How is the REE number on a tank used

[NAM001]

I guess this should be a basic question but I am lost for and explaination. My tanks have REE#s on them from like 94-99. Is this number a reference to a proceedural document or is it a value to use in a standard equation. Such as the # is the immediate expansion recovery amount to pass. expands 200 units and when vented it must be able to recover 198 of the 200 units if the ree is a 99. Is it an actual limit of some sorts? I ask because my hydroer says he doesnt do + hydro's because he doesnt have the documents to do it. If i am not mistaken the name is on the tank depends on the ree value. faber-faber, seaperls-faber, XS-faber. Ie al lp95's but different REE numbers.

Thanks

 

[halocline]

The REE stamped on the tank is a volume in cubic centimeters. This is the maximum total expansion of the tank when subjected to test pressure. The standard hydrotest does not have a maximum; the tank simply has to return close enough to its original volume so that it 90% of the expansion is lost when the tank is depressurized. I'm not sure I'm explaining it exactly correctly, but I think that's the gist.

For example, lets say one of LP95s has a REE of 95. That means to get the plus rating the tank can't expand more than 95 cc when the tester fills it with water to 4000 PSI. (2400 x 5/3). That's how freakin simple it is to give a tank the plus rating; you'd really think that more professional hydro shops would be able to do this.

Getting back to the example, lets say the tank expanded 90 cc, then, when depressurized, contracted back down 82 cc. So the permanent expansion was 8 cc. 8 is less than 10% of 90, so the tank passes.

 

[NAM001]

Ok so based on that and what I have got from other sources How dies this sound,

ree=95

If expansion exceeds 95 it fails
if it is less than 95 then look at depressurized amount if < 10% of expansion it passes if less than 5% it is good for + rating.

Still with that I cant understand why they would have to look up in a book to find out how to do a + recertification.

I have also heard that the + rating is done with a higher test pressure.

 

[halocline]

Ok so based on that and what I have got from other sources How dies this sound,

ree=95

If expansion exceeds 95 it fails
if it is less than 95 then look at depressurized amount if < 10% of expansion it passes if less than 5% it is good for + rating.

Still with that I cant understand why they would have to look up in a book to find out how to do a + recertification.

I have also heard that the + rating is done with a higher test pressure.

The 5% bit is not true, the higher test pressure is not true. It's amazing how much BS there is floating around (not a very appealing image, if you think about it) regarding tank hydro test. If the tank expands more than the REE, it fails the plus, if not, it passes. It is certainly possible, I guess, that the tank would not expand beyond the REE number, meaning it would qualify for the plus, but then not return 90% to the pre test volume, and as such, be condemned for failing hydro test.

The hydro test is a test of the tank's elasticity, which I'm guessing is the most accurate indicator of it's ability to withstand pressure.

The reason a tester might have to research a tank for the plus rating is to get the manufacturer's REE number. That number is stamped on newer LP fabers (and maybe others) but not on the older LP72s, like mine. So the tester might have to contact the manufacturer to get that number. They are also "supposedly" able to calculate it based on precise measurements of the tank, but that is WAAAYYY beyond the ability of the knuckle-draggers running hydro shops around here. Luis H does it, but he's a professional mechanical engineer and a truly smart person. I've had conversations with hydro testers that make Donald Trump look like Stephen Hawking. There's got to be some smart ones somewhere on this planet, just apparently not in the Alamo city.

 

[NAM001]

That all makes sense. So (as I don't have al tanks) that would mean there is no ree number on an al tank.
The local tester here had told me that there was something along the lines of you presureize it measure remove pressure and measure again. if my tanks measurement after venting was 20 or less then it passed and if it were less than 10 it passed the plus. all mine went back to less than 1. They just said oh well we don't do plus testing.

The 5% bit is not true, the higher test pressure is not true. It's amazing how much BS there is floating around (not a very appealing image, if you think about it) regarding tank hydro test. If the tank expands more than the REE, it fails the plus, if not, it passes. It is certainly possible, I guess, that the tank would not expand beyond the REE number, meaning it would qualify for the plus, but then not return 90% to the pre test volume, and as such, be condemned for failing hydro test.

