Shops in the area that fill using a water bath

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FlyinV
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Shops in the area that fill using a water bath

Post by FlyinV » Tue Oct 15, 2013 11:07 am

Are there any shops in the area that still put tanks in a water bath when they fill them?
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Re: Shops in the area that fill using a water bath

Post by Desert Diver » Tue Oct 15, 2013 11:17 am

Last time I got fills at Edmonds they were underwater. Why?

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Re: Shops in the area that fill using a water bath

Post by JasonDiver » Tue Oct 15, 2013 11:22 am

Anacortes dive shop uses water. Why? I am interested in this topic.

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Re: Shops in the area that fill using a water bath

Post by Jeff Pack » Tue Oct 15, 2013 11:38 am

Some folks believe it cools the tank/gas, some folks believe careless fill operators can get water in the tank, others claim the water creates a temperature differential between the cooler metal surface, and the hot gas that creates issues in the tanks metal integrity, etc.

I just use fans, and pipe cooler outside air in for the compressor. Might be my imagination, but goes along with IR testing, my tanks and compressor run cooler.
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Re: Shops in the area that fill using a water bath

Post by CaptnJack » Tue Oct 15, 2013 11:41 am

FlyinV wrote:Are there any shops in the area that still put tanks in a water bath when they fill them?


What is "the area"?
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Re: Shops in the area that fill using a water bath

Post by kdupreez » Tue Oct 15, 2013 11:42 am

FlyinV wrote:Are there any shops in the area that still put tanks in a water bath when they fill them?


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Re: Shops in the area that fill using a water bath

Post by Dusty2 » Tue Oct 15, 2013 11:47 am

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Re: Shops in the area that fill using a water bath

Post by FlyinV » Tue Oct 15, 2013 11:49 am

The Area = The Northwest
Just wondering since I read an article about filling in a water bath and that it wasn't a useful technique.
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Re: Shops in the area that fill using a water bath

Post by Desert Diver » Tue Oct 15, 2013 12:37 pm

It seems to me that it must provide better fills. Others say it doesn't. I almost always fill tanks 2 at a time and my compressor shuts off on a pressure switch. Next time I fill I will put one in water and leave one in air. Then I'll check them the next day and we will have an answer.

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Re: Shops in the area that fill using a water bath

Post by CaptnJack » Tue Oct 15, 2013 12:48 pm

FlyinV wrote:The Area = The Northwest
Just wondering since I read an article about filling in a water bath and that it wasn't a useful technique.


The answer is "it depends" on:
fill rate
tank material (steel, aluminum, or composite)
tank size (aka volume to surface area ratio)
starting pressure
ending pressure
air temp
water temp
compressor temp (just started or run for a long time already and making the hottest gas it can on that day?
compressor cooling (extra coils, chilled coils etc)
compressor filtration (ie oversized filters would let the gas from a small compressor cool alot before it even got to the tank)

and probably a few more variables I can't think of off the top of my head.

In some circumstances its useful, in others its not. Given the state of the internets, you will be able to find a virtually infinite number of circumstances and people arguing about it.
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Re: Shops in the area that fill using a water bath

Post by Desert Diver » Tue Oct 15, 2013 1:22 pm

CaptnJack wrote:
FlyinV wrote:The Area = The Northwest
Just wondering since I read an article about filling in a water bath and that it wasn't a useful technique.


The answer is "it depends" on:
fill rate
tank material (steel, aluminum, or composite)
tank size (aka volume to surface area ratio)
starting pressure
ending pressure
air temp
water temp
compressor temp (just started or run for a long time already and making the hottest gas it can on that day?
compressor cooling (extra coils, chilled coils etc)
compressor filtration (ie oversized filters would let the gas from a small compressor cool alot before it even got to the tank)

and probably a few more variables I can't think of off the top of my head.

In some circumstances its useful, in others its not. Given the state of the internets, you will be able to find a virtually infinite number of circumstances and people arguing about it.


So under which of the circumstances would it not provide a benefit assuming water temperature cooler than filling tank temperature?

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Re: Shops in the area that fill using a water bath

Post by CaptnJack » Tue Oct 15, 2013 1:50 pm

Desert Diver wrote:
CaptnJack wrote:
FlyinV wrote:The Area = The Northwest
Just wondering since I read an article about filling in a water bath and that it wasn't a useful technique.


