PDA

View Full Version : Does your LDS use a tank of water when filling your tank?



LRDWILDER
06-23-2008, 13:28
So recently I read somwhere that alot of LDS are not putting tanks into cooling water as they fill them?

Whats your experiance? Do they do it? Do you care?

I can't remember where I read it, but somewhere it talked about it perhaps not being necessary if filled slowly? Is this right????

ScubaToys Larry
06-23-2008, 13:32
Correct... they should not be put in water - and they should be filled no faster than 300 psi per minute.

cgvmer
06-23-2008, 13:37
Putting them in water is a "solution" to the problem of the tank getting hot when filled too fast. When the real solution is as Larry stated, don't fill fast and let the hear dissipate without being cooled.

mchain
06-23-2008, 13:45
The Dive shop where I got my open water did in fact place the tank in water but I have no idea how fast they were filling.
Is that a dangerous practice?

ScubaToys Larry
06-23-2008, 13:53
It is against the tank manufacturers recommendations, as it increases the chance of water getting in a tank (if empty and not careful) and it does nothing except encourage people to fill too fast - which is dangerous. But I guess if they fill slow, and are careful not to get water in the valve - it would not actually hurt anything - but a tiny flow restricting device in the line would do much more for the safety of the fill station and help get good fills.

Damselfish
06-23-2008, 14:06
a lot more shops used to fill in a water tank, but over the years it's gone out of style.

ianr33
06-23-2008, 14:16
Correct... they should not be put in water - and they should be filled no faster than 300 psi per minute.

So filling a tank in 10 seconds would not be a good idea ?? I thought I was just getting prompt service :smiley36:

captain
06-23-2008, 14:18
Is filling in water bad. No not if done right. I fill my own tanks and I fill in water but the design of the water tank will not allow the tank valve or filler to get below the surface of the water in the water tank. My compressor fills an 80 in 25 minutes, I would say that is pretty slow but the difference in filling dry or filling wet is 200 psi less when the dry filled tank cools. If I didn't fill wet I would have to wait for the tank to cool down and top it off.
Of course you can always overfill by 200 or 300 psi when filling dry so that once the tank cools it is at rated pressure but do most shops do it that way.

mselizann
06-23-2008, 14:22
I rented tanks from a shop that did this- and b/c of them just wanting to fill as fast as possible they couldn't even get the pressure to 3000.........more like 2700- bad practice if you ask me

Navy OnStar
06-23-2008, 14:49
I have heard but not confirmed that placing the tank in water and fast filling can lead to metal shear. It may take many repetitions of this to actually occur and end up in a decrease the life of the tank because it fails hydro or it may lead to catastrophic failure.

Placing the tank in water will cause the outside to remain relatively cool while the inside gets hot. The different temperatures causes a shear stress that if allowed to get great enough could cause some or total metal separation.

in_cavediver
06-23-2008, 16:40
Frankly, I don't buy the metal shear arguement. I think the temps required to do this would be greater than the failure point on other items.

Filling in water isn't required nor recommended by the manufacturers so why do it. Some places use it to cool faster fills, others do it in a mistaken notion the water will help in a tank rupture (it won't, not enough of it). In the end though, as long as fill rates are kept in check and the valve/whip is keep dry, it doesn't really matter.

ReefHound
06-23-2008, 17:03
Placing the tank in water will cause the outside to remain relatively cool while the inside gets hot. The different temperatures causes a shear stress that if allowed to get great enough could cause some or total metal separation.

What about when your tank is hot from the sun and you jump off the boat/dock into cold water?

Navy OnStar
06-23-2008, 17:08
Frankly, I don't buy the metal shear arguement. I think the temps required to do this would be greater than the failure point on other items.

Filling in water isn't required nor recommended by the manufacturers so why do it. Some places use it to cool faster fills, others do it in a mistaken notion the water will help in a tank rupture (it won't, not enough of it). In the end though, as long as fill rates are kept in check and the valve/whip is keep dry, it doesn't really matter.

The physics behind the metal shear are valid, however, as you stated, the question is the temperature differntial between the inside and outside of the tank being great enough to cause failure. I don't believe the difference is geat enough to cause any damage over a few normal fills in water, or many, many normal fills in water for that matter. The real problem may occur over the life of the tank when this has been done repeatedly. Chances are it may just fail hydro 10 years down the line when it should've lasted for 12 or 15 or 20. Or maybe it pases hydro but if it is fast filled in water one time to many the tank could fail.

