|
Post by nikeajax on Aug 21, 2023 16:39:32 GMT -8
Hello Fred We don't need to have the same view on a topic . I will find it more interesting to read the opposite , especially if it is based on facts that are new for me . And you knew a lot about this valves and regs. that I don't knew . Up to now , I see no reason for both of us to apologise and I am sure this will last on . Let us diver be colleagues . Greetings Rainer Bravo, Herr! Der beste Weg zu lernen: Ich sage den Leuten immer: „Ich muss nicht Recht haben …“ Bravo, sir! That's the best way to learn: I always tell people, "I don't need to be right..."JB
|
|
|
Post by vance on Aug 21, 2023 18:21:01 GMT -8
I just remembered that there were balanced HP poppets that had the cylindrical seat insert.
|
|
|
Post by Fibonacci on Aug 25, 2023 16:43:03 GMT -8
Referring to Luis' comments from the other post:
The Kraken first stage is a direct copy to the Royal Aqua Master, the Conshelf and the Aqua Lung Titan. It was very intentionally designed to use all the same exact parts, using the same dimensions and the only variation would be either a manufacturing flaw or minor manufacturing tolerances. The drawings specify fairly tight machining tolerances and very tight concentricity tolerances for the first stage.
But I had no involvement on the manufacturing or the quality control.
Always good engineering practice to use standard off the shelf components where possible. In my industry the Design and Release (D&R) Engineer is always responsible for liasion with the supplier right up to launch 'OK to Go' signoff and volume production. It would be unusual not to do so.
There are usually many technical questions to answer and even suggestions from the supplier for small changes to aid production which then have to be updated by the D&R in the 3D CAD and officially re-released with appropriate version control.
Regarding Quality Control, in my industry we have Significant Characteristics (SC) and Critical Characteristics (CC) that are treated differently. A typical CC would be the fastening of a seat belt bolt, a DC nut runner torques the bolt, adds a paint dot and barcodes that vehicle to progress down the line. It cannot progress if the CC rated bolt hasn't been torqued correctly, and the QA process can pull up a record of every vehicle in case of a warranty or other issue.
For the Kraken, the drawings may indeed show tight tolerances, but there needed to be at least some QC process to identify certain key areas (like the HP bore, definitely a CC in my book) to be checked with a suitable Go/No Go gauge. Otherwise how do we know those original design close tolerances were actually met?
If you are referring to the lack of concentricity between the imprint on the seat caused by the volcano orifice (as seat misalignment) that is very common on RAM, Conshelf, Titan and others. That is not unique to the Kraken. I have serviced many of those regulators (RAM, Conshelf, etc.) and the imprint is rarely concentric. That is why when a seat is removed it can never be reused. That is even addressed in Pete Wolfinger, “Regulator Savvy Book”.
Agree there is always some degree of misalignment, but on my Kraken (using Trident HP seats) the significant amount of misalignment eventually led to a metal-on-metal touch condition and failure of the HP seat.
I have never heard that the lack of concentricity resulted in a seat failure, just by itself, as long as the seat is not reinstalled (because it will never realign perfectly).
Agree, they will never re-align and shouldn't be re-used.
However all of the HP Seat failures used brand new HP seats.
HP Seats can and do fail by a number of reasons. But before I can comment on Fibonacci regulator, I will have to read that thread to find out more details.
Here's a summary:
- Kraken bought new in 2017 and shipped to Australia.
- Used a couple of times in a pool to get used to DH diving... all good so far.
- Taken on a LOB trip to PNG, had issues from Day 1 with variable WOB, wet breathing, exhaust hose floods.
- Eventually the HP seat failed by Day 3 on a 20m dive, taken out of service.
- Contacted Bryan on my return to Australia, he asked for it to be returned to him in the US.
- Bryan agreed the Trident HP seat had indeed failed and serviced the reg, but using new Trident HP seats.
