Off-Board Gas Block

(Sept, 2009)
Curt McNamee, from Silent Scuba, LLC, has put together a 3-gas, gas block that can be used on almost any rebreather. So far, he has developed kits for the KISS Classic, Sport KISS, and all the rEvo models. 

A new users perspective and installation
 
The Quick Facts and Benefits:
 
- Eliminates the existing KISS O2 Add valve, bleeder and hoses
- 3 gases now at your fingertips- Dil, O2, and off-board gas
- Fast and easy Dil flushes
- Now the Primary Dil addition method along with the current KISS ADV as backup
- Easy to add O2 below 300 ft (when your on-board O2 flow stops)
- Uses standard, easy to find and affordable, LP (BCD Style) Quick Connects
- Nice and easy to control all your gases when scootering
 
Web Album
The Gas Block
 
In the picture, you can see the Dil (orange) button is raised, for easy location. Next is the O2 (yellow), then off-board (black) buttons. The graphics on the block allow for easy reference of where each feed connection is made.
 
A kit is being developed, along with detailed instructions (including a video), by Curt McNamee of Silent Scuba.  The kit will contain all the required parts, and customisable hoses, for a perfect fit for each diver. 

     
My completed Classic KISS kit                                                        Installed & Ready to Dive
 
 
 
The Story and Install Steps:   (Scroll down for install pics)
 
So I decided it was time to attach an off-board set-up to my Classic KISS (CK). After looking around for existing solutions, and ideas to make my own version, I settled on working with Curt McNamee of Silent Scuba to adapt the 3-gas Add block to my CK in a similar method he used to attach it to rEvo rebreathers.

The project started with several emails back and forth with Curt to determine the best approach for attacking the unique aspects of the CK, in relation to the rEvo. The CK's conversion is complicated by the fact that the existing O2 add button is also the bleeder valve. Curt did a great job of sourcing a combination bleeder/filter/check valve to be connected in the system alongside the new add-block.

Along with the bleeder details, we also needed to work out the best way to deliver the gas to the head.
 
As you may know, there is an 'extra' port into the head opposite the factory O2 port - we decided against using that port, as it connects into the Inhale side of the head, and the risk of an O2 spike was too great for comfort, given the lack of mixing that would normally occur while traveling through the scrubber, if the gas was added on the exhale side.

The only logical way to proceed was to have the new gas block's return line enter the head along with the bleeder assembly - as I was not wanting to drill holes into the head. I've heard that you can use an appropriately sized straight thread to connect to the pipe-threaded port used in the head, but this appears to be taking a chance of damaging the threads, and therefore the head - not something I wanted to risk!!  
 
After some research, we decide to go with a T-connector what used the same pipe-thread as the existing elbow as our primary approach, with a couple of back-up plans, just in case, consisting of various adapters and swivels.  From there, it's easy enough to adapt to standard Scuba connections.

With all the parts ordered, the journey was about to begin...


As soon as I got home from work in the morning (I work nights), the car was loaded up with all my gear for a weekend of tinkering and test diving. The timing of my visit worked out great - Mel was teaching classes this same weekend, so the plan was to complete the mod Friday and I'd accompany the class during their dives to test out the mods. 

I headed down to Curt and Mel's place late morning on the Thursday of the Labour Day weekend (2009) - Timing my arrive for just after dinner. This would give me time to settle in from the trek down from Vancouver (BC, Canada) to Seattle, Wa - Any of you that has had the joy of crossing the boarder on a long weekend know what I'm talking about.  

Getting across with a car load of dive gear, including tanks, BOBs, drysuit, and general clothes and things for a weekend does get a few glances from the boarder guards. They really want to make sure you are actually diving for fun! (Not trying to hide contraband, or take a job away from someone.)  After dealing with the boarder, and the hour + wait just to get to the booth, I headed straight down, with a brief stop for gas and dinner. 

I got to the house at around 1730 (5:30pm), which was earlier than originally planned - due primarily to the surprisingly reasonable long-weekend wait at the boarder. I unpacked my gear and started working right away.  

