How to figure out the best tank to buy?

[TechBlack]

You are correct. The + rateing is a DOT only thing. TC does not have a + rateing.

In canada you should fill to the TC stamp specifications. Ei: 184 bar. Most dive shops just don't know what they are doing. Most don't even have bar on their gauges.

The only pickle you end up in is with grandfathered DOT tanks from before there was a TC. They follow DOT rules.

wow, learn something new everyday!

 

[JimC]

Incidently, this is why you can not get a + redone when you hydro in Canada. Such a thing does not exist.

 

[sprange]

Incidently, this is why you can not get a + redone when you hydro in Canada. Such a thing does not exist.

Jim,

Can you point me to any official bulletin/etc regarding TC regulations? I hate having to beg for a 2600 psi fill (here in Canada) while the shop tech searches diligently for the + stamp on my tanks. I fear that if I simply circled the the 184 with a black permanent marker I'd end up with 180 psi fills.

Sean

 

[JS1scuba]

Scuba Cylinders that get "+" rated for filling are full to the working volume only AFTER they are filled to the "+" amount.

For example an LP 95 is a 2400 psi "+" tank. This means that it has 95 cuft when filled to 2640 psi at 70 degrees.

At first hydro you need to ask for the "+" rating again. If it passes on the + then you get to keep it. If it fails you cannot get the "+" rating again. If they did NOT do the "+" test you cannot go back and get it again.

For a full comparison of LP, HP, and 3442 cylinders visit our tank spec page.

TANK SPECS AT TDL

Cheers

 

[francousteau]

Scuba Cylinders that get "+" rated for filling are full to the working volume only AFTER they are filled to the "+" amount.
..........
TANK SPECS AT TDL

Cheers

I still wonder why they don't rate the LP tanks at 2640psi in the 1st place. DOT dumb regs, I guess.

Joel- nice tank spec page

 

[spectrum]

I still wonder why they don't rate the LP tanks at 2640psi in the 1st place. DOT dumb regs, I guess.

Joel- nice tank spec page

They probably recognized the higher capability once some wee in the field and this offered continuity, just a guess.

Then again it could be some bizarre holdover like the 9/10 of a cent on gallon of petroeum fuel.

Pete

 

[spectrum]

How should I go about figuring out the best tank for me?

Did you get what you needed from this thread?

 

[JimC]

Jim,

Can you point me to any official bulletin/etc regarding TC regulations? I hate having to beg for a 2600 psi fill (here in Canada) while the shop tech searches diligently for the + stamp on my tanks. I fear that if I simply circled the the 184 with a black permanent marker I'd end up with 180 psi fills.

Sean

Unfortunatly, TC lets CSA write the guide lines. and CSA charges money for them.
Most current one can be purchaced at:
http://www.csa-intl.org/onlinestore/ISO_Search_Results.asp?query=B340&x=0&y=0


Grand Father clause for old tanks:
http://www.tc.gc.ca/acts-regulations/general/t/tdg/regulations/tdg001/part_5.htm#Class 2, Gases
Section 5.10.2.*


You might try pointing them at the clearly marked 184bar on the tank and see what happens. Good luck.

 

[D1V3R]

It sounds like a hp 80 and a hp 100 would be perfect for you

I own a pair of each, along with a pair of 120's, but thats for doubles

 

[BigTuna]

Thanks for clarifying things, folks, especially TechBlack, Spectrum and JS1Scuba.

So now I know that LP gas volume ratings refer to 2400 psi + 10% = 2640 psi, and HP ratings refer to 3442 psi.

Because I'd like to limit the absolute amount of weight I need to heft, it looks like my choice would be between a LP85 and a HP100, both of which weigh about 33 pounds.

How much gas I will get in a fill turns out to depend greatly on how much pressure the operator puts in the tank. Here are some numbers I ran for the two tanks for various fill pressures (in psi):

LP85
2400 --> 77 cuft (same as Al80!)
2640 --> 85 cuft
2800 --> 90 cuft

HP100
2640 --> 77 cuft (Al80 again!)
2800 --> 81 cuft
3000 --> 87 cuft
3200 --> 93 cuft
3442 --> 100 cuft

Surprisingly (to me), a modest overfill of the LP85 can result in about the same gas volume as a modest underfill of the HP100. Not surprisingly, both are much better providers than an AL80, when they are filled properly.

As a firm believer in Murphy's Law, I'd describe the numbers as saying that an LP85 and an HP100 provide nominally the same gas volume in the fill pressure ranges I'd expect, altho more times than not I'd get somewhat more gas from a HP100.

Balancing this is that the HP tank is more expensive (maybe even 50% more from some sources) and that its pressure adds some additional stress on the first stage regulator (which translates into an unknown reduction in reliability and an eventual increase in maintenance cost).

So I conclude that, comparable as the two tanks are, the LP85 looks a little better to me. Decent gas volume (especially if I can get a bit of an overfill), lower cost, and better reliability. [But I can see how somebody else might come out with the opposite conclusion.]

Time to stop analyzing....
Thanks again!