Tank overfill

[pickens_46929]

Thought the Faber 85's were 85 cu. ft. @ 2400 psi and ~93 cu. ft. at +10% or 2640 psi?

Dave

Guess I answered my own question by browsing the board and reviewing the Faber website... they make working pressure during the first 5 years as +10%... so it's only 85 cu. ft. at 2640 psi.

Guess I'll have to start overfilling...

Dave

 

[scubafanatic]

Thought the Faber 85's were 85 cu. ft. @ 2400 psi and ~93 cu. ft. at +10% or 2640 psi?

Dave

Hi Dave,

...unfortunately, ya thought wrong....current generation LP steel tanks are 'full' @ 2640 psi...and when you re-hydro them you need to specify to the testing facility that you want your LP 85 tested to retain it's 2640 psi rating, otherwise they may only recertify it to 2400 psi, leaving you with only a 77 cu. ft. tank.

Karl

 

[padiscubapro]

Thought the Faber 85's were 85 cu. ft. @ 2400 psi and ~93 cu. ft. at +10% or 2640 psi?

Dave

nope faber 85s are 85 at working pressure which is 2400+10% overfil..or 2640

 

[padiscubapro]

Need to check with a Tute engineer That's more like 2.5 lbs and only 0.2" longer -- in other words a fair chunk more metal in the European tank.

Not sure at all about the first example, the really small tank. The second example is using about 8% more steel, for about the same tank surface area (pi-r-squared-h)

The europen tank is LIGHTER, therefor LESS metal.. In the second example the US tank is first.. you can see it is slightly longer, weights less and the diameter is smaller, whic means that the cylinder walls are thinner..

 

[David Thiesfeld]

I've enclosed a couple PDF scans of the faber data sheets, for what I believe to be is the same tank as the 108. The US tank is rated for 184 bar, and the european tank is rated for 203 bar.

 

[Leadking]

But where are the 4000 psi Fabers? There aren't any! So pump away at your own risk!

 

[padiscubapro]

But where are the 4000 psi Fabers? There aren't any! So pump away at your own risk!

There are plenty of high pressure fabers (300 bar / 4350 psi) but the largest they come in is 12l, that would be about 127 cuft per cylinder, unfortunately ther is no us equivalent (that would be a 78 cuft tank @ 2640)

the closest tanks I could find were 250bar/3625 psi

vol dia len P KG
15 203.6 605 184 16.9 DOT 3AA / TC3AAM
15 203.8 615 250 18 ITALIAN STANDARD

11.96 171.6 665 184 13.3 DOT 3AA / TC3AAM
12 171.8 670 250 13.9 ITALIAN STANDARD
12 174.6 670 300 17.5 TRG (GERMANY)

The next step up is 300 bar/ 4350 psi, as you can see the biggest difference was the largest cylinder only about 2.4 lbs difference (wall thickness is going to be very close sincle length is only slightly longer), but on the slightly smaller cylinders the weight difference is small even though higher pressure cylinder is larger. The closest 300 bar cylinder does have a thicker wall as expected 2.8mm (.11 inches / ~7/64 of an inch) but rember its slightly over 1.6 times the pressure..

 

[jonnythan]

I'm still not seeing "the same tanks." I see weights that are off by 2-3 pounds, lengths that are off by an inch or two, etc. I know nothing about the engineering involved, but there are differences there.

 

[padiscubapro]

I'm still not seeing "the same tanks." I see weights that are off by 2-3 pounds, lengths that are off by an inch or two, etc. I know nothing about the engineering involved, but there are differences there.

Where do you see an inch or two?? The greatest difference I showed is 10mm which is less than 1/2 an inch.. What you should really be concerned with is wall thickness..
On the two cylinders around 12l the difference is only about 1 lb.. You will not find things exactly the same especially since the euro standard for valves is m25x2, (stems are usually slightly longer) The longest US valves I have seen have under 1 inch (25.4mm) of thread (although a US DOT cylinder COULD be designed wih a m25x2 valve), where most of the european specs specify 30-35mm of thread.. which corresponds nicely to the SLIGHTLY longer european cylinders (like I said earlier they typically have slightly longer "necks" )
For europen 232bar cylinders they have less metal than our 184bar cylinders..

 

[jonnythan]

Yeah.

They're different tanks. You might want to say they have equivalent strength and properties, but they're different tanks.