The truth of the matter is: There IS a shear stress placed on the metal when tanks are filled in water. The faster the fill the more stress. This is true in or out of water. This is one of the reasons why hydro's are required. The repetetive stress of pressurizing the tank is another.

What I don't know is how many fills like this does it take to cause damage. I haven't seen any test data on this so I won't even try to make a guess. It may take thousands or tens of thousands of fills due to the low temperature differential to achieve damage. But even the smallest repetetive stress done over and over will eventually cause damage.

I choose to go with the slow fill in air and wait a little longer for my tank to get filled. Why do something that could cause damage even if it is years down the line.

Like you said, the manufacturer doesn't recommend it so why do it?

TommyB
06-23-2008, 17:35
Here's some good reading on the why not too

Why don't you put my cylinder in a water bath when you fill?
The counterproductive practice of wet filling in the SCUBA industry is declining, but still common even in the face of strong arguments against the practice. Read what the experts say about wet filling at these links:

"The Case for Dry-Filling Scuba Tanks" by Fred Calhoun, PE" (http://fillexpress.com/library/tankfill.pdf)
http://fillexpress.com/library/tankfill.pdf

"Filling Cylinders in Water--Time to Review" by Bill High, President of Professional Scuba Inspectors, Inc. (http://www.psicylinders.com/library/Current/wetfills.htm)
Wet Fills (http://www.psicylinders.com/library/Current/wetfills.htm)

CompuDude
06-23-2008, 19:38
Filling in water is bad. It doesn't actually help, for starters. There is a tiny difference in interior air temp... IF you take at least 30 minutes to fill the tank. Not enough to matter, though.

Secondly, you've greatly increased the odds and risk of getting water inside the tank, which WILL cause serious issues, especially with steel tanks.

And finally, in case of an actual failure, you've just added a considerable amount of shrapnel to the explosion, in the form of the tank the water is kept in.

All around a terrible idea. Falls under the category of "seemed like a good idea at the time", but now with a broader understanding of the factors at play, every organization that has actually researched the issue has come out against it.

captain
06-23-2008, 20:33
Frankly, I don't buy the metal shear arguement. I think the temps required to do this would be greater than the failure point on other items.

Filling in water isn't required nor recommended by the manufacturers so why do it. Some places use it to cool faster fills, others do it in a mistaken notion the water will help in a tank rupture (it won't, not enough of it). In the end though, as long as fill rates are kept in check and the valve/whip is keep dry, it doesn't really matter.

The physics behind the metal shear are valid, however, as you stated, the question is the temperature differntial between the inside and outside of the tank being great enough to cause failure. I don't believe the difference is geat enough to cause any damage over a few normal fills in water, or many, many normal fills in water for that matter. The real problem may occur over the life of the tank when this has been done repeatedly. Chances are it may just fail hydro 10 years down the line when it should've lasted for 12 or 15 or 20. Or maybe it pases hydro but if it is fast filled in water one time to many the tank could fail.

The truth of the matter is: There IS a shear stress placed on the metal when tanks are filled in water. The faster the fill the more stress. This is true in or out of water. This is one of the reasons why hydro's are required. The repetetive stress of pressurizing the tank is another.

What I don't know is how many fills like this does it take to cause damage. I haven't seen any test data on this so I won't even try to make a guess. It may take thousands or tens of thousands of fills due to the low temperature differential to achieve damage. But even the smallest repetetive stress done over and over will eventually cause damage.

I choose to go with the slow fill in air and wait a little longer for my tank to get filled. Why do something that could cause damage even if it is years down the line.

Like you said, the manufacturer doesn't recommend it so why do it?

Tell that story to my steel 72 that was made in 1956 and just passed hydro again.

Geoff_T
06-23-2008, 20:38
Filling in water is bad. It doesn't actually help, for starters. There is a tiny difference in interior air temp... IF you take at least 30 minutes to fill the tank. Not enough to matter, though.

Secondly, you've greatly increased the odds and risk of getting water inside the tank, which WILL cause serious issues, especially with steel tanks.

And finally, in case of an actual failure, you've just added a considerable amount of shrapnel to the explosion, in the form of the tank the water is kept in.

All around a terrible idea. Falls under the category of "seemed like a good idea at the time", but now with a broader understanding of the factors at play, every organization that has actually researched the issue has come out against it.


Agree though there was this one place that actually had their fill bath made of what looked like 1/4" plate steel. That would help wcontain and direct upwards a blast. However there was mildew and other forms of nastyness liveing in and around the bath. So in that case i was much more worried about somthing makeing it into my air and lungs.

