Looking for a good fill on my HP steel 100's

[rob1967]

I know it's hard to get a good fill out of steel HP tanks, but I can't help but notice my buddy gets great fills from his LDS, I think they crank them up to 3700 or so, and are always at 3500 by the time they cool down.

As for me, both LDS near me seem unwilling to crank them up over 3500. They fill to 3500, let them cool off, then top them up to 3500. For same-day fills, they loose up to 400 psi, and even I leave them there for a week, they still loose at least 200 psi by the time I get to the dive site.

My question is: is it ok to fill HP tanks to say 3700 or 3800, knowing they will cool down to 3500? I don't see a problem with it, but my LDS doesn't agree.

 

[BKP]

Don't see why that should be necessary. I have HP100's as well, and often have the same issue -- they heat up like toasters, and lose a few hundred psi on cool-down.
Two of the sites I frequent do their fills with the tanks immersed in water-filled barrels. I always get a solid 3500 fills there, and they're cool when I get the tanks back. I don't understand why all fill stations don't use immersion -- leads to much happier customers.

 

[captain]

Drop them off one day and go back the next day to pick them up. Bring a pressure gauge with you and show them they are below 3500 and asked that they be topped off. Do this enough and they may get the idea.

 

[a22shady]

Most times I get fills they are at or above the 3400 mark. I dont see why you couldnt get the full 3442--3500psi fill especially if you leave the tanks over night. They fll it let it sit for overnight or few hours and top it off.

 

[rob1967]

Drop them off one day and go back the next day to pick them up. Bring a pressure gauge with you and show them they are below 3500 and asked that they be topped off. Do this enough and they may get the idea.

Aha, well, see, what they do, is they wait until I show up, and top them off then, so they have 3500 when I pick them up. Or, if they don't have 3500 psi, I get them to top them off, but they then cool down to 3300 or even down to 3100. And seeing as we are doing cold-water diving, I loose another 300 psi in the first 5 min of the dive before the "real" SAC rate kicks in.

I just love diving so much, I want to get the max bottom time out of each dive... My SAC rate is good, but some of my buddies use 120s, so it's hard to keep up with them.

 

[rob1967]

Like for example, last week, one of my tanks had 3400 in it, so the guy gets a bit snippy, saying, "well, they are rated to 3442 psi, so I can put in the 42 psi if to want", yadda, yadda, fogetaboutit!

So of course, that tank was down to 3100 psi when I went to go use it a few days later!

 

[GrumpyOldGuy]

Like for example, last week, one of my tanks had 3400 in it, so the guy gets a bit snippy, saying, "well, they are rated to 3442 psi, so I can put in the 42 psi if to want", yadda, yadda, fogetaboutit!

So of course, that tank was down to 3100 psi when I went to go use it a few days later!

I use the suggestion Captain had (bring a tank checker, use it and insist on a full tank). It does mean being an a-hole and getting that last 42PSI a couple of times. After a couple of trials, my LDS now pumps my tanks +200PSI cause he knows it will save him the hassle of topping off later.

By the way, have you checked your tank for a slow o-ring leak at the valve neck and checked your SPG against some type of standard. Either one can mislead you.

 

[Aqua-Andy]

What most dive shop employees do not and or do not want to understand is that the rated pressure is at 70 degrees Fahrenheit. If the air in the tank is hot, than the rated pressure is actually higher. Also don't forget just because the tank is cool that does not mean all the air inside is cool.

 

[zimmo]

What most dive shop employees do not and or do not want to understand is that the rated pressure is at 70 degrees Fahrenheit. If the air in the tank is hot, than the rated pressure is actually higher. Also don't forget just because the tank is cool that does not mean all the air inside is cool.

This is not true. The temperature has to do with the steel, not the gas. As you heat steel it's strength decreases so in reality the rated pressure would be lower at higher temperatures.

 

[skankpile]

This always happens to me when I'm onsite somewhere... the guys that won't fill my HP to 3700 will easily pump an al80 to 33-3400 so it will cool to 3K...I just scratch my head. Anybody who fills steel will know you can get an easy 500psi swing.

My favorite fill-do's are the people with the 3200 pneumatic cutoffs who don't know how to adjust them and just say we do this for safety... sorry.