- Trident HP seat failed again after about 6 dive trips, the last faiure with characteristic off-centre horseshoe shape. - Also reported by others with 2017 production models.
- Contacted Bryan, said he didn't know why it failed again (!)
I agree any tolerance in the the HP Volcano orifice would be taken up by the HP o-ring tending to center it in the bore.
However the upper HP bore (where the HP seat travels) may be slighty larger, off-axis or slightly tapered from specifications.
If you designed the Kraken HP bore to closely match the Aqualung Titan (which has a tight tolerance between the OEM Blue HP seat to bore) but for whatever reason Bryan ended up using the Trident Black HP seat (with quite a loose tolerance to bore) in production then that may explain the failure mode. The Trident seats would be quite off-centre and could possibly also cant in the bore giving the horseshoe shaped impression? There would also be batch-to-batch tolerance in the diameter of the Trident HP seats.
Maybe Bryan used OEM Blue HP seats on early Kraken production, but then shifted to Trident around 2017?
As detailed in the earlier part of this thread, with Bryan very sadly unable to comment I am trying to piece together what the root cause may be... I love diving my Kraken but just cannot trust it till we have a data-driven solution to the early HP failure issue.
Luis, as the original Kraken D&R engineer you are probably the only person left who can shed some technical light on this issue, so I'm seeking your help please.
|
|
|
Post by luis on Aug 25, 2023 18:32:13 GMT -8
Hi Fibonacci,
First, let me state that I just read your last post, per your request, but I haven’t had time to read the entire thread, so for the most part, I am only addressing this last post. If you see my recent post at VDH, you will see that I was not even able to go to the Heritage Diving event in honor of Bryan…
You have some very good points about your industry, but I am not even sure what is your industry, automotive maybe? In any case diving is not really my industry, at least not anymore. I think that you are aware, that regulator design is really just a hobby for me. Actually, to be fair, I retired about 1.5 years ago as a Navy civilian engineer… so I don’t have any industry anymore… 😊
You are probably aware that I was never part of VDH. I have never received any compensation and as a typical hobby, it actually cost me money to work on my regulator designs. I have spent only my own personal money on design development and testing and never expected any compensation… after all, it is a hobby.
Also, it doesn’t sound like your company, in your industry, can be compared to VDH, in the Scuba industry. VDH was a one-man operation. And I am just glad that it was around to produce all the reproduction and replacement parts that Bryan supplied to all of us.
I am very sorry about the issues you have had with your Kraken, and as we all know; we do not have Bryan to try to help you out anymore. I will try to help you as much as I can, but some of the conversation may have to go private. Maybe we can have a phone conversation or a Zoom meeting. I realize we have a large time zone difference, but my schedule is flexible.
I have been approached by a scuba regulator company to start new production on the Kraken, therefore I cannot share a lot of design information in public. That is all I can say on this subject.
I don’t know how accurately you have measured your Kraken (or if you can take precise dimensions), but if you can take precise dimensions, I can verify compliance with the design or not.
The Trident seat has never been my preferred choice, but it has been acceptable to many users. IMHO, there is no question that the Aqua Lung seat is much more durable. The material properties are probably the biggest difference. The dimensional properties are probably very close, but I have not confirmed that.
You may also have a defective volcano orifice. That is a very easy fix. An Aqua Lung volcano orifice drops right in as a replacement. You can actually replace all the internal parts with Aqua Lung parts. That is not to say that Aqua Lung parts cannot also have a defect (or that they are any higher quality than Bryan’s parts), but as the largest scuba manufacturer, I would hope that they have a good quality control program. This is just a shotgun approach. I would do it since I don’t have the precision measuring instruments to rule out a main body defect.
If you actually had metal-to-metal contact with the volcano orifice, that volcano orifice is shot anyways, even if it wasn’t at first…
Let me know if you have the means to take precise dimensions and if you would like to do a private Zoom meeting. I can setup the meeting.