Point is in addition to the possable shchere stress there are also biological issues involved in keeping a tub of standing water around your shop.

captain
06-23-2008, 20:43
The pressure and cubic foot rating of a tank is based on a standard temperature of 70 degrees F so if the tank has been filled to 3000 psi at 70 degrees and the temperature in the sun is now 100 degrees the pressure is going to be 100 or 200 psi higher and this is not considered an overfill.

crgjpg
06-23-2008, 21:56
I dont know how the LDS fills the tanks. But after reading this thread, I now have some valuable information and check how the LDS fills the tanks.

CompuDude
06-24-2008, 00:37
Filling in water is bad. It doesn't actually help, for starters. There is a tiny difference in interior air temp... IF you take at least 30 minutes to fill the tank. Not enough to matter, though.

Secondly, you've greatly increased the odds and risk of getting water inside the tank, which WILL cause serious issues, especially with steel tanks.

And finally, in case of an actual failure, you've just added a considerable amount of shrapnel to the explosion, in the form of the tank the water is kept in.

All around a terrible idea. Falls under the category of "seemed like a good idea at the time", but now with a broader understanding of the factors at play, every organization that has actually researched the issue has come out against it.


Agree though there was this one place that actually had their fill bath made of what looked like 1/4" plate steel. That would help wcontain and direct upwards a blast. However there was mildew and other forms of nastyness liveing in and around the bath. So in that case i was much more worried about somthing makeing it into my air and lungs.

Point is in addition to the possable shchere stress there are also biological issues involved in keeping a tub of standing water around your shop.

The quote I've heard is this:

"The explosive potential in a fully charged 80cf aluminum SCUBA cylinder is approximately 1,300,000 foot pounds -- enough to lift a typical fire department hook-and-ladder truck over 60 feet in the air."

The best way to channel that much energy being released at once is to drill a hole directly into the ground, line it with concrete, and fill the tanks in there. 1/4" plate steel seems really thick, but it's not as strong as you'd think, and makes an unfortunately good source of shrapnel. Worse when you consider a seldom-considered quality of water: It makes a lousy absorber of force, except in massive quantities. Instead, because water does not compress very well, it actually does a perfect job of transmitting the entire shock wave force of the explosion outwards... which smashes whatever container it's in to smithereens.

Don't fill tanks in water, people. It's not safe. It doesn't help in any meaningful amount.

Black-Gorrilla
06-24-2008, 01:53
Larry... question directed at you as a store owner (if you dont mind)
how should i go about telling a LDS that i want my tank filled at 300psi per minute (10minute per tank to fill) and not in water? i have no problem telling someone anything... but i also like these places and some of the people that work there (some)
Thanks.

Geoff_T
06-24-2008, 03:02
Filling in water is bad. It doesn't actually help, for starters. There is a tiny difference in interior air temp... IF you take at least 30 minutes to fill the tank. Not enough to matter, though.

Secondly, you've greatly increased the odds and risk of getting water inside the tank, which WILL cause serious issues, especially with steel tanks.

And finally, in case of an actual failure, you've just added a considerable amount of shrapnel to the explosion, in the form of the tank the water is kept in.

All around a terrible idea. Falls under the category of "seemed like a good idea at the time", but now with a broader understanding of the factors at play, every organization that has actually researched the issue has come out against it.


Agree though there was this one place that actually had their fill bath made of what looked like 1/4" plate steel. That would help wcontain and direct upwards a blast. However there was mildew and other forms of nastyness liveing in and around the bath. So in that case i was much more worried about somthing makeing it into my air and lungs.

Point is in addition to the possable shchere stress there are also biological issues involved in keeping a tub of standing water around your shop.

The quote I've heard is this:

"The explosive potential in a fully charged 80cf aluminum SCUBA cylinder is approximately 1,300,000 foot pounds -- enough to lift a typical fire department hook-and-ladder truck over 60 feet in the air."

The best way to channel that much energy being released at once is to drill a hole directly into the ground, line it with concrete, and fill the tanks in there. 1/4" plate steel seems really thick, but it's not as strong as you'd think, and makes an unfortunately good source of shrapnel. Worse when you consider a seldom-considered quality of water: It makes a lousy absorber of force, except in massive quantities. Instead, because water does not compress very well, it actually does a perfect job of transmitting the entire shock wave force of the explosion outwards... which smashes whatever container it's in to smithereens.

Don't fill tanks in water, people. It's not safe. It doesn't help in any meaningful amount.

