Doing AN/DP with FFM, Realistic?

[Addicted2H2O]

I have a couple hundred FFM dives (max depth was maybe 22ft in the aquarium here however) so I am following this thread but with little capacity to input.

But this made me curious...
Where are these people and what are they doing? I hate reinventing the wheel so I would look to these procedures - but I am skeptical they exist. At least locally here in the Seattle area we have a bunch of recreational FFM divers and none of them are doing deco dives on a FFM. The PSD and scientific folks using FFMs are prohibited by our OSHA statutes from doing any kind deco. And the commercial divers who are doing deco are not doing any self-initiated in-water gas switches and not using FFMs either (they are using helmets and have a DSO running the switchblock).

So who's doing "very technical" dives like AN/DP on FFMs? Are they in the USA, EU, Asia?

Maybe there aren't. Maybe I'm an idiot and need to not bother with AN/DP because honestly, I prefer diving my ffm to a conventional mask and reg. But the fact that we have RSV's, even ones being made by a ffm manufacturer suggests there are tech dives being made with ffm's where gas switches are necessary. Or maybe it's just so ffm divers can dives doubles/sidemount. Is it so far outside the realm of possibility to think people do it? And without incident? I'll keep my opinions to myself from here on out and wait until I have actual tech experience before I decide to offer up any other points to ponder from here on out.

 

[tbone1004]

@Sh0rtBus RSV's and switch blocks are intended primarily for public safety divers which is the largest market for them.
Used typically in one of two ways. One would be switching from surface supplied to on-board bailout as is the case with helmets, and the more likely scenario being a switch from primary gas supply to a pony bottle. Prevents them from having to remove the mask if there is an equipment malfunction/failure, or they for whatever reason ran out of gas.
Post #21 on this thread shows a video that @Lake Hickory Scuba made outlining how Bryan uses his switch block which is IME the most common use of the devices.

 

[JohnnyC]

Maybe there aren't. Maybe I'm an idiot and need to not bother with AN/DP because honestly, I prefer diving my ffm to a conventional mask and reg. But the fact that we have RSV's, even ones being made by a ffm manufacturer suggests there are tech dives being made with ffm's where gas switches are necessary. Or maybe it's just so ffm divers can dives doubles/sidemount. Is it so far outside the realm of possibility to think people do it? And without incident? I'll keep my opinions to myself from here on out and wait until I have actual tech experience before I decide to offer up any other points to ponder from here on out.

It's not about keeping your opinions to yourself, asking questions is a great way to learn, you just need to be prepared to have your opinion dissected, and sometimes that's tough to deal with. It's like your OOG sharing plan. I fully admit I straight up baited you, because it was clear that you hadn't critically considered what you were planning (and also I can be a d**k, sorry, I wasn't in a great mood when I posted). But now, maybe you will consider all the angles the next time you want to do something that could have some potential downfalls.

The way we need to approach situations like this is from a problem -> solution thought process, and we need to make sure we fully understand the problem, the solution, and any other problems that the solution presents. If the problem it creates outweighs the benefit of the solution, we need to reevaluate. And that goes for so many things in this sport.

For example, let's say you're absolutely beholden to maintaining FFM use even in an OOG scenario. It has to go both ways, and it has to 1) maintain the FFM, and 2) never leave your buddy with a potential for water ingress. So we know that unplugging anything is out of the question because that breaks #2. So we need to figure out how to plug in without unplugging anything on his side so we can solve both #1 and #2.

Ok, so he needs a port that we can additionally add gas to, so how to we do that? Well, there are non-switching manifold blocks, y-blocks, splitters, that sort of thing. That could let you add gas through more than one port, and there's no fumbling to switch. Ok, so we have the beginnings of a solution. Now how do we deliver that gas? Well we don't want to be one long connected chain the whole dive, so we're going to need to be able to plug and unplug as necessary. Great, we have QD's available! Moving forward, we have the beginnings of a plan coming together!

So what issues do QD's cause? Well, water ingress is one, poor tolerances are another, fine motor control is a third. Well, those three pretty much knock most QD's out of the running because we can't do #2. Ah HA! Swagelok QC6's have a DESO option, they're very well constructed, and they're large enough that it doesn't take fine motor control to function. That removes all three problems! Great! So what we end up with is a splitter manifold that has one hose from the block to the FFM regulator, one hose from the divers tank, and one hose with a QD female on it. We'll use female so that the male side donating can purge the stem if necessary. See, we anticipated a problem that could occur so by simply make sure each part is on the optimal side, it allows us to have a verification of function built in to the system.

