What doc is needed for a + plus hydro?

[tmassey]

In my continuing quest to get a + hydro (I can't post the thread 'cuz I can't post URL's but it's on the board...), I've now acquired a Faber tank with REE number engraved on the tank! Time to try to get a + hydro again!

However, in talking to a couple of LDS, they all say some variation of, "Nobody will give a + hydro because you need special training/certification/test equipment/etc." However, from what I've read and from what I've been told, none of this is true. My understanding is that it's the exact same hydro, and as long as the test passes, and if the REE number is known, I should be given a + hydro.

I've even been told that there is DOT paperwork to this effect. However, I cannot find anything that states this. In fact, while I've found DOT paperwork that describes exactly what needs to be done to hydro a tank, I can't find anything that mentions + hydros in any way.

So, in short: could someone point to me documentation that I can present to the hydro people (prefereably nice, simple, official DOT paperwork!) that explains what it takes to meet a + hydro so that I can see if they'll follow it for me?

Alternatively, if you have any suggestions of how you have been able to get a + hydro from a place that had previously been resistant, I would be happy to hear them. Or if you work for a hydro shop and can help me explain to them what they need to know, that would be greatly appreciated, too!

Thank you all again very much for you help.

 

[Cave Diver]

Here are a couple of threads that may help:

http://www.scubaboard.com/forums/tanks-valves-bands/296069-plus-rating-hydro.html

http://www.scubaboard.com/forums/tanks-valves-bands/206936-getting-rating-hydro-w-o-ree-number.html

 

[tmassey]

Thank you for the links. I had read one, but one I hadn't.

There was a mention of "HMR or the CGA Pamphlets". From what I can see, the CGA pamphlets are not available (at least from the CGA), but the TOC's are: www cganet com/customer/publication_list.aspx?mode=c (grr! Still can't post URL's.)

I can't seem to find any info on the 'HMR pamphlets'.

I have called several local hydro companies previously and asked about a + hydro. All said that they would not do it, which is why I'm hoping to tactfully, kindly, gently provide them with official documentation and attempt to persuade them to reconsider...

 

[halocline]

You need to talk directly with the guy that's going to do the hydro, not just whoever answers the phone at the hydro shop. Eventually you will find the right guy. Just tell him the REE number is on the tank. Skip the dive shop, there are many hydro facilities in any decent sized town because all fire extinguishers need hydro testing. The plus rating as just part of the same test; the tank expands when pressurized to test pressure, they measure how much, then they release the pressure, they see how close to the original volume it returns to. 90% return or more, it passes. The plus rating is based on the amount of expansion at test pressure, which they need to know in order to calculate the percentage of return to original volume.

Talking to most dive shops (there are exceptions, I'm sure) about hydro testing rules and procedures is like talking to a wall.

 

[oxyhacker]

You've doubtless learned from the previous threads cited, no special training, certification or licensing is necessary; any shop that can hydro scuba tanks can do the "+" as long as they can find the REE for the tank (or want to do some ungodly calculations).

HMR means Harzardous Materials Regulations (or something like that). The HMR is actually just the part of the CFR (code of federal regulations) that deals with hazardous materials (which is what compressed gas is) but the DOT people like to refer to it as the HMR rather than the CFR for reasons that are unclear to the outsider. The CFR/HMR is all on the net where you can access and search it, a heck of an improvement over ten years ago when one had to go to the nearest big city or law school library to find a copy.

As you found, the CGA pamphlets are not cheap. It's a hell of a thing when you got to pay some private entity $50 a page just to find our what the law of the land is! However the info on the "+" is all in the HMR, and the CGA stuff adds very little relevant to scuba tanks. Oh, hydro shops are required by law to have hard copies of both the CFR and the relevant CGA Pamphlets, so they have no excuse for saying they don't know and can't find out.

Finally, don't fixate too badly on the plus. By all means try to get it, but it probably isn't worth driving hours away to get it. I have identical tanks that are both plus rated and not, and it never seems to make a difference on the fills I get.

Thank you for the links. I had read one, but one I hadn't.

There was a mention of "HMR or the CGA Pamphlets". From what I can see, the CGA pamphlets are not available (at least from the CGA), but the TOC's are: www cganet com/customer/publication_list.aspx?mode=c (grr! Still can't post URL's.)

I can't seem to find any info on the 'HMR pamphlets'.

I have called several local hydro companies previously and asked about a + hydro. All said that they would not do it, which is why I'm hoping to tactfully, kindly, gently provide them with official documentation and attempt to persuade them to reconsider...

 

[Hallmac]

Bring it to Missouri and I'll do it.

 

[Scott L]

Finally, don't fixate too badly on the plus. By all means try to get it, but it probably isn't worth driving hours away to get it. I have identical tanks that are both plus rated and not, and it never seems to make a difference on the fills I get.

I agree.

