buoyancy will move closer to neutral but will remain negative when empty for even better buoyancy characteristics. The LP-95 will be replaced by the E8-119. The LP-104 will be replaced by the E8-130. Plus ratings are no longer needed..

The LP104 (which was actually a plus-rated to 2640) was replaced by the E130. However, it isn't the exact same tank (4# lighter). My guess is that they were doing what they always implicitly had because so many people overfilled them, so they made it official at 3442 instead of the HP spec. They actually had to get a waiver to do it.

In any case, I plan on printing out that PST spec and attaching it to the tanks when they go to hydro to try to make sure it is done right. Considering the prices people charge for hydro up here ($75!) I may try to find the companies that do it and have it done directly.