REE for PST LP72

[captain]

Keep in mind that the plus was instituted during World War II as a means of saving on steel to make cylinders by carrying more gas in fewer cylinders. Today only divers are interested in the plus. Commercial gas is priced by the cubic foot, and if a welder runs out of gas he stops and gets a full cylinder, it doesn't matter to him if the cylinder has 2500 psi or 2000 or 500.
Divers get charged by the tank no matter the size.
Get to LDS to charge by the actual cubic feet and they would have a monetary interest in the plus.
or maybe not because they charge the same for an 18 cu/ft pony as for a 130.

 

[Bob DBF]

Then it really is just the extra cost ($125) for the custom + stamp (that's not in standard die sets) and am inability to do simple mathematics that keeps the bulk of shops from being able to offer + hydros?

The last hydro shop I delt with was a fire extinguisher company, scuba and steel tanks in general were virtually none of their business, they take a one size fits all approach. The simple math was that it was not worth their time.



Bob

 

[2airishuman]

Then it really is just the extra cost ($125) for the custom + stamp (that's not in standard die sets) and am inability to do simple mathematics that keeps the bulk of shops from being able to offer + hydros?

It's really unusual to see a + made with a + stamp. Usually they use a chisel and hit it twice.

In practice, there are two reasons why you might not get a +:
1) The hydro shop doesn't do + stamps because they don't train their people to do it and don't have a procedure in place for dealing with it. This is common a fire extinguisher places, because fire extinguishers can never benefit from a + stamp.
2) The hydro shop can't document what the REE value is to their satisfaction. Generally they like to see it stamped on the cylinder. There is no universal reference for REE values, so if it's not there, it's all about what documentation the shop happens to have and how picky they are in applying it.

Remember that these are regulated entities that are very procedural in their thinking. If they don't have a procedure for it, they're not going to do it.

There are two theoretical reasons that I've never actually run into.
1) The cylinder passed visual and the basic hydro but was over the REE. I've never heard of this actually happening.
2) The hydro shop measures expansion by measuring the amount of water pumped into the cylinder, instead of the amount of water displaced from the container the cylinder is in. That's allowed by the regs for the hydro but not for the +. Nobody I've run into does hydros that way, and I believe it's considered an obsolete technique.

 

[Rred]

The DOT stated that a REE number must be assigned to a particular lot of tanks, i.e. all made on the same machinery in the same production run from the same batch of raw material. This is to ensure that the raw material hasn't varied much (as it can) and that the machinery was adjusted to the same specs, i.e. the pressure and stroke of the machine is the same, more or less.

They do refer to a specific procedure in the CGA-5 manual (compressed gas association) which the DOT adopts as a federal standard, for determining the REE number based on the physical specs of a tank, particularly and critically including the measurement of the tank wall thickness in multiple places. If you consider *that* procedure ain't gonna happen in your typical hydro station, and that it has to be done for at least three tanks from the same production lot...this is why "finding" your REE number can be rather difficult unless the maker was kind enough to stamp it on the tank.

"1) The hydro shop doesn't do + stamps because they don't train their people to do it"
Shop training? I thought the monkees had to be certified by an approved training agency, and that would include way more than "rightee tightee leftee loosie". Wrong again, huh?

" and don't have a procedure in place for dealing with it."
Well yeah. Instead of saying "Hey Bob, here's your bill for 32 tanks" now they'd have to say "Hey Bob, you owe me 27 tanks and, uh, let's see, that's 32 less 27, uh, yeah, five more tanks at the plus price, uh, that's seven fifty more than, uh..."
Instead they ALL just chant the same mantra "That's illegal" and the way they all chant the same total BS is why I disrespect every one that chants it.

"2) The hydro shop can't document what the REE value is to their satisfaction."
See now, that I could respect. "We can't recertify it unless there's a REE number stamped on the tank or certified by the maker" would be just as easy to say, and not too hard to understand.

"2) The hydro shop measures expansion by measuring the amount of water pumped into the cylinder, instead of the amount of water displaced from the container the cylinder is in. That's allowed by the regs for the hydro but not for the +. Nobody I've run into does hydros that way, and I believe it's considered an obsolete technique."
Again, "We don't have the equipment that's required to test that way, sorry" would cut a whole lot more mustard than the bogus "That's illegal".

If you knew that your regulator could be serviced, if you knew that o-rings could be replaced, and yet, your LDS said to you "You'll need a new regulator, those parts CAN'T be replaced its ILLEGAL" how much respect would you have for them?

