100cf vs. 90cf vs. 80cf: Big difference?

[ClayJar]

The + is with the hydro, and you can get a plus with subsequent hydros, if they do the procedures to test to the + (and the tank passes to the +, of course).

 

[Dash]

Ok maybe somoen can explain this, not to belabor the point, but it confuses me. Below is a description of a new tank. It clearly says 85 and 2400 psi. Below that it says it is a 2400 psi tank and can be overfilled to 2640.

Is this not a 85cf tank @ 2400 psi? Just checking.

Faber 85 Cubic Foot 2400 psi Cylinder with Thermo Nitrox Pro Din/K Valve

* Brand New 2006 Manufacture
* Faber Steel 85
* 2400 psi with a 10% Overfill Rating to 2640 psi
* 7 inch Diameter
* 25.9" Tank Height
* 31.2 lbs. Tank Weight
* negative -3.8 lbs full / 2.32 lbs empty Buoyancy in salt water
* Triple coated with spray galvanize, white powdercoat, polyeurethane

 

[Hoosier]

It is 85cf at 2640 psi and 77cf at 2400psi.....

 

[FredT]

All Exemption tanks (Faber, PST and Worthington ~3450 psi rated bottles anyway) are rated at actual volume at stamped pressure. The E tanks do not have a + rating from the factory but are permanently rated for the + pressure anyway. i.e. fill to stamped rated pressure at 70°F. Higher pressures are OK in a hot fill as long as the tank COOLS to stamped pressure at 70°f.

How the LDS actually interprets things is anybodys guess since many LDS seem to dream up their own rules in an opium den, but that is how the actual DOT rules work.

FT

 

[LobstaMan]

As far as the plus rating goes, it seems to me it's up to your LDS. One of my LDS will fill my 72s(both last 60s vintage and plus stamped) only to the operating pressure of 2250. The other one(the one I tend to frequent, even though a longer ride) will give me the 10% plus fill. I don't think you'll be able to force the LDS to fill your tank any more that they want to.

LobstaMan

 

[eandiver]

since many LDS seem to dream up their own rules in an opium den, but that is how the actual DOT rules work.

FT

:lol: :lol: :lol: :lol:

I feel that way about a lot of my local LDS's. Fortunately the one I do use will fill my E7-100's to the + pressure. They also do the VIP and hydro's.

 

[rjack321]

The + is with the hydro, and you can get a plus with subsequent hydros, if they do the procedures to test to the + (and the tank passes to the +, of course).

There's almost no way to fail a "plus proceedure" since its basically a math exercise. I suppose if you have a giant pit that changes the wall thickness you could fail on the plus rating math, but in that case you'd also fail the visual.

So the only LP tanks without plus rating are almost always those where the hydro facility didn't bother to go through the mathematical gyrations to renew the plus.

Big secret #2, the TC rating in bar is the same as the DOT psi rating plus 10%. They don't use pluses up there, they just rate them right in the first place.

 

[danlucretia]

Ok, i've read most of the info above and some of it is not making sense

1. all tanks, steel or aluminum have a weight difference between full and empty and they all seem to be around 6.75 to 8.0 lbs in wt difference.
The LP95 weighs 41.0 lbs with a negative 8.0 full and 0.0 empty and the aluminum 100 weighs 49.0 lbs with air and is negative 5.4 full and plus 2.0 empty.
All of the in water weight can be offset by the amount of lead you carry around your waist.
I would say the LP95 is the better of the two as the carry weight is lighter and it can be overfilled which the aluminum can not.

 

[ClayJar]

There's almost no way to fail a "plus proceedure" since its basically a math exercise.

(emphasis mine)

There are also almost no users named ClayJar that post here. The Packers almost beat the Saints (so it counts as a win, right?). Saying it "almost" can't happen is a nice way of saying it can, regardless of why. As for that, under 49 CFR 173.302 section b, "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."

So the only LP tanks without plus rating are almost always those where the hydro facility didn't bother to go through the mathematical gyrations to renew the plus.

I would not purport to know how often this applies, but if the hydro facility does direct expansion tests instead of water jacket tests, DOT regulations forbid that method from be used to re-qualify a cylinder for a 10% overfill "+" marking, if I am informed correctly. (I don't have a direct reference to that reg or the reasoning behind it in front of me, so feel free to point out changes about which I'm unaware or misconceptions that may apply.)

Oh, and there's that pesky "almost" again. Almost none of the bodies in our solar system are stars, so we can ignore that one exception with impunity, right?

(Oh, and of all the cylinders in service, almost none have exploded, so why do we even have the regulations in the first place?)

 

[reeldive]

How the LDS actually interprets things is anybodys guess since many LDS seem to dream up their own rules in an opium den, but that is how the actual DOT rules work.

FT

Ahh yes that is true. Also worth mentioning is the cal. tolerance of the gages. From what I've seen they can differ by + or minus 100 or more psi