what stops lifejackets freezing?

[tim_ber]

When CO2 dashes into the jackets, what stops the liquid (becoming a gas) making the bladder brittle and crack?

 

[pampas]

Always thought they are compressed gas? filled volume enough to fill the bladder. stand to be corrected. .

 

[tim_ber]

Always thought they are compressed gas? filled volume enough to fill the bladder. stand to be corrected. .

Yes, you are probably right, but just like a CO2 fire extinguisher, the compressed gas expands, absorbs heat and hence could freeze things couldn't it (such as the bladder)?

So wondering how they stop this- will keep googling

 

[prv]

Always thought they are compressed gas? filled volume enough to fill the bladder. stand to be corrected. .

You don't have to compress CO2 all that far before it turns into a liquid - 50-odd bar from (possibly unreliable) memory.

Interestingly, you can't turn it into a liquid just by cooling it - at normal pressure it goes straight from gas to solid and vice versa, which is why it's useful for keeping stuff cold without meltwater swilling around.

tim_ber is right that it will absorb heat from the surroundings as it rapidly expands; I guess it's just that a lifejacket-sized bottle doesn't absorb enough to start freezing things at normal temperatures.

A possible partial answer is that Hammar tout un-freezability as one of the advantages of their inflator system. Because the bottle is stored inside the bladder, the gas doesn't have to flow through any valve as it's released (it does flow through and around the puncturing mechanism, but I guess not through a constricted channel). They imply that other makers' jackets (with an external bottle and a channel to the bladder) might freeze if operated at arctic temperatures; I don't know if this is a real consideration or just marketing.

Pete

 

[jwilson]

You don't have to compress CO2 all that far before it turns into a liquid - 50-odd bar from (possibly unreliable) memory.

Interestingly, you can't turn it into a liquid just by cooling it - at normal pressure it goes straight from gas to solid and vice versa, which is why it's useful for keeping stuff cold without meltwater swilling around.

tim_ber is right that it will absorb heat from the surroundings as it rapidly expands; I guess it's just that a lifejacket-sized bottle doesn't absorb enough to start freezing things at normal temperatures.

A possible partial answer is that Hammar tout un-freezability as one of the advantages of their inflator system. Because the bottle is stored inside the bladder, the gas doesn't have to flow through any valve as it's released (it does flow through and around the puncturing mechanism, but I guess not through a constricted channel). They imply that other makers' jackets (with an external bottle and a channel to the bladder) might freeze if operated at arctic temperatures; I don't know if this is a real consideration or just marketing.

Pete

Recently fired a number of oldish gas cylinders in manual lifejackets out of interest, as part of a regular 48 hour stay-inflated check. As the exteriors looked a bit corroded (even though they weighed as full) I had already bought new cylinders. The grotty-looking cylinders all worked fine, and got frosty cold as they emptied. The bladders got cold but not noticeably stiff. This was indoors in a chilly spare room - maybe 12C.

 

[tim_ber]

Interesting, thanks for that.

 

[KellysEye]

>The bladders got cold but not noticeably stiff.

Agree. Jane and I fired our life jackets during a seas survival course and noticed no problem with the bladders. We were in a swimming pool at the time with a life raft in front of us. There shouldn't any problems because they've been around for years.

 

[macd]

It doesn't freeze because it boyles.
Sorry. Off now...