BSAC avoids annual VIP

[NAM001]

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.

give me a link to the calculator you are using. the ones i have used are all at 1 atm. second -60 dew point is nothing to be proud about when you need -50 for the chemicals to start to work. aside of that the condensation, like i said before is is a combined product of both pressure and temp. you can have a tank with -200f for a dew point and you can get it to condense with enough pressure, It might be 20kpsi but you can do it. 20kpsi is for all purposes a non issue is our tanks.

I just dhecked one here Dew Point Calculator put 1% rh at a temp of 70f and it called dew point at -33 there is no pressure factor that can be entered on this calculator. However the 1% rh is the product of the pressure mechanically removing water. so it would be about 1% rh under atm=1 given that then the dew point of -33. Im open to using your calculator. 1/2 % is wmewhere between -33 adn -85f.

My gut says that if you are getting dew at 20 something is wrong especially at 3500 psi.

3500 psi is right at 240 bar and if you compressed air at 100% humidity the 240 bar would mechanically dropthe rh at 1 atm to .4% rh and that is down around -60. with a rh of 14% at 70f the dew point is 20f.

 

[BRT]

give me a link to the calculator you are using. the ones i have used are all at 1 atm. second -60 dew point is nothing to be proud about when you need -50 for the chemicals to start to work. aside of that the condensation, like i said before is is a combined product of both pressure and temp. you can have a tank with -200f for a dew point and you can get it to condense with enough pressure, It might be 20kpsi but you can do it. 20kpsi is for all purposes a non issue is our tanks.

I just dhecked one here Dew Point Calculator put 1% rh at a temp of 70f and it called dew point at -33 there is no pressure factor that can be entered on this calculator. However the 1% rh is the product of the pressure mechanically removing water. so it would be about 1% rh under atm=1 given that then the dew point of -33. Im open to using your calculator. 1/2 % is wmewhere between -33 adn -85f.

FREE Dew Point Calculator | Alpha Moisture Systems
Now put it at 3500 psi and see what happens

 

[NAM001]

FREE Dew Point Calculator | Alpha Moisture Systems
Now put it at 3500 psi and see what happens

you will have to tell me how to do that i get a lot of errors.. I put -65 for dewpoint at atmosheric presure hit calculate now what?

 

[BRT]

you will have to tell me how to do that i get a lot of errors.. I put -65 for dewpoint at atmosheric presure hit calculate now what?

First I click on the temperature units and change to F and the pressure units and change to PSIG so it works with my mind. Then input -65 under "Dewpoint at atmospheric pressure" and enter your tank pressure under "Line Pressure" With -65F as atmospheric and 3500 psig under line pressure it returns around 31 deg F as the dew point under pressure. This is just the first calculator I googled today. There are others I have used.
At -80 atmospheric dew point it returns about 8 deg F at 3500 psi, which is ok for my conditions usually.

 

[NAM001]

First I click on the temperature units and change to F and the pressure units and change to PSIG so it works with my mind. Then input -65 under "Dewpoint at atmospheric pressure" and enter your tank pressure under "Line Pressure" With -65F as atmospheric and 3500 psig under line pressure it returns around 31 deg F as the dew point under pressure. This is just the first calculator I googled today. There are others I have used.
At -80 atmospheric dew point it returns about 8 deg F at 3500 psi, which is ok for my conditions usually.

yep i see what it is doing. I can not dispute it but I do believe it is probably correct. I had said that the dewpoint was a conbo of both temp and pressure. as far as any one normal they would only have to drain the tank to say 100 psi a to store them in the garage in the winter given that it would have a -33 dew point. I also tried your calculator for a -90 atm dew point at 3kpsi adn it gave me a -10 pressure dew point. same tank at 100 psi -63. Even with the numbers from your calculator for those that are warm water or water above 40 degrees it becomes a moot issue.

 

[BRT]

yep i see what it is doing. I can not dispute it but I do believe it is probably correct. I had said that the dewpoint was a conbo of both temp and pressure. as far as any one normal they would only have to drain the tank to say 100 psi a to store them in the garage in the winter given that it would have a -33 dew point. I also tried your calculator for a -90 atm dew point at 3kpsi adn it gave me a -10 pressure dew point. same tank at 100 psi -63. Even with the numbers from your calculator for those that are warm water or water above 40 degrees it becomes a moot issue.

I got into it because I was finding little rust spots in the bottom of my tanks. Just little harmless ones but I wanted to figure out why. You can imagine how corrosive 32% is at 230 bar if there is ANY water present. The problem isn't with the water temperature but with the storage/transport temperature. We carry ours across the Cascades to dive in the wintertime. Typical temperatures are below 20F and could be below zero F.

 

[NAM001]

I got into it because I was finding little rust spots in the bottom of my tanks. Just little harmless ones but I wanted to figure out why. You can imagine how corrosive 32% is at 230 bar if there is ANY water present. The problem isn't with the water temperature but with the storage/transport temperature. We carry ours across the Cascades to dive in the wintertime. Typical temperatures are below 20F and could be below zero F.

I agree the PPO2 is a rusting factor. if you are going to store tanks vent them to below 100 psi and you should never have any problems. If its too cold then store indoors. I think the condensing of your tanks at 3500 and mine at 100-2500 is a major difference. by your linked computer dropping pso from 3500- 3000 drops dew oint 10 degrees. In my neck of hte woods I can not remember temps low enough to effect an al 80 let alone my lp tanks. dropping psi to 100 kicks pressure dew point down to below -30s.

 

[Pavao]

SITA (Scuba Industry Trade Association) gathered the failure rates from the UK test houses
The cylinders at most risk are 3Lt and smaller, where the thread might fail.
.

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

Each sector of the diving industry must do their own risk assessment; recreational or oil & gas are just two sectors.

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.

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

What do you mean by 3Lt?

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

Lol I know what a 3 liter cylinder is, it’s exactly what I use on my rebreather, and that’s why I was specifically asking about them, as they ARE used for recreational diving, same industry sector SITA did it’s risk assessment.

So, now that we’ve stablished that, are the cylinders most at risk, according to the risk assessment SITA did, and SITA concluded the smaller cylinders used in recreational diving are most at risk of failure, are they gonna have a different inspection schedule?

 

[chrisch]

...
So, now that we’ve stablished that, are the cylinders most at risk, according to the risk assessment SITA did, and SITA concluded the smaller cylinders used in recreational diving are most at risk of failure, are they gonna have a different inspection schedule?

I did answer this before but if you missed it the answer was no. All UK tanks are covered by the same testing schedule, including small volume tanks for bailout, rebreather and suit inflation purposes. The only other schedule is for the tiny cylinders used in dSMB and very old BC which are exempt from any testing at all.

 

[Pavao]

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.

It’s not standard procedure for any tank to be breathed dry, yet it keeps happening, how do you know which ones have water in it unless you inspect it?

The small dSMB tanks are drained every use.

I confess I don’t know what a DSMB tank is. Is that a CO2 cartridge? Can you please post a link to one of these so I can see what you’re talking about

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.

Again, it isn’t a common thing to empty any scuba cylinder, but it does happen with a certain frequency. It’s not standard for a lot of things to happen on scuba, yet they happen, often. Ever been on any charter boat? You can even search this very forum here and you’ll find months worth of reading about stuff divers do that make you scratch your head and go, huh?!?!?

By the way, right now I cannot think of single small cylinder, anything smaller than the ones used as main tanks, that I have ever failed from the inside, plenty failed from pitting/rust on the outside.
All the ones with water inside were main tanks, the pictures I posted are all AL80s

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

I’m not sure why you guys keep bringing up metallurgic, oil and gas industry, etc…