10% overfill / Plus + rating on Steel LP tanks

[neil]

MikeFerrara once bubbled...
DOT regs are often hard to figure out and even harder to figure out when and to whom they apply. No dive shop made up the story about a plus rating only being good for the first hydro period because that statement is made in MANY diving and dive equipment texts. I don't think this is a lie either because I just looked at some old steel 72's and there is no ree number while my PST tanks do have one.

Mike,
I'd like to see one of those texts if you remember which you saw the misinformation in. Your old 72's don't need REE #'s because there is ANOTHER way, the older way of determining the expansion limits. Again, the math is in the CFR for anyone to read, and hydro testers are supposed to know this stuff. Don't even THINK of asking me how to work those math formulas

Neil

 

[rjens]

I am still a relative newbie, but thanks to this board I am learning quickly. This weekend I rented Faber Steel LP 95s. My fill was 2400psi (so I was really diving an 88??) When I looked at the marks on tank there was a "+" on it, so when I went in for a refill (in Monterey) I asked for a fill to 2640 because the tank was + rated.

The fill tech mumbled something about the + being out of date, and hadn't been applied to the last hydro, so he could only fill to 2400. I thought I had read in a previous thread (which I couldn't find) that the + was applied at the first hydro, and from then on it applied and the tank could get a 10% overfill.

So here is the question. How does the + and 10% overfill work for LP tanks. Also, (a second semi-related question) Why are tanks labeled based on their capacity when overfilled -- shouldn't the FABER Steel LP95 really be an LP88 if it can only be filled to 95 via an overfill?

Can someone explain this in clear layman's terms so I can can speak intellengently with the next fill tech I deal with. If this was already covered in a thread feel free to point me to it, I tried searching for this but couldn't find what I was looking for.

Thanks
RJ

 

[Uncle Pug]

Tanks need to be stamped with the + at each hydro to carry the 10% overfill forward. Many hydro testers do not want to or know how to do the calculations necessary to + certify a tank and so it doesn't get done. If the tank has an REE number stamped on it that makes it easier for the hydro tester to + rate the tank.

As for why manufacturers over state the capacity of their tanks... I think that may have something to do with marketing.

 

[MechDiver]

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

 

[DA Aquamaster]

The Faber tanks should have an REE number and most hydro testers will do the plus rating if they have the number and if you ask. Others will do it if you can bring in documentation from the tank manufactuer of the required specs. I have not met one yet that will actually do the calculation even though it is spelled out in the regs.

 

[ScubaJewel]

Technically its not an "overfill" at all. Technically it is always illegal to "overfill" a high pressure cylinder for commerce.

Its actually a surplus fill allowed until the first Hydro date and then only if the tanks continue to meet certain specifications past their initial hydro date.

A hydro test facility usually needs to be asked to recertify tanks for a surplus fill (at least here in Seattle) or they won't do it and most up here won't do it anyway because it takes more time to test a tank in that manner, Much to my dissapointment.

I heard that if you fill your own tanks for personal use you never have to have them Hydroed! The hydro only needs to be completed if the tank is filled for commerce... Kind of scary...

Julie

 

[Genesis]

I heard that if you fill your own tanks for personal use you never have to have them Hydroed! The hydro only needs to be completed if the tank is filled for commerce... Kind of scary...

Julie

Why is that scary?

If its your tail, and you blow yourself up, its you, right?

(PS: I fill my own tanks with my own compressor, but I still have them Hydroed...)

 

[rjens]

Sounds like a 2400 psi is what I should expect for rental LP tanks. Same with 3000 - 3200 psi fills I have been getting on rental HP tanks. That's ok, the larger tanks make my trim better and I carry less weight on my waist.

Thanks for the quick answers

RJ

 

[Ontario Diver]

A couple of comments

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

Second, the + mark doesn't work any more in Canada. The tanks are rated for the US working pressure plus the 10% right off the bat. (of course, if the fill station isn't using BAR they might not figure that out )

The best answer I ever got for the reason why the tanks are referred to by thier "overfill" capacity is MARKETING!

 

[captain]

I have 6 steel 72's a couple of which date back to the mid 50's. None have been hydroed in the past 15 or 20 years but only I fill them from my compressor and I inspect them internaly yearly to make sure no water has entered them and no rust exist other than surface flash rust which is impossible to prevent on bare steel. I do not use boots or put stickers on them that could prevoke or hide corrosion damage. I fill to the + rating pressure of 2475. The life time on properly cared for steel 72s is indefinite. I feel perfectly safe with this. I don't believe anyone can come up with a pure failure of a steel 72 that was not in some way caused by abuse in some way. However if they were aluminum I definately get them hydroed and eddy current inspected.

Captain