BSAC avoids annual VIP

[Edward3c]

I’m referring to what you’ve said here

Are the cylinders most at risk gonna have a different inspection schedule?

That’s for the industry sector to decide once they’ve done their risk assessment. For recreational diving no.

 

[NAM001]

I can not think of a properly running compressor that would pump air such that would condense inside a tank. Yes one could speculate that in the right conditions you have 99.99% rh at 3k psi. but that is not even a problem. If this is boring sorry. at 1 atm air will hold the max of < 3% volumn. if i squeeze this air to 10 atm that then most it can hols is .3% by volumn make it 200 atm as in a 3000 p al 80 and you have 3 / 200 or .015 percent volumn content. That is dry air and if you could possibly get a drop of moisture because of the cold it will surely evaporate when the tank warms.

that means on a 20 lrt tank ( I will treat it as quarts.) you have 640 ounces in that tank 100% rh is .03 of 640 or 19 oz under 200 bar that will be 19/200 or all most 1/10 oz of water in the 80 cu/ft. how many drops is that. not much and if it all condensed that would leave those few drops if perfectly dry air in a cylindar with a few drops in the bottom. and that can not happen. I dont know how to compare pressure to temp in the aspect of lowering temp 50 degrees will condense moisture = to what 50 bar will do. I suppose that the chemical drying is what gives that condensation protection over the mechanical condensation. I say that because using only mechanical water removal that air remains 100% rh but under different pressures. chemical drying lowers it in the HP mix. I would guess that given pumping 100% rh air compressing it to 200 bar and resulting in a say .5% rh would say (very crudely) 99.5% is equal to a 120 or so drop in temperature if you start to condense in this case at -50f. If that were fact then going to -20 temps should not cause condensation in the tank. let alone the idea that as you use that air the gas will hold more liquid and consume the few drops in the bottom of the tank. GOOD THING THAT TANK BOTTOMS ARE THICKER THAN THE SIDES. This is all off the top of the head hypothysis but something to think about if you are worrying about water in the tank from being in your garage in freezing weather.

 

[NAM001]

Not pumping my own air and no idea what the dewpoint of the air I get would be (would the shop know if I asked?), but:

You sure are making me think about what temperature to keep my tanks in over the winter and if maybe bringing them out of the cold garage (where they have a nice sbungeed to the wall / "rack of sorts" spot) into the warm house is not that dumb of a thought even so there their precence will be opinionated about by the significant other...

IMO you have to have a really bad filling system to justify worrying about your tanks getting winter wet in the inside. If need be . vent them to 100 psi. The amount of water that the gas can hold can not be over countered by low temps. here is why ..... ambient air can hold say 3% by volumn. after pumping to 3k it can hold max 1/60 of 3%if it is not dripping inside with 3k psi in the tank then when you vent the amount of moisture stays the same but the amount the gas can hold increases so you can not get water in your tanks from temp. The more psi drops the more the dew point drops. Here is perhaps another way to visulize it. at 3kpsi your tanks gas can hold the max of 2 spoons of water. and the content is 1/2 spoon. now you vent and the gas can now (molicules further apart) CAN HOLD 10 SPOONS AND YOU STILL HAVE ONLY LESS (less because of the vent) than 1/2 SPOON OF WATER IN THE GAS. another is to think about your home windows they are clear in the winter because there is not enough RH to fog the window.

 

[chrisch]

...
Are the cylinders most at risk gonna have a different inspection schedule than the rest?

Yes. The high risk is tanks that are emptied underwater and thus get a small amount of water (and salt) in them. These high risk tanks are therefore the ones that are frequently drained underwater. They are fitted to dSMB and are opened underwater to inflate the dSMB.

As is the case now they will continue to be exempt from any testing whatsoever. So the highest risk tanks are not tested at all. But this doesn't matter as they are not filled in the shop by an employee - they are filled by the diver

 

[chrisch]

I can not think of a properly running compressor that would pump air such that would condense inside a tank. ....

Spot on the money there.

 

[Pavao]

That’s for the industry sector to decide once they’ve done their risk assessment. For recreational diving no.

Maybe I misunderstood you, I thought you said 3 litter bottles and smaller

The cylinders at most risk are 3Lt and smaller, where the thread might fail.

What do you mean by 3Lt?

Yes. The high risk is tanks that are emptied underwater and thus get a small amount of water (and salt) in them. These high risk tanks are therefore the ones that are frequently drained underwater. They are fitted to dSMB and are opened underwater to inflate the dSMB.

As is the case now they will continue to be exempt from any testing whatsoever. So the highest risk tanks are not tested at all. But this doesn't matter as they are not filled in the shop by an employee - they are filled by the diver

You had pony tanks on that list earlier

Not true. The number of cylinder failures was a critical part of the reason that the UK did not adopt annual tests. The data shows there was no need to do so.

To the best of my memory nearly all the catastrophic failures in the UK have been pony tanks and water ingress due to breathing dry was the diagnosis in most cases. There is also an issue with the mini tanks used on dSMB and some old fashioned BCs. These do not need a test at all and are frequently subject to water ingress as they are emptied underwater as a routine event.

 

[Edward3c]

What do you mean by 3Lt?

3Lt means 3 litre, commonly used as pony or rebreather cylinders.

 

[chrisch]

..
You had pony tanks on that list earlier

Yes. the "pony" small bailout tank is a standard scuba tank (3 litre is the normal size and that is what Ed is referring to - to answer you question to him)

The highest risk tanks are those that get water in them. A bailout only gets water in it if it is breathed dry. However, this is not a standard procedure for bailout tanks. The small dSMB tanks are drained every use.

The 3L/pony/bailout tanks are the higher failure as they do, presumably, get emptied from time to time. It is still a very very low risk because it is not a common thing to empty a bailout for any reason. Larger bailouts like Alu40 or 7L of the type used by rebreather and other more experienced divers also probably benefit from being checked over if they have been emptied as those types of user probably are much more confident in taking the valve out and checking and more aware it needs to be done.

For a metallurgic point of view the size of the tank is irrelevant.

 

[BRT]

Not pumping my own air and no idea what the dewpoint of the air I get would be (would the shop know if I asked?), but:

You sure are making me think about what temperature to keep my tanks in over the winter and if maybe bringing them out of the cold garage (where they have a nice sbungeed to the wall / "rack of sorts" spot) into the warm house is not that dumb of a thought even so there their precence will be opinionated about by the significant other...

If the shop has the air tested they should know. There are pressure/dew point calculators online that can take an atmospheric pressure dew point and return a dew point at pressure. Then it all comes down to how cold your garage gets.

 

[BRT]

IMO you have to have a really bad filling system to justify worrying about your tanks getting winter wet in the inside. If need be . vent them to 100 psi. The amount of water that the gas can hold can not be over countered by low temps. here is why ..... ambient air can hold say 3% by volumn. after pumping to 3k it can hold max 1/60 of 3%if it is not dripping inside with 3k psi in the tank then when you vent the amount of moisture stays the same but the amount the gas can hold increases so you can not get water in your tanks from temp. The more psi drops the more the dew point drops. Here is perhaps another way to visulize it. at 3kpsi your tanks gas can hold the max of 2 spoons of water. and the content is 1/2 spoon. now you vent and the gas can now (molicules further apart) CAN HOLD 10 SPOONS AND YOU STILL HAVE ONLY LESS (less because of the vent) than 1/2 SPOON OF WATER IN THE GAS. another is to think about your home windows they are clear in the winter because there is not enough RH to fog the window.

This is simply not true. Air at a -60 dew point will condense water at 3500# and 20F. Look at a pressure/dew point calculator.