10% overfill / Plus + rating on Steel LP tanks

[FredT]

If the tank ever has a hydro done and it does not get a +; it can never go back and get one.

According to US DOT any hydro can have the + reapplied, if the conditons for the plus are met. TC may have other rules.

However the answer above is a convenient one for both fill staiton operators and hydrotesters, which is probably why it persists in being passed around like the other urban legends.

FT

 

[pasley]

Ummmm, not an expert, but what about metal fatique? Should you not hydro them on a regular schedule to ensure that has not occured?

 

[Uncle Pug]

Ummmm, not an expert, but what about metal fatique? Should you not hydro them on a regular schedule to ensure that has not occured?

"What about the metal fatigue from pumping them up for a hydro... surely eliminating that stress would help them last a little longer."

I wouldn't say that... but I can imagine hearing someone else say that.

 

[captain]

"What about the metal fatigue from pumping them up for a hydro... surely eliminating that stress would help them last a little longer."

I wouldn't say that... but I can imagine hearing someone else say that.

I would agree that a hydro adds more stress by applying more pressure on the tank than it would see in normal service but as long as the elastic limit of the metal is not exceeded it should not add to metal fatique. If you did not know the history of a tank than yes a hydro would be prudent because you would not know if the tank had ever been over pressured beyond the metals elastic limit or subject to excess heat that could have affected the heat treatment. If I bought a used tank I definately would have it tested. I know the history of my tanks so I don't feel I am gaining any safety by having them hydroed.

Captain

 

[Ontario Diver]

According to US DOT any hydro can have the + reapplied, if the conditons for the plus are met. TC may have other rules.

However the answer above is a convenient one for both fill staiton operators and hydrotesters, which is probably why it persists in being passed around like the other urban legends.

FT

That piece of information was passed on to me by a TC Hydro inspector. So I guess the rules up here are different.

Thanks

 

[crispos]

I don't have much to add to this interesting thread, except to say, if you don't like the fill, fill it yourself, because I am the one who has his head next to the tank. Many divers fill Faber 98's (ScubaPro calls them 95's) to 3000 or more. Make sure the valve can handle the pressure, especially the burst disc.

 

[oversea]

If out of first hydro, the + procedure has to be done for the next, and subsequent hydros. It is not done automatically, and some facilities can't do it. So technically, the fill person was correct to only go to 2400.

I have no idea to your second questions other than "because".

MD

SO IF ONE WERE TO BUY 95 LP CYLINDERS WITHOUT THE PLUS, NEW FROM MFG ARE THEY 95'S OR 85'S?

 

[rjens]

SO IF ONE WERE TO BUY 95 LP CYLINDERS WITHOUT THE PLUS, NEW FROM MFG ARE THEY 95'S OR 85'S?

Oversea,
As I understand they are 86.5's. According to the Diverlink Tank Specs (see previous posts) the Faber/Scubapro LP Steel 95 holds 95.1CF when filled to 2640 PSI, which I calculate converts to around 86.5CF at 2400. The way I understand it works is the tank is originally rated at 2400 PIS until it receives its first hydro. At that time it can be "+" rated (if tested for such). After which it can receive fills up to 2640 PSI (+10%). However the + is only good until the next hydro. If at that time the authorized fill reverts back to 2400 unless the testing is done to reauthorize the "+" value.

To the Experts,
Thanks for the excellent explanations. If my explanation above is incorrect, please feel free to correct me.

RJ

 

[BrianM]

Hi all,

I am wondering if anyone here can answer a question for me....

I know new LP cylinders are rated for 2640 psi because of the + 10% rating....well what about tanks that are a little older and the last hydro wasn't a + rating? Can I have them hydro'ed next time and ask for a + 10% cert? I know there is a good chance they wont pass and it may not be worth it to try, but I am mainly just asking theoretically: Can you have an LP tank re-hydroed for the "+10% cert" after it has been hydro'ed for 2400 psi???

I have 2 OMS 125 LP cylinders which were made in the late 90's and hydro'ed in 2001. They are plenty of gas for me at 2400 but I am just curious to know all my options.

Thanks

Brian

 

[LUBOLD8431]

First of all, I believe the + rating is ridiculous, and you should be able to fill all LP tanks to 2640.

That being said, yes, they can be retested, and as long as they pass the criteria, they can get the + rating. Usually, many hydro retesters never go thru the hassle of doing the + rating. You usually have to ask for it.