Does you lifejacket have a pressure release valve?

[tim_ber]

This thread:
http://www.ybw.com/forums/showthread.php?p=3772098#post3772098
prompted me to think of the following:

I have taken apart very old and well constructed life jackets.

They had pressure release valves.

I have some modern double cylinder lifejackets; they too have valves.

My single cylinder lifejackets do not have pressure release valves.

Now, considering the above thread where the weld or something burst, a valve would have perhaps solved the problem or at the least stopped the rupture by releasing excess pressure and at least one side of bladder would have maintained pressure.

Double cylinder ljs have to have valves because one 66g cylinder is enough to fill lj, so 2 cylinders would blow the welds.

BUT even with 33g or 36g cylinders, the cyclinder may not be empty when the lj is fully inflated, so there is an equilibrium of pressure between almost empty cylinder and full bladder. So the welds have to withstand excess pressure. A valve would solve this by allowing the cylinder to empty and allow an set and accurate pressure in the bladder.

Am I right?

Poll does not reveal ID.
Mulitple choice as you may have more than one type of lj.

 

[dt4134]

BUT even with 33g or 36g cylinders, the cyclinder may not be empty when the lj is fully inflated, so there is an equilibrium of pressure between almost empty cylinder and full bladder. So the welds have to withstand excess pressure. A valve would solve this by allowing the cylinder to empty and allow an set and accurate pressure in the bladder.

Could you explain what you're trying to say there again.


Of course the pressure is going to equalise between the cylinder and fully inflated bladder. I don't know what you mean when you're talking about emptying the cylinder any more than that. When designing it they will have calculated what the pressure would be when the bladder is inflated. With a single cylinder LJ there is nowhere else for any gas to come from to give pressure above what they've calculated. What do you mean by excess pressure?

 

[tim_ber]

Of course, anyone who has read the previous thread mentioned above and hasn't checked their lifejackets will of course be doing it soon, won't they? !

I know I need to check the welds on my older ljs.

 

[tim_ber]

Could you explain what you're trying to say there again.


Of course the pressure is going to equalise between the cylinder and fully inflated bladder. I don't know what you mean when you're talking about emptying the cylinder any more than that. When designing it they will have calculated what the pressure would be when the bladder is inflated. With a single cylinder LJ there is nowhere else for any gas to come from to give pressure above what they've calculated. What do you mean by excess pressure?

A lj with a release valve that activates at x psi could be pumped up with a compressor delivering 3x psi and the bladder will always remain at x psi owing to the release valve.

Do the manufacturers calculate the volume the liquid co2 will produce (or the pressure) and make their bladders accordingly, or the cannisters small enough.

I believe the co2 cannisters have more liquid co2 than required and do not empty when they have filled the bladder, so the bladder is still under pressure.

E.g. if I placed a 66g cylinder instead of a 33g cylinder, all that liquid co2 sloshing in the cylinder will be trying to turn to gas and will be exerting more pressure on the welds on the lj would it not?

Did that make sense; I may have the physics totally wrong and am open to more info. I haven't given it a tonne of thought and I am getting older at a frightening pace.

 

[Hoolie]

... ... ...
Do the manufacturers calculate the volume the liquid co2 will produce (or the pressure) and make their bladders accordingly, or the cannisters small enough.

... ... ...

I'm sure that is the case.
Personally I have never come across a lifejacket with an automatic pressure release valve. But why would you need anything like that if the pre-calculated pressure/volume is correct?

 

[tim_ber]

I'm sure that is the case.
Personally I have never come across a lifejacket with an automatic pressure release valve. But why would you need anything like that if the pre-calculated pressure/volume is correct?

To solve the problem in the thread that dylan posted.

The valve would have vented, the bladder would not have burst, the lady would have had some inflation rather than a flapping piece of fabric around her neck.

 

[dylanwinter]

don't trust them anymore

To solve the problem in the thread that dylan posted.

The valve would have vented, the bladder would not have burst, the lady would have had some inflation rather than a flapping piece of fabric around her neck.

I am concerned that there are too many ways that these can fail

not go off..... or burst when they do

regardless of whether you are the most anal maintenance person on the planet

this from sailing anarchy

Posted Today, 12:20 AM
AFter doing the PAC Cup and then all 4 of us pulling the rip cord on our inflatable jackets at the island and only having two out of the 4 work - I've been ocean racing with a paddle style PFD jacket ever since. However it does need a crotch strap I spent about 15 minutes in the pool with all my gear and found that the paddle style jackets which are great for arm movement and clear harness belts will ride up on your chest and be an issue like what was reported recently about the Farallon island accident.

there is also an incident reported in a Sf Harbour yacht race where a MOB removed his life jacket so that he could get back onto the boat

until I can find failure data for these things I think thatI willbe making more use of solid ones

