10% overfill / Plus + rating on Steel LP tanks

[DA Aquamaster]

The criteria for the "+" rating is based on the amount of expansion that occurs during the hydro test and this is what the wall stress calculation is based upon.

The hydrotest equipment not only pressurizes the tank to the required test pressure but also incorporates a mamometer to measure how much the tank expands under pressure and whether it returns to it's original volume within allowable limits. The tank needs to meet tighter standards to qualify for the "+" rating than it does to just pass the hydrotest. If I remember correctly 1% expansion during the test with no permanent expansion after the test is permitted for a "+" rated steel tank.

As for the calculation, if the tester is testing many of the same types of tanks, all he needs to know is the allowable temporary and permanent expansion limits for that particular tank and he will know whether it meets the "+" criteria as soon as the test is complete. The hydrotester also must record the numbers from the hydro test and keep them on file.

 

[John Hoffer]

Uncle Pug:

>>>Thanks . . . for pursuing and posting to this topic.<<<

Thanks for the thanks.

DOT is slow. Initially I was guessing that it would take three months to get a written response from them. Nearly seven months lapsed. Somewhere in there I sent them a reminder letter. Wow. They make other federal agencies look good, real good. I mean, these were not hard questions.

In any case, this experience confirms, again, that written responses are more thoughtful than off-the-cuff telephone responses.

-John

 

[Braunbehrens]

I just posted this info to another thread not too long ago, but have mislaid it. You can get the list of the Hydro facilities in your area from the DOT. It's a pdf document.

Just call the ones close to you and find out which one will do a + rating. Most won't even deal with scuba at all. I'm pretty sure you want an "A" facility, not "B" but double check on the document once you find it.

99% of LDS do not do any hydro. They take your tank, and put it in the back of the shop. Once a week, they take it to the cheapest local hydro place, and have all the tanks hydroed.

The reason you don't get a + rating, is because the LDS doesn't give a rats behind, and the cheapest hydro place doesn't do +. So take your tanks to the hydro place yourself. It's fun anyway, to check out those places.

BTW, what the DOT regulation is, etc. is really pretty irrelevant. What you want, basically, is whatever will make the shop happy so you can get fills. No sense beating your head against a wall.

Sorry you got flamed last time, that really stinks.

 

[neil]

lal7176 once bubbled...
So what exactly is a RE number that seems to be the golden key to get a "+" rating?

The REE number is the elastic expansion rejection limit for the cylinder. It is computed or set by the manufacturer and stamped on the tank. If you want to see the math, use the CFR reference that John Hoffer posted.
Neil

 

[DA Aquamaster]

I checked with my freind the hydrotester yesterday and the REE number is the maximum value allowable when the permanent expansion is subtracted from the total expansion during the hydrotest. If the tank exceeds the REE it may still pass hydro but would not qualify for a "+" rating.

He will test the tank for a plus rating as long as it has a REE number stamped on it or if the owner can bring in documentation of this number from the tank manufacturer.

Some tank trivia.....Catalina and Luxfer aluminum 80's expand about 70 cc during the hydro test with about 2.5% to 2.7% permanant expansion. Kidde 80's have a little heavier walls and exapand about 65cc.

Most steel tanks run around 1.7% permanent expansion and fail the test if they exceed 10%. Aluminum tanks have no set limits, but when they fail, it tends to be dramatic with 120cc total expansion and lots of permanent expansion so a bad 80 is easy to detect at hydro.

 

[Dryglove]

Thanks for the clarification on the REE number.

 

[MikeFerrara]

Paul is right. Few shops do hydro testing. We send them out. As I understand it some hydro facilities will and some won't restamp the plus rating. I own a shop and I don't lie to any one. I have no reason to. Some of you are paranoid enough that I think you need medical attention. 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.

On another point Paul is wrong in that we don't just go to the cheapest local hydro facility. We go to the only local hydro facility. There is one other but they don't do hydro testing either they ship them to Indianapolis and sometimes it takes a month to get the tank back.

Now, we used to just pass on the cost of the hydro to the customer with ZERO mark up. We just recently started tacking on a couple dollars for our trouble. In all the tanks I have sent for hydro I haven't made enough money to compensate me for the time it took to write this post. We handle it as a faver to our customers and would prefer folks drive down the street and handle it themself. Oh and I'm happy to provide the address and phone number. Although after dealing with some of the BS we see posted on this board I doubt they would continue to take scuba tanks.

 

[MikeFerrara]

Braunbehrens once bubbled...
BTW, what the DOT regulation is, etc. is really pretty irrelevant. What you want, basically, is whatever will make the shop happy so you can get fills. No sense beating your head against a wall.

Sorry you got flamed last time, that really stinks.

you have a point. A plus stamped on your tank won't help you get a cave fill.

So much time spent on a insulting shops and a stinking 10%

The time would be better spent learning to dive so the 10% wasn't so important. Ya think.

 

[Braunbehrens]

Mike, I think the problem is that the dive stores have too much to do to really research the hydro issue.

You CAN get replussed. No doubt about it.

I'm not paranoid, my local shops are great, but it's the same wherever you go.

Most salespeople know less than most well informed consumers.

Most dive shops I know tack on quite a bit for a hydro. There is a hydro place that does it for $8, but no local store will do it for less than 20, and several quoted me twice that and even more if I want the + rating.

Ridiculous.

However, not all stores are alike. If you're local, and DON't need a + take your tank to Steeles.

 

[MikeFerrara]

Braunbehrens once bubbled...
Mike, I think the problem is that the dive stores have too much to do to really research the hydro issue.

You CAN get replussed. No doubt about it.

I'm not paranoid, my local shops are great, but it's the same wherever you go.

I wasn't really refering to you

Most salespeople know less than most well informed consumers.

Sales people? hehe...Around here the only sales people are the owners.

I had a guy e-mail me and ask if I had any positions open. I e-mailed him back that I did. He asked what the job payed. I told him that it was a dive shop and that it didn't pay anything and that in fact it might cost him something. LOL