DIN over 3000 PSI?

[spectrum]

I've just been lurking since being soundly thrashed last week for saying 3442 psi is the same as 230 bar, but since this thread comes up again and again, can somebody clue me in- where does 3442 come from??

As I understand there are certain restiictions and requirements regarding high pressure cylinders defined as 3500 PSI and above. PST's prior generation of HP cyinders were 3500 PSI, I have a pair of 100s. They have pure DIN valves.

The 230 BAR gets them below that and I believe is part of what lets the adequate yokes sneak under the wire with the dual use valve. Even though 3442 is a screwy number to us in the states 230 BAR is a nice enough number for the metric world.

Pete

 

[Curly]

Many thanks for all the valuable feedback. Most helpful.

 

[pescador775]

All modern regulator yokes can easily withstand 4000 psi. Same with the yoke valve and O rings. However, the valve itself must have been manufactured after 1977 (Sherwood) and be in good shape. For use above 3000 psi, you really should use the high pressure urethane O ring. This is milky white in appearance and is fairly hard (90 durometer). Years ago, I machined some yoke valves to fit the PST HP tank which has a 7/8 UNF thread. Never had a problem. The standards committees are not necessarily experts. They just have to check around to get some opinions and vote. It means little. The manufacturers, once they see the new standard, adjust the performance claims to meet the standard. It should be the other way around but the standards committees set conservative limits to account for old, obsolete equipment which may be still in service.

 

[SCUBA-J]

CGA G-7-2003 Compressed Gas Association, Inc Pg 5

5.3 Valves on air cylinders

Connections CGA 850,CGA 851 ,CGA 853 and CGA 855 have been assigened for use with self-contained undwater breathing apparatus(SCUBA) based on historical use and the SCUBA regulator and ancillary equipment designs..Except for CGA 852 which may be used for cylinders cylinders to 5500 psig at 70*F these connections may be used with cylinders rated up tp 3000 psig at 70*F filled in a manner that complies with the rating for the cylinder.

Connection CGA 851 is limited standard cylinders valve yoke connection for pressures up to 3000 psig for SCUBA air .Its is limited to use in SCUBA .

What is is saying CGA850 (yoke ) is good only to 3000 psig , if its over it should be DIN.

 

[Curly]

The plot thickens...

My LDS owner is a gearhead, so I asked him. He replied, as stated in this thread, that it depends on the yoke. He said that most modern yokes are rated for 3500 PSI and it should say on the side of the yoke.

So...to make things really confusing, the yoke says "3000 psi, 232 bar." The confusion is that 232 bar is 3410 psi. So he's going to ask the Aqualung rep to get to the bottom of the PSI/bar confusion.

Meanwhile, it looks like the DIN conversion kit for that model (Aqualung Cousteay 1st) is no longer available -- it's not on their price list.

 

[pescador775]

This USD yoke was manufactured in 1976. It is rated for 4,000 psi (yoke strength) which means it has a yield to failure of about 10,000 psi. If you use a "10,000 psi" urethane O ring on your valve there is very little likelihood of anything leaking or blowing out at pressures up to 4000 psi. However, to be conservative I use yokes only up to service pressures of 3500 psi. Personally, the misinformation bandied about yoke clamps and valves is annoying. The ISO has done their share. When we joined the ISO, and the ISO voted on the standard, USD had no choice but to drop the advertised rating to 3,000 psi service pressure.

 

[pescador775]

232 bar is approx 3364 psi. (A bar is 14.5 psi). The US tank manufacturers have diddled with this number by using a different set of standard conditions (22C vice 20C). Thus, they come up with 3442 or whatever. The people who make the HP tanks know that they are safe to use with yoke valves and this is what they came up with to comply with the unreasonably restrictive ISO rule.

 

[SCUBA-J]

Do what ever you want , I would use DIN. SCUBA always wants to play it safe , put if you have to spend $50.00 they find a loop hole to run the cheapest set up they can get away with.

 

[pescador775]

Do what ever you want , I would use DIN

Thanks, that's kind of you.

 

[XJae]

232 bar is approx 3364 psi. (A bar is 14.5 psi).

one bar = one atmosphere = 14.7 psi