I want a 70N one please


Dylan

 

[tim_ber]

I am concerned that there are too many ways that these can fail

not go off..... or burst when they do

regardless of whether you are the most anal maintenance person on the planet

this from sailing anarchy

Posted Today, 12:20 AM
AFter doing the PAC Cup and then all 4 of us pulling the rip cord on our inflatable jackets at the island and only having two out of the 4 work - I've been ocean racing with a paddle style PFD jacket ever since. However it does need a crotch strap I spent about 15 minutes in the pool with all my gear and found that the paddle style jackets which are great for arm movement and clear harness belts will ride up on your chest and be an issue like what was reported recently about the Farallon island accident.

there is also an incident reported in a Sf Harbour yacht race where a MOB removed his life jacket so that he could get back onto the boat

until I can find failure data for these things I think thatI willbe making more use of solid ones

I want a 70N one please


Dylan

Yes, like a lot of overpriced and under-engineered sailing kit, life jackets need to be better.

But that would mean the companies only make 100% to 200% profit instead of their goodness knows what % profit (just guessing there, but greed seems to have overcome doing a proper job - all in mho of course)

Funny thing is, I started off with those big orange foam ones and then bought the inflating ones because of the bulk of the orange one. Oops.

 

[tim_ber]

And another thing...

One of the old beaufort (I think) life jackets that I examined had a manual pull mechanism that required none of those silly little green clips that cost about £3 or are included in re-arming kits.

Think of how much money has gone into tooling for the injection moulding of those clips.

So to rearm the old jacket, you simply used a new cylinder.

 

[salinia]

To solve the problem in the thread that dylan posted.

The valve would have vented, the bladder would not have burst, the lady would have had some inflation rather than a flapping piece of fabric around her neck.

The reason it didn't hold air was because there was no glue holding the flange of the breather pipe to the bladder, of course the main reason was that the lifejacket was beyond it's useful life.

 

[tim_ber]

The reason it didn't hold air was because there was no glue holding the flange of the breather pipe to the bladder, of course the main reason was that the lifejacket was beyond it's useful life.

Excellent. Well done for that. I stand corrected. What make of lj was that one then?

Still, Dylan has a point.

If these darn things have such a short life, foam maybe the answer. (Until someone starts making them decently - doulble bladders, a reinforced area over that tube. Materials with a greater longevity.

Oh I hear cries of cost.

Nope, I keep failing in business coz I do a good job and don't charge enough.

I certainly have reservations about them now that I didn't have until Dylan made this issue viewable (so to speak).

And so far, we're not sure even new ones will work.

As Dylan said, time for some serious research.

Now that would be a good article for the mag. They'd have to test over a 1000 of different brands for me to become satisfied though.

 

[dylanwinter]

the data exists

Excellent. Well done for that. I stand corrected. What make of lj was that one then?

Still, Dylan has a point.

If these darn things have such a short life, foam maybe the answer. (Until someone starts making them decently - doulble bladders, a reinforced area over that tube. Materials with a greater longevity.

Oh I hear cries of cost.

Nope, I keep failing in business coz I do a good job and don't charge enough.

I certainly have reservations about them now that I didn't have until Dylan made this issue viewable (so to speak).

And so far, we're not sure even new ones will work.

As Dylan said, time for some serious research.

Now that would be a good article for the mag. They'd have to test over a 1000 of different brands for me to become satisfied though.

the data must exist

but it is not on the web

unless some-one knows otherwise

as for the failure of the glue

why use a glue that will fail with time?

Anyone on here who sells life jackets

Dylan

 

[prv]

The reason it didn't hold air was because there was no glue holding the flange of the breather pipe to the bladder

That surprises me, having seen the video of it (failing to) go off:



You can clearly see gas escaping from somewhere around the side that did inflate, so regardless of the oral tube it must have had a leak on that side as well. It's not clear that any gas even made it into the half where the oral tube was, so while that was obviously a failure waiting to happen, I think something else in fact failed first. My best guess, from the way the gas was spraying out, is around the cylinder thread.

Pete

 

[dylanwinter]

partially unscrewed

That surprises me, having seen the video of it (failing to) go off:



You can clearly see gas escaping from somewhere around the side that did inflate, so regardless of the oral tube it must have had a leak on that side as well. It's not clear that any gas even made it into the half where the oral tube was, so while that was obviously a failure waiting to happen, I think something else in fact failed first. My best guess, from the way the gas was spraying out, is around the cylinder thread.