Thanks
|
|
|
Post by Fibonacci on Aug 25, 2023 19:25:24 GMT -8
Hi Luis Many thanks for your reply... Yes automotive is my field, specialising in injection moulded plastic and soft interior trim... so very different from VDH or the wider SCUBA industry. However some things are the same, establishing Master control reference points, tolerancing and overcoming production variation to (hopefully) avoid failure modes and expensive warranty issues or recalls.
I'm trying to eliminate one variable at a time with the Kraken, I inspected the volcano orifice edge under a loupe and it still appears unmarked, maybe it got very close and HP air lifted the edge of the seat near where the pin fits? Anyway this time I stripped and ultrasonically cleaned the Kraken, replaced the -006 o-rings (incl cupped backing ring) and used my last OEM Aqualung Blue HP seat. It locked up solidly at 135psi imnediately, and for 5mins, 30mins then overnight. I will dive it (shallow!) with the new Blue HP seat and report back.
I'd rather not strip it down again to remeasure everything again and lose a brand new Blue HP seat.
I have access to Mitutoyo bore gauges (both telescopic and small hole type) plus a Mitutoyo reference micrometer so can measure the HP bore diameter quite accurately, but of course accurately measuring the position of the axis will take a Metrology lab.
From earlier in this thread: 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 Titan HP bore has two diameters with a distinct step:
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.
|
|
|
Post by SeaRat on Aug 25, 2023 21:33:23 GMT -8
Just so everyone will know, I have heard over and over again on these Kraken discussions that the seat cannot be reused. The reason stated is that the "seating" on the seat is never the same, and the seat therefore will never seal again. Kraken HP seat failure 4 by fibonacci101, on FlickrBut over the years several of us have reused these worn seats. But to do so, we had to recondition them on a knife sharpening stone. I did this on my marble stone. It takes some work, but it can be done, and you have a new sealing surface. This could be done if out on a remote dive site without parts. However, saying that, it is always better to replace the seat with a new one, if that option is available. John
|
|
|
Post by luis on Aug 26, 2023 6:45:27 GMT -8
The HP seat is not allowed to move sideways. In the past 50+ years I have serviced hundreds of first stages with this design, including Conshelf, RAM, Aqua Lung Titan, and now Phoenix and Argonauts, and I have never seen any indication of the seat ever touching the sides of the bore. The “seat-subassembly” is fairly tightly guided between two points. As you know, in a three-dimensional space all you need is two points to define a straight line. The “seat-subassembly” consist of the seat, the pin, and the pin-mushroom-guide. These three components fit fairly tightly with each other and there is a large overlap on the fit between the pin and the seat, and the pin with the pin-mushroom-guide. This large overlap in the fit, keeps all three components working together as one unit. The parts are tight enough to avoid any side shifting or any angulation between the parts. Even with the old pin design in the RAM and Conshelf, that had the “head” at one end of the pin, this subassembly was tight enough to move together as a unit in a straight line with no side motion or angulation. Did I mention, this is a mature, almost 60-year-old design. The new straight “headless-pin” in the Aqua Lung Titan, etc. (and now the Phoenix and Kraken) is a lot tighter than the old design.
