One SPG only..?

[VeniVidi]

The point at which you had to shut off a tank, your dive ended.

When your dive ended you ether have enough gas to get home or don't. Having a second SPG isn't going to help you one iota at this point.

Absolutely right - from the rational point of view.

I was referring to the mental aspects which may severely interfere in such a situation that lies partly beyond the rational. Sometimes additional information, and be it superfluous, may help to reconcile and give some hint what to do next (at least I am structured like this).

 

[Rubis]

Keep in mind you are asking DIR divers to explain you the DIR way ... no offense intended in my (and other people) posts.

If you need some reassurance maybe you are diving beyond your level of confort. Maybe it is just a matter of more practice or as you said as it is a mental issue just getting more confidence in your capabilities

 

[vlada]

Thanks all for your helpful answers - I start to understand.

Yet I think this is apparently not only the mental awareness that is required but also the mental coolness. I agree that in most of the dives one knows (especially by experience) what one's gas consumption rate is and subsequently what residual gas supply still is in the tank. And yet you can get into non-forseeable situations where you have to shut off your tanks and solve other problems at the same time. If this is furthermore coupled with varying depth ranges and higher breath rates and you still know what is in your tank then you all have my deepest respect.

I am not so presumptuous to claim that I am ever capable of attaining this "Jedi-knight"-type of self-control. There are situations out there that I cannot anticipate and thus control or influence (we're dealing with nature, at last). And a additional back-up is incredibly comforting, especially when one has survived a precarious situation. Probably that is the point that distinguishes the DIRs from the rest of the (divers) world.... Thanks again.

I think you are being slightly sarcastic because the answeres do not quite make sense for you. The reason they do not make sense is that you are missing a big picture

I do not claim to be DIR, but took couple of GUE courses - none of us are super human as a result of those. Most of us would have increased breathing rates should few problems present themselves underwater at the same time

The reason you do not care and do not need SPG is that your rock bottom (i,e, minimum back gas amount) calculations already take all that into account. Rock bottom calc would involve SAC of 1 or even 1.5 cu.ft per min for cold water - this is about twice my normal consumption. The same calculation assumes my buddy's gas consumption would double as well - assuming we never overstay rock bottom - we know that if one of us or both had left valve problems and lost use of SPGs, we both still have plenty of time to get to our first deco stop at a leisurely pace of 10ft/min - because that is the way we planned it

Does is make any sense to you or did i make it worse?

 

[novadiver]

no problem. I may just PM you since I find it's easier to have a conversation without any interuptions.

Sounds good to me

 

[novadiver]

Nova diver, et al... please resist the urge to turn this thread into and excuse for me to shovel you down the old chute of oblivion.

As it stands you are fine. But it is only inches to the door.

Very well understood on this end . in the future I'll use the PM option to talk to divers on this forum, I did not intend for this to happen. that's why I put the disclaimer in that I wasn't concidered DIR.

 

[AndrewJD]

This is a post from a thread a while back "Does anyone carry a second SPG?" in the Basic Scuba Forum. I think it explains pretty well why only one SPG is used in DIR.

"An SPG provides the diver with information on his/her gas supply. That information is critical in determining one thing. When to end the dive and proceed to the surface be it cave, wreck or deep ocean with deco.

The argument for a second SPG when diving manifolded doubles with an isolation valve is trying to address three things.

The first is a difference in available gas between the primary and the backup regulators most likely cause by the left post being shut down and/or the isolation valve being shut. With two SPGs a diver would be able to see that one is moving while the other is not thus identifying that there is a problem.

The second is an SPG failure. If the SPGs aren't giving the same reading and the left post and/or isolator is open then one of the SPGs is malfunctioning.

The third is a diver having to isolate either the left or right cylinder or shut down the left or right post due to system failure. An SPG on each post means a diver will always be able to know the contents of each cylinder.

How are these three issues addressed with out adding an SPG?

Assuming a diver is breathing off of his primary regulator attached to the right post and the SPG is attached to the left post the diver will know that there is a problem if the SPG doesn't move. The first thing to do is check both the left post and the isolator valve. If the valves are open, then the SPG is malfunctioning and it's time to go home.

If the diver is breathing off of his/her back up attached to the left post and his/her gas supply is dwindling faster then expected, then there is a problem. The first thing to do is check the isolator valve.

If the diver needs to isolate either tank due to loss of gas and/or shut down one of the posts due to second or fist stage failures then the SPG is not needed anymore because the diver is on his/her way home. He/she will either have enough gas or not. (He/she should if the team has done its gas management properly)

What problems arise from adding a second SPG?

Now there are two gauges that need to be checked which increases task loading. There are additional failure points introduced into the system. The diver is not as streamlined. If one SPG is malfunctioning, does the diver continue the dive using the backup SPG?

Adding a second SPG attempts to engineer a solution to problems that can be handled through diving protocols while introducing additional task loading, potential for system failure and reducing streamlining. So why do it?"

Jonathan

 

[VeniVidi]

Keep in mind you are asking DIR divers to explain you the DIR way ... no offense intended in my (and other people) posts.