Hmm while I don't agree with wet filling tanks I do have to question this quote. Haveing seen the accident photos from several tank explosion I don't think it is enough to send a ladder truck 60 ft up. But it is enough to rip the back wall of a small shop apart and kill anybody near by. The other thing is that while water does transmit force wonderfully the force will still have a tendancy to to to the path of least resistance. In the case of a box with five closed sides and one open side the tendancy should be for much of the force and water to blow upwards. As for wether or not 1/4 inch steel would save my life well I don't realy want to find out myself. It will however stop a 22-250 round fired at 30 yards however it will not stop a 30-06 round fired at the same distance. For those of you who are not gun litterate think M-16 but not ak-47.

What this means in context of this argument. A properly constructed steel box should cut down on small shrapnil fragments, the real question however is if a whole 2'x3' plate is going to rip off and decapitate you.

Once again don't wet fill

cajunfla
06-24-2008, 04:31
My local LDS has what appears to be well over 100 tanks for rentals. They also run a dive boat that makes 2 runs a day on weekends. Anywhere from 20 to 30 people, doing a 2-tank dive on each run. After the morning run the tanks are driven back to the LDS in a pickup, and refilled. This is a minimum of 80 tanks a day needing refills, plus whatever tanks are rented out on an individual basis. As far as I can tell, they fill them quite quickly (10 maybe 15 minutes) just to keep up with demand.

character157
06-24-2008, 07:39
I know one of the LDS in my area fills in water...I did see them not use the tank for a guy one day. He had steel tanks and requested fills without the water for the reasons stated above. The shop owner did not seem to mind, but the guy getting the fills was dropping off 3 to be picked up later that day. I guess the steels get hotter or something.

Navy OnStar
06-24-2008, 08:04
Tell that story to my steel 72 that was made in 1956 and just passed hydro again.

Great. Like I said I don't know how many fills it would take because the temp differnce is so low and I haven't seen any testing on it. I deal a lot with repetetive stresses on metals working with aircraft. The temp difference is a stress, however small. You may never see it with your tank where someone else might.

Black-Gorrilla
06-24-2008, 10:38
I guess the steels get hotter or something.

steel tanks get significantly hotter then the aluminum tanks.

captain
06-24-2008, 10:41
It was fairly routine to fill tanks in water years ago. The main reason it was discontinued was because of improper fill procedures that was blowing water into tanks. I can't ever recall anything about temperature shear being a problem. As someone said before what about jumping in 40 degree water with a tank heated to 110 degrees in the sun. That is a lot more sudden change in outside to inside temperature than takes place over a 10 or 20 minute fill.

whitworthsa
06-24-2008, 10:41
Filling in water is bad. It doesn't actually help, for starters. There is a tiny difference in interior air temp... IF you take at least 30 minutes to fill the tank. Not enough to matter, though.

Secondly, you've greatly increased the odds and risk of getting water inside the tank, which WILL cause serious issues, especially with steel tanks.

And finally, in case of an actual failure, you've just added a considerable amount of shrapnel to the explosion, in the form of the tank the water is kept in.

All around a terrible idea. Falls under the category of "seemed like a good idea at the time", but now with a broader understanding of the factors at play, every organization that has actually researched the issue has come out against it.


Agree though there was this one place that actually had their fill bath made of what looked like 1/4" plate steel. That would help wcontain and direct upwards a blast. However there was mildew and other forms of nastyness liveing in and around the bath. So in that case i was much more worried about somthing makeing it into my air and lungs.

Point is in addition to the possable shchere stress there are also biological issues involved in keeping a tub of standing water around your shop.

The quote I've heard is this:

"The explosive potential in a fully charged 80cf aluminum SCUBA cylinder is approximately 1,300,000 foot pounds -- enough to lift a typical fire department hook-and-ladder truck over 60 feet in the air."

The best way to channel that much energy being released at once is to drill a hole directly into the ground, line it with concrete, and fill the tanks in there. 1/4" plate steel seems really thick, but it's not as strong as you'd think, and makes an unfortunately good source of shrapnel. Worse when you consider a seldom-considered quality of water: It makes a lousy absorber of force, except in massive quantities. Instead, because water does not compress very well, it actually does a perfect job of transmitting the entire shock wave force of the explosion outwards... which smashes whatever container it's in to smithereens.

Don't fill tanks in water, people. It's not safe. It doesn't help in any meaningful amount.