 

[captain]

Here is what I feel is the real issue. The + was instituted during World War ll as a way to save steel and transport more gas in the same number of cylinders. Now there is no real need for the + other than divers wanting it.
The commercial gas industry sells and buys gas by the cubic foot so they don't really care how much is in the cylinder as long as it is filled to the stamped working pressure and contains the amount of cubic feet they paid or sold it for everyone is happy. The welding shop gets what it paid for and when the cylinder is empty they just grab another one.
If it were as it is in the scuba industry, where you pay by the tank and not by the cubic feet then the welder might be more interested in a plus.
Bottom line is don't sweat it too much. If it is really important to you get a compressor and fill to what ever you want.

 

[artek]

49 CFR section 173.302a(b) allows for tanks stamped with the "+" to be overfilled 10% EVEN IF THE TANK DID NOT GET A "+" STAMP ON SUBSEQUENT HYDROSTATIC TESTING. If the "+" was originally stamped on the tank, it can be overfilled by 10% so long as the tank's vis and hydro are current.

 

[duckbill]

49 CFR section 173.302a(b) allows for tanks stamped with the "+" to be overfilled 10% EVEN IF THE TANK DID NOT GET A "+" STAMP ON SUBSEQUENT HYDROSTATIC TESTING. If the "+" was originally stamped on the tank, it can be overfilled by 10% so long as the tank's vis and hydro are current.

Untrue.

49 CFR section 173.302a(b):
"(b) Special filling limits for DOT 3A, 3AX, 3AA, 3AAX, and 3T cylinders. A DOT 3A, 3AX, 3AA, 3AAX, and 3T cylinder may be filled with a compressed gas, other than a liquefied, dissolved, Division 2.1, or Division 2.3 gas, to a pressure 10 percent in excess of its marked service pressure, provided(i.e. ALL of the following are met):
(1) The cylinder is equipped with a frangible disc pressure relief device (without fusible metal backing) having a bursting pressure not exceeding the minimum prescribed test pressure.
(2) The cylinder's elastic expansion was determined at the time of the last test or retest by the water jacket method.
(3) Either the average wall stress or the maximum wall stress does not exceed the wall stress limitation shown in the following table:
Type of steel Average wall stress limitation Maximum wall stress limitation
I. Plain carbon steels over 0.35 carbon and medium manganese steels 53,000 58,000
II. Steels of analysis and heat treatment specified in spec. 3AA 67,000 73,000 III. Steels of analysis and heat treatment specified in spec. DOT-3T 87,000 94,000
IV. Plain carbon steels less than 0.35 carbon made prior to 1920 45,000 48,000
(i)(A) The average wall stress must be computed from the elastic expansion data using the following formula:
S = 1.7EE / KV−0.4P
Where:
S = wall stress, pounds per square inch;
EE = elastic expansion (total less permanent) in cubic centimeters;
K = factor × 10−7experimentally determined for the particular type of cylinder being tested or derived in accordance with CGA C–5 (IBR, see §171.7 of this subchapter);
V = internal volume in cubic centimeter (1 cubic inch = 16.387 cubic centimeters);
P = test pressure, pounds per square inch.
(B) The formula in paragraph (b)(3)(i)(A) of this section is derived from the formula in paragraph (b)(3)(ii) of this section and the following:
EE = (PKVD2 ) / (D2 −d2 )
(ii) The maximum wall stress must be computed from the formula:
S = (P(1.3D2 + 0.4d2 )) / (D2 −d2 )
Where:
S = wall stress, pounds per square inch;
P = test pressure, pounds per square inch;
D = outside diameter, inches;
d = D–2t, where t=minimum wall thickness determined by a suitable method.
(iii) Compliance with average wall stress limitation may be determined by computing the elastic expansion rejection limit in accordance with CGA C–5, by reference to data tabulated in CGA C–5, or by the manufacturer's marked elastic expansion rejection limit (REE) on the cylinder.
(4) An external and internal visual examination made at the time of test or retest shows the cylinder to be free from excessive corrosion, pitting, or dangerous defects.
(5) A plus sign (+) is added following the test date marking on the cylinder to indicate compliance with paragraphs (b) (2), (b)(3), and (b)(4) of this section."

This is all clearly determined at the last testing, not just the manufacturer's initial test, and is only valid until the term of the certification or recertification has expired (5 years).

Electronic Code of Federal Regulations:

-------------------------------------------------

For further proof that the "+" mark has to be requalified, see the following. Obviously there would be no need to stamp any more "+"s on the cylinders if the initial manufacturer's mark was sufficient for all time:

49CFR
§ 180.213 Requalification markings.
(f)(3) For designation of special filling
limits up to 10% in excess of the
marked service pressure for cylinders
conforming to § 173.302a(b) of this subchapter,
the marking is as illustrated
in paragraph (d) of this section, except
that the ‘‘X’’ is replaced with a plus
sign ‘‘+’’.