Stage Regs

[Tortuga68]

To be clear I open my slung cylinder valve at the surface and shutoff my inline sliding valve at the second stage. When I deploy/gas switch I just switch the inline valve over to on and begin using it. I like using them so far since I don't have to worry about turning on the cylinder valve underwater.

Not to labour the point that others have already made, but... essentially what you're doing is replacing one valve with another valve, and creating additional potential problems in the process. Not sure why turning the cylinder valve on underwater would be something to worry about, is it the positioning or what is the issue?

 

[mikecotrone]

No to labour the point that others have already made, but... essentially what you're doing is replacing one valve with another valve, and creating additional potential problems in the process. Not sure why turning the cylinder valve on underwater would be something to worry about, is it the positioning or what is the issue?

Its not a problem .. I am new so my muscle memory says it's easier to click a slider than turn a valve. That will change with Experience I am sure I do like the simplicity of the slider though.

 

[Tortuga68]

Well.. the way to build muscle memory is by practice, not by substituting another procedure

 

[elan]

No and maybe. When I referenced Free flow in my posts above I was talking about free flow because of the position of my Second stage (facing up) then it usually free flows when I am in colder water and deep. In my previous posts I wasn't referencing a free flow based on 1st stage failure. I hope this clears that part up. That is why I like the inline shutoff valve. It just takes muscle memory and training to remember to open when you deploy.

I am not sure if your scenario would be the case, but I am sure it's possible If I as unlucky enough to find myself in that position I would have to switch off to my contingency deco plan and use my backgas for Deco.

Well I understand that you referenced the second stage free flow but this fact does not prevent 1st stage freeflow from happening

And they do happen. Happened to me once this year

But regardless its for you and your team to manage those risks

 

[PfcAJ]

You WANT the 2nd stage to be able to freeflow... They work as an OPV should the first stage malfunction, resulting in high IP.

By leaving the system turned on and then shutting down the 2nd stage, you risk a hose rupture. This is why argon regs have an OPV installed.

 

[DA Aquamaster]

As Elan suggested earlier and as AJ elaborates above, an OPV of some sort is essential in the system.

Nearly all second stages use a downstream design so that it can vent excess pressure in the event of a leak in the high pressure seat in the first stage. The few regs that are not downstream biased use a separate OPV on the first stage or in the hose assembly.

If the HP seat is leaking into the Ip section of a reg that is pressurized but not being used, the IP will continue to build until the hose ruptures at somewhere between 300 and 500 psi depending on the hose. That will leave you with an unusable deco reg regardless of whether or not you lose all the gas.

So to accomodate your shut off valve (which is just a crutch for turning off the valve on an uinactive bottle) you have to add an OPV to the first stage. You've now added a valve that can fail (closed as well as open) a few more o-rings that can leak, and an OPV that can fail and/or leak.

As I stated initially - you've now added a great deal of complexity and the number of things that can now go wrong all to overcome a skills deficiency.

Let's just agree not to dive together until you get it figured out and start thinking through some of your configuration decisions.

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An in line shut off only makes sense in a very limited range of applications - such as in the O2 line of an eCCR rebreather to allow a very rapid way to shut off and then manage the gas flow if a solennoid sticks and tries to continuously inject O2 into the loop. And even then the practice is questionable.

IMHO they have no place at all in an OC configuration.

 

[mikecotrone]

As Elan suggested earlier and as AJ elaborates above, an OPV of some sort is essential in the system.

Nearly all second stages use a downstream design so that it can vent excess pressure in the event of a leak in the high pressure seat in the first stage. The few regs that are not downstream biased use a separate OPV on the first stage or in the hose assembly.

If the HP seat is leaking into the Ip section of a reg that is pressurized but not being used, the IP will continue to build until the hose ruptures at somewhere between 300 and 500 psi depending on the hose. That will leave you with an unusable deco reg regardless of whether or not you lose all the gas.

So to accomodate your shut off valve (which is just a crutch for turning off the valve on an uinactive bottle) you have to add an OPV to the first stage. You've now added a valve that can fail (closed as well as open) a few more o-rings that can leak, and an OPV that can fail and/or leak.

I very much appreciate how you explained this to me. Also Thank you for not giving me some B.S. Soap Box type of "Because I said so and I have 10000+ dives" answer. This really helps me

I never did think about the pressurization through like that and it makes 100% sense. Obviously my drysuit 1st stage has an OPV, but since my instructor recommended the shutoff valve I kind of didn't research it like I would normally do. I do see that being a problem which indeed is a crutch for my newness to using stage bottles. I have not experienced a hose rupture yet so I really didn't think it was that common so I really appreciate the experienced explanation. I am not too proud to learn

As I stated initially - you've now added a great deal of complexity and the number of things that can now go wrong all to overcome a skills deficiency.

Let's just agree not to dive together until you get it figured out and start thinking through some of your configuration decisions.

Today I agree that I need to get more decompression dives under my belt in which I only have 5 so far. I am not experienced enough to dive with you or guys at your level yet for sure. After some more experience and since I have residence in NC/VA also perhaps we can dive together some day

An in line shut off only makes sense in a very limited range of applications - such as in the O2 line of an eCCR rebreather to allow a very rapid way to shut off and then manage the gas flow if a solennoid sticks and tries to continuously inject O2 into the loop. And even then the practice is questionable.

