Short Fills In HP Tanks

[fppf]

3AA steel and aluminum tanks have a test pressure that is 5/3rds the service pressure. The test pressure for most steel special permit tanks is 3/2 the service pressure.

So, for a 3442 psi special permit tank the test pressure is 5163 psi. For a 3000 psi aluminum tan it would be 5000 psi and for a 2400 psi steel tank it would be 4000 psi.

Actually, special permit cylinders have the test pressure "TP" and displacement numbers "REE" stamped into the cylinders. Worthington's test pressure on a 3442 is 5250

 

[iztok]

I see plenty of short filled AL80s so dive a premium steel cylinder and forget about it.

One I dove today was at 3400psi in the water at 46F water temp. (AL80)

 

[ROMO DIVER]

The only trouble I have ever had with HP tanks (besides the afore mentioned fast fills/human error) concerns getting nitrox fills. If a shop does partial fill nitrox and their O2 cylinder is a little low you can have trouble topping off a partially used nitrox HP tank with the correct percentage. Some shops use boosters but a lot do not. Your only option is to drain the tank and start fresh. This is both time consuming and cost money as you pay for a whole tank and not just the little extra O2 you need.

 

[fppf]

The only trouble I have ever had with HP tanks (besides the afore mentioned fast fills/human error) concerns getting nitrox fills. If a shop does partial fill nitrox and their O2 cylinder is a little low you can have trouble topping off a partially used nitrox HP tank with the correct percentage. Some shops use boosters but a lot do not. Your only option is to drain the tank and start fresh. This is both time consuming and cost money as you pay for a whole tank and not just the little extra O2 you need.

Most shops just charge one price for tank fills, no matter how much is left. So I really don't care if the drain it or not.

Boosting oxygen is a dangerous affair, it is not to be taken lightly and should only be done when needed.

 

[dannobee]

Wanna bet?

Nope!

I had just rebuilt my big haskel (8AGD-14) and decided to test it out with a friend on an HP80. We equalized at ~1800psi, then fired up the haskel. SIX seconds later the gauge on the fill station was at 4200psi and still climbing before I yelled "shut it off!" The fill station bypass was set at 3900 and the Haskel pumped right past that with the bypass wide open and screaming. :shocked2: Then I rechecked the performance graph of the Haskel and saw that it was over 350 cfm. Well, duh, I should've remembered that.

I know a few people who fill their doubles in a minute or less, and have been doing it like that for years.

 

[The Kraken]

Just my opinion, but I think in most of the cases the short fill is just an indicator of laziness or sloth upon the part of the tank filler.

I took one of those little tape label making machines and printed out "FILL PRESSURE: 3442# COLD" and put at the base of the valve on all my HP tanks.

Iffen it ain't 3442# or better, it ain't filled . . . so I'll pay yer fer whut ya put in thar.

the K