Thursday Evening:
 
This was my first in-person look at the gas block. It is really a nice looking piece of gear!   It is a really robust, has some weight to it which helps to keep it in place. The chrome finish looks very slick, and the 'graphics' help make everything idiot proof (as much as any CCR part can be, anyway). It's comfortable in the hand, and has a ring mounted on the rear and 4 holes in a square pattern that can be used for mounting. All-in-all, you have a lot of options.
 
All the hose connections are made with BCD style QCs. This is a simple, but highly valuable feature - Not only can you accept gas from pretty much anyone (for example, you could steal a little 'dil' from you OC buddy's tank), you could even share yours if needed. This also gives you a way to add O2 from a compensated reg, getting past the inherent depth limitations of the KISS valve.  A secondary advantage - the block is portable! If you have multiple rigs, you only need 1 block. Just set-up the hoses for each unit and move the block depending on which you feel like diving.
 
Because of it's portability, you can move it from one rebreather to another if you have more than one, and take it off when not in use. 
                      
 
The first order of business was the strip my unit right down. Stand, BP/W, tanks, for starters, then I removed the MAV, SS hoses, and the elbow going into the head. I Kept the LP swivel elbow (going into the 1st stage) that was attached to the SS hoses, to be used later. That was followed by both reg assemblies (O2 and Dil).  In the end, I was left with the aluminum case and the head. (I kept the scrubber canister attached to keep it standing upright, as I found it easier to work on like that.)
Now that we had a blank canvas to work on, we were free to start the real work.
 

    
Everything Stripped off - Including the regs              The factory elbow has to go too
 
(I didn't need to remove the Dil Reg and manifold, but I used the opportunity to clean up all the hoses)
 
Fairly quickly, we determined that our primary plan (the T-Connector) wasn't going to work. The hose routing would be virtually impossible to keep neat, or would require cutting away parts of the housing. Obviously, we preferred to avoid either of those options - Good thing for back-up plans!  Using the parts we had available, we came up with what I now believe to be a solution that is superior to our original plan and (my) expectations...
 

     
What we thought we would need                                                                       What we ended up using - Plus a 90 degree elbow, not shown :)
 
We installed a 90-degree NPT to Standard thread Elbow, with the connection pointing straight back. To this, we attached an Omniswivel 2-port 1st stage pivot swivel, giving us port access facing both upward and downward. Since the pivot swivel is a standard LP connection, no adaptors were required for the Orifice assembly, which reduced the length, part count, and complexity of the assembly.
 
The assembly itself consists of a filter, orifice, and an in-line check-valve. The check-valve serves dual purpose, Stopping gas back-flowing through the orifice to the non-compensated O2 reg (while injecting gas), and preventing any water (possibly introduced while connecting to the off-board port underwater) from reaching the orifice. Either cause would create a danger of possible damage or even blockage/failure. The entire assembly was attached to the lower access port on the new swivel.
 
We tried installing the O2 tank and discovered that there was a minor interference between the tank and swivel. We prevented any issues by adding a 'Spacer Hose' - A length of hose that was split along it's length and installed over the existing tank mount. This jogged the tank enough to eliminate the interference.
 
     
Orifice Assembly Installed                  The Spacer Hose Installed 
 



    
Perfect Clearance!                            Top Down View
 
 
By this time, I was getting mighty tired from being up all day, and the night before, so work was stopped before tackling the hoses. We did have a pretty good idea of what was required for the following morning, so it was easy to get to bed without fear of some major problem getting in our way.

Friday:
 
Since I had been up for 33 hours by the time I went to bed, I decided to sleep in a little, and didn't get up until around 0900. (everyone else was up by 0500) After a leisurely breakfast, I went back to the garage to continue the project, with Curt, at around 1000.
 
We used self-installed LP hose connectors, which allowed us to easily make each hose the exact right length. (These connectors are the same sold for hose 'repair.')
 
