PST LP 95 Failed first hydro-Rare?

[fireboat]

HI Guys, My 5 year old PST LP 95 just failed it's first hydro at my LDS. It wasn't from rust, they said it failed to return to specs after testing. The shop said the tank had probably been over-pressurized. I bought this tank from a guy on Ebay in the Fla Keys a little over a year ago (I notice he is still selling used PSTs). I never over-pressured it and I usually stored it with about several hundred pounds in it.
My question, with all the threads on how people are regularly are over-filling these tanks, are there other tanks like mine that are failing there first hydro?

 

[Hoosier]

Sure, it can be happened. Depending on the type of diving and location, overfill is the common practice, specailly LP tanks. It used to be called, "Cave fill." I have seen many LP tanks up to 3000 psi. You never know how much abuse it was when you got the tank from unknown source.


If you want to get rid of it, please let me know...

 

[oxyhacker]

HP PSTs have a reputation for failing hydro more frequently than LP and other tanks.

The HP PSTs are supposed to be hydrotested to only 3/2rds of the working pressure, instead of the 5/3rds LP steels are tested at, and PST specifies a special procedure under which the tank is "exercised" by pressurizing it to just short of 90% of the test pressure, then depressurized before the actual test is performed.

If a shop in unaware, or neglects to do, either of these steps properly, a good tank will often fail. Hydro shops are required to log the test pressures and results. If you have any reason to suspect the shop did not know what it was doing, and didn't follow the PST protocols, you should ask to see the test results for your tank.

 

[PerroneFord]

Maybe I missed something, but the OP said he has a *LP95*, not a HP PST tank.

Cave fills are still very common here in cave country. The difference is that we fill them SLOWLY so the tank doesn't heat cycle much. When you overfill, and you do it quickly, the tank gets very hot. This is bad for the tank. As you have found out.

Be VERY careful when purchasing used tanks. Or purchase them with the assumption that they will fail their next hydro.

 

[Debraw]

It is also VERY common for over-fills in Florida. They are famous for it.
It is very interesting to hear that

"The HP PSTs are supposed to be hydrotested to only 3/2rds of the working pressure, instead of the 5/3rds LP steels are tested at, and PST specifies a special procedure under which the tank is "exercised" by pressurizing it to just short of 90% of the test pressure, then depressurized before the actual test is performed."

I did not know this. We do not sell PST's and never did. Would it be common for shops that do or did sell them to have this knowledge?

 

[Debraw]

Maybe I missed something, but the OP said he has a *LP95*, not a HP PST tank.

I think Oxyhacker was just making a general comment that the HP tanks fail more than the LP's, kind of like saying, I haven't heard of "that" but I have heard of "this" .

 

[H2Andy]

I have seen many LP tanks up to 3000 psi.

3500 to 3600 is what i usually get

 

[ChrisA]

Many divers in Florida routinely overfill their tanks. Kind of figures why he sells tanks that are just short of 5 years old. Around here it is hard to find someone willing to overfill tanks.

 

[modivin]

3500 to 3600 is what i usually get

Me too. My LP95's get 3,600, but SLOWLY like PerroneFord says...

 

[PerroneFord]

Many divers in Florida routinely overfill their tanks. Kind of figures why he sells tanks that are just short of 5 years old. Around here it is hard to find someone willing to overfill tanks.

We've got steels that routinely get overfilled that pass hydro all the time. In fact, I dove a steel tank in the gulf from our shop that passed hydro in december. Original hydro was in 1974.

Overfilling does not HAVE to make a tank fail. It's just when morons do it, they heat them up. Then they fail.