The answer is "it depends" on:
fill rate
tank material (steel, aluminum, or composite)
tank size (aka volume to surface area ratio)
starting pressure
ending pressure
air temp
water temp
compressor temp (just started or run for a long time already and making the hottest gas it can on that day?
compressor cooling (extra coils, chilled coils etc)
compressor filtration (ie oversized filters would let the gas from a small compressor cool alot before it even got to the tank)

and probably a few more variables I can't think of off the top of my head.

In some circumstances its useful, in others its not. Given the state of the internets, you will be able to find a virtually infinite number of circumstances and people arguing about it.


So under which of the circumstances would it not provide a benefit assuming water temperature cooler than filling tank temperature?


Topping off partially filled lp108 steel tanks 8 at a time from a 3cfm compressor on a 40F day. The temp difference between the metal of those tanks and ambient air is basically nil. Yes they the gas inside gets warmer, but +1F ends up being inconsequential. Smaller the volume they need, the less heat they will gain and the less useful getting rid of that heat a tiny amount faster will matter.

Remember its the gas inside the tank which is warm. You have to transfer that heat to the metal, then you can either transfer that heat to ambient air or to the water in the bath. The rate limiting step is often the transfer of heat from the gas inside to the tank, not from the tank to its surroundings. This is especially true for steel tanks.

Converssely, filling a 6cf aluminum inflation bottle from a 12cfm compressor a bath makes a huge difference - although you still have to let the 6cf bottle sit in the water for awhile and then retop it to achieve 3000psi. So what's the point if you must retop the bottle 400psi vs 800 psi? You still have to top off your 6cf bottle.

The drop in pressure or lack thereof is what creates people's perception of "useful" or "beneficial". That pressure drop is some sort of nonadradic equation of the variables above. Sometimes the rate of heat transfer is so tiny it becomes not worth the bother or impossible to measure any post fill pressure drop that baths become pointless.
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Re: Shops in the area that fill using a water bath

Post by kdupreez » Tue Oct 15, 2013 2:17 pm

I know that my steel tanks will drop about 300-350psi when i fill them from my banks.. so all I do is overfill them with about 400psi.. so when they cool down, they are at the pressure i want..

Some shops however will not overfill for liability, so a water bath can help them get to a stable rated pressure easier without giving customers a "short fill" when the tanks have cooled down..
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Re: Shops in the area that fill using a water bath

Post by Nwbrewer » Tue Oct 15, 2013 2:25 pm

To me as the owner of the tanks being filled, any perceived advantage of the water bath in cooling the tanks is greatly outweighed by the increased chance of negative consequences associated with getting water blown into my tanks.
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Re: Shops in the area that fill using a water bath

Post by DiverChris » Tue Oct 15, 2013 2:40 pm

I believe one of the reasons water baths were used originally was in case a tank failed during filling. The water bath would absorb some of the energy of the explosion.


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Re: Shops in the area that fill using a water bath

Post by CaptnJack » Tue Oct 15, 2013 3:20 pm

DiverChris wrote:I believe one of the reasons water baths were used originally was in case a tank failed during filling. The water bath would absorb some of the energy of the explosion.


-Chris


While it sounds plausible, this definitely does not work. The water bath container ends up adding to the shrapnel flying around.
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Re: Shops in the area that fill using a water bath

Post by Paulicarp » Tue Oct 15, 2013 9:35 pm

CaptnJack wrote:
DiverChris wrote:I believe one of the reasons water baths were used originally was in case a tank failed during filling. The water bath would absorb some of the energy of the explosion.


-Chris


While it sounds plausible, this definitely does not work. The water bath container ends up adding to the shrapnel flying around.


Plus, if the idea is that you fill a tank faster because it's in a water bath, how much faster do imagine you can fill it without increasing the likelihood of causing a catastrophic failure? I really don't want to be the one to find out.

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Re: Shops in the area that fill using a water bath

Post by coulterboy » Tue Oct 15, 2013 9:58 pm

Paulicarp wrote:
CaptnJack wrote:
DiverChris wrote:I believe one of the reasons water baths were used originally was in case a tank failed during filling. The water bath would absorb some of the energy of the explosion.


-Chris


While it sounds plausible, this definitely does not work. The water bath container ends up adding to the shrapnel flying around.


Plus, if the idea is that you fill a tank faster because it's in a water bath, how much faster do imagine you can fill it without increasing the likelihood of causing a catastrophic failure? I really don't want to be the one to find out.