Hmm while I don't agree with wet filling tanks I do have to question this quote. Haveing seen the accident photos from several tank explosion I don't think it is enough to send a ladder truck 60 ft up. But it is enough to rip the back wall of a small shop apart and kill anybody near by. The other thing is that while water does transmit force wonderfully the force will still have a tendancy to to to the path of least resistance. In the case of a box with five closed sides and one open side the tendancy should be for much of the force and water to blow upwards. As for wether or not 1/4 inch steel would save my life well I don't realy want to find out myself. It will however stop a 22-250 round fired at 30 yards however it will not stop a 30-06 round fired at the same distance. For those of you who are not gun litterate think M-16 but not ak-47.

What this means in context of this argument. A properly constructed steel box should cut down on small shrapnil fragments, the real question however is if a whole 2'x3' plate is going to rip off and decapitate you.

Once again don't wet fill

Problem with water in an explosion is that it transfers force. If you've ever been stupid enough to drop a lit firecracker into a full (or even half-full) beer bottle you will know this. You would think the water would take the path of least resistance but the truth is that the water couldn't move fast enough and the bottle turned into shrapnel. In the case of a tank in a water bath though I would agree that your guess of the whole steel plate ripping off is more likely than turning 1/4" steel into shrapnel.

captain
06-24-2008, 11:04
I worked for Praxair the commercial gas supplier and I am sure some of you have seen their 18 wheelers on the road with a tralier load of various gas cylinders. When filling them we manifolded all cylinders of a particular gas together and filled all at one time. The cylinders were filled under a constant water spray to keep them cool. We had a chart that listed what the full pressure was at the temperature the cylinders were be filled. If the temperature was above 70 degrees F we filled to a higher pressure than what was the cylinder's rated pressure to be sure our customers were getting the cubic feet of gas they paid for and if the temperature was below 70 degrees we underfilled to be sure we weren't giving away gas we were not getting paid for. The pressure at 70 degrees is the magic number that determines if a cylinder is over or under filled.

in_cavediver
06-24-2008, 12:00
Problem with water in an explosion is that it transfers force. If you've ever been stupid enough to drop a lit firecracker into a full (or even half-full) beer bottle you will know this. You would think the water would take the path of least resistance but the truth is that the water couldn't move fast enough and the bottle turned into shrapnel. In the case of a tank in a water bath though I would agree that your guess of the whole steel plate ripping off is more likely than turning 1/4" steel into shrapnel.

First, the point of the 1/4 plate enclosures is to deflect force. If secured well, it will deflect much of the explosive force away. Water isn't a benefit there but some still like to use it.

Again, the only real issue is contamination. I am sure there is a lot of microscopic metal damage done each fill cycle due to any number of factors. I don't believe its significant enough to cause an issue in the scuba range though.

Hot fills are a fact of life in other areas. I've personally seen numerous SCBA bottles hot filled at the limit of the fill system. (IE the safety orifice in the whip). 45cft or 0-2016psi in only 1-2 minutes. They get hot but they seem to take it as many have hydro dates back in the 80's. (20+ years)

LRDWILDER
06-24-2008, 12:20
Yeah I've noticed the same thing...I mean on a liveabord they hot hill the heck outa things and certainlly don't take there time about it either!

CompuDude
06-24-2008, 13:16
Hmm while I don't agree with wet filling tanks I do have to question this quote. Haveing seen the accident photos from several tank explosion I don't think it is enough to send a ladder truck 60 ft up.

The math is accurate, for what it's worth... it's been well vetted. It's a theoretical calculation that's fairly impossible to demonstrate in real life, of course, not something that's actually going to happen. Mathematically it's quite possible to determine the potential stored energy in a tank, and compare it to the energy needed to lift an object that weighs, say, 1000 lbs, one foot off the ground. It's pure math that doesn't take into consideration the efforts that would need to be made to channel all the force in one direction, etc.

Point is, which many people have seen, scuba tanks have a LOT of power hidden in them, and filling them is dangerous, even though it seems so routine. It doesn't happen often, but when something goes bad, it goes VERY bad.

How much energy is there in a filled scuba tank (http://biobug.org/scuba/scubatank/)

This is just a side discussion, of course. I know that we're in agreement... wet fills are bad.

Hot fills aren't good for tanks either, but that's an entirely different discussion. Some tanks deal with them fairly well, other tanks can go from brand new to failed hydro in just 5 years.

diver-wife
06-24-2008, 15:31
I have seen a dive shop put a fan on the tanks while they fill them, then lightly spray them with water, just enough to cool them (kinda like us sweating), anyone see anyharm in this?

ReefHound
06-24-2008, 15:35
I think spraying is 10x worse than immersion as far as the risk of getting water in the tank.

in_cavediver
06-24-2008, 15:52
I think spraying is 10x worse than immersion as far as the risk of getting water in the tank.