Curt showed me the best way to figure out the hose lengths (from his experiences on the rEvo) by temporarily securing the block to my HP gauge hose with a zip-tie in the location I wanted it when fully assembled. Each hose already had a QC on one end, which was connected to the block - We could then accurately measure the length by routing the hose to the final position and marking the cut-off point.
 
The O2 supply to the block and the orifice come from swivel elbows on the O2 reg, and the Dil supply comes off the manifold's front port using another elbow.
 
The O2 1st stage to Orifice assembly hose was done in essentially the same way, with the exception of using a 2nd stage fitting rather than a BCD QC style. The assembly is 'permanently' attached to the unit, so a QC just doesn't make sense here.
 
 
    
The O2 Side reg, ready to Install                                      The O2 Side, Completed




    
Swivel on the Manifold, for feeding the block                       The return hose goes over the loop
 

After making and connecting all the hoses, I was surprised to realize we were finished the mod! Time now for the all important first test ... I opened my tanks, the system pressurized, and it was great - no leaks! A few quick button presses later it was confirmed everything was working as expected. There wasn't really a lot more I could do without being in the water, so dry testing was fairly limited.
 
Once we figured out the kit of parts that would be needed, I helped Curt make an instructional video and stills of how to do the mod. I think he's planning on cleaning them up a bit before anyone sees them, so you'll have to make do with my pictures for now. :)
 
Everything was done by 1100. I was surprised how quickly that all came together. I think the video actually took longer than anything.
 
Now that I had a dive-able rig again, I started putting everything back together.
 
I use a custom travel stand, that I designed, to raise the unit up, and for holding my Argon bottle.
For more information on my custom Universal CCR Travel Stand, Click HERE. (Link opens in a new window)
 
Once that, and the BP/W were reattached, I cleaned up the hose routing a little, added my monitoring system (dual, 3-cell computers - VR3 w/URM & a Shearwater Pursuit)
        
 
 
The rest of the day was spent doing some personal errands before having a nice dinner with Curt, Mel, & her students at a local pub. It's nice to relax a little! The remainder of the evening was spent preparing for the test dives (getting my other gear ready) and starting this report.  
 

Test Dives!
 
Saturday:

Woke up at 0500 to prepare for our diving. We wanted to be on the road no later than 0545. As anyone that has done a class with Mel knows, Curt has a hot breakfast ready to go, then it's rush, rush, rush, to get out the door.

The plan was for Alki Cove 2, a nice training/testing site with shore entry.  I've been to this location several times for the various courses I've taken with Mel, so I felt very comfortable getting into the water here for the initial testing.  Those of you that have been here will now understand why we left so early! Alki Cove is a VERY popular site for OW classes, so if you don't get there early parking is impossible and you can't see anything due to silt. ;-)

The day started out pretty miserable - rain and cold - Summer decided to take a break. We loaded the cars up and got on the road as planned. The weather started to clear up a bit on the way, but started raining again shortly after we arrived. Luckily, we managed to find street parking right at the cove.
 
The first part of the dive I spent getting used to the block, how to hold it, and generally taking it easy. I figured out a way to mount it that worked really well for me. I can now EASILY access the controls with BOTH hands. No more needing to pass anything to my other hand to add gas.
 
A couple of habits became apparent pretty quickly - I had to break my muscle memory from my old O2 button - I kept grabbing my pressure gauge by mistake, since I didn't have a button to stop at before getting to the gauge. The other was that even though I knew I didn't need to change hands, I kept doing it!  (I carry my light in my right hand most of the time - I don't have a scooter, so I prefer to hold the light with my dominate hand.)
 
The positioning turned out to be even more perfect than originally planned - because I decide to have my block more central, I can access all my breathing gas controls and suit inflation without having to more my hand more than a couple of inches. It's so convenient, I found I was lightly holding the block just because it was a comfortable place for my arm.
 
A little longer into the dive I started playing with some other options - Adding off-board gas & dil flushes.
 
