Tank overfill = mini hydro?

[imwright1985]

ok then why was my tank fill at divers direct in west palm 3050 when i checked as it came off the whip then when i got to my dive site a couple hours later it was 2680? Ohh it was checked with the same gauge both times so i dont think the gauge has an error of almost 400 psi and i have heard that about their fills many times unless you leave your tanks and tell them to top off later rather than give them about 15-20 mins to fill.

It depends on a ton of things like how much air is flowing into the tank per min and the material of the tank. Most of your tanks have probably been filled slower than what DD did to mine which is why you havent see that high of a pressure difference. If the fill guy is cautious enough to not let the whip ever hit the water then there is nothing at all wrong with it, best way to get a completely 100% safe and acurate fill would be to either be cautious to not let the whip hit water ever submerge entire tank and fill slowly (to also check for possible leaks) or to dry fill it very slowly if fill guy might not be competant enough to keep the whips completely dry between fills

 

[Doc Harry]

...Back to the tank fill and hydro test, these pressures are obviously well within the elastic region....

Are you sure of this? If so, wouldn't my report from hydro show a 0% permanent exapnsion?

But it is not 0%, it is more like 1.5% which demonstrates that hydro pressures push the inelastic region of the curve.

A fill to 3,900 PSI does not quality as a mini-hydro, who ever says that has no concept of how to perform a hydro.

The hydro pressures are clearly defined by the DOT and the special permits.

 

[Thalassamania]

Good shops do cooler fills with soaking the tanks while filling them and filling slower than other places, this gives them the more accurate PSI and you more fill. Divers direct does hot fills and on an al80 i walked out with 2680 when i hit the water. if i use my usual shops when i hit the water the lowest they are is 3080 and usually run about 3200. beings that hydros are done at 5000psi on al80's im not too worried about the extra 200 on a fill, and the overfills strain harden the metal which causes it to loose elasticity so it is possible for overfills to cause a tank to eventually fail hydro

The Case For Dry-Filling Scuba Tanks, by Fred Calhoun, PE

 

[Davidstealey3]

very good article. fill slow and let cool top off.

i know some shops are overwelmed by the amount of tanks they have to fill at any given time, but add more banks and whips, have more tanks to rent, or the diver needs to be aware of the time it takes to get a GOOD COOL FULL FILL and be happy.

 

[Wayward Son]

go to fill express & get your tanks filled.

I *like* FE & get fills there when I'm in the area. But there ain't no "cool & top off", they fill them, hand them to you & when you load them in your car they're too hot to keep your hand on for more than a few seconds.

 

[imwright1985]

I heard fill express is awsome with fills, wish they were more local. I usually keep an eye on my tanks when they are getting filled so am not too worried with where i go and not all of the places soak tanks. I just know that my experience with a fill at divers direct was a joke so im avoiding fills there now. i would rather wait around 10-15 mins more and get a good fill from them slowing the flow than get shorted by 400 psi

 

[NJDiver07866]

lost 800 PSI? This means about ~160F change in tank temp...talk about a hot fill...

 

[imwright1985]

lost 800 PSI? This means about ~160F change in tank temp...talk about a hot fill...

it was 400 and my valve was hot enough i had to sit the tank down like 3 times from back of store to my car

 

[WD8CDH]

Shops that need to fill a lot of tanks should just get more fill whips. It's better to fill several tanks slowly at the same time than to fill them one at a time quickly. If shops were smart enough to abandon their water tanks, they would have plenty of room. The industrial gas industry has been doing this for decades. They usually fill 10, 20 or more cylinders at a time, never in water.

But also, shops should realize that if the tank gets to no higher than 130F, they can legally fill over the service pressure as long as the tanks are at or under the service pressure when cooled to 70F.

 

[imwright1985]

I think its just the fact most shops fillers are prettymuch chimps that go and do the same thing repeatedly all day and dont think ok im filling this much and when tank cools to room temp which is usually 75-80deg tank will be about x-psi, I know force-e is local to me and they accuratly fill for the most part, but they do soak tanks. (i dont know if they used to soak tanks or not, but know they had a tank fail in their shop and take most of a guys hand off, so might be as a kinda safety precaution to keep rapture from being as critical, i dont feel like figuring out if it would help in that situation)