The hydro test is a test of the tank's elasticity, which I'm guessing is the most accurate indicator of it's ability to withstand pressure.

The reason a tester might have to research a tank for the plus rating is to get the manufacturer's REE number. That number is stamped on newer LP fabers (and maybe others) but not on the older LP72s, like mine. So the tester might have to contact the manufacturer to get that number. They are also "supposedly" able to calculate it based on precise measurements of the tank, but that is WAAAYYY beyond the ability of the knuckle-draggers running hydro shops around here. Luis H does it, but he's a professional mechanical engineer and a truly smart person. I've had conversations with hydro testers that make Donald Trump look like Stephen Hawking. There's got to be some smart ones somewhere on this planet, just apparently not in the Alamo city.

---------- Post added September 22nd, 2015 at 02:00 AM ----------

Looks like the REE is used differently depending on whose tanks.

XS Scuba - Cylinder Info

 

[Couv]

Hello KWS,

If you are in the Houston area, contact Roger at Western Sales & Testing of Deer Park, Inc He is very knowledgeable re re-qualifying all sorts of cylinders, including scuba, and will plus test your tanks and stamp them as required. You can have your tanks VIP tested and stickered there too for a very reasonable price.

 

[JohnN]

I have some Norris HP120 tanks (300 bar valves) that are stamped with an REE value. I understand the purpose of REE for LP tanks, but what is it used for with HP tanks?

 

[NAM001]

i JUST DID some reading and found an article that said for the 3442 tanks ther are under a different set of rules. The rules are that a ree is stamped on the tank. pass or fail is not based on the perminante expansion but the presureized expansion of hte ree. where lp tanks are concerned the ree determines if the tank gets a + the 90-% return to original expansion determines pass or fail. the hp tanks do not use teh 90% thing only the ree value for maximum expansion.


though not correct i am sure,,, look at it as the 3442 includes the 10% over and that will make the the ree value boss when it comes to pass or fail and not the perminant expasion criteria.
someone can explain it better i am sure . look at one of my previous posts and there should be a link of the article i read. I think this is it. XS Scuba - Cylinder Info

I have some Norris HP120 tanks (300 bar valves) that are stamped with an REE value. I understand the purpose of REE for LP tanks, but what is it used for with HP tanks?

 

[JohnN]

i JUST DID some reading and found an article that said for the 3442 tanks ther are under a different set of rules. The rules are that a ree is stamped on the tank. pass or fail is not based on the perminante expansion but the presureized expansion of hte ree. where lp tanks are concerned the ree determines if the tank gets a + the 90-% return to original expansion determines pass or fail. the hp tanks do not use teh 90% thing only the ree value for maximum expansion.


though not correct i am sure,,, look at it as the 3442 includes the 10% over and that will make the the ree value boss when it comes to pass or fail and not the perminant expasion criteria.
someone can explain it better i am sure . look at one of my previous posts and there should be a link of the article i read. I think this is it. XS Scuba - Cylinder Info

Thanks, but these are 3500 PSI tanks (stamped on the tank and they have 300 bar DIN valves)

 

[rjack321]

I have some Norris HP120 tanks (300 bar valves) that are stamped with an REE value. I understand the purpose of REE for LP tanks, but what is it used for with HP tanks?

Its a maximum allowable expansion in mL (cubic cm)
My lp cylinders have REEs on them, < than REE = pass for a +
My bank bottles all have REEs on them too, some of those are lp cylinders eligible for +s some are 4500psi bank bottles which aren't.
All my 3442 and 3500 psi tanks have REEs on them too, that is the max allowable expansion in CCs. If they are > the REE they fail

Basically the REE is a mega cheat so the hydro shop doesn't have to do a lick of math at all. < REE = pass (and + eligible if manufactured under 3AA specs)

If a 3AA tank is over the REE it can potentially still pass under the 90% rule. This is actually pretty rare. LP72s in hard to plus rate without the REE because you need the wall thickness and a whole bunch of other variables, plus math and more math. Hence they are typically only tested against the 90% rule which doesn't mean they aren't good to 2450...

AL3000 tanks are only evaluated under the 90% rule.