If the guy said "We're not authorized to work on that brand, it needs special tools, you'll have to go to a franchised repair shop" would you think somewhat better of them?

The really nice (or horrifying) thing about + stamping is that when I queried the DOT on this they took months, literally, to come up with answers. And the last conversation literally had a DOT rep saying "Sorry it took so long, but those regulations are so old and arcane we couldn't actually find them for a long time....it looks like the rules for SCUBA tanks are long overdue for a re-examination."

Said re-examination won't happen unless the DOT gets a LOT of written requests so they can justify the procedure. But, as they said, it is LONG OVERDUE.

 

[2airishuman]

The DOT stated that a REE number must be assigned to a particular lot of tanks, i.e. all made on the same machinery in the same production run from the same batch of raw material. This is to ensure that the raw material hasn't varied much (as it can) and that the machinery was adjusted to the same specs, i.e. the pressure and stroke of the machine is the same, more or less.

That is not my understanding. My understanding is that the REE is calculated based on average measured wall thickness from three cylinders of the same design from the same manufacturer. There is no requirement to re-calculate the REE for each batch of raw material or when changing from one machine or die to another, as long as the size and pressure rating is the same and the manufacturer is the same.

Whether this is a good idea or not is a separate question.

"1) The hydro shop doesn't do + stamps because they don't train their people to do it"
Shop training? I thought the monkees had to be certified by an approved training agency, and that would include way more than "rightee tightee leftee loosie". Wrong again, huh?

Individual test operators are usually trained by someone else at the shop. Small shops use a purchased curriculum.

Training does not need to cover things that they don't do. There's no hydro shop anywhere that can test every size, type, and application for high-pressure cylinders that has ever existed.

" and don't have a procedure in place for dealing with it."
Well yeah. Instead of saying "Hey Bob, here's your bill for 32 tanks" now they'd have to say "Hey Bob, you owe me 27 tanks and, uh, let's see, that's 32 less 27, uh, yeah, five more tanks at the plus price, uh, that's seven fifty more than, uh..."
Instead they ALL just chant the same mantra "That's illegal" and the way they all chant the same total BS is why I disrespect every one that chants it.

No, they would have to have a procedure in place for determining whether the cylinder could eligible for a + rating if the test passes, determining the REE, calculating the actual elastic expansion, documenting everything properly, and applying the stamp. Their test operators are essentially production line workers, and this stuff is a big deal to them.

The really nice (or horrifying) thing about + stamping is that when I queried the DOT on this they took months, literally, to come up with answers. And the last conversation literally had a DOT rep saying "Sorry it took so long, but those regulations are so old and arcane we couldn't actually find them for a long time....it looks like the rules for SCUBA tanks are long overdue for a re-examination."

Said re-examination won't happen unless the DOT gets a LOT of written requests so they can justify the procedure. But, as they said, it is LONG OVERDUE.

It's an orphaned area because everything is eventually going to switch to the international standards, which don't use + ratings.

 

[ScubaBunga]

ok, I found it - Questions about LP72 tanks
There is lots of info there - a lot of work on his tanks to get these ree values, may even have the spreadsheets somewhere in that post.
For those really into math (or in need of material to get to sleep), here is the CGA document explaining the process: https://law.resource.org/pub/us/cfr/ibr/003/cga.c-5.1991.pdf

 

[Rred]

The incredibly odd thing about the CGA (Compressed Gas Association) specs, is that if you actually contact the CGA and ask for a referral to a member company, which is about the only way you might find someone with the right equipment AND the book at hand, the CGA won't or can't refer you to any members.

So there's a CGA procedure and spec, which has been cited into federal code, but the only way to find a CGA member is to go making phone calls or finding ads in the Yellow Pages (ha) that might get you an answer from a member. Who apparently is allowed to confirm that they are a member, even though the CGA will not disclose any of their names.

All considered, it will typically be cheaper to buy a whole new tank with a REE number stamped on it, than to find and employ a shop that understands the process!

 

[captain]

You have to be a member of CGA to get any information from them.

 

[Rred]

"get any information" is one thing, but "Can you refer me to any members in my area?" is quite another. This is the first time I have ever had a "member organization" refuse to make any referrals to local members, or even to acknowledge whether there ARE any members. Local or otherwise.

They make Masonic Secrets seem like mass-marketed tabloids in comparison.