Great! We have a solution where we can plug in gas to a FFM diver that keeps the FFM on the divers face, and never puts them in a position where they could have water ingress! We don't have any switchblocks that require manipulation, we don't have any twist-to-lock collars that would require lots of fine motor control, we have chosen hardware that it well-made and toleranced correctly so that parts should mate together without issue, and we have a verification and clearing method to make sure the donating diver can positively insure flow.

But we have a couple problems. How does the donating diver supply gas? Well, there's the QD on a second stage, which we already decided wasn't a good idea, so what's the easiest way to solve that? Well, most second stages have a free LP port, maybe we could just use another hose dedicated to a donatable QC? Sound ok? So that's one problem, and easily solved. But what about locking the QD? The Swagelok's don't have a locking mechanism. Now it becomes a choice. Do we decide the whole endeavor is wasted because we can't lock the QD's? Or do we decide that because the Swagelok QD's have such a positive latching and unlatching force that we could get away without it? Hmmm, that's a tough one. What are your thoughts on it?

What do you think about the solution I've just put forth, and what are some things I may not have thought about? To the other guys reading this, how about @Sh0rtBus gets the first crack at this? We can all use this example as an exercise in thinking through from a problem to a solution. After he's chimed in, let's all discuss some other possible solutions, we all know the simplest is half mask and second stage, but let's just assume that's not possible right now.

 

[Addicted2H2O]

I do see your solution and agree it's a much better option than what I presented. But again I have zero tech experience, and therefore very little previous knowledge of things like DESO Q6 fittings and how they work compared to the standard QD fittings I'm used to in the rec realm of diving. I do agree that sometimes QD fittings can be a bit finicky so yes Q6 would be a better option, albeit a touch more expensive. But we're talking life support gear so it's a necessary cost for ffm diving with regards to gas switching/sharingB. Honestly I should probably be using them for regular single tank diving, too, for the sole purpose of being able to donate air in the event of an OOG diver. So that's something for me to consider.

Did you mean to say most 2nd stages have a free LP port? Or should that read "most 1st stages have a free LP port" for connecting a dedicated donatable hose? If we replace the QD on the 2nd stage, though, that sort of negates using the extra port for a donatable hose. But we have ato account for time to disconnect the 2nd stage from it before plugging it into the OOG diver's ffm, or any other connection that needs to be made. So maybe the donatable hose is a better option and we maintain a regular octo w/o any fittings so we can donate to a traditional diver as well. The main problem I see in all of this when trying to donate to an OOG ffm diver is assuming they have the same fittings to mate up to those the donator has. If it's the donator's buddy, then those chances are probably pretty likely. But if it's an insta-buddy or some other random OOG diver those chances start to dwindle pretty rapidly. Something else to consider would be possibly carrying a pony that's set up for a ffm OOG situation. Then there's no tethering to worry about. But we still have the issue of Q6 vs locking QD and honestly I'm not certain which option presents less risk of failure. So I'm kind of at an impasse as to where to go next.

 

[JohnnyC]

I do see your solution and agree it's a much better option than what I presented. But again I have zero tech experience, and therefore very little previous knowledge of things like DESO Q6 fittings and how they work compared to the standard QD fittings I'm used to in the rec realm of diving. I do agree that sometimes QD fittings can be a bit finicky so yes Q6 would be a better option, albeit a touch more expensive. But we're talking life support gear so it's a necessary cost for ffm diving with regards to gas switching/sharingB. Honestly I should probably be using them for regular single tank diving, too, for the sole purpose of being able to donate air in the event of an OOG diver. So that's something for me to consider.

