Review Dräger Shark teardown

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Geo7

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Hi all, for a long time I was curious about the Dräger Shark, and dove it on a full mask once, but never bought one. The parts kits were outrageously expensive and I kept a note with a warning to not pick one up cheap that needed service. Then my friend @Golan68 (who does his own maintenance on his german cars, motorbikes and Scubapro Pilot) bought one and took it apart. We discovered typically quirky but impressive german engineering (think rear-engined sports cars). So… I bought a few regs and this thread is the result. @Golan68, @rsingler and @lexvil got their hands on some Shark regs as well, and our goal with this project was to learn about this amazing reg design and share our findings for your entertainment and perhaps for reg manufacturers to revisit some ideas that Dräger applied. I am initiating this thread, but @Golan68 kickstarted this and the rest of the team contributed a lot and will chime in. It’s a discovery in progress.

The Dräger Shark is a discontinued reg, with part support dropped at the end of last year. Some retailers may carry parts at outrageous prices like 155 Euro for a 1st stage kit. Dräger is a german company that we here know for their military LAR-V rebreathers and the recreational Dolphin rebreather that was an abandoned attempt to make recreational divers happy. Dräger's business is in the medical market, and they supply breathing equipment and other safety gear to firefighters. Dive gear is a small part of their business. The Dräger Shark was intended to be used mainly with the Dräger Panorama Nova Dive full face mask by law enforcement divers, military, commercial and rescue divers. In short, well funded agencies that could afford the maintenance. The Shark has been replaced by the SECOR 7000 which is a more conventional end-barrell balanced design.

Why are we interested in the Dräger Shark? Well, the 2d stage seems a close relative of our beloved Scubapro D400. Both have a center-balanced valve and co-axial exhaust membrane. And it is “Made in Germany”. So expectations were high.
 

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Geo7

Geo7

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Let’s look at the 2nd stage housing first:

It is quite small, meaning it has miimized dead space for CO2 buildup in a full face mask. The plastic used seems to be ABS, not the nylon of modern regs, but it seems sturdy. The EPDM exhaust cover twists on and off easily, what a treat compared to a D400! It actually fits a D400 well enough to be useable. The diaphragm retaining ring has a bayonet, and no friction washer. You are supposed to wet the membrane to twist the bayonet over it.

The Shark comes as a basic housing, on which two different mouthpiece adapters are screwed. One for a regular mouthpiece, another for the P-Port of the full face mask. Very important: To unscrew either mouthpiece adapter, you have to losen the internal locking screw first, otherwise you’d damage the locking part of the port adapter. The mouthpiece adapter interchanges with a P-port for the Panorama full face mask (hereafter FFM). Both the P-Port tube and the mouthpiece have a diffuser built in that channels the air but probably limits Venturi to prevent free-flow.
 

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Geo7

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Next, the valve assembly.

This makes me wish Scubapro would adopt this all-metal construction, although I like the D420 and can't find a fault with its plastic design. The Shark valve is similar to the D400 but is fully balanced, removing the downstream bias (in fact Dräger state it is an upstream valve) to make it work with a wide range of IPs (6-14 bar / 90 - 200 psi), and make it possible to put an OPV on the hose for FFM use so a free-flow won't blow the mask off the face, nor create noise to interfere with communication over the FFM. For normal use there is an OPV in the end-port screw, and it vents into the reg.

The central valve housing part must be a-magnetic steel like 316 or better. There is an old version that seals the bottom part of the poppet with an aerospace type spring-loaded teflon seal. Wow, I have never seen anything like that in a SCUBA reg (nor anywhere else, because I am not an engineer).

Several 2nd stages our small group has were leaking past those exotic seals that need replacement, but that exotic seal is no longer offered by Dräger. One used second stage I disassembled had an o-ring instead of the exotic seal. That seal is not captured by a groove in the old version but it seems to work as the IP holds it in place. We may need further testing of this improvisation to provide a verdict (or perhaps others have experience with it already and can let us know).

The next part is pretty impressive: The original style valve housing seals the flow with a metal cone against a well captured o-ring that is not easy to remove from the valve housing. Brilliant, as you don't need seats. instead, the o-ring seals the airflow and seems almost maintenance free. The service intervals for the Shark recommended o-ring changes every year, but the valve was apparently left alone and serviced or replaced by the factory every 6 years. Golan finally managed to remove that o-ring.

The original version has not been serviceable for a while now, and instead the old valve housings were exchanged for a new upgraded version (there was an upgrade kit available). The new version contains a simpler valve housing that lacks the o-ring and provides a sharp metal edge to seal against a new type of cone that is teflon coated. I can see setting marks in those teflon cones, but guess these last a long time (if you don’t scratch the sealing area while disassembling). The new popped has an o-ring groove like the D400. What is included in the annual 2nd stage parts kit is almost nothing, just 4 o-rings.
 

