Does diaphragm first stage free flow when it fails?

[nohappy]

From my understanding, diaphragm first stage is a design of upstream valve (right?). Does that mean it won't free flow when it fails(e.g. freeze in cold water)?

 

[ScottFL78]

I live in Florida so its none of my business but here is a good video.

 

[KevinNM]

Don't get too wrapped up in the upstream or downstream stuff. For example there are a couple of downstream regulators sold by Poseidon. One of these is the XStream Deep MK3, which is one of the very few regulators approved for cold water service by the US Navy because it is extremely resistant to freezing up and free flow in very cold water.

Authorized for Cold Water Service: What Divers Should Know About Extreme Cold
http://www.navsea.navy.mil/Portals/103/Documents/SUPSALV/Diving/11-01-2016.pdf

 

[Patoux01]

If I remember correctly, the US navy sent 2 divers on a suicide mission, and then blamed the regs (Apeks) when they died instead of manning up. They eventually blamed the operator too, but yeah. Details surrounding death of USN divers +1 year ago finally released under FOIA So the fact a reg is or is not "US Navy approved" doesn't necessarily mean much.


Back to the question, most regs will freeflow on a freeze afaik.

 

[tr3a]

Diaphragm first stage will cause freeflow when frozen.
Have had fail closed once due to mechanical break down.

 

[Storker]

2nd stage freeflows after surfacing are par for the course if you're diving when the top side temp is near- or sub-freezing. A mite annoying, but nothing more. I've never experienced or seen a 1st stage freeflow due to freezing even if l have a few dives in sub-6C water and sub-freezing topside temps. If I were you, l wouldn't worry. At least if you're using a cold water compatible reg set.

 

[rjack321]

IP creep is the most common failure on a diaphragm 1st and yes it leads to a leaking 2nd stage (various rates of leaking depending on the creep)

 

[Jonny Wishbone]

IP creep occurs when the HP seat does not mate up right to make a 100% seal. sometimes the seat surface winds up with too many tiny grooves in it or it becomes too puckered from the spring pressure to seal properly. IP creep is an indication you need a new HP seat , cone module or other mating surface which really isn't dictated by a diaphragm or piston.

 

[halocline]

From my understanding, diaphragm first stage is a design of upstream valve (right?). Does that mean it won't free flow when it fails(e.g. freeze in cold water)?

No, that's not correct. The 'upstream' part of the valve is not the part that freezes; it's dry. The ambient chamber, which has the big spring and is separated from the dry part of the regulator by a thick rubber diaphragm, is the part that's exposed to water and thus freezes. This is less common in diaphragm regs than in flow-through piston regs due to the path of rapidly decompressing air, but in both cases it can cause a free flow.
That's why sealed regs (meaning the ambient chamber is not exposed to water) are preferred in cold water.

 

[2airishuman]

From my understanding, diaphragm first stage is a design of upstream valve (right?). Does that mean it won't free flow when it fails(e.g. freeze in cold water)?

Typically, regulators fail open (freeflow), but not always. This is true of both diaphragm and piston designs. It is not a guarantee, however, as regulators that aren't supposed to be able to fail closed occasionally do exactly that.