Fills dry or in water bath?

[Bob DBF]

My guess is that the water baths were removed because it is a pita to lift tanks in and out, never mind the chance of injury. Back when my LDS had a water bath, my double 72's and Faber 120 never went in anyway. Without the water tank, it didn't seem to me there was much, if any, difference in the time or quality of the fills.

I never saw how having a water bath at room tempature, or higher, and increasing will make much difference than air cooling. Since the heat is generated in the tank, filling then removing the tank from the water bath limits any cooling the water can do, and leaving it in increases the water tempature which decreases its effectiveness, never mind limiting the number of fills per day. If the water bath was recerculating and cooled this can help, I have not seen one like that, but I live a sheltered life.


Bob

 

[RayfromTX]

Someone tell me how water can defy the laws of mechanics and physics to slip through a valve that is closed.
I really need to know.

A little water splash here or there while the whip is disconnected and if it gets in the valve or the whip it will get pushed in during the fill. Wet hands grab a valve, water runs into the opening and collects in the threads. Whips lie on the floor and wet tanks drip on them. It's not that it can't be avoided, it's that an effort at keeping things dry in a wet environment must be made by people that are getting in a hurry and slinging around heavy weights. How do I know they are in a hurry? Fooling with putting tanks in a tank of water to speed the process is all the evidence I need. I know people that I would trust to get it right and people that I wouldn't. The fact that it happens behind a closed door is one reason why I fill my own.

 

[RayfromTX]

My guess is that the water baths were removed because it is a pita to lift tanks in and out, never mind the chance of injury. Back when my LDS had a water bath, my double 72's and Faber 120 never went in anyway. Without the water tank, it didn't seem to me there was much, if any, difference in the time or quality of the fills.

I never saw how having a water bath at room tempature, or higher, and increasing will make much difference than air cooling. Since the heat is generated in the tank, filling then removing the tank from the water bath limits any cooling the water can do, and leaving it in increases the water tempature which decreases its effectiveness, never mind limiting the number of fills per day. If the water bath was recerculating and cooled this can help, I have not seen one like that, but I live a sheltered life.


Bob

Galvanized or white tanks have a low emissivity rate. They don't radiate their heat very quickly and in the presence of other warm objects their net rate of heat loss is rather low. Water changes the main heat transfer mechanism to conduction which is far more effective even with a low deltaT.

Good air circulation can help increase the convective heat exchange in a dry fill setup.

Evaporation from the tank of water and the surface of the wet tanks have some cooling effect with the wet method. Heat of vaporization is non-trivial.

 

[Flycaster]

The most reputable dive shop I've ever visited (and now frequent) does wet (water bath) fills. I can imagine water getting in the cylinder if it's done carelessly, but I don't see anything inherently wrong with cooling the tank while filling. The compressed air is bone dry so claims of "condensation" are nonsense.

What he said

 

[tbone1004]

@rjgiddings the problem with the logic of going to pick them up in a few days from a business perspective is you have to put everything back on the whips to top off and since time is $, that makes the fills cost more because there is twice as much labor going into it....

 

[dead dog]

Nobody in Seattle is in a hurry...have you drove in Seattle traffic? Nobody here even wears a wristwatch. so, no sense of urgency. Ever. About anything. Go get your tanks in a few days.

That's because you're looking at your new cell phone every 10 minutes.

 

[Still Kicking]

@rjgiddings the problem with the logic of going to pick them up in a few days from a business perspective is you have to put everything back on the whips to top off and since time is $, that makes the fills cost more because there is twice as much labor going into it....

Not to mention the problem of storage. I work in a large, busy shop (50-100 fills per day) and our tank storage area is generally full with VIPs and hydros. Storing and tracking tanks after fills isn't practical and most customers don't want to make two trips anyway.

We fill tanks slowly in water. When the tank is full (but not overfilled) I give the customer a choice: they can take their tank as-is and know that it will lose some pressure when it cools off or, if they have time, browse the store for a while and I'll top it off when it's cooled down. It seems to work well and customers are happy with the arrangement.

 

[MaxBottomtime]

I worked at a shop that was located at a busy marina with nearly a dozen dive boats. We sometimes filled 100+ tanks per day. I always overfilled tanks a little in water. One day a guy dropped off some aluminum 80s and went to lunch at the restaurant upstairs. hen he returned he asked how much pressure was in his tanks. I told him 3300psi. He had me drain 300psi out of each tank. That was the only time I ever heard of someone having too much air.

 

[NAM001]

I took the PCI class and they suggested not to water fill. We've been filling tanks since the fifties I'm a third-generation diver and I can tell you without a doubt The fill is better in a water bath.. I made an attempt to defy my family history and the results were time consuming tedious filling operations. We use cool well water daily fresh. I am not a tank monkey I am a local fill station operator who believes the anything I can do to give my customers an efficient better fill is worth doing. We Bank 5000 PSI in our Cascade and the air goes through your standard Lawrence Factor filters changed out before scheduled intervals the, auto bleed system works flawlessly and our air continually test clean O2 compatible. I would be worried if another fill station operator did not know as much about their personal fill station system as we did however I cannot worry about what other people do only what I do.

The PCI class stated that the thermal conductivity was so low on scuba tanks that it didn't make a difference. I also fill aluminum tanks in the water bath and I can tell you from personal experience over probably close to 10,000 air fills the water is working in the way of what you anticipate cooling the fill. Again I could see how water could get in there where the bad operator however the whole idea is to avoid bad operators and just a quick glance at how they work should be enough to tell you whether you need to get your tanks filled somewhere else.

Worth adding is if I do hot fill a steel cylinder and pull it out of the bath it will still settle quite a bit. The trick is to still fill slow and let the tank settle in the bath while hooked up to the filling regulator. I can't imagine anyone would do any differently but I don't know how everyone works. We use Aqua environment regulators on our fill panel and I am able to dial the pressure and use the line valve to control the flow rate.

The occasional dry fill that I do is typically because the gentleman bringing the doubles and did not remove his back plate and harness setup I don't care particularly too well to put the gear in tub because it just makes a big wet mess taking it out of the store.

Everyone has their preference this is mine.

You have probably adressed every important point of this issue. Its all about knowing what you are doing. Most tank monkeys do not. By theory the dry process is the best but in reality customer demand rules. I FILL AT HOME WITH A WET TOWEL ON THE TANK. That is a wet fill.

 

[NAM001]

Not to mention the problem of storage. I work in a large, busy shop (50-100 fills per day) and our tank storage area is generally full with VIPs and hydros. Storing and tracking tanks after fills isn't practical and most customers don't want to make two trips anyway.

We fill tanks slowly in water. When the tank is full (but not overfilled) I give the customer a choice: they can take their tank as-is and know that it will lose some pressure when it cools off or, if they have time, browse the store for a while and I'll top it off when it's cooled down. It seems to work well and customers are happy with the arrangement.

OUt of curiosity what is your definintion of over filled????? Has an AL tank filled to 3100 and allowed to cool to 2800 been overfilled????