Using unidentified DOT cylinder in Canada

[derwoodwithasherwood]

I was given a free steel tank c/w yoke valve. It seems a bit of an odd size, and bears only DOT markings. While it appears to have a galvanized coating of some sort underneath, it has been painted black and if the paint job wasn't done at the factory then it was at least done quite professionally. Unfortunately, the paint makes it difficult to make out the manufacturer's mark, but I think it's PST -- looks like the mark is a stylized P with something else tucked in, similar to their trademark. DOT is followed by 3AA, the working pressure is 3,000psi and the initial test date of 12/77 is followed by +. The serial number ends in the letter U. Opposite side of the cylinder shows it has been hydro tested 3 more times in it's life, but never with the + added (it is now over due for testing). There are no further markings anywhere that I can find. Diameter of the cylinder is almost exactly 7" and the height from the bottom to the base of the valve neck is 24".

So, first question: This cylinder has no TC markings. Can I still use it in Canada?

Second, I understand that TC doesn't use the + system, but just rates the equivalent cylinder working pressure to 3,300psi. Assuming the answer to question 1 is yes, can it be filled to 3,300 or just 3,000?

Finally, anyone have any idea what the capacity of this tank is? I've looked at a variety of on-line charts and can't find this size/pressure listed in any of them. Taking a guess at the wall thickness, I come up with something just over 83 cu ft. at 3,000psi or almost 92 cu ft. at 3,300. If I did the math right ;-) Anyone know for sure?

 

[montyb]

Hi:
Sounds like one of the sherwood tanks made by pst - at 3000 psi its an 86 cu ft, at 3300 psi its a 95 cu ft. What kind of valve does it have on it - does it look like the original - does it have the sherwood logo. I picked up one when it was listed as a steel 80 - sent it in for hydro and they said it was a 72. But found someone that knew tanks and with the weight of the tank, size - length and width - and id numbers turned out to be a real treasure - Its my primary tank to dive with.
Actual specs
marketed capacity -- 94.6
Actual capacity -- 86.63
Overfill capacity -- 95.25
Working pressure 3000, 3300 with 10% overfill
Length 25"
Dia -- 7.00"
Empty weight - 39 lb.
Buoyancy Empty (-6.00 lb)
Buoyancy Full (-13.3)

Hope this helps -- montyb
(if it is that tank and you don't want it - pm me)

 

[derwoodwithasherwood]

Hi:
Sounds like one of the sherwood tanks made by pst - at 3000 psi its an 86 cu ft, at 3300 psi its a 95 cu ft. What kind of valve does it have on it - does it look like the original - does it have the sherwood logo. I picked up one when it was listed as a steel 80 - sent it in for hydro and they said it was a 72. But found someone that knew tanks and with the weight of the tank, size - length and width - and id numbers turned out to be a real treasure - Its my primary tank to dive with.
Actual specs
marketed capacity -- 94.6
Actual capacity -- 86.63
Overfill capacity -- 95.25
Working pressure 3000, 3300 with 10% overfill
Length 25"
Dia -- 7.00"
Empty weight - 39 lb.
Buoyancy Empty (-6.00 lb)
Buoyancy Full (-13.3)

Hope this helps -- montyb
(if it is that tank and you don't want it - pm me)

The valve is indeed a Sherwood valve. The total length including the neck is 25" and the weight including the valve, boot, tank protector and ~500 psi air is 43lbs on the bathroom scale, so it sounds like you nailed it. Thanks. If the lack of TC approval means I can't get it tested and use it up here, I'll keep you in mind. I shudder to think what shipping to Arizona would cost though.

 

[montyb]

Dont worry about the shipping cost - if you decide - just let me know
montyb

 

[BigFoot Diver]

Take a look at this:

http://www.tc.gc.ca/Quebec/en/tdg/messageBottles.htm

Older tanks would appear to be exempt from the TC markings.

 

[wedivebc]

I rented one of those this summer while camping in Wa. It looked like a '72 but the air just kept coming. The shop had filled it to 3300 and I got 2 45min dives out of it.
Good score! I think bigfoot is correct about TC exemption

 

[Ontario Diver]

Tanks manufactured AFTER Jan 1/93 must have a TC stamp. Since your tank is prior to that, a DOT stamp is sufficient. You should be able to get it tested.