So, the “seat-subassembly” is guided by two points:The first guiding/ constraining point is at the balancing chamber O-ring. By definition, a dynamic/ sliding O-ring seal like this has to be a tight fit to avoid any high-pressure gas leak. So as long as there is a seal, this is also a tight lateral constrain. The back-up ring is designed to keep the O-ring from extruding, but you could say that the combination of both rings will definitely constrain any lateral motion. The second constrain/ guiding point is on the “pin-mushroom-guide” interface with the guiding hole (and the HP diaphragm contact point). This is not as tight fit, but it doesn’t need to be. It is tight enough and far enough to provide a very good guide. The distance between the two guiding points is also what keeps the “seat-subassembly” from moving sideways or at an angle. And once the HP diaphragm takes a set, the “pin-mushroom-guide” will be fixed and not allowed to move sideways. This lateral constrains occurs as soon as the IP is adjusted or sooner. The motion of the “seat-subassembly” is in a straight line sliding between the two restricting points mentioned. Also keep in mind that there are no side forces driving any lateral motion. Occasionally lack of lubrication on the O-ring will cause some squealing, but that is a very high pitch, with extremely miniscule displacement issue… no lateral motion. I hope this explanation is clear… I know it is long, but I want to make sure it is clear. Let’s be clear, I am not trying to defend the Trident seat, but the side clearance of the seat is not the issue. The lack of concentricity on the seat imprint is determined during assembly by where the “pin-mushroom-guide” lands on the HP diaphragm. Once that relationship is “broken-in”, you do not want to disturb it by removing the seat and reinstalling. The clearance around the “pin-mushroom-guide” is small, but that clearance and the combination of all other tolerances is enough to explain the offset. But that offset is fixed during operation (until the next rebuilt) and it causes no harm. Note: If there is a poor seat guide issue, is not due to the diameter of the seat, but maybe if the pin is loose inside the seat. You could check that, but keep in mind that once it is assembled, the compression on the “seat-subassembly” will keep the relationship between the components fixed. The second subject:The “first-stage” bore is actually composed of three distinct diameters (not counting the snap-ring groove). Take a look at the attached diagram. The concentricity between the three diameters is critical and is specifically addressed on my drawings, but to be fair, the way this is machined, there is no reason to have any misalignments between the bore diameters. The smallest diameter is for the volcano orifice O-ring landing and leading to it is a conical ramp to compress the O-ring during assembly. This bore is the only one with a critical O-ring sealing surface finish requirement. The clearance between the volcano orifice and the ID of the bore is driven by the O-ring gland design and the Aqua Lung design complies with the Parker O-ring “bible” so my design just copied it. Even do, it is a high-pressure seal, I prefer to use a standard 70 durometer O-ring since the clearances meet the specifications and 70 durometer is more compliant to minor defects. The next diameter is just clearance for the seat and the long spring. Now, between the second and the wider third bore diameters there is a very critical ledge. This ledge is the support for the balancing chamber. Without this ledge, you do not have a balanced first stage. The tank gas pressure thrust pushes and holds the balancing chamber against this ledge. The balancing chamber never moves from this ledge. It is fixed to it. During assembly the short spring will press the balancing chamber against the ledge to take up tolerances, but that spring is really not needed. Other similar regulators with the same design (like Voit, Mares, Dacor, etc.) did not include this little spring to fix the balancing chamber. If you are familiar with the coil spring equation you will know that very short spring is very stiff relative to the longer spring, but the spring is not needed since the pressure thrust will fix the balancing chamber. In reference to the balancing chamber O-ring and back-up ring. The recommendation is to use a standard 70 durometer O-ring with the modern black hard rubber back-up ring. The back-up ring keeps the softer more compliant O-ring from extruding even with very high modern tank pressures. I will look at your dimensions later, but at first glance I don’t see anything that concerns me. This is enough for now.
|
|
|
Post by antique diver on Aug 26, 2023 7:50:01 GMT -8
Luis, thanks for all the information. I understand most of it, haha.
However, adding this just in case you missed this photo on the first page of this discussion. This is what started the whole misalignment discussion. That is the absolute worst alignment that I have ever seen in this type of regulator, (and I have seen a bunch from 1970-current date). Somebody must have done something really wrong to have this happen! I don't see how regulator parts tolerances could have been far enough off to create this mess. Also look at the ragged appearance of the center orifice! Looks like someone assembled it with a hammer drill.
|
|
|
Post by luis on Aug 26, 2023 8:38:42 GMT -8
Luis, thanks for all the information. I understand most of it, haha.