- I attached my 40% BOB to the external connection and shut down my O2. I ran the unit in SCR for over 30 min with very little effort. It was far easier than trying to do the same thing with the stock KISS ADV. No having to suck the loop way down and using lung pressure - which as you probably know gets old very fast if you have to do it frequently, such as when doing anything SCR. :)
 
- The Dil flush is one place where the block really shines!  If you press the button all the way down, the Dil comes into the loop as fast as you can vent it. You can do an entire loop flush just by pressing the button and letting the gas bubble past your lips. Sure you may get a little water in, but very little - the gas is coming out that fast. This is good for clearing the loop of 'unknown' or dangerous contents, without having to breath it first. You can even 'mash' the block, like with a power BCD inflater, and only press the Dil button, since the others are recessed. Super easy for high speed, emergency, flushes.
 
When we surfaced, I was pleased to see that the rain had cleared and it was actually getting fairly sunny - much more enjoyable.
 
The second dive, also at Alki, was spent continuing to get used to the new controls. A few more accidental pressure gauge grabs, but otherwise, just a nice sightseeing dive.
 
Both of those dives were about an hour long and just a little over 100' (30m)
 
 
Saturday evening was primarily spent preparing for Sunday - Loading up Curt's boat with our gear, and packing my other stuff back up in preparation for returning home after the Sunday dives. 
 
The only change I made to the system was to add a LP Swivel to the external gas connector, to improve routing when connecting off-board.
 
With the Swivel installed for the off-board connection
 
Sunday:
 
Like Saturday, we got up at 0500 and were out the door before 0600. This time it wasn't for parking, but to get  ahead of any traffic, and (I think) to be nice to me by getting back earlier, so I wouldn't need to feel rushed to get home in time for work that evening. The weather didn't improve any from Saturday morning, then got worse from there.
 
We went out to Lake Washington to dive on the 2 Navy Bombers that crashed during training flights in 1956 and 1947. I've been on one the 1956 one a few times before, but it's still a neat wreck. These were purely fun dives - I wasn't planning on doing anything fancy with the new block, other than use it.
 
With the exception of the rain and wind - quite heavy at times - everything went great. The block is so easy to use, and I felt more comfortable with something that was easy to find, and felt nice and sturdy. (The original button always seemed a little small and delicate to me.)
 
One thing I found interesting on these dives (~150' (50m), 1 hour each) is that I actually felt more relaxed than similar dives done previously. Due to various factors (less than 10' (3m) vis, 46F on the bottom, with a nice balmy thermocline to 66F at 40' & darker than a night dive - yes, darker), this could easily be compared to a 200' (60m) or more dive, yet having the ease of use and control of my gas management, and knowing I have more options to deal with any issues, the dive seemed more like a deep recreational.
(Please don't read that to say I didn't take the dive seriously, but that I felt better about it.)
 
A couple of Pics, getting ready to jump in on the first dive:
 
    

 
Final Thoughts:
 
I am VERY happy with this modification. Easier, Stronger, Better than the normal set-up, and uses universally standard QC connectors. By removing the existing KISS O2 Add valve and bleeder system, I have only added a few more parts to my system and feel that the extra robustness, and options, of the off-board kit far outweigh any possible negatives.
 
With the way we set-up the system, the ADV is still available, as a redundant back-up, if needed. If the ADV starts to act up, I can remove the diaphragm and put in a blanking plug, essentially removing the ADV, but maintaining the system integrity. In fact, I believe this could probably be done in the field with minimal materials (a blanking plug) and allen wrench.
 
I do recommend adding the swivel elbow to the off-board nipple. It improved the routing of the hose from my BOB, and didn't try to move the block around. I was using a miflex hose for my off-board connections, so between the swivel and the hose's flexibility, I didn't even notice it.  (You can kinda see it in the above lake pics)
 
 
Thanks to Curt and Mel for supplying the place to stay and assistance in getting everything together and tested. And a special thanks to Mel's students for putting up with me while they were doing their course stuff.

For some additional Pics that didn't make it into this report, including my nifty new hose routing, Click Here.
For imformation on the Universal CCR Travel Stand, Click Here.