"+" stamps are still available in Canada but the hydro testing facility must have a special permit to do them. I do not know of any 3000 psi tanks that get +'d.

 

[derwoodwithasherwood]

Well this has turned into an interesting little goose chase. Kind of fun in a warped sort of way. First of all, I want to thank those that responded. Sorry but it looks like I'll be keeping this cylinder, plus mark or no.

Anyway, back to the paper trail: I looked up Bigfootdiver's link and started following the trail. Along the way, I found answers to a lot of questions and myths I've seen posted on Scuba Board.

It meandered through the Transportation of Dangerous Goods Act, so I read that. That refers you to the version of TDG in effect in 2001, so I read that. TDG does indeed allow use of a pre-1993 cylinder that meets the requrements of 49 CFR in the US (that's the law setting the standards for the DOT marks). However, the section of 49 CFR (part 107) referenced by TDG has nothing to do with DOT marks. Maybe it's a typo or maybe the sections have been re-numbered or something in the intervening years, 'cause the appropriate section is now 173.

173.302(c) lays out the "Special Filling Limits" for the 3AA cylinders. This is the part that allows the + mark. There's 4 different possible ways to allow a + mark: The US law includes calculations for maximum wall stress or average wall stress and provides a limit for each. Or the tester can refer to the CGA Pamphlet C-5 to calculate elastic expansion rejection limit. Or the tester can refer to the manufacturer's REE number marked on that particular cylinder. Satisfying any one of the 4 allows a + mark. There is no limitation to how many times a cylinder can be + rated. There is no requirement for the + mark to be maintained continuously -- it can be dropped and then picked up again at a later test. But it may not be "special filled" that extra 10% unless it was + rated on it's most recent test and the + mark was appended to that test date.

I have not been able to find any Canadian requirement that the test facility be specially certified to apply a + mark nor have I been able to find any requirement that the + mark be continuously maintained in Canada. I have seen suggestions that this is the case on other Scuba Board threads. These requirements may be specified in some other piece of legislation that I have not yet found. Does anyone know what legislation that might be?

For that matter, does anyone know of a facility (scuba or otherwise) in Ontario that can and does do the required math and applies the + mark?

 

[Ontario Diver]

I am currently certified by TC to do hydrostatic testing. I specialize in testing breathing air systems including SCUBA. Our "+" certifaction is pending. It is a separate process and adds an addendum to your certification allowing the facility to do "+" testing.

Reading TDG is only part of the issue, there are grandfathered permits, specific exemptions, CGA and CSA rules as well. There are also a number of TC "because that is the way that we do things" that you have to learn. I will state for the record that the people at TC are great to deal with if you ask instead of rant and recognize that you have to do it thier way. But as long as you do it thier way - you have no legal liability.

+ testing isn't calculated much inside of Canada after 93 because the 10% overfill is included in the BAR working pressure rating.

 

[derwoodwithasherwood]

I am currently certified by TC to do hydrostatic testing. I specialize in testing breathing air systems including SCUBA. Our "+" certifaction is pending. It is a separate process and adds an addendum to your certification allowing the facility to do "+" testing.

Ah yes, I do recall some other posts that suggest you are more than an unemployed IT manager from Toronto. You have mentioned something about testing SCBA cylinders in the past. So it begs the questions: Who is your company, and how far in the future is "pending"? (If I may be so bold.)

Reading TDG is only part of the issue, there are grandfathered permits, specific exemptions, CGA and CSA rules as well. There are also a number of TC "because that is the way that we do things" that you have to learn. I will state for the record that the people at TC are great to deal with if you ask instead of rant and recognize that you have to do it thier way. But as long as you do it thier way - you have no legal liability.

CGA and CSA. Two more private consortiums that derive profit from convincing governments that they know what they are talking about and then charge dearly to let the select few know what the laws are adopting by reference.

I'm not surprised that there might be different levels of qualifications for testing facilities. I would be surprised if that has somehow been manipulated into modifying the grandfathering of pre-1993 DOT cylinder marking though. Does something somewhere actually say that + marks must be continually maintained?

+ testing isn't calculated much inside of Canada after 93 because the 10% overfill is included in the BAR working pressure rating.

I assume you are referring to cylinders manufactured after 1993 with TC markings, not grandfathered DOT cylinders?