Filling scuba tanks

[stretchthepenn]

I just finished taking the PSI/PCI tank inspector class, and "hot fills" vs. water baths was one of the subjects my instructor covered extensively. In short, everything the previous posters said is correct; filling tanks in a water bath is at best useless and is often dangerous.

Add these two reasons to the anti-water-bath column:

• Fill stations' water baths are usually thin-walled containers, not blast chambers. Water is incompressible, so if a tank blows while in the fill container, the shock wave will turn the fill station container into high-speed shrapnel.

• The heat-dissipating properties of a fill station's water bath are negligible unless the water bath is actually an ice bath. BUT, if the ice bath isn't accompanied by an incredibly slow fill, the sharp temperature differential between the hot gas on the tank's inside and the ice bath on the tank's outside will only induce metal fatigue. You'd be better off doing a trickle-speed fill to keep the temperature down in the first place or doing a standard-speed fill, letting the tank air-cool, and topping off later.

 

[divezonescuba]

I actually had a recently open water certified diver from SSI file a QA complaint against me with PADI few years ago because our shop did not fill tanks in a water bath. That’s what SSI taught them and he was extremely upset that we did not. He even went so far as to say that if he let the tank cool down before using it it would then only be half full.

I have to admit that I eventually got tired of disabusing him.

PADI notified me of the complaint and the fact that since I did not violate any PADI standards that I did not need to respond unless I was inclined to do so.

Another reason is that Electricity and water don’t mix well.

 

[tursiops]

I actually had a recently open water certified diver from SSI file a QA complaint against me with PADI few years ago because our shop did not fill tanks in a water bath. That’s what SSI taught them and he was extremely upset that we did not. He even went so far as to say that if he let the tank cool down before using it it would then only be half full.

I have to admit that I eventually got tired of disabusing him.

PADI notified me of the complaint and the fact that since I did not violate any PADI standards that I did not need to respond unless I was inclined to do so.

Another reason is that Electricity and water don’t mix well.

LOL.. Is this the same SSI that is taking over the scuba business from PADI, in another thread?

 

[ScubaBunga]

from this link: PSI-PCI - Filling Cylinders In Water - Time to Review
it overall doesn't matter (but dry is better) as long as the person doing the fills understands that it's best to slow fill: cylinders, when filled at the industry recommended fill rate of 300-600 psig/min, do not get hot
The article mentions several issues with wet filling which makes it harder to get a proper/correct fill.
Happy reading.

 

[Diving Dubai]

Out here, where we have a hot climate, there are 3 methods of ensuring a good fill.

1. Fill the cylinder, let it cool and then top off. he easiest way, but generally you need to leave the cylinder overnight.
2. Have the compressor shut off set to a value that "overfills" the cylinder so that when it cools the correct pressure is reached
3. The most expensive, have a chiller fitted to the output of the compressor (think Intercooler) which significantly cools the air so that you get the right fill.


Because we have a humid environment dryers are used too so we don't get condensation.

@stretchthepenn beat me too it in his description of water baths and is 100% correct. Anyone believing a water bath is good practice has been sold a lie.

 

[papaouiee]

I appreciate all the replies. I read the article that someone put up the link too. All I can tell you is my experiences. I welcome the thread to continue, which I will site what I see so far.

1.) In the article, the author quotes a statement from the folks at Pressed Steel Tanks. I had a dealership with them for several years and discussed the issue with the chief engineer and he told me in absolutely no terms do not let anyone fill "our" tanks unless it's in water; they can be damaged easily that way. This tells me the author of that article had their own agenda and were not totally objective; typical of the paranoia the certifying agencies so love to preach. The total emphasis is on "protecting your a*s"; with no regard to damage you cause to other people's property.

2.) I own 8 Pressed SteelTanks, myself. 2 each of the 3442PSI high pressure tanks; 65, 80, 100 and 120 cubic feet. I have been filling them myself in a tub of water with a small compressor which takes approximately 20 minutes to fill an 80 cubic foot tank. If I fill them to 3450 when I get out the lake they have 3450 in them; give or take 50 PSI. Also, keep in mind that the rating is at 70 degrees Fahrenheit, and living and diving in 100 degree weather; one would think the tank would show higher, but they don't. Of course we keep them in the shade while diving with other tanks.

I have filled my tanks hundreds of times and never have had any water in them. The presence of water in a tank that results from filling them in water happens when the operator filling the tanks does not fill them properly. You have to start the tank filling with the top part of the tank out of the water. Let it fill for a hundred or two pounds of pressure, then dip it in for the complete coverage in the water. Setting the whole tank in the water before applying pressure to the system is what lets in water.

3.) My dive buddy, who has aluminum 80's, will take them to be filled at the shop and they fill them in a matter of 2-3 minutes (I know this is a hot fill but let's face it.....hot filling is what most dive shops do; they do not want to take the time to do it right) and stop at 3000PSI. When he gets to the lake he will have anywhere from 2500-2700 if lucky. This poses a danger for him when we plan dives that require a proper fill so when the dive is completed, he has a safety reserve. Call it what you want but the bottom line is that an unfilled tank is a danger to a diver who depends on that tank being filled as one paid to have it done.

Would love to hear from the people that make the tanks; they are the real experts!

 

[Chilly_Diver]

Surprised we don’t hear of all the deaths and ruptured tanks down in N. Florida from the self serve air stations considering they are being dry filled to 3800 psi in the hot sun..... oh wait....

 

[Schwob]

When he gets to the lake he will have anywhere from 2500-2700 if lucky. This poses a danger for him when we plan dives that require a proper fill so when the dive is completed, he has a safety reserve.

The only dive anyone can plan for is for the fill one actually has. Top off or re-plan. A short fill is inconvenient, should be dealt with at the filling facility, is cheating frankly, but unsafe or posing a danger it is not. Having a 2500psi fill but insisting on executing a dive plan that counts on having a 3000PSIi fill, that is posing a danger and blaiming anyone else for that other than the person insisting on executing that dive plan (the diver) seems like very flawed logic.

 

[gcarter]

My HP tanks are slow filled to 3900 psi, allowed to cool for 5 minutes, topped again to 3900. I arrive at a dive site with my advertised 3400 - 3500 psi. Filling in water is not necessary. The speed of the fill and how hot it is allowed to get are the important bits.

Arrived at the St. Lawrence for a dive tonight. When I set up my gear, the tank, which had been in the (covered) back of my truck all day read 4000 psi. 5 minutes in the water it was reading 3500 as it cooled off. The point is, normal temperature fluctuations will raise the pressure. That's normal. I don't stress about my tanks being filled to 3900 psi because it isn't done fast.

 

[papaouiee]

The only dive anyone can plan for is for the fill one actually has. Top off or re-plan. A short fill is inconvenient, should be dealt with at the filling facility, is cheating frankly, but unsafe or posing a danger it is not. Having a 2500psi fill but insisting on executing a dive plan that counts on having a 3000PSIi fill, that is posing a danger and blaiming anyone else for that other than the person insisting on executing that dive plan (the diver) seems like very flawed logic.

I surely used the wrong word, danger, when I expressed my feelings there. I should have said, a destruction of a trip, or a situation that ruined the planned dive. Believe me it has happened to us. And yes, you are right; we would never take that attitude and try to conserve air. We both know what we need to do what we want to do; and that is the point Im saying that a short fill can ruin a day, weekend or even more.