Did you mean to say most 2nd stages have a free LP port? Or should that read "most 1st stages have a free LP port" for connecting a dedicated donatable hose? If we replace the QD on the 2nd stage, though, that sort of negates using the extra port for a donatable hose. But we have ato account for time to disconnect the 2nd stage from it before plugging it into the OOG diver's ffm, or any other connection that needs to be made. So maybe the donatable hose is a better option and we maintain a regular octo w/o any fittings so we can donate to a traditional diver as well. The main problem I see in all of this when trying to donate to an OOG ffm diver is assuming they have the same fittings to mate up to those the donator has. If it's the donator's buddy, then those chances are probably pretty likely. But if it's an insta-buddy or some other random OOG diver those chances start to dwindle pretty rapidly. Something else to consider would be possibly carrying a pony that's set up for a ffm OOG situation. Then there's no tethering to worry about. But we still have the issue of Q6 vs locking QD and honestly I'm not certain which option presents less risk of failure. So I'm kind of at an impasse as to where to go next.

Yes! Good catch. first stage, not second stage has a free LP port. There are a couple typos in my post that I didn't catch until I just re-read it. Most of my first stages have at least one free LP port, so one extra hose is easy to add. This way you'd still have your FFM, your octo, your LPI, and the additional QD-end hose for plugging in. Obviously if you don't have a free LP port you'd have to look at a different solution.

The important part is the second part of your second paragraph. It's that type of critical thinking that you need to use when you approach problems like this. You're on the right track looking at how all of these different aspects come into play. You're seeing that it's a much more complicated solution than "I'll just have a QD."

Good job on the analysis! I think if you apply that same sort of logical thinking you'll be able to come to a safe solution that works for you and your buddy, whether that's forego the QD option and stick with a normal second and half mask, a plug in option for your backgas, a plug in pony, etc.

And this isn't just a technical thing, your situation is entirely recreational, but the same thought processes apply. Obviously there are considerations in technical diving that make everything more complicated, but it requires the same level of analysis.

 

[tbone1004]

@Sh0rtBus
so this discussion is quite a bit more involved than I think you realize. @JohnnyC, @kensuf, myself and others are not only looking at this from a FFM perspective, but as mentioned earlier, this is a discussion point for CCR diving. In CCR, there are basically 3 types of QD's used, BCD inflators, CEJN fittings *the Omniswivel and cheap type knockoffs*, and QC6's.
2/3 of my CCR's are set up for QC6 *the third one still needs a LOT of work, gotta love homebuilds, maybe next year...* Why? I get really cheap fittings thru work, and it's the current standard for the KUR in cave country so it makes my rig compatible with more people. All of that said, I keep a pair of adapters in my wetnotes that allow me to receive gas from a BC Inflator hose and another one to receive from a CEJN fitting.

My FFM is set up a little funny, and not really the "simplest" option since it is used for both scientific/working type dives, and as an IWR rig. Did some adjustments after watching @Lake Hickory Scuba 's video since he puts more hours on his in a month than I do in a year...
On the mask, I have a CEJN fitting on the second stage to make storage and surface time easier. It used to be directly attached to the block, but having the CEJN fitting on the mask means I can get fully kitted up without the FFM sitting on my head which is nice. Outlet of the switch block has a hose with locking CEJN fitting on it and a bolt snap so it can stay secured if not plugged in. CEJN fittings up here because they are small and light. QC6's are way too big and heavy to put directly on the second stage, and since this QD isn't used underwater, I'm OK with it. If for whatever reason things go really sideways, I can grab that adapter from my wetnotes and plug directly into the mask. It will be really uncomfortable, but it's possible.

My switchblock is setup with a pair of QC6's and has a bolt snap that clips to my left shoulder d-ring. Two reasons for the dual QC6's. For IWR use, there is no guarantee that you will be able to have a dedicated rig and since my regulators all have QC6's on them for CCR use, this allows me to just grab the FFM and switchblock and get in the water ASAP. If it was a dedicated first stage regulator it would involve bottle switching, getting a dedicated bottle, etc. and that's impractical. Since IWR requires both pure O2 and gas for "air breaks" *usually EAN32 for us*, the switch block is necessary to be able to do those gas switches. Like @JohnnyC mentioned, you don't want to ever be without gas, so the solution is the switch block. It also makes it a lot easier for me on working dive trips to be able to switch between FFM and normal configurations without changing regulator configurations.
Switchblocks.
I use the Omniswivel. The downside to the omni is it won't "lock" in one position or the other, though if you switch it by accident, I want to see how you did it. @Dive Right In Scuba did a video on it a few years ago with Mike beating it against the table and it wouldn't move. From a tactile perspective, it's really easy to confirm which gas you are on since the knob points to the side that you are breathing, but it's a bit harder to see for tenders/buddies if you want to incorporate that into a no-tox drill for decompression diving.
The Ocean Reef that Bryan uses is a bit nicer IMO because it has the locking collar for either position that makes it more obvious to a buddy/tender to see which gas you are on. The Sartek is even nicer IMO since it is delrin and is light enough to mount directly to the second stage so now it is right at your face.

