Argonaut Kraken exhaust loop flooding issue...?

[reefrat]

There is also the way that Apeks make their exhaust valves. Instead of multiple ribs (6) extending from the center of the valve they have one thicker rib that forms a bar across the mushroom valve, it works well but you need to make sure it is installed with the rib positioned horizontally or exhalation resistance increases discernibly.

 

[Fibonacci]

Exhaust efforts will be a bit higher, whether unacceptably so I don't know... the tapered ribs should give a more progressive release.
At present I would happily accept a higher WOB vs random exhaust loop floods!

The ribs still need a small radius added at the apex as you can see a tiny red stress riser where the ribs join the hub.
I will look into getting a couple rapid prototyped for trials...

Edit: See attached pic of rub marks on the diaphragm where it has impacted the exhaust valve, not sure if this is related to the flooding issue but those rub marks look odd.
The two crescent shaped rub marks are from a stand-off rib on the exhaust valve housing designed to prevent the diaphragm from holding the valve shut.
I split the can to check for debris and the diaphragm went back in a different position.

 

[Fibonacci]

Playing about with a Royal Aqua Master fitted with a DBE (virtually identical to the Kraken's exhaust valve set-up) and discovered the edge of the valve can catch up in the support spider and stay there.

Wondering whether the diaphragm being so close (see image above) could push the valve in a certain way where it catches up till the next breath and may contribute to the hose flooding issue?

 

[tbone1004]

@rhwestfall I doubt WoB on exhale would be consequential since the exhaust valve basically sucks the air out of your lungs as it is above your head so WoB on exhale should actually be a negative value. Increasing the resistance there wouldn't really matter. Curious to see about the diaphragm @Fibonacci. I may have to go around some of my parts bins and see if I have an Apeks valve or something else comparably sized to try out

 

[rhwestfall]

you say "sucks" - which would then explain the flooding as it is being held open with moving gas until the water (leaking in) replaces the volume of air in the hose... it would also mean an induced free-flow all the time...

 

[TectonicDrake]

Hard exhaust is the same issue I'm having with mine. I'm glad this post has given me a few things to try before sending mine in! Gonna get an o-ring kit for the dsv and maybe a new exhaust valve and try the silicone seal trick.

 

[tbone1004]

you say "sucks" - which would then explain the flooding as it is being held open with moving gas until the water (leaking in) replaces the volume of air in the hose... it would also mean an induced free-flow all the time...

not quite.
The inhalation diaphragm is still above the exhalation diaphragm, so it can't "suck" harder than the inhalation diaphragm needs to be "sucked" to induce a freeflow provided the cracking resistance is set higher than the distance between the two diaphragms.
It does explain the flooding though, but with the diaphragm facing "up" when horizontal, there isn't a whole lot you can do about it

 

[Fibonacci]

Hard exhaust is the same issue I'm having with mine. I'm glad this post has given me a few things to try before sending mine in! Gonna get an o-ring kit for the dsv and maybe a new exhaust valve and try the silicone seal trick.

I DID send mine back to the US at Bryan's request after the HP seat failed as well!

He serviced the Kraken and replaced the HP seat for free which was good but the returned parts show a very strange wear pattern where the HP Volcano Orifice had engraved the HP Seat so far off centre it hit the inner metal support for the pin, venting HP air through to the loop.
I have pulled apart quite a few Conshelf XIV and Cousteau SEA's and never seen this sort of very off-centre wear pattern. Bryan was at a loss to explain why this would occur, which makes me feel uneasy about it re-occurring.

New o-rings in the DSV, new exhaust valve in the Kraken can, wagon wheel valves OK, hoses all in near-new condition, clamps tight. The exhaust loop STILL floods randomly in specific conditions... !

Body horizontal, head slightly down, paused after just breathing out.
I want to be able to concentrate in this position, waiting for some tiny critter to move into the right spot for the shot, not waiting for the dreaded glick-glick-glick as the loop floods!

The Kraken can exhaust valve is very thin and flexible silicone rubber... as pointed out earlier, I think the volume of air in the loop pushes it up in certain conditions allowing water to flood in. It takes a big effort to push out the water in a totally flooded loop, usually needing a drastic change in body position to assist... very disconcerting!

There are now FOUR independent reports of this Kraken loop flooding problem, and quite possibly many more.
I think it is now time for Luis and Bryan to step up, investigate this matter properly and issue a fix.

 

[TectonicDrake]

I have not done really any troubleshooting since I just received my Kraken used and only been on one dive and some pool practice with it. I have a DSV rebuild kit coming, and the person I bought it from had different hoses on it than what it came with. I've got original hoses coming as well. The exhaust seal looked good last night if it happens again with the new hoses and the dsv rebuild. I will replace that exhaust valve and possibly add some silicon seal to keep it pulled down. I'll keep this post bookmarked and come back after I've tested it.

 

[Luis H]

A flooded hose will happen if the valve is not sealing well. The valve has to be only stiff enough to hold their shape. They are not intended or designed to hold back any pressure. They just have to hold their shape and keep contact with the sealing surface.

I already suggested to put a drop of silicone seal/glue under the arrow head in the stem to make sure the valve center is held tight against the spider support. I have seen mouthpiece valves were the stem is a just a bit long, the valve is a bit loose, and they leak. If the center of the valve is not tight against the spider, the edge may not make good contact with the sealing surface.

The exhaust valves in the Argonaut are basically off-the-shelf standard design. I do not know where Bryan gets them or who makes them (I do not work for VDH and I have no financial involvement with VDH or the production of the Argonaut).

I am sure that Bryan picked those valves from the same supplier that makes them for other scuba regulators. They are the same that are used in the exhaust of some single hose regulators.

I do not have drawings for the valves. I didn’t design them. I just designed the cans (and the rest of the Argonaut using as many standard parts as possible).

The interface for the valve is just the same as in other exhaust valves and it is very possible that many other mushroom valves will fit it.

Adding stiffness to the valve will not improve the sealing edge contact unless the issue is an uneven or rough contact surface. The sealing surface of the can was designed to be flat and smooth to provide a good sealing surface.

I have seen a very small piece of sea-weed stuck in the sealing surface of a single hose exhaust. It was causing an amazingly annoying amount of leak.

A very small leak during the exhalation is normal (but not flooding). I have not experience any flooding in any of my regulators since I have been using mushroom valve exhaust. I have had flooding many years ago, but that was with a duckbill. I never found the problem, but I am sure it was just some debris/ foreign matter.

The valve getting caught under the edge can be a problem and that is why the spiders have 4 to 6 legs to support the mushroom valves from getting folded back with back differential pressure.

If you have had flooding, more than once, there is something wrong with the interface between your valve and your can.

You can try checking the sealing edge doing a light test. In a dark room shine a small light into the exhaust horn and see if there is any light leak around the edge of the mushroom valve.