However, adding this just in case you missed this photo on the first page of this discussion. This is what started the whole misalignment discussion. That is the absolute worst alignment that I have ever seen in this type of regulator, (and I have seen a bunch from 1970-current date). Somebody must have done something really wrong to have this happen! I don't see how regulator parts tolerances could have been far enough off to create this mess. Also look at the ragged appearance of the center orifice! Looks like someone assembled it with a hammer drill.I agree that it looks very bad. And your statement about the pin orifice goes back to my note above. I think that I have seen that picture before, but I have not actually inspected the part to look at the surface. One observation from the picture is that the material crack and the volcano orifice imprint do not seem to be in the same spot. I do not know this for a fact, but that is my observation from the picture. The volcano orifice imprint seems to be the lighter color curve to the right of the material crack. There seems to be a matching imprint circle on the other side of the pin hole.
The crack doesn't follow the shape of the volcano orifice, but the imprint marks does look like a volcano orifice. This is not unusual for crack propagation.
If you draw a circle on the "whitish" mark, it is possible that the misalignment is actually not as bad as the material crack would lead you to believe. The imprint and the crack are not necessarily in the exact same location. The crack may have initiated on the inside edge of the imprint, but the imprint is wider and toward the outside. The crack just started at a high stress point.
|
|
|
Post by luis on Aug 26, 2023 9:43:44 GMT -8
I thought that I have seen that picture before. My memory is not as bad as I thought! This thread is from 5 years ago. scubaboard.com/community/threads/argonaut-kraken-hp-seat-failure.568952/#post-9792959Here are some related pictures with some marks. And this is what I wrote 5 years ago. Five years apart and I still see the same things... not too bad... I still don't know how the crack started, but the crack propagation is not totally unusual. Once a crack starts it can follow different pasterns depending on stress, etc.
|
|
|
Post by antique diver on Aug 26, 2023 13:40:25 GMT -8
I have seen plenty of those crappy black ones torn up but not just like this one. Could just be a distortion from camera angle, but if you take dividers or calipers to measure from outer volcano mark to edge of hole on the left side and compare it to the right side you will clearly see a marked difference. Not concentric.Do you think it could be photo angle distortion causing that discrepancy? (doesn't look like it to me, but then my eyes are probably older than yours. I would not resort to using poppets with the thin black rubber-like seat again when better ones (blue) are available from Aqualung. Had problems for years with those black ones from USD and Mares both. At least for now the better ones are still available. I hope! Down to my last 6.
|
|
|
Post by luis on Aug 26, 2023 14:32:42 GMT -8
I have seen plenty of those crappy black ones torn up but not just like this one. Could just be a distortion from camera angle, but if you take dividers or calipers to measure from outer volcano mark to edge of hole on the left side and compare it to the right side you will clearly see a marked difference. Not concentric.Do you think it could be photo angle distortion causing that discrepancy? (doesn't look like it to me, but then my eyes are probably older than yours. I would not resort to using poppets with the thin black rubber-like seat again when better ones (blue) are available from Aqualung. Had problems for years with those black ones from USD and Mares both. At least for now the better ones are still available. I hope! Down to my last 6. Hi Bill, I totally agree that the volcano orifice imprint is not concentric. But I think that it is not as bad as the cracked material makes it look. You can see the red circle is not concentric with the seat. I added the red circle to try to trace what it looks to me as the imprint. My eyes were also younger at the time. I did that in 2018. Note: from what I recall, I used a perfect circle to trace what looks like the imprint. Using a circle, makes the assumption that the face of the seat is close enough to perpendicular to the camera view, that it looks like a circle and not an ellipse. From my picture, the red circle looks to me like a reasonable match… to a circle. It is just an approximation... BTW, this black seat is not the same as the old US Divers black hard rubber seat from the 60’s and 70’s. This one is probably a Trident after-market seat and the material looks like some kind of plastic, like nylon or Delrin or something similar. But even the looks of the seat, doesn’t look like the quality of the Aqua Lung seats. IMHO, The Aqua lung seat are just fantastic. I have easily over 400 dives (probably well over 500) on my Kraken since the last rebuild. Some of those dives are over 200+ feet on Trimix and at least one is past 300 ft. I just got back from the Red Sea and the regulator performed as good as ever. Thanks
|
|
|
Post by vance on Aug 26, 2023 15:09:12 GMT -8
This is a long and complex thread with lots of opinions and conjecture going around (and around...). However, the OP's original problem hasn't been addressed, as far as I can tell.