If the tank is hooked to the whip before spraying- there is ZERO chance of water getting in during the fill.

The real risk of water is when hooking up a wet fill whip or from a wet valve surface prior to hookup. Once the hookup is made, its watertight. (just like diving). If there is water inside the hookup, it will end up in your tank.

One last note - remember scuba air is very dry so a 'little' water from condenscation wouldn't likely be an issue.

ReefHound
06-24-2008, 16:49
I think spraying is 10x worse than immersion as far as the risk of getting water in the tank.

If the tank is hooked to the whip before spraying- there is ZERO chance of water getting in during the fill.

The real risk of water is when hooking up a wet fill whip or from a wet valve surface prior to hookup. Once the hookup is made, its watertight. (just like diving). If there is water inside the hookup, it will end up in your tank.

One last note - remember scuba air is very dry so a 'little' water from condenscation wouldn't likely be an issue.

Agreed. The only way I see water being a problem in filling tanks sitting in a tub of water is if the fill op is careless about inserting and removing tanks causing water to be splashed onto the valve before attaching whip. Or dropping the whip into the water. Act with care and water should never get on the valve or fill whip. But spraying water on the tanks will result in water all over the valves and fill whip, where it can drip into the whip when the whip is disconnected.

Aussie
06-24-2008, 17:36
I was at a shop which had the lines from the compressor to the storage banks feed through a freezer. The idea is to cool down the air from the compressor before it went into the banks and to remove more moisture via the filters.

The amount of water removed before the filters was amazing and they said that the filters had a much longer life before servicing than before.

Then to finish off they did a quick fill on a steel cylinder and I was again amazed that the cylinder was so much cooler.

BTW I havnt seen a shop over here that fills in water.

Aussie

longtailbda
06-24-2008, 18:17
Local lds uses only slow fill, they're good that way.

DUnder
07-03-2008, 13:55
A LDS that I rent tanks from at a popular dive location does use a wet tank to fill.

cummings66
07-03-2008, 17:01
Just today I had to tell a dive shop employee why the idea of filling in water was not a great idea. I've been on record here there and elsewhere that it's a poor idea and not really needed if you fill the cylinders correctly in the first place.

violakat03
07-09-2008, 01:21
An interesting discussion. When doing our checkouts the place we were diving at filled our tanks in a tub of water .. I don't think they took 10 minutes to fill either, but I wasn't exactly timing them. When I asked, they explained that it was to keep the temperature of the tank cooler so that the fills were more accurate, so I'm guessing they haven't taken the time to research that thought process.

SlvrDragon50
07-12-2008, 22:11
I asked somone who worked with tanks for the past decade or so and has been certified by most makers like Catalina and Luxfer. He said it was a good idea to fill in water but only because heat is bad. I'll post his full reply later when I get on a computer.

blueeyeddiver
07-12-2008, 22:24
Most of the LDS that I've been to in Austin do not fill in water. The one that does were pretty good about filling them pretty slowly, and submerged them less that half way.
I would think that slow fills would be in a shops best interest as it give the customer time to do a little shopping &/or get to know the customer.

marchand
07-12-2008, 22:52
A lot of places around here used to have refrigerated baths to fill the tanks in so that when the tanks hit the water they wouldn't loose a few hundred pounds. I believe Dive Outpost in Lauraville, Fl still has one. Cave divers are so unforgiving about getting a fill under 3800psi.

digitalman
07-12-2008, 22:56
My LDS has a water tank for filling, but I've never seen them use it. Most of the fills are done beside the tank. Not sure what the fill rate is. I'll ask next time I'm getting a fill.

wmspdi
07-15-2008, 23:21
My LDS still fills my steel tanks in a water jacket but dry fills the aluminum tanks. He said the side walls of the aluminum tanks are too thick to have much of an effect in the internal air temperature of the aluminum tanks, but the water will have a cooling effect on the thinner walled steel tanks. All tank/fill whip connections are made outside of the tank. He also clears the air line and dries the DIN connector before hook-up.

andyrent
07-27-2008, 15:01
The four or five dive shops that I have worked with all did dry fills. I haven't seen a tank being filled in a water bath. Nice discussion, very good information for me to know, as a new diver.

firemedic8082
11-04-2008, 18:59
The longer they take to fill the tank while I wait, the greater the chance I find something I "have to have." Sounds like a great business practice to me....keep slow filling those tanks.

texdiveguy
11-04-2008, 21:40
"Does your LDS use a tank of water when filling your tank?"

