Serviceable Gas Injection System for the Dolphin

The depth compensation side of the O2 circuit MUST be removed from the first stage regulator. not to do so, Could Kill You

Its worth pointing out that I like Gordon Smiths method as it works well in deep water. Something we find hard to get here unless you take a shovel with you on a dive. Our average diving depth here is 10m,  30feet

However it doesn't quite suit the type of diving that we do up here in the tropics as we find the needle valve works better for us in shallower waters.

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After I developed the first combination of needle valve and Clippard bypass valve into a compact unit. I realized that sometime it would need to be serviced, however due to its design it was doomed as a throw away device.

I had given a replacement unit much thought but was continually plagued by the same problems of size and the ability to buy off the shelf parts needed to replicate the unit as required.
I could have totally custom built a valve and bypass block but felt that by making something that could easily be built from off the shelf parts, made this system within reach of everyone and not just a select few with the necessary machinery and engineering skills to build it.
Over a period of months I amassed a huge collection of just about every 1/4 and 1/8th size 
brass fittings and proceeded to spend many hours doing what my wife frequently called "playing with my blocks".

I finally came up with a design that would allow easy field repairs and or replacement if required including better physical strength to the old design. Picture below left is the first compact gas injection valve with a Swageloc needle valve  silver soldered to a Clippard manual bypass valve. On the right is the new design slightly larger but still very functional and above all can be built easily with a minimum amount of tooling .

        

The next set of pictures are breakdowns of the valve and its parts, you can click on the image to enlarge it for a closer look. it is worth noting that I took all of the original brass fittings and cut them down as small as possible with a hacksaw and re-tapped some of the threads where required. If you look closely at the pictures you will see that the brass Tee was cut down quite a lot and a tap passed right through the center, making it possible to condense its physical size without eliminating the thread depth of the fittings screwed to it.  

                    

In the next set of shots you can see the valve lying separated for servicing and the original valve next to it for a size comparison. With oxygen not being the kindest on plastics and rubber seats making the unit able to be dismantled makes this so much easier to repair- replace as required without major rebuilds or modifications. Flash it ain't , practical it is. On the right you can see the very first unit made up from brass fittings with no attempt at the time to shrink the size down.

                

Lastly are pictures of the original test valve constructed using full size fittings and physically larger than the others however still dived by Frank Feather, as he says if it ain't broke don't fix it and there certainly is some truth in that saying.


Febuary  2005

Here is the lastest offering after testing and slightly changing the configuration in PNG (December 2004) I decided to stay with the design but try once again and make it smaller. I went back to the first design and tried again and this was the result.

    

Valve on the left is the proto-type and on the right is the condensed version ready to install in the StingRay rebreather.

 

Below is my old page which I tacked onto this one outlining my first valve and construction, I keep it now for interests sake as to what has been rebuilt over the years.

Gas Metering + Manual bypass Valve


Here is a quick page outlining the gas by and needle valve I made.
It wasn't easy to merge the two together and I wouldn't advise anyone to do this unless you know what you are doing as it is tricky
However now 80 hours have been had in the ocean testing this setup it is looking very promising, also having the stop cock is a good safety and transport device should you forget to turn off the o2 or as in my case the valve was knocked in rough seas and I lost a good portion of my o2 during the trip out to the dive site.

Please note :

I am at this moment in the process of rebuilding this system, not because there is anything wrong in the design but assembly and dis-assembly is near on impossibly with this valve so I am going to make another but this time it will be able to be completely dismantled even in the boat meaning I can replace it or service it if I have to in a pinch.
The goal is always to keep it all simple and serviceable with standard off the shelf parts that can be replaced easily.
 

                       

The two main parts  I used are the Clippard Minimatics MJV-2 manual bypass valve and the Swadgelok fine metering valve

B-SM2-S2-A

Below in the alternative to porting the valve block, it
is simpler but a little larger this way but works exactly the same.

Its worth pointing out that I like Gordon Smiths method as it works well in deeper water. Something we find hard to get here unless you take a shovel with you on a dive.

However it doesn't suit the type of diving that we do up here in the tropics as we find the needle valve works better for us in shallower waters.

Copyrightę2001,2002 Tubbies Rebreather Pages

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ou can see with the old design it was a good size and very light weight