He's having better luck with new blue seats, but not much better. Failures after 20 dives is really bad! What can be going on with his 2017 Kraken to make this failure keep occurring?
|
|
|
Post by vance on Aug 26, 2023 15:12:44 GMT -8
I thought that I have seen that picture before. My memory is not as bad as I thought! This thread is from 5 years ago. scubaboard.com/community/threads/argonaut-kraken-hp-seat-failure.568952/#post-9792959Here are some related pictures with some marks. And this is what I wrote 5 years ago. Five years apart and I still see the same things... not too bad... I still don't know how the crack started, but the crack propagation is not totally unusual. Once a crack starts it can follow different pasterns depending on stress, etc.
I see the white mark showing the fairly concentric volcano impression, and I am wondering if this particular seat has been reinstalled, and just got the worst possible reseat position? That might account for the stress cracks?
|
|
|
Post by Fibonacci on Aug 26, 2023 17:03:51 GMT -8
Morning everyone Many thanks for the detailed initial reply luis, it goes a long way to understanding the complexities of both the regulator design and the potential paths for failure. The black faced HP seat was the one Bryan removed when he serviced my Kraken initially, it was in the reg from new. It appears he was using the Trident HP seats in his overhaul kits, as the one that also failed shortly after looked similar. Here is the HP seat I removed from my Kraken before replacing it with a OEM Blue AL seat, it came from a VDH overhaul kit (so I assume Trident) and hadn't failed. Yet. As stated I have no confidence in this reg using Trident HP seats Kraken HP seat Trident 2 by fibonacci101, on Flickr Kraken HP seat failure 2 detail by fibonacci101, on Flickr However as vance says all the background about how the first stage HP bore diameter nor the HP seat diameter doesn't matter as with all the tight tolerances involved they should never go very far off centre. Mine is not the only Kraken suffering from premature HP seat failure! Circle back and look at the one posted by duramax Duramax Kraken HP seat failure by fibonacci101, on Flickr Or by a Scubaboard member who had a similar issue: I too had issues with the IP spiking, resulting in the octopus beginning to free flow as a tell tale sign.The HP seat had similar markings (see photos below). I went through three OEM HP seats in total, over about 130 dives total. Two were brand new and one was a an old spare I had lying around that looked good to the eye, but failed after 2 dives. I dive most days so this isn't a case of the reg sitting in a cupboard for ages.These failures were after Jerrie at DiverdownDH did a full service and rebuild on the reg, including photos, so we can be sure it was assembled correctly since Jerrie is not just some random technician but comes recommended by Bryan (VDH was closed due to covid, and a message on his website directing servicing to Jerrie).So there are a number of similar Kraken HP seat failures being reported, fitted by different people (incl two accredited techs) that feature off-centre engraving and premature failure. Some Kraken owners have never experienced any of the three issues that plagued mine (intermittent WOB and hose flooding caused by the exhaust valve suction cupping to the diaphragm. wet breathing caused by a distorted exhaust valve seat, and the HP failures), some have experienced one or two. I cannot win the lottery but in the 'swiss cheese' mode of failure managed to experience all three on my Kraken! If a Kraken II is in pre-production then I think this HP seat issue should be given close attention to avoid further unexpected failure modes, and robustly fixed if a root cause can be identified. The Trident seats appear to be part of the problem but not the whole problem. This has been driving me crazy since 2017!
|
|