Argonaut Kraken exhaust loop flooding issue...?

[Fibonacci]

Was just noticing the difference between the aftermarket hoses and the original hoses I just bought. They fit vastly differently and the hose thickness was much different so the clamps maybe couldn't honestly tighten enough to get the job done on the hoses he put on. I've thrown an ip gauge on it and it will go to 135 and maybe creep 4-5 psi to 140 and won't budge. From what I can tell this is completely normal.

Yep a stable IP of 135 +/- 5psi is fine.
Looking forward to the results of your dive test!

 

[TectonicDrake]

One of the fixes solved the issue. It stayed clear the whole time. Im not sure but I maybe got a very very small amount of water in while doing a very weak exhale at one point. But it was a miniscule amount. Didn't even require any extra effort to clear it. It was nowhere near plugging the exhaust so I just rolled it out and it never happened again. So the caulk is a great trick.

 

[lexvil]

Dove the Kraken today, 50, 65 min. No flooding or leaks at all. All I did was put the G250 exhaust mushroom in and the one that I feel may have done it was lap the seating surface until the low spots were evened out.

 

[Fibonacci]

Good news, so the root cause of the flooding problem does seem to be the uneven surface of the spider!
Roughly how much material did you need to remove?
Did the G250 diaphragm have ribs or need silicone sealer under the arrow?

 

[lexvil]

Good news, so the root cause of the flooding problem does seem to be the uneven surface of the spider!
Roughly how much material did you need to remove?
Did the G250 diaphragm have ribs or need silicone sealer under the arrow?

No idea how much was removed but it was very little, my hope/guess is the tiny low spot just gave a path for the leak under whatever specific condition encouraged it. The G250 valve looks and feels, to me, identical to the original.

I don’t nor can I claim the problem solved because of the intermittent nature of the problem, I did one dive without problem, your mileage may vary. It is promising.

 

[Couv]

@lexvil Could I impose on you to update this thread with your experience since you last modified the DBE? A detailed description (with pictures if possible) of the changes made would be much appreciated. I just spent two weeks with this same annoying issue albeit intermittent.

If I followed correctly, you abraded the valve seat until flush, replaced the valve with a G250 valve, and beefed up the valve stem arrowhead with sealant. But I don't want to start sanding/bonding/changing until I have a clear understanding-especially if you've had a recurrence.

BTW Before this trip, I did the @rhwestfall "o-ring treatment" to the valve stems. I think I used size -006 seals. All the cage valves seem very air tight, but the exhaust valve is still suffering.

TIA

Couv

 

[lexvil]

Hi Robert, not a lot of testing since, playing with single hose stuff, I’m going to Curacao next week, I may pack the kraken and do more testing, if not I’ll try it out in Monterey. Diving has been spotty locally so the kraken has been resting. I never did the beef up only the lapping and the G250 valve.

 

[Fibonacci]

@couv I will be diving with my 'overhauled' problematic Kraken over the Easter break, a mix of fairly deep and shallow dives is planned.
The spider is now totally flat after resurfacing by VDH on a replacement top can... certainly improved on the light leak test vs the original which leaked like a sieve!
Will report back...

 

[John C. Ratliff]

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.

View attachment 483495

I'd like to add another potential reason for the flooding. Your photo of the diaphragm shows that it at times the exhaust mushroom seals against the diaphragm. Upon inhalation, it will pull down, and has the potential to open the exhaust mushroom.

I mention this as it is similar to the problem I had with my Healthways Scuba Deluxe regulator. But mine was the opposite problem, as I was using it with no exhaust valves in the mouthpiece. The original Scuba Deluxe had very small exhaust valves in the mouthpiece and I was hoping that I could reduce the fairly high inhalation and exhaust resistance by removing them. What actually happened was that my exhaust exhalation backed up into the intake can, and pushed the diaphragm out enough to completely block the exhaust mushroom in the can. I solved that problem by glueing a nut to the area just beyond the exhaust mushroom, so that the diaphragm could not seal against the exhaust mushroom.

In your case, with the AK, it appears that the mushroom makes a seal against the main diaphragm, and upon inhalation, opens it. This is a function of the improvement in both the main diaphragm and exhaust mushroom, which are both now much more flexoble than their peers from the vintage era.

I know that you think the small knobs on the exhaust spider is the problem, but I don't think that's the main problem. It could contribute to leaking a small amount of water into the exhaust loop, but probably not the massive flooding you reported here. That is more likely the main diaphragm suction I mentioned above, abpnd fitting and ribs won't help that problem. What will help is a physical barrier that prevents the diaphragm from sealing against the exhaust mushroom. It's the same problem, in the opposite direction, as I had with my Healthways Scuba Deluxe regulator. Healthways recognized the problem, and in their Healthways Gold Lable Scuba (third generation), incorporated a brazed metal bumper to keep the main diaphragm off the exhaust mushroom.

So if the problem continues (which I suspect it will), try glueing a plastic piece to hold the diaphragm away from the exhaust mushroom.

SeaRat

 

[Fibonacci]

Thanks for your insight... could well be a contributor.
The original pic earlier in this thread shows rub marks where both the exhaust valve and the stand off rib had been impacting the outside of the diaphragm quite hard. Suction when inhaling could affect the exhaust valve... but the standoff rib is meant to limit proximity of the two components.

The main flooding happened only in certain positions, but it did happen quite consistently:

Body horizontal, head slightly down, breath cycle paused after having exhaled​

To me that indicates that sealing of the exhaust valve against the spider is the main cause... but perhaps not the only cause.

Is it a case geometry issue as well?
Surface area of the exhaust mushroom valve vs captured volume in the exhaust hose overcoming clamp force and lifting an edge? The hose flooded in about 15 seconds so quite a volume of water entered.
The Nemrod Snark III has a huge exhaust valve with an integral central standoff boss and two pins for example...

Compare to the Aqualung Mentor exhaust with three radial standoff pins for the diaphragm

Will do more tests over the break and add to whatever @couv and @lexvil may find out...