Rusty cylinders-need help!

[BRT]

It's not that the calculator is incorrect, your understanding is incorrect.

-60F is pressure dew point at service pressure.

The dew point of the air in a scuba cylinder is typically -60F dew point @ 4,500 psi. (Meaning the cylinder walls would need to be @ -60F for condensation to occer)

It is not 38F, do you realize the issues that would cause?

Further, the desiccant in the dryer cartridges isn't capable of drying the air to those dew points you suggest, the desiccant will always dry lower than -40F unless it's saturated.

If you explain where your getting this from I can help you understand it better, but I assure you I know what I'm talking about here.

So please, put in a -60 dewpoint at 3500 pounds and see what the dewpoint is at atmospheric pressure.

 

[BRT]

It's not that the calculator is incorrect, your understanding is incorrect.

-60F is pressure dew point at service pressure.

The dew point of the air in a scuba cylinder is typically -60F dew point @ 4,500 psi. (Meaning the cylinder walls would need to be @ -60F for condensation to occer)

It is not 38F, do you realize the issues that would cause?

Further, the desiccant in the dryer cartridges isn't capable of drying the air to those dew points you suggest, the desiccant will always dry lower than -40F unless it's saturated.

If you explain where your getting this from I can help you understand it better, but I assure you I know what I'm talking about here.

I would also invite you to look at 4.1.2 of this document.

https://scubaengineer.com/documents/hse_moisture_levels_in_compressed_air.pdf

 

[Cio]

So please, put in a -60 dewpoint at 3500 pounds and see what the dewpoint is at atmospheric pressure.

It's like-125F

What's your point?

 

[Cio]

I would also invite you to look at 4.1.2 of this document.

https://scubaengineer.com/documents/hse_moisture_levels_in_compressed_air.pdf

Yes the standard for dryness for breathing ar is given at atmospheric conditions which correlates to wet air at typical service pressures.

Air in these systems is dried beyond what the standard calls for because of the equipment needs. The standard is just a bare minimum, correcting the standard for pressure does not demonstrate what is actually at the filtration outlet.

There is also the properties of the drying media, Two types of media are used for drying, alumina and molecular sieve. Alumina holds a decent amount of water and dries to -40 or greater, never more than -80F. Molecular sieve doesn't hold alot of water but can get down to -100F for applications that require that.

These desiccants don't care what pressure ether are used at, they dry the air stream to greater than -40F/-100F pressure dew point at the drying pressure. That's how they work

Neither of these desiccants can be used to dry air to 38F, this can only happen after saturation, and then only for a short time as it gets worse quickly. A cartridge can not be designed to do this. A refrigerated dryer can, but that's not whats typically used for hp breathing air filtration.

I build high pressure gas systems, I have seen pressure dew point meters installed and showing these dew points so I can assure you, this is how these systems operate. I get how you could be confused but your document only points out things the industry is well aware of and has accounted for. The standard of for the breathing air, doesn't need to account for the equipment, that's outside the scope.

 

[BRT]

Yes the standard for dryness for breathing ar is given at atmospheric conditions which correlates to wet air at typical service pressures.

Air in these systems is dried beyond what the standard calls for because of the equipment needs. The standard is just a bare minimum, correcting the standard for pressure does not demonstrate what is actually at the filtration outlet.

There is also the properties of the drying media, Two types of media are used for drying, alumina and molecular sieve. Alumina holds a decent amount of water and dries to -40 or greater, never more than -80F. Molecular sieve doesn't hold alot of water but can get down to -100F for applications that require that.

These desiccants don't care what pressure ether are used at, they dry the air stream to greater than -40F/-100F pressure dew point at the drying pressure. That's how they work

Neither of these desiccants can be used to dry air to 38F, this can only happen after saturation, and then only for a short time as it gets worse quickly. A cartridge can not be designed to do this. A refrigerated dryer can, but that's not whats typically used for hp breathing air filtration.

I build high pressure gas systems, I have seen pressure dew point meters installed and showing these dew points so I can assure you, this is how these systems operate. I get how you could be confused but your document only points out things the industry is well aware of and has accounted for. The standard of for the breathing air, doesn't need to account for the equipment, that's outside the scope.

I guess your air must be really dry and you will never have problems with rust spots. Unlike the rest of us.

 

[rob.mwpropane]

I don't understand? The air in my tanks always seems to be pretty dry? This is after an additional 3 part filter was added to the system to reduce moisture to something like 99.3% or 99.7%? Is thus not true?

I've opened up my tanks.... they look the same as when I closed them?

 

[Gone for diving]

Since we have the experts here,,,
How does silica gel compare to alumina?
besides that silica can be dusty and is bad to breath,?

 

[Cio]

Since we have the experts here,,,
How does silica gel compare to alumina?
besides that silica can be dusty and is bad to breath,?

Temp range for silica isn't so good and cant get down as low as alumina.

 

[Cio]

I guess your air must be really dry and you will never have problems with rust spots. Unlike the rest of us.

All my tanks look perfect, literally every one.

Look at the cylinders at any fire department, they will be prefect too, there is a reason for that. Not SCBAs, the cascade cylinders which are steel. All new systems are 6K as well, which makes your wet air theory even worse in their case. (but yet no corrosion?)

If you need a quick reference, here is a blurb from Sauer I pulled off my email.
Refridge dryers for 37-41F and absorption down to -40F PDP @ 5,000 psi.

Absorption means desiccant BTW. This is referring to a PSA dryer that regenerates itself but its the same media in disposable cartridges. I can dig deeper if you still aren't convinced.

 

[BRT]

All my tanks look perfect, literally every one.

Look at the cylinders at any fire department, they will be prefect too, there is a reason for that. Not SCBAs, the cascade cylinders which are steel. All new systems are 6K as well, which makes your wet air theory even worse in their case. (but yet no corrosion?)

If you need a quick reference, here is a blurb from Sauer I pulled off my email.
Refridge dryers for 37-41F and absorption down to -40F PDP @ 5,000 psi.

Absorption means desiccant BTW. This is referring to a PSA dryer that regenerates itself but its the same media in disposable cartridges. I can dig deeper if you still aren't convinced.

View attachment 693077

Did you notice that they can achieve a pressure dewpoint of 37-41 deg F? This is entirely inline with what I have been saying. An expert such as yourself must have some air tests that have been returned to you. Mind posting one?