Filling Tanks

[Razorblade]

pescador775 once bubbled...
Of course, any physicist of high school stature will tell you that aluminum conducts heat faster than steel...

Okay so the thermal conductivity of Al is 237 W/m.K at reasonable temperatures (around 300K), while for Steel its 50.2 W/m.K
So can someone tell me why people claim that with steel tanks you can feel the heat buildup by touching the tank and not with Aluminum unless the tank was filled fast?
Is it because steel is stronger therefore requiring thinner walls?

 

[Uncle Pug]

Razorblade once bubbled...
Is it because steel is stronger therefore requiring thinner walls?

 

[sheck33]

ICUROK once bubbled...
Just remember these stores are run buy professionals that know what they are doing. If they cant fill your tank at a full fill at the norm of 70 degrees, then do what I do find another store..


Scott =-)

professionals, ha
yea, i have seen some of the pro's at work in diveshops.....
pleazzzzzzzzeeee

 

[bhapps24]

I just leave it at the shop when i pick it up the next day i ask them to top it off. there always happy to do so and i always get a good fill. simple and it works.

 

[notabob]

Unfortunately dropping the tanks off and picking them up the next day is not always an option. Especially when the nearest LDS is an hour away...

I don't have a problem waiting in the shop a little bit while they let the tanks cool before topping them off, but around here most shops' idea of a good fill is something that will leave you at 5% under rated when the tanks cool if you're lucky. Including the top-off. It's a happy day when I throw my reg on and get 2640 the next morning!

-Roman.

 

[bhapps24]

You have a good point notabob. I guess I'm fourtunate to have the Lds 15 min out of the way on my way home from MY 8-5

 

[DA Aquamaster]

I have bene filling scuba tnaks for years and my observations are that:

1) aluminum tanks dissipate the heat faster and benefit less from a water bath.

2) A fill rate of 300 PSI/min will overheat a steel tank in open air and you will lose around 250-300 PSI when it cools. And it takes longer to cool to ambient temp than an aluminum tank.

3) A water bath does present a risk of introducing water into the tank if it is done without taking the proper precautions of opening the valve a bit to blow any trapped water out of the tank valve before attaching the fill whip. (But then this is sort of like saying diving can cause the bends without proper precautions. I do not think the use of water baths should be eliminated, instead I think that the people who use them improperly should be eliminated. )

4) A water bath does allow for an easy leak check of the tank o-ring, the valve o-ring and the burst disc. In my experience this is the only time it gets done in the real world before your buddy notices bubbles where they aren't supposed to be. This is a definite advantage of using a water bath.

 

[nyresq]

I have been filling tanks for a few years at scuba stores I've worked at, and as a firefighter on a dive team (both SCBA and SCUBA). I've taken courses from PSI and from Bauer compressors.
One common problem everybody keeps jumping on with this topic is, "getting water in the tanks". This is only going to happen with improper filling technique.

Step 1- open tank valve for a few seconds to blow out any water AND dust that may be in the valve threads or yoke stem.

Step 2- open the fill whip for a few seconds to blow out any water or dirt that may be in the whip from the yoke or din screw opening to the valve.

Step 3- connect the whip and open the tank valve to pressurize the whip and valve (if tank is empty, then open fill valve and put in a hundred pounds).

Step 4- place tanks into water tank and fill.

Step 5- when desired pressure is reached, turn off tank valves and fill whip BUT DO NOT BLEED the whip yet.

Step 6- take the tank out of the water and wipe dry with a towel around the valve. Bleed and disconnect the whip, wipe down whip connector AND blow out whip end to make sure there is no water left in the whip.

If these steps are followed there is no possible way for any water to enter the tanks. assuming your using dry clean air. You're blowing out both sides of the connection, and once pressurized, water is not going to fight its way past a few hundred pounds of air and into the tank.

And any amount of heat that can be quickly dissapated from the metal is only going to be better and less stress on the tank. less temperature change to the tank equals better tank life.;-0

 

[mrducks]

steamboat dive shop in branford florida has ice cubes in refrigerated fill vat.
they blow lp tanks (doubles) with mix to "cave diver pressure levels" lol
fill tank slow or use a coolant 4 an honest fill!
never allow any moisture to get inside tanks. eom

 

[JohnStrr]

Good post nyresq,

I do wet fills as well (I still do 'em slow but hey, not only is it like 107 degrees here in Texas , I have found leaks that needed fixing because of it) and luckly I was trained properly as you were. I haven't really seen the need to wipe down the yoke and whip after the fill since both valves are shut when I take them apart, but purging any water from both the whip and the tank valve before AND after the fill, is not only smart (since I fill OUR rental tanks) but it's just basic courtesy (I don't want any excess water blown into my first stage and I sure don't want to do it to a customer, assuming the water dosen't evaporate imediately ). Whatever arguments there may be, IMHO if done properly, I don't see the problem.