DIR with a Double Hose Reg

[Danny D]

Yes, this is true they are not the same.
However, lets pretend that the OC double hose is a rebreather and you have a 7ft second that you could donate.. Could you not use the rebreather DIR rules for a set of doubles with a Dble Hose reg and a 7ft 2nd ? No I guess you can't because you wouldn;t be able to still have the air go through the Dble hose if there was a failure...

I just wanted to bring something a little different to the board for discuddion that all everyone has good points.

 

[scubafanatic]

......... about the OOA rebreather scenario......the consensus view in an OOA emergency is the OOA diver will most likely go for the 1st working regulator he/she sees, and grab it with little/ no warning....which will flood the rebreather loop. Now you've got 2 divers having to do good-old-fashoned buddy-breathing, on maybe a 20--30 cu.ft bail-out bottle....not a pretty picture!

Karl

 

[John C. Ratliff]

I have a twin manifold set up with two regulators off two different valve placements on a set of doubles. Sherwood made a valve in the 1970s that would handle this situation. I have my double hose on the center post, and a single hose on the tank post, which I have oriented backwards and on the right cylinder. This would give two completely independent systems.

DIR is based upon a concept that the regulator will fail, and that backup is necessary. This is now necessary, due to the complexity of the regulator itself, the number of O-rings involved, and the lack of maintenance on the regulators. By adding this complexity, they have also added to the potentials for incidents involving gear/human interface situations.

Remember, when you add a safety measure, that measure must also be evaluated for the safety problems the particular solution to a different problem could present. It's called, in safety language, a Failure Modes and Effects Analysis. The more measures you have, the more potential failures you have. Components are normally analyzed for what a failure will do (what effects it will have) upstream and downstream of that failure in an industrial setting. In diving, it would be what measures that failure would require of the diver, and how it would affect the gear around it.

For instance, the most redundant system you can have is two separate regulators on two separate valves, and switch between the two regulators (each with their independent octopus regs and SPGs). But if their is a failure in one regulator, the air is shut off. Therefore, one SPG will read zero pressure. If a diver unfamiliar with the system tries to access the octopus of the shut-down system, he could be in for a surprise.

Two-hose systems have very few moving parts, especially for the single-stage units (Mistral and Viot 50 Fathom), and these parts are not dependent upon O-rings. They may leak, but failure is less probable than with a system that uses O-rings. Therefore, with the double-hose/single-hose duel regulator system, that diver is probable less likely to encounter a failure that with some of the DIR equipment configurations.

SeaRat

 

[Lane Zimmer]

scubafanatic once bubbled...
......... about the OOA rebreather scenario......the consensus view in an OOA emergency is the OOA diver will most likely go for the 1st working regulator he/she sees, and grab it with little/ no warning....which will flood the rebreather loop. Now you've got 2 divers having to do good-old-fashoned buddy-breathing, on maybe a 20--30 cu.ft bail-out bottle....not a pretty picture!

Karl

What's neat about the RB 80 is that there is an integrated OC bailout switch on the mouthpiece. Having good team awareness will rule out the little/no warning that your buddy os OOG. Typically, light signals are used to get a buddy's attention before they even reach each other. All the donor has to do is turn the switch and he's on OC, which takes less than a second. Another neat thing about the RB 80 is that the long range divers use double 121's filled to 3500 for bailout, plus stages used to drive the breather. That equates to about 300 cu.ft of bailout on their back plus whatever is in the stage, which is plenty. The donor won't have to buddy breathe because he still has the backup reg around his neck, while the OOA diver has the 7ft hose.

The RB 80 is really different compared to some other rebreathers out there.

 

[Danny D]

HAHA

Ok how about this situation.....

1. double tanks...

2. That manifold that has the airpost in the middle and one on the left post ( I think it is a Seatec maybe ?)

3. Royal Aquamaster Double hose regulator with a rebreather SDV O/C bailout integrated mouthpeice. The Royal is mounted on the center air post.

4. On the left post is an 1st stage and second stage with 7ft hose,
bc inflator hose, and a lp hose running to the double hose mouthpeice reg as well as a hp with pressure guage


This setup should satisfy all the requirments of DIR in the Rebreather sense of it.

 

[pipedope]

Is not unique to the RB80.

 

[Lane Zimmer]

Not quite...

4. On the left post is an 1st stage and second stage with 7ft hose, bc inflator hose, and a lp hose running to the double hose mouthpeice reg as well as a hp with pressure guage

In the event of a 1st stage failure, all the second stages will freeflow, including the OC bailout switch. If you shut this post down, your buddy will not be able to use the 7ft reg because your reg will freeflow like crazy. Even if you turn the switch to use the DH, the OC will still dump unused gas.

Also, if the right tank neck o-ring or burst disc fails, where do you isolate? I'm not sure about that type of manifold, but wouldn't shutting down the middle post also turn off the DH reg? I'll have to check. In this situation, what does your buddy have left if he goes OOG?

Now, what do you do when the diver uses a drysuit and heavy steel doubles? You won't be able put both inflation hoses on the same post because you lose redundant bouyancy.

My 2 cents

 

[Lane Zimmer]

I didn't claim it was unique...I'm sure others have it. It's just a neat feautre to have, and it's a breather that I'm familiar with

 

[Danny D]

NONONONON i want to revise what I said last night


Middle post has double hose on it with two lp hoses comming off of it. One is the reg for the O/C bailout integrated mouthpeice, the other is for the bd inflator.

Right post has another first stage with a 7ft hose and reg , also the hp guage comming off of it.

Now this is the exact set up using a rebreather for DIR so it can be used with the old Dble Hose reg becuase it is the same principle. If your dble Hose first stage fails (which is almost unheard of , but if it does) then you can still get the air from the Bailout reg comming off the Dble Hose. this is possiblebecuase it comes from a unrestricted compartment in the back of the reg body(nothing can block the flow of the gas to the Bailout unless you bend it shut with a hammer).
So whith that said you now have your reserve air. Onto your buddy. The buddy system comes off that left post. Just like with a rebreater their is one 7ft hose and it is seperate O/C for your buddies bailout purposes if his fails. So I think that now satisfies all the requirments except for the isolation valve on the tanks?

 

[Lane Zimmer]

Still not there...

You still have no way of isolation. I never heard of a manifold with 3 posts. If there is such a thing, please give me some details. I'm curious to how it works.

As far as the hoses, you have be quite confused.

You have the 7ft hose comming off the right post with the spg. On the left post, what length hose do you have? is it another 7ft or something shorter? Also, if your donating from the left side, you run the risk of the post "rolling off", leaving your buddy with nothing. Running out of air twice is not going to go down without a big panic.

Let me sum up the gear you have in this setup:

2 separate 1st stages
2 second stages
PI hose
Single SPG

What you have there is the basic gear for diving doubles in both hogarthian and DIR, just in a really different configuration. However, a basic fundamental of hogarthian diving is being broken. With the redundancy of the 1st stages, why even use the DH reg? Leave it home and use the ones you have.

Now this is the exact set up using a rebreather for DIR so it can be used with the old Dble Hose reg becuase it is the same principle

Nope. There are no regulator hoses that come off the rebreather to supply gas. All LP hoses originate at a 1st stage, either from the doubles or a stage. The breather is plugged in like a second stage to recycle gas, making it necessary to bring along. The left post has the spg, backup reg and drive gas for the rebreather plugged into a switchblock. The right post has the 7ft hose, PI hose and OC bailout for the mp.

I hope i'm not comming off as a "DIR a**hole". I'm trying really hard not to. I just want to show that it's less than optimal to use the DH reg on OC.

My 2 cents