Kraken HP seat and other issues

[antique diver]

Very nice drawing!

Now I begin to wonder if the small end of the pin may be sealing somewhat more than on previous models of seat or pin in the small bore at end of seat poppet. Air has to pass through there. Opening the cylinder valve may, as already mentioned, slam the seat into the orifice with more force than if air escaped more readily around the tip of pin. ? does that make sense?
I'm just kind of grasping at straws at this point.

I know that I have posted this photo before, but while we are on the subject of blown seats, this green thing was what I believed to be an Aqualung seat that briefly was available before the newer blue model. Now I wonder if these that I obtained from a dealer were not actually Aqualung, but instead some cheap junk aftermarket job.

This one failed in my RAM and blocked the airflow while I was underwater. I had been below 100', but luckily was finishing up the dive in 25-40' of water. It started being a bit difficult, then pretty quickly ended up completely shutting off the air supply. I think it was about 2013-2014:

The reason for posting this multiple times is to alert anyone using this type to cease all diving with it, and replace with the blue Aqualung item.

[Fibonacci]

Aug 8, 2023 14:59:23 GMT -8 vance said:

I have always thought the Kraken is awesome, and have always applauded the production of a modern DH regulator. I'd love to see more of them. I was hoping Old Mossback's regulator, the SeaWolf, would see the light of day, but it isn't likely unless someone else takes up the mantle.

After I have retired and have way too much time on my hands, I will need a project... hmm...

[duramax]

Hi Fibonacci

Here is the image of the HP seat from my Kraken.

<a data-flickr-embed="true" href="https://www.flickr.com/photos/198929471@N03/53108594947/in/dateposted-public/" title="IMG_6871"><img src="https://live.staticflickr.com/65535/53108594947_21a3d3ce9f_z.jpg" width="480" height="640" alt="IMG_6871"/></a><script async src="//embedr.flickr.com/assets/client-code.js" charset="utf-8"></script>

[nikeajax]

Here ya go mate!



JB

[duramax]

Thanks

[Fibonacci]

Thanks duramax
OK seems very similar offset to the others, around 0.23-25mm

HP Seat Check 3 by fibonacci101, on Flickr

[nikeajax]

So, ummm, shouldn't these seats last, oh, I don't know, 100+ dives? That's disappointing to say the least!

OK, now I'm curious, would these seats last longer at lower pressures?

JB

[SeaRat]

Aug 16, 2023 16:16:31 GMT -8 nikeajax said:

So, ummm, shouldn't these seats last, oh, I don't know, 100+ dives? That's disappointing to say the least!

OK, now I'm curious, would these seats last longer at lower pressures?

JB

The interesting point is that these seats are not seated when off the tanks. It is only when the regulator is pressurized that the seat "seat." So it seems that there are issues concerning the pressurization, and lower pressures could help. But if they are off-center, the lower pressure would only postpone the inevitable. I have seats on my MR-12 and Trieste that are decades old and still work well. Same is said for my other makes of regulators using a diaphragm first stage (original Healthways Scuba, Conshelf, etc.).

John

[nikeajax]

So, if I'm understand you, it's like a piston reg, in that, when it's pressurized, the seat goes slamming-up into the volcano orifice? So would a more resilient seat be in order then?

JB

[Fibonacci]

OK this has been bugging me...
I stripped the Kraken down, Citric acid pickle then an ultrasonic clean for (another) service.

Here's the most recent Kraken Trident HP seat, which seems to have a bit more concentric engraving (but still not good!) and an even circular impression. It was still holding IP OK before I tore it down, but I wanted to try and gather as much info as I could about the problem. Standard data-driven FMEA procedure
Kraken HP seat Trident 2 by fibonacci101, on Flickr

Here's the Kraken HP Volcano Orifice, seems flawless to me and not too sharp!
Kraken HP volcano orifice by fibonacci101, on Flickr

I found an AL Titan in my bag of old regs and pulled it down to check bore measurements, was locking up crisply and holding IP just fine.
The HP bore has two diameters with a distinct step:
HP Volcano Orifice dia 10.95mm
Bore Upper dia: 11.70mm
Bore Lower dia: 11.05mm
HP Seat dia: 11.45mm

Here's the Titan HP Seat, note concentric even circular engraving
Titan OEM HP seat by fibonacci101, on Flickr

[Fibonacci]

SeaRat said:

The interesting point is that these seats are not seated when off the tanks. It is only when the regulator is pressurized that the seat "seat." So it seems that there are issues concerning the pressurization, and lower pressures could help. But if they are off-center, the lower pressure would only postpone the inevitable.