IMHO they have no place at all in an OC configuration.

Totally makes sense!

 

[down4fun]

Its not a problem .. I am new so my muscle memory says it's easier to click a slider than turn a valve. That will change with Experience I am sure I do like the simplicity of the slider though.

Just going to add my two cents here spend it however you want
I have seen a rebreather diver with an inline shutoff on his bailout gas have a problem and it was enough for me not to ever use one. We were doing a shore dive out to a wall that drops off 300+. At about 70 feet he starts having a problem i can tell just by his body position, trim goes, fidgeting etc. I ask if he is okay and get the so-so and he points to his loop. I gesture that we thumb the dive. I tell him to hold so i can swim up and tell the others we are aborting. By the time i return he has bailed out. We start the swim back and he is wildly checking his gauge. I have my bailout bungied and by now have my reg in my hand for donation. We are both wearing two bailout a deep mix and a 50%, he goes to switch to his rich as he has run out of deep (that's another story) but the inline shutoff has a piece of shell stuck in it and he cant get gas. He ends up on my bailout while we get the shell out of his slide lock. Everything turned out fine but he was quite shaken. It was the typical not one thing goes wrong but three or four. Granted we had no deco and were shallow enough we could have gone for the surface if he had too. But had that been at the end of the dive planned it would have been another story. In any case I love to crawl through tight wrecks and can just imagine a piece of debris getting stuck just the way that shell did. SO no inline shutoffs for me. Deep mix is around my neck so i will know if it free flows and the deco gas is charged and turned off.

 

[DA Aquamaster]

I very much appreciate how you explained this to me. Also Thank you for not giving me some B.S. Soap Box type of "Because I said so and I have 10000+ dives" answer. This really helps me

I never did think about the pressurization through like that and it makes 100% sense. Obviously my drysuit 1st stage has an OPV, but since my instructor recommended the shutoff valve I kind of didn't research it like I would normally do. I do see that being a problem which indeed is a crutch for my newness to using stage bottles. I have not experienced a hose rupture yet so I really didn't think it was that common so I really appreciate the experienced explanation. I am not too proud to learn

I came off a bit harsh and I apologize for that, but gas switches as still the number 1 killer of technical diving so I tend to discourage any corner cutting there as a matter of general principle.

You are correct that it is far too common to get an authoritarian "because someone said so" answer or to get a very non explanatory "just do it this way" answer or it's close cousin the "ask your instructor" answer.

In some cases it is to prevent someone from learning to dive on the Internet, but in some cases it is because the diver (who is often a very good diver who has solid techniques and lots of experience) was never fully told the reasons why and never thought it through. As an extreme example I spent about 10 minutes last winter assembling my gear and biting my tongue while a very well known and respected GUE instructor gave an incorrect mechanical explanation of regulator balancing as a justification for his configuration choices. The student was from Europe and obviously spent a great deal of money coming to the US to get instruction from this person. Now, there was no malice in giving the misinformation and it in no way reduces or suggests a lack of diving ability on his part, it just underscores the problem that develops when/if you learn the what or how of something without really thinking through the whys beyond "because so and so says so" or "because that's how lots of very knowledgable and experienced divers do it".

I encourage anyone to ask "why?" and if neccesary to keep asking why until you get to a solid explanation/rationale for doing it that way as well as the context of where and why the practice was developed. That approach will help you learn more as a diver and also works well in assessing how much a prospective buddy or instructor really knows about technical diving as opposed to just rote learning.

 

[mikecotrone]

I came off a bit harsh and I apologize for that, but gas switches as still the number 1 killer of technical diving so I tend to discourage any corner cutting there as a matter of general principle.

You are correct that it is far too common to get an authoritarian "because someone said so" answer or to get a very non explanatory "just do it this way" answer or it's close cousin the "ask your instructor" answer.

In some cases it is to prevent someone from learning to dive on the Internet, but in some cases it is because the diver (who is often a very good diver who has solid techniques and lots of experience) was never fully told the reasons why and never thought it through. As an extreme example I spent about 10 minutes last winter assembling my gear and biting my tongue while a very well known and respected GUE instructor gave an incorrect mechanical explanation of regulator balancing as a justification for his configuration choices. The student was from Europe and obviously spent a great deal of money coming to the US to get instruction from this person. Now, there was no malice in giving the misinformation and it in no way reduces or suggests a lack of diving ability on his part, it just underscores the problem that develops when/if you learn the what or how of something without really thinking through the whys beyond "because so and so says so" or "because that's how lots of very knowledgable and experienced divers do it".

I encourage anyone to ask "why?" and if neccesary to keep asking why until you get to a solid explanation/rationale for doing it that way as well as the context of where and why the practice was developed. That approach will help you learn more as a diver and also works well in assessing how much a prospective buddy or instructor really knows about technical diving as opposed to just rote learning.

Thanks again DA. I just removed all 4 shutoff valves from my 4 stage regulators. I will focus my skills / drills on my Sunday quarry dive to switching gases while opening my cylinder valve.