Hell no and glad they don't!

bsktcase93
11-21-2008, 09:16
the lds by me used to use it and when we fill them at the fire house we fill them dry

thebuck
11-23-2008, 12:18
I've only seen one place locally that had a tank of water for filling, though they didn't use it when i was getting tank fills.

IrishSquid
11-23-2008, 19:42
All of this made me think and wonder; is there a record or knowledge of a tank ever having catastrophic or explosive failure on the back of a diver at the surface or underwater?

CompuDude
11-24-2008, 16:32
All of this made me think and wonder; is there a record or knowledge of a tank ever having catastrophic or explosive failure on the back of a diver at the surface or underwater?

Not that I've ever heard of. The dangerous time is during the filling process. If it holds then, short of a fire or other major physical damage to the tank, you're generally fine.

IrishSquid
11-24-2008, 20:41
Not that I've ever heard of. The dangerous time is during the filling process. If it holds then, short of a fire or other major physical damage to the tank, you're generally fine.

That's what I was thinking, just didn't know for sure, and was curious as all get out.

ektess1
11-24-2008, 22:59
My shop overfills dry. When it cools it is a good fill. Don't know how bad it is for the tank, but I get what I went ther for.

ScottW
11-25-2008, 08:41
My shop overfills dry. When it cools it is a good fill. Don't know how bad it is for the tank, but I get what I went ther for.
Overfilling and fast is a dangerous process since it weakens the metals over time and as a tank owner I would be upset if my LDS did that to me. The best method is a slow fill.

in_cavediver
11-26-2008, 05:20
My shop overfills dry. When it cools it is a good fill. Don't know how bad it is for the tank, but I get what I went ther for.
Overfilling and fast is a dangerous process since it weakens the metals over time and as a tank owner I would be upset if my LDS did that to me. The best method is a slow fill.

If the tank is 'overfilled' when filled and hot but reaches stated pressure at 70 degrees after it cools, then the tank wasn't overfilled. The pressure rating is temperature dependent. Higher temps means higher pressure, lower temp means lower pressure (to a point, usually 200-300psi)

Empacher
11-26-2008, 14:25
My shop has a water tank, but I've never seen them use it....It does take a while to fill my high pressure tank

UCFKnightDiver
11-26-2008, 14:41
most of mine do, one guy I know keeps his water tank stocked with ice lol, or used to at least

Jack Hammer
11-27-2008, 11:13
I've had 3 shops tell me the same reason for why they don't use water baths for filling. They say it's a PITA lifting heavy tanks in and out of it all day and having to either keep changing the water out or keep it running to maintain a cool temp. Plus they say it doesn't make enough difference in fill pressure, maybe 100psi, so they have to come back and top it off after it cools anyways. Might as well save their backs and be able to fill more tanks in the same amount of time.

Jack

elijahb
11-27-2008, 16:56
My lds doesn't have a tank of water for filling. They do hot fills of the cascade dry! There cascade has 2 pressures 3000 psi and 4000psi. They fill 4 tanks from 300 to 3000 in less than 3 mins.... (this has been my experence with them when filling takes between pool sessions) Can someone explain why this is not safe?

acamato
11-28-2008, 23:28
My LDS uses a water tank. However they do not submerge the whole tank in water.

LRDWILDER
02-09-2009, 07:36
Wow this thread went sig longer with sig more oppinions then I thought...Interesting stuff thanks everyone!

chilly willy
02-09-2009, 15:31
When I started diving (in the 70's) almost all the dive shops used wet fill tanks, now all of those same shops dry fill.

bottomdweller
07-13-2009, 21:33
My lds sometimes uses the water tank under the fill station, but sometimes they do not? I have never ask why, but now I just might.

bigman241
08-06-2009, 22:51
I know i am new and have not done my ow. But hearing the words catastrophic failure in a sentence with a 3000+ seems bad to me. Reminds me of the scuba tank through a concrete wall on myth busters. I can see the poor diver blasting around the ocean's floor because of some dumba** at a fill station :smiley11:
I have heard but not confirmed that placing the tank in water and fast filling can lead to metal shear. It may take many repetitions of this to actually occur and end up in a decrease the life of the tank because it fails hydro or it may lead to catastrophic failure.

Placing the tank in water will cause the outside to remain relatively cool while the inside gets hot. The different temperatures causes a shear stress that if allowed to get great enough could cause some or total metal separation.