Is that setup for everyone? Oh hell no! but my FFM is special use case and has some compromises for convenience with those special use cases.

Now, switch block or just a splitter?
The pro of the switch block is you isolate your gas sources. That is critical to me if you are using different gases, so removing it is simply not an option for IWR. You also get positive confirmation of which gas you are breathing.
With the splitter, you have 2.5 ways of knowing which gas you are breathing. The half is if you run out of gas and plug something in, you know there is nothing left so you have to be breathing offboard. Option 1 is you can shut bottles off. I don't really like that method for backmount since you have to reach back and shut the valve off. Really not ideal IMO and it also means that if you have to go to the other bottle, you have to open the valve. Not great for emergency scenarios. Option 2 is you can set it up for IP priority. With IP priority, you have to set your primary regulator at a higher IP than your secondary. @Luis H has experimented with this using his Argonaut Kraken on a small backmounted bottle for reserve with an IP around 110, then using sidemount bottles with "standard" 130-140psi IP for his primary. The IP differential for this has to be large enough that when you inhale, the IP drop does not go below the IP of the secondary regulator. Depending on your first stage, the differential may only be a few PSI *think Scubapro MK25/Atomic*, or it may be quite high *think Scubapro MK2* based on their flow characteristics. This setup works quite well and is reliable, but without checking SPG's, you can't validate which source you are actually breathing off of. You can put inline shutoffs on there, but by the time you do that, I don't think you are any better off than just using a switch block.

 

[Addicted2H2O]

So then your recommendation is using a switchblock/RSV like the Sartek or Ocean Reef offerings? Also, I'm not certain what a CEJN fitting is. Is it similar to the fitting on the LP inflator hose? I get a bit lost in your description of how you have it all set up. Any chance you could snap a couple pics if/when you get some time?

 

[tbone1004]

@Sh0rtBus
You can't go wrong with any of the switch blocks if that is the route you want to go with. I have access to dealer pricing with Omniswivel which made my choice much easier due to cost, but if I did it again, for my setup I would still use the omniswivel, but that is for my particular setup.

For all intents and purposes, my setup is the same as Bryan's in the video I linked in post 21. I use a different switch block and different quick disconnects, but the general setup is the same.

CEJN 221 fittings are those from Omniswivel, Ocean Reef, Poseidon, Apeks, and several others. They are basically high-flow BC inflators. Piranha sells some that are similar but much cheaper. Unfortunately they are not compatible with CEJN fittings, but if it's just yours, they're cheap and you can get them with locking collars which some people like. @The Chairman had them on his CCR and we were cursing the lock a few weeks ago, but that's because someone was lazy after a dive in the salty stuff.... If you use them in salt, make sure you spin them open and closed in the rinse tank a few times and give them a good soak.

 

[Addicted2H2O]

So the CEJN fittings actually "lock" into place via the spring-loaded collar. So then would they be acceptable for the donator to share gas with a OOG diver as @JohnnyC was describing in his earlier post? As an alternative to both QD and Q6? I'll go back and look at Bryan's video again and pay closer attention to his rig.

 

[tbone1004]

@Sh0rtBus all of the CEJN fittings lock like a bc inflator locks. If you watch the @Lake Hickory Scuba video, you can see on the second stage, there is a non-locking quick disconnect at the mask itself. Several reasons why you may choose to use non-locking there, but it's personal preference. If you look at the switch block itself, there are locking collars on the female side. This works somewhat like the screw collars on a carabiner where when it is screwed into the "lock" position, you can't disconnect it. One extra step to make sure that you don't accidentally disconnect it underwater. Video showing that function below. Downside is they are really annoying with gloves on because the knurling isn't very big, nor are the quick disconnects do you have to make sure you can manipulate them.