Not naming the LDS, I have witnessed the catastrophic failure you're talking about. No bueno!
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Re: Shops in the area that fill using a water bath

Post by Nwcid » Tue Oct 15, 2013 10:21 pm

One thing I have found interesting is that in Fire/EMS filling tanks is generally done in some kind of "container". A lot of fire stations have big steel enclosures that the tanks go in. Others basically have heavy wall pipe you drop the tank into it.

I have not seen anything like that in SCUBA yet.
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Re: Shops in the area that fill using a water bath

Post by CaptnJack » Tue Oct 15, 2013 10:36 pm

Nwcid wrote:One thing I have found interesting is that in Fire/EMS filling tanks is generally done in some kind of "container". A lot of fire stations have big steel enclosures that the tanks go in. Others basically have heavy wall pipe you drop the tank into it.

I have not seen anything like that in SCUBA yet.



They exist and are commercially available. Scott Christopher's fill station has one although it won't hold doubles.

However, this
Others basically have heavy wall pipe you drop the tank into it
sounds alot like a mortar to me ;)
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Re: Shops in the area that fill using a water bath

Post by Nwbrewer » Wed Oct 16, 2013 8:32 am

CaptnJack wrote:

However, this
Others basically have heavy wall pipe you drop the tank into it
sounds alot like a mortar to me ;)


But that makes it your neighbor's problem, not yours! :taco:
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Re: Shops in the area that fill using a water bath

Post by rcontrera » Wed Oct 16, 2013 5:54 pm

CaptnJack wrote:sounds alot like a mortar to me ;)

That is the idea. If a tank fails, the "pop can" directs the force of the blast straight up instead of out. Most dive shops don't use them because they are expensive. Plus, as has already been mentioned, you can't drop a set of twins into them.

Image

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Re: Shops in the area that fill using a water bath

Post by nwbobber » Thu Oct 17, 2013 6:27 am

This is an interesting subject. I keep hearing about the water bath causing water problems inside the tank. This could only happen if there were water somewhere on the whip or the valve before the whip was pressurized, otherwise the pressure differential would keep the water at bay. Can the higher temperature differential be causing condensation on the walls of the tank during the fill, thus causing flash rust? If so it would seem filling slower would be the best way, keep the delta T to a minimum.
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Re: Shops in the area that fill using a water bath

Post by BillZ » Thu Oct 17, 2013 7:56 am

nwbobber wrote:This is an interesting subject. I keep hearing about the water bath causing water problems inside the tank. This could only happen if there were water somewhere on the whip or the valve before the whip was pressurized, otherwise the pressure differential would keep the water at bay. Can the higher temperature differential be causing condensation on the walls of the tank during the fill, thus causing flash rust? If so it would seem filling slower would be the best way, keep the delta T to a minimum.



Not if you have dry air inside your tank, which you should have unless the compressor filtration where you got your fill is bad. It takes moisture in the air to cause condensation.

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Re: Shops in the area that fill using a water bath

Post by CaptnJack » Thu Oct 17, 2013 8:24 am

rcontrera wrote:
CaptnJack wrote:sounds alot like a mortar to me ;)

That is the idea. If a tank fails, the "pop can" directs the force of the blast straight up instead of out. Most dive shops don't use them because they are expensive. Plus, as has already been mentioned, you can't drop a set of twins into them.

Image


This is much different than a steel tube set in the floor. The mesh baskets distribute the force of a rupture in many directions.

nwbobber wrote:This is an interesting subject. I keep hearing about the water bath causing water problems inside the tank. This could only happen if there were water somewhere on the whip or the valve before the whip was pressurized, otherwise the pressure differential would keep the water at bay. Can the higher temperature differential be causing condensation on the walls of the tank during the fill, thus causing flash rust? If so it would seem filling slower would be the best way, keep the delta T to a minimum.


No properly filtered air has a way lower dew point than this (-65F).
The issue with water baths is that people either drop the whip into the bucket or it gets into the valve opening when the tanks are dunked, this is especially likely if the tanks are put into the bath before the whips are hooked up. Basically having lots of water around the whip/valve at fill time generally means some gets into the whip or valve opening and then blow into the tanks during the fill. A few drops each eventually evaporating (in the dry fill gas) still leads to corrosion where it sprays into the tanks, generally in a splatter pattern on the bottoms.
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