WaScubaDude
08-06-2009, 23:10
Both of my LDS's have water tanks but dont use them unless you ask nice, or just put your tank in when you arrive.

bigman241
08-07-2009, 07:23
I was looking at tildens scuba shop in the keys properly where we will do our ow. I noticed on the pics of there fill station there is a nice size water tank under the fill hoses.

IndyDiver
08-07-2009, 09:36
Since this thread seems to have come back to life, I suggest the following link for some good background reading on the myths and physics of dry vs. wet filling:

http://www.fillexpress.com/library/dryfills.pdf

2Dogs
08-20-2009, 01:23
It may have prevented this here in Australia:

ttp://www.macleayargus.com.au/news/local/news/general/man-loses-hand-in-scuba-tank-explosion/1598708.aspx


Very Sad :frownyes:

cummings66
08-20-2009, 11:27
People may think that but it wouldn't have done a thing. The energy released from a cylinder exploding is strong enough to lift a locomotive. A small water bath won't do a thing. In fact, those heavy steel containment devices that are commonly used are little more than an aid to make sure it goes straight up instead of out and that's probably a better safety measure.

DivingCRNA
08-20-2009, 12:55
I prefer when they use air or another breathable gas to fill my tanks.... :smilie39::smilie39::smilie39:

CompuDude
08-20-2009, 13:43
People may think that but it wouldn't have done a thing. The energy released from a cylinder exploding is strong enough to lift a locomotive. A small water bath won't do a thing. In fact, those heavy steel containment devices that are commonly used are little more than an aid to make sure it goes straight up instead of out and that's probably a better safety measure.

Correct. Plastic tubs, or even metal boxes, merely add shrapnel to the explosion. It takes an in-floor concrete containment system (very rarely implemented) to contain an explosion (or at least redirect it straight up) to any significant degree. There are also actual blast containment boxes that cost $60k+, but I've never actually seen one used.

cummings66
08-20-2009, 16:21
The shop where I got my PSI cert done had a containment system which was a metal cylinder with a secure latch for the lid, it was made out of 1/2" steel plate, I've seen the same thing elsewhere. I think it could handle about 6 cylinders, had to weight a ton. The only issue is you can't fill my doubles with them.

The theory is that if a cylinder blows the top lid will slow it down and it'll go straight up like a missile since it's not going outwards. Will it work? Hope so. Expensive to boot.

CompuDude
08-20-2009, 16:45
The shop where I got my PSI cert done had a containment system which was a metal cylinder with a secure latch for the lid, it was made out of 1/2" steel plate, I've seen the same thing elsewhere. I think it could handle about 6 cylinders, had to weight a ton. The only issue is you can't fill my doubles with them.

The theory is that if a cylinder blows the top lid will slow it down and it'll go straight up like a missile since it's not going outwards. Will it work? Hope so. Expensive to boot.

Hope it's actually rated to contain a tank rupture, and not just something someone threw together thinking "this should do it!"

Assuming it is, however, that's a great setup. I'd venture to say less than 5% of dive shops have any sort of containment system, however. And those that are filling in tubs of water are usually either using a simple plastic tub of water or a bin made from sheet metal, neither of which will do anything to contain an explosion, and in fact could add significant shrapnel to the equation should a rupture occur. Scary.

in_cavediver
08-20-2009, 16:58
The shop where I got my PSI cert done had a containment system which was a metal cylinder with a secure latch for the lid, it was made out of 1/2" steel plate, I've seen the same thing elsewhere. I think it could handle about 6 cylinders, had to weight a ton. The only issue is you can't fill my doubles with them.

The theory is that if a cylinder blows the top lid will slow it down and it'll go straight up like a missile since it's not going outwards. Will it work? Hope so. Expensive to boot.

Hope it's actually rated to contain a tank rupture, and not just something someone threw together thinking "this should do it!"

Assuming it is, however, that's a great setup. I'd venture to say less than 5% of dive shops have any sort of containment system, however. And those that are filling in tubs of water are usually either using a simple plastic tub of water or a bin made from sheet metal, neither of which will do anything to contain an explosion, and in fact could add significant shrapnel to the equation should a rupture occur. Scary.

We have these at our FD. These do not contain the explosion, they merely direct it. The goal is the protect the operator with 'weak' sides and strong sides. The weak goes thus reducing the load on the rest of the structure. It is still a massive bit of metal to direct this. If I recall, a true rupture requires replacement of the containment system as its deformed in absorbing the energy. The goal is survival and reduced injuries to the operator.

cummings66
08-20-2009, 17:36
That is what I was trying to say, it's a system meant to send the rupture upwards and not outwards, it doesn't contain it in one spot. It just redirects it.