Pete

partially unscrewed cylinder would seem to be a common reason for a failure

however, I would say that this was a design fault

dunno about you guys but I seldom check my wheel or cylinedr head nuts


I think it needs a spot of lock tight or a tightening ring

some eay of stopping that from happening should be designed

my cylinders hang down

an invitation to any thread to ease rather than tighten

Dylan

 

[prv]

partially unscrewed cylinder would seem to be a common reason for a failure

however, I would say that this was a design fault

dunno about you guys but I seldom check my wheel or cylinedr head nuts

I do check the cylinder on my old manual jacket. Not quite every time I put it on, but pretty regularly. Must be some kind of OCD, it's not necessary to check *quite* that often

I think it needs a spot of lock tight or a tightening ring

some eay of stopping that from happening should be designed

Already done, on the Hammar fittings on the jackets kept on KS. They now glue them in, and sell the replacements already glued into a suitable piece of plastic that slots into the inflator.

Pete

 

[dt4134]

I believe the co2 cannisters have more liquid co2 than required and do not empty when they have filled the bladder, so the bladder is still under pressure.

I believe they have the required amount although of course there will be small variations within manufacturer's tolerances. Obviously the inflated bladder and 'empty' cylinder are pressurised above atmospheric pressure but they will be at the same pressure. Not sure of your definition of empty.

Seems a pressure release valve would just be another component that could fail and would anyway have a finite design life. Just like the glue.

 

[FishyInverness]

Anyone on here who sells life jackets

Dylan

Guilty,

I have also been trained to service them, though we haven't gone through with the full authorisation yet, so I am technically trained but not authorised...

Happy to offer any answers I might have in my limited knowledge...

(I can't answer your Glue question though Dylan - I suppose that to use an adhesive which wont inherently damage the bladder on application means that the best 2nd choice is to use one that may degrade over time. A service includes a full pressure test using a calibrated manometer and a special compressor, so obviously the servicing is designed to pick up on and prevent a catastrophic failure such as you experienced, before it happens.)

Incidentally Tim ber...I have no idea where you got your figures from, but 200% markup on lifejackets? I'm afraid nowhere near!

 

[dylanwinter]

great post

Guilty,

I have also been trained to service them, though we haven't gone through with the full authorisation yet, so I am technically trained but not authorised...

Happy to offer any answers I might have in my limited knowledge...

(I can't answer your Glue question though Dylan - I suppose that to use an adhesive which wont inherently damage the bladder on application means that the best 2nd choice is to use one that may degrade over time. A service includes a full pressure test using a calibrated manometer and a special compressor, so obviously the servicing is designed to pick up on and prevent a catastrophic failure such as you experienced, before it happens.)

Incidentally Tim ber...I have no idea where you got your figures from, but 200% markup on lifejackets? I'm afraid nowhere near!

so on your pressure tests.... have you ever had one fail?

how often do you pick up one and find that the CO2 cylinder has come loose enough to cause a failure

Dylan

 

[FishyInverness]

so on your pressure tests.... have you ever had one fail?

how often do you pick up one and find that the CO2 cylinder has come loose enough to cause a failure

Dylan

Ah, now you see, the actual experience of servicing is where I can't help i'm afraid...I'm trained, but GF haven't yet decided to bite the bullet and go through with full authorisation for a service centre. So I know what to do, i've done practices, I just haven't done any actual servicing!

I have checked over quite a few lifejackets on an informal basis though, just the basic 6 monthly stuff that anyone can do (though scarily few I have done it for knew what they were supposed to be doing or looking for!) and have to say that of the ones i've done (somewhere in the region of 30 lifejackets) I had one with a loose bottle - I couldn't say that it was loose enough to cause a failure, but it did require approximately a quarter turn to seat it properly.

 

[bbg]

partially unscrewed cylinder would seem to be a common reason for a failure

however, I would say that this was a design fault

dunno about you guys but I seldom check my wheel or cylinedr head nuts


I think it needs a spot of lock tight or a tightening ring

some eay of stopping that from happening should be designed

my cylinders hang down

an invitation to any thread to ease rather than tighten

Dylan

I don't know about other models, but the Spinlock Deckvest has a "double green" indicator that shows through a window in the LJ when it is fully armed.

Due to the nature of the sailing I do, I tend to wear a LJ a lot of the time that I am sailing. Personal preference.

Also due to the nature of the sailing I do, I am often out in **** weather, so the LJ gets wet, and often salty.

My standard practice is to bring the LJ home, inflate it orally, rinse it and hang it to dry. Then repack it. Pretty much every time I go sailing.

For me it is like any other piece of equipment. I wash my clothes when they're dirty, rinse my drysuit after it gets salty. Then let them dry before putting them away.

I get the feeling a lot of people just take off their (wet, salty) lifejackets and hang them in a damp locker. Not the best way to treat something that you have bought to help save your life.

All in my (very rarely humble) opinion.