LDS Won't + 10% Fill Plus Rated Tank?

[boulderjohn]

As for filling tanks and following policy, in my experience, you have all sorts of people with all sorts of training levels and experience filling tanks. Here are some examples just from my experience.

1. In a dive operation I used frequently, one day one of the people doing the fills only filled my LP tanks to 2400, saying that was the limit on the tanks. I showed him the + sign and explained about it. He had never heard of it, and neither had the shop manager.
   1. Once appraised of the situation, the shop manager was willing to go to 2500, but not to 2640, because that was too dangerous. He said complaining about a 2500 fill on a 2640 tank was "splitting hairs."
   2. That same shop had a policy of filling AL80 tanks to 3300 to make customers happy with their fills. That was not dangerous.
   3. One of the other employees at the same shop, their tech diving instructor, usually filled my tanks to about 3600.
2. When the manager listed above said that complaining about a 2500 fill was splitting hairs, I switched to another shop for fills, and they routinely fill my LP tanks to 3400--sometimes above.
3. A recent thread on ScubaBoard was about the shop listed in item #2 refusing to fill any tank of any composition that was 20 years or more old. I asked them about that, and they were surprised. They said they had no such policy and routinely filled tanks over 20 years old, only restricting old aluminum tanks with the known alloy problem. When I posted that in a thread, others said they had encountered the "no tanks older than 20 years" policy there or in another store in that chain.
4. I ordered a set of LP steel tanks through a dive shop, and when they came in, an employee helped me open the box, etc. He asked me what kind of tanks they were--he had never seen such heavy tanks with round bottoms. This would have been the employee who would have been filling them normally, but they let me do it myself.
5. I was recently getting fills in a shop that had a whole new fill station, and the man doing the fills said it had a governor that would not allow fills above 3100. I had HP tanks with me, and I told them they had to go higher than that. He had never heard of such a thing, but he did change the governor so I could get my fills.
6. I friend of mine worked in another shop, and someone brought a LP steel 72 in for a fill. The guy on duty hooked it up to the compressor and got it started. My friend happened to walk by the fill room and look in. He rushed over and shut it off. The tank was covered with rust and had not been hydroed or inspected in nearly 25 years.

 

[shurite7]

At a DEMA show in LAS a gentleman gave a talk about tanks. He stated a tank that had a plus (+) rating meant it was capable of holding more gas than rated on the cylinder; example, a 72 rated at 2250 filled to 2250 held 72cft of gas; filled at 2450 meant it held more than 72 cft of gas. This created an uproar with some people in the audience. Some were giving the T sign for stop, others baulked stating he was incorrect and a few shouted out he was flat out wrong. His talk prompted me to seek information about the claim because I had learned, via informally from others - meaning people who believed they were right, but didn't really know, was not what the gentleman stated.

After the show I contacted a couple of sources that specialize in compressed cylinders. This is what I learned. It depends on the manufacturer. Some tanks are rated (I am going to use the ST72 for simplicity) to hold 72cft when filled with the additional plus {+} rating, i.e. 2450. Some are rated full when filled to 2250 with an additional few cft of gas when filled with the extra 10%. In short, verify with the manufacture to determine what the capacity is when it comes to the plus {+} rating.

On another note, if a lower pressure (commonly referred to as low pressure, which is innacurate because all scuba tanks are considered high pressure by CGA and DOT) steel tank marked with a plus {+} on the original hydro stamp can be marked again with a plus {+}, even though the previous hydro(s) did not receive the plus {+} rating, after previous hydro tests. Examle for clarification, original hydro date is 4**75+, next hydro 5##77, next hydro 3^^96, current hydro 8>>15+. Some hydro inspectors, visual inspectors, dive shop employees, and cylinder owners are unaware of the plus {+} rating, while others are aware of it and understand it. Just because someone (owner, employee, tester, inspector) doesn't know about it doesn't mean he/she is an idiot; they simply don't know what they don't know. Whether or not they want to learn about it or stick to ignorance is a completely different story. Some people never deal with cylinders that have the plus {+} rating. I didn't learn about it until I went through tech training and found out why tech divers prefer the lower pressure tanks when it comes to gas blending.

 

[Gareth J]

This has been an interesting thread for me, not being from the USA.

