Short fills- how short is too short?

[SparticleBrane]

 

[diverdowndh]

If a tank is supposed to be filled to 3000psi, then it should be filled to 3000psi. BUT... there is a 5psi change for every 1 degree. Tanks are going to get hot when filled, whether fast or slow. Even slow fills get hot inside, as building pressure always creats heat. A tank filled to 3000psi, when end up 2800-2900 if filled correctly. Some opperators will fill to 3200 to put the tank at 30 when cooled.

I definitely like your thinking - I recently went to Belize and after looking over every tank they had "full" the best was about 2800. All week the most I ever saw in a tank was 2900, I personally thought it sucked. I've dove all over and when I pay the usual exhorbitant prices to dive, I want every pound of air that I pay for.... 3000lbs. I have never seen it an issue other than this past trip either!

 

[kidspot]

... question...

Years ago I remember dive shops set the tank to be filled in a 50 gal. drum of water while filling... today all I see (although this is a limited sampling) is "set the tank on the floor, attach the whip... hit the air"...

Would putting the cylinder in water during the fill help with a full fill by acting as a heat sink? "Back When", I seem to recall they did it "in case the tank ruptured"... but that was 30 years or so ago...

Is there any reason they don't set the tanks in water these days??? Safer tanks? Better inspections? Just curious...

I asked my lds about this as well and their answer was "Doesn't take long for the water to be as hot as the tank is ... what good will that do?"

The second most common reason I've read is that this is the most likely point for moisture entry into the cylinder.

to the O.P. - I rarely get a fill under 2900 psi, and normally (Except when they hire a new tank guy) my fills on AL80's come back at 3100 after cooling. My shop takes 20 minutes to fill a tank, which isn't real fast (tank still gets a bit warm though)

For EANx fills I've rarely seen one approach 3000 psi, they have usually been 2800psi after cooling off. My last boat trip my cylinder was only filled to 2200psi ... but what can ya' do once you're on the water? "Spilled milk" is all at that point I guess... (btw - it was still a nice 45 minute dive with 150ft vis )

Aloha, Tim

 

[1_T_Submariner]

I commomly get 3000 in my Hp120 instead of 3500. I just figure I'm paying the same as if it where an 80 and I get about 105 cu/ft.

 

[eliminator]

The store I do the occasional charter with usually has tanks with anywhere from 2650-3000 PSI in their AL80s. My air consumption is pretty good compared to some of the others I dive with, so when we check tanks and one of them is 3000 and the other is 2700, guess which one I get..... I kinda get peeved about having a tank below 3000, but it all works out in the end.

Now, the other shop I get my personal fills from is great with Nitrox. I have an "Unlimited Nitrox" for a year on two of my AL80 tanks. They uaually get withing 1% of the mix I want and they always fill tanks to 3000-3200, which in my books is good. It only cost $100CDN to register each tank with them. So, although Ive only been on the unlimited plan for about a month now, I've already made money if I had gone with the $12 a fill for the Nitrox.


elim

 

[eliminator]

Oh, just remembered this

One of the guys I dive with use to get really low filles (2500 range) from the next town over. So before he got his tanks filled, he would chuck them in a snow bank for a few hours in the winter, or leave them in his cool basement the other months. He said it worked.

And then I guess the reverse would work....is a tank is low, I guess you could leave in in a warm spot for abit to "warm it up" I'm not talking open flames or anything, but maybe some sunlight on the direct portch instead of in the cool dark garage before you head out for a dive.

elim

 

[fishb0y]

And then I guess the reverse would work....is a tank is low, I guess you could leave in in a warm spot for abit to "warm it up" I'm not talking open flames or anything, but maybe some sunlight on the direct portch instead of in the cool dark garage before you head out for a dive.
elim

Ummm... how does that put more air in your tank? Did you think about what happens if you put your tank back in the cool water?

 

[kidspot]

true - I plan on losing 100psi when I jump in just from the water cooling things off ... 200psi if they've been sitting in my car all day

 

[The Kraken]

Ummm... how does that put more air in your tank? Did you think about what happens if you put your tank back in the cool water?

Spot on, Fishb0y . . .

Only the pressure changes, not the volume.

the K

 

[Potapko]

I was diving with a charter operator last weekend and they had us check our tank pressure before the boat left. I usually had 2700-2800 psi in an AL80 ("full" at 3000 psi) and the DM always asked if I would like a "full" tank. I didn't think that a few hundred psi/10 BAR was a big deal, at least not big enough to bother to change the tank.

Where do you draw the line with short fills on recreational dives? Does it depend on the depth/current/temp?

(I'd make a poll, but I just don't care anymore )

Anything below 200 bar is too short!