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Geo7

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Last not least the 1st stage:

Are you ready for this? A dry-sealed balanced piston. No Schrader valve, no constant bleed (Sherwood), no Christolube filling (Atomic). It is however horribly over-compensated for depth (0.5 bar per 10 meter / 7 PSI per 33 feet). This did not matter for the intended use case of commercial diving down to 40 meters / 130 feet (below that they use Kirby Morgan gear).

Under the EDPM cover is a metal plate that transfers the environmental pressure to a massive spring holding plate that contains an allen screw that positions the seat (the seat is embedded in a metal case). Three steel pins transfer pressure to the main piston. The main piston is short and contains a floating seat in its center. It seems the seat is fixed by the allen screw, and the spring-loaded piston moves against it to seal. When the piston is pushed into the reg, the air flows through five radially positioned ports in the piston into the LP chamber and from there into the LP ports.

The piston also has a narrow extension that extends into the HP area of the reg, where it is sealed by an HP o-ring, but also a teflon support ring, probably to avoid extrusion, as public safety divers in Germany (the intended market for the Shark) often dive with the the Dräger PSS set using 2 x 5L 300 bar sets (2 x 53 cuft at 4250 psi). We recommend to use an airgun to remove the HP seal, as we already damaged two of them and the pair costs 50 euros to replace.

To reduce friction of the piston, it is sealed with a quad x-ring that is backed by a thin teflon support ring. Another wide teflon anti-friction ring is on the piston. Again, I have never seen this in SCUBA regs…

The tricky part of this reg is the unlocking of the 1st stage, as the entire piston complex is held by a safety spring that acts as a locking spring. I had to buy a bearing removal tool recommended by Golan and carefully unwind the flat safety spring from the grove above the plate that holds the main spring. This only works if compressed by the bearing pulling tool. But careful: you have have to remove the allen screw before you compress the system, as it could damage the seat. Seats and the locking spring are hard to come by. You’d probably be looking at donor regs. Working on this 1st stage is tricky, but the reward is a dry-sealed, compact, high performing 1st stage. The hose routing is actually quite nice too.
 

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Geo7

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Overall, I am impressed by the engineering that went into this reg. Actually you could argue that it is over-engineered, and I love that. I like how the exterior design is simple and "form-follows-function" but internally they tried to perfect this reg with state of the art materials and designs from pneumatic, hydraulic or aerospace applications.

The closest thing to this you could buy today is a Scubapro D420 which has an injection molded plastic valve housing, which may perhaps be more advanced and better performing than 316 steel, but I’d still take steel or titanium. Sadly, this seems a thing of the past. Think of how many more manufacturing steps you need in order to cut the valve housing, and then you still have to make a barrel for it. Compare that to the completely round Apeks barrels or Scubapro plastic barrels and you can guess what the future will look like.

Looking at this discontinued design, I have to ask myself whether it is worth going to such a complex to manufacture design over a Mk10/G250 or Mk25/D420? Has reg design reached its peak in the 1990s, or were the Dräger engineers able to add some tricks that are worth considering in future reg designs? The Shark has the reputation of a robust, bulletproof design. I bet it’s advantages can only be discovered by diving it day-in-day-out in environments like the german North Sea while working in a commercial fashion. It is not a reg with low cracking pressure and adjustable Venturi. In that regard I suspect it will breathe better at depth where the large cross section of the the valve opening allows for superior flow. Stay tuned for further reports…
 

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lexvil

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Thanks for posting this George, I plan on doing some extended use this weekend, these are nicely engineered and well made, first stage is exceptionally intriguing in its design.
 

axxel57

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Thanks a lot, guys!
I bought me an Uwatec Nemo, which seems to be the same as the Draeger Shark, last year, and had a lot of fun finding out how it works and dismantling the 2nd.
Without schematics or manual I didn't find out how to finally dismantle the valve, but it was clear that it is a Central Balanced Valve.
I didn't come up with the idea of a completely balanced valve, that's why the OPV irritated me.
When I tried to open the 1st I failed to remove the safety spring from the groove, so I left the reg for the moment to first find more information about it.
The only thing I finally came up with, was the information that after removing the Allen Screw one had to compress the whole inside to remove the spring.
I tried, but I don't had the right tool and it did not move, so I was not sure if the information was correct, so I left it for later.
Thanks your work I guess I will soon go back to work with this quite special design.
So guys, thanks again!:bullseye:
 

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Geo7

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Very nice, thanks! I have to give credit to Golan for figuring this all out, as we had no manuals at the time...

In the 1990s Dräger's venture into the recreational diving market used UWATEC as a distributor for the rebreathers and the regs. So yes, the Nemo seems identical to the Shark to me, and I have taken both apart. Differences seem to be between subsequent iteratios of the reg.

The early versions of the 1st stage held the EPDM cap o with a snug ring like yours, and they then used a tube that gave better protection (I'll send some more pics soon), but is very hard to remove. It also seems the yoke conversio kit might have been manufactured by Aqualung? We are sitting tight for Rob to post his analysis which will likely blow us away as usual.
 

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