In the UK most cylinders are 232 bar WP (working pressure), 348 TP (Test Pressure). If you are filling cylinders you are not supposed to fill beyond the working pressure. If you are worried about the pressure drop after cooling, then you top up again later when the cylinder has cooled, back to the 232 WP.

I said most cylinders have a working pressure of 232 bar, that is not exclusive, I have aluminium cylinders that are 208 bar (from memory), and you can get High Pressure cylinders (300 bar).

I am not keen on 300 bar cylinders personally, there are not that many facilities that can fill to 300 bar, and fewer that actually give you the 300 bar when they do. 300 Bar cylinders are also bl***y heavy.
Also, mixing gas in 300 bar cylinders (if you intend to fill to 300 bar), is more complicated.
I would prefer to go up a cylinder size than have 300 bar cylinders.

If you are the compressor operator, you can refuse to fill any cylinders if you are unhappy with it in anyway.

In the few commercial facilities I have filled cylinders, they had a pressure regulator set at around the 232bar down stream of the compressor / bank, upstream of the filling whips to ensure you didn't go beyond the 'usual' working pressure.

 

[runsongas]

i think you mean 232 bar working pressure, 348 test pressure (3/2 test pressure). 12L 232 bar is roughly equivalent to 3442 psi HP100

 

[Gareth J]

i think you mean 232 bar working pressure, 348 test pressure (3/2 test pressure). 12L 232 bar is roughly equivalent to 3442 psi HP100

Good Catch, you read what you think you typed !
Amended OP.

 

[Divin'Papaw]

The shops I use down here in South FL (both SW and SE coasts) fill my LP tanks to 3000 psi. I'm good with that.

 

[halocline]

He’s right and wrong. If the cylinder isn’t rated for a + rating, one cannot be assigned. But if it was assigned a + rating at manufacture, it may be maintained.

All 3AA spec scuba tanks were given plus ratings at manufacture. If they do not qualify (or the tester doesn't bother testing) for the plus rating at a subsequent hydro, they certainly CAN be re-tested and given the plus rating at the next hydro. Since all the tanks referenced in the first post of this thread were plus rated at manufacture, they can be re-qualified with plus rating at any hydro test.

So the shop owner was not right and wrong, he was just wrong. This bit about tanks only having the plus rating for the 1st five years has been sticking around dive shops forever. I can't count how many times I've heard it.

Unfortunately, the bottom line with getting your tanks filled at a dive shop is: They own the compressor, they make the rules, dumb or otherwise.

 

[BRT]

Remarkably complex issue for something that should be simple. Why don't manufacturers have a single standard with standard pressures for each tank? All this talk of REEs, plus signs, overfilling etc are signs of total confusion in a relatively mature industry. You can't blame tank monkeys or shop owners from not wanting to do anything that could in any way violate an insurance regulation. Nor should they have to read pages of minutiae to understand what they can and can't do. At some point, a shop will overfill a tank past its DOT mandated pressure, an accident will happen and the party will be over.

No.

 

[Bob DBF]

Remarkably complex issue for something that should be simple. Why don't manufacturers have a single standard with standard pressures for each tank? All this talk of REEs, plus signs, overfilling etc are signs of total confusion in a relatively mature industry. You can't blame tank monkeys or shop owners from not wanting to do anything that could in any way violate an insurance regulation. Nor should they have to read pages of minutiae to understand what they can and can't do. At some point, a shop will overfill a tank past its DOT mandated pressure, an accident will happen and the party will be over.

It is not a complex issue, and isn't that hard to understand and give a proper fill. The service pressure, and + have been used since WWII so it's not a new thing. I don't blame the tank monkey, unless he is the owner, at which point we will talk. The REE has no meaning, unless you are talking with the hydro guy.

My big problem with old 72's is some tank monkey that knows everything, thinking its a HP 100. 3442# is a bit more overfill than I'm comfortable with having.

No.

A more concise answer.

 

[Divin'Papaw]

My big problem with old 72's is some tank monkey that knows everything, thinking its a HP 100. 3442# is a bit more overfill than I'm comfortable with having.

I’ve had similar experiences. I’ve had more accidental 3500 psi fills in my LP85s than I’ve had 2400 fills. My LP85s DO NOT have a + from their recent hydro. Since the shops I use all fill LP tanks to around 3000 I didn’t feel the need to pursue getting them + hydroed.