If you need some reassurance maybe you are diving beyond your level of confort. Maybe it is just a matter of more practice or as you said as it is a mental issue just getting more confidence in your capabilities

Thanks Rubis

This is exactly the reason why I posted my question here - to get some genuine answers without any distractions from the pro vs anti DIR arguments.
Actually, I am not diving beyond my level of comfort. I am eager to learn and just thinking things over by checking any perceivable situation where I, as a person, may fail. The SPG-question is something that is bothering me for quite a while because it is a mechanical part, apart from me, and is immune against emotional conclusions. Sometimes a person need a "objective" guide to have a new starting point when things get wild.

So, no excuses, you folks helped me out on this, in a really constructive way.

 

[Spectre]

I am not so presumptuous to claim that I am ever capable of attaining this "Jedi-knight"-type of self-control. There are situations out there that I cannot anticipate and thus control or influence (we're dealing with nature, at last). And a additional back-up is incredibly comforting, especially when one has survived a precarious situation. Probably that is the point that distinguishes the DIRs from the rest of the (divers) world.... Thanks again.

This may not come out right, but I, by no means mean, to imply anything offensive by this statement.

One unmentioned but -necessary- requirement to overhead diving is specifically your ability to keep your cool. If you are not comfortable with your situation, you should -not- be there. When the fan get slammed with the brown stuff, if you don't have the confidence to stay cool and deal with the problem, you are likely to end up very much a statistic.

The way I see it, if I lose my pressure guage, the dive is over. We're out of there. My personal feeling is that if the team doesn't have enough gas to get out at that point [which would make for an egregious gas planning/management failure], I don't think I really wanna know ]. You can either worry about your gas, or be secure in knowing you planned correctly and there -is- enough. Taking the time to worry about how much you -actually- have is just an unnecessary distraction IMHO.

 

[WJL]

Thanks all for your helpful answers - I start to understand.

Yet I think this is apparently not only the mental awareness that is required but also the mental coolness. I agree that in most of the dives one knows (especially by experience) what one's gas consumption rate is and subsequently what residual gas supply still is in the tank. And yet you can get into non-forseeable situations where you have to shut off your tanks and solve other problems at the same time. If this is furthermore coupled with varying depth ranges and higher breath rates and you still know what is in your tank then you all have my deepest respect.

I am not so presumptuous to claim that I am ever capable of attaining this "Jedi-knight"-type of self-control. There are situations out there that I cannot anticipate and thus control or influence (we're dealing with nature, at last). And a additional back-up is incredibly comforting, especially when one has survived a precarious situation. Probably that is the point that distinguishes the DIRs from the rest of the (divers) world.... Thanks again.

I would like to address your questions in two different ways.

First, you are over-estimating the ability of DIR divers to employ the Force. DIR divers aim to minimize the need to make up a plan on the fly during an emergency. The idea is actually to try and avoid having to make too many important decisions during a stressful situation underwater by planning out the dive with the team before it starts. This includes planning gas management. The team plans for a complete gas failure by at least one team member at the point where it is the hardest and longest to get back to safety, taking into account an allowance to deal with the emergency, and also taking into account the likelihood of higher gas consumption during an emergency. How much gas should the remaining team members have in that scenario for everyone to get back safely and make all required stops on the way? This is decided before the dive starts. The dive ends for the whole team when the pre-planned limit is reached. So even if there is an equipment failure at that point, such as loss of an SPG, or even total loss of a team member's gas, the team already knows it has enough gas to get everyone back safely. If the failure happens before that, the dive is terminated, and there is by defintion more than enough gas to get back. So having an extra SPG for one diver adds nothing to the safety of the team. Note that this type of planning depends on the unity of the team and excludes solo diving.

Second, what are you gaining by having two SPGs? (I am assuming that you are diving with essentially one air source, such as manifolded doubles or a single tank, and not independent doubles - which would not be DIR anyways.) With two SPGs, you need to look at both of them. If they read the same, you simply have a good idea of how much gas you have. If one fails, or has a reading different than the other one, aren't you going to terminate the dive immediately? It would seem that a second SPG adds another item of equipment that like all equipment sooner or later will fail, but the addtional item does not help you in any appreciable way.

 

[VeniVidi]

This may not come out right, but I, by no means mean, to imply anything offensive by this statement.

One unmentioned but -necessary- requirement to overhead diving is specifically your ability to keep your cool. If you are not comfortable with your situation, you should -not- be there. When the fan get slammed with the brown stuff, if you don't have the confidence to stay cool and deal with the problem, you are likely to end up very much a statistic.

The way I see it, if I lose my pressure guage, the dive is over. We're out of there. My personal feeling is that if the team doesn't have enough gas to get out at that point [which would make for an egregious gas planning/management failure], I don't think I really wanna know ]. You can either worry about your gas, or be secure in knowing you planned correctly and there -is- enough. Taking the time to worry about how much you -actually- have is just an unnecessary distraction IMHO.

Hi Spectre

Also here, no excuses. You raised a valid point, although I have not mentioned overhead environment, so far. But taking into consideration that the DIR diving emerged from cave diving, it is a valid point.

I agree with you on what you have said. Everything is absolutely o.k. from the rational standpoint. Only, who or what tells you that you stay cool if a calmity occurs? I know, a lot can be anticipated by schooling and training - my thought just circle around the residual risk of irrational behavior pattern by unvoluntary emotional overcomes. And I am convinced that any person has his/her personal stress threshold. So why not anticipate?