Yes, but when unpressurised the HP Seat in the Spring Block is kept tensioned against the Volcano Orifice by the Long Spring #6 which in turn is tensioned by the Short Spring #4 which also tensions the Filter at the other end. Which is why there is an engraved mark... if it was not tensioned when at rest the HP seat would be pretty much unmarked.

So maybe I'm looking at the wrong end of the problem, could it be how centred the HP Seat (mounted in its Spring Block with two o-rings) is in the bore?
The 90 Shore A o-rings would keep the stem concentric to the Block, but the HP seat carrier itself needs a tight fit in the bore.

Kraken Exploded View BOM HP SIDE REV 2 by fibonacci101, on Flickr

Titan
Bore Upper dia: 11.70mm
HP Seat dia: 11.45mm
Clearance : 0.25mm or ~0.125 per side, tight!
OEM HP Volcano Orifice dia 10.95mm

Kraken
Bore Upper dia: 11.60mm (remeasured using Mitutoyo bore gauge)
HP Volcano Orifice dia 11.0mm

Aqualung (Blue) HP Seat dia: 11.45mm (new)
Trident (Black) HP Seat dia: 11.23mm (just replaced)
Trident (Black) HP Seat dia: 11.20mm (failed, photo eariier)

Blue HP Seat Clearance : 0.15mm or ~0.075 per side, very tight!
Replaced Black HP Seat Clearance : 0.37mm or ~0.185 per side, loose
Failed Black HP Seat Clearance : 0.40mm or ~0.20 per side, very loose, and close to what was measured in the other off-centre failed Trident seats!

So it would seem the problem with the Trident seats used in a Kraken is not the seal compound failing but the relationship of the diameter of the carrier to the bore!

The smaller Trident seat would allow it to almost rattle down the bore, and find an off-centre spot to seal..
I suspect this would cause some scrubbing of the seat surface too.
It could conceivably cant as well, resulting in the distinctive 'horsehoe' shaped engraving.

I have one new Blue AL HP seat left, will fit it during service and report back... fingers crossed

[antique diver]

Fibonacci, I think you may have found that at least some of the issue may be with the Trident seats. I hope so.

Possibly adding to the problem could be the backup ring (item 6 in the Kraken schematic). In 1980 Aqualung replaced the -06 size backup with a smaller -05 size to help stabilize the HP seat. Since that date I have always used the -05 split Teflon ring in Aqualung and Mares regulators.  Continue to use the -006 oring over the Teflon backup.

 I recommend that change along with only using the blue Aqualung seat... I never had a problem with that combination.

Here's the 1980 Memorandum:

[vance]

Has there been any issue when using the old style one piece balance blocks?

[duramax]

In the thread on Kraken O-rings, Luis posted the following:

I recommend 70 durometer for all the O-rings in the Argonaut.

The only dynamic high pressure O-ring (in the balancing chamber) has a back-up ring, so there is little chance of extrusion. I have always used 70 durometer in this application and never had any issues.

So this raises the question for the 006 o-ring (7, in diagram) 70 or 90 Duro?

[cg43]

Hello

Fbonacci writes:
"Yes, but when unpressurised the HP Seat in the Spring Block is kept tensioned against the Volcano Orifice by the Long Spring #6 which in turn is tensioned by the Short Spring #4 which also tensions the Filter at the other end. Which is why there is an engraved mark... if it was not tensioned when at rest the HP seat would be pretty much unmarked."

Every 1. Stage is full open unpressurisited because the big IP spring has many times the power of the smal springs
that try to press the seat against  the orifice . 

Greetings   Rainer