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Post by blackwaterdiving on Jul 19, 2023 17:41:54 GMT -8
For the kraken owners, has anyone had luck finding orings or a kit that you can rebuild the kraken with? Seems like my orings are either to big or to small. O rings look good in this one but still be nice to change them out.
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Post by antique diver on Jul 19, 2023 18:28:06 GMT -8
For the kraken owners, has anyone had luck finding orings or a kit that you can rebuild the kraken with? Seems like my orings are either to big or to small. O rings look good in this one but still be nice to change them out. I was under the impression that all the orings in the Kraken were standard sizes. Is it possible that you don't have a full range of sizes? |
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Post by luis on Jul 19, 2023 18:34:10 GMT -8
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Post by scubalawyer on Jul 19, 2023 19:42:46 GMT -8
For the kraken owners, has anyone had luck finding orings or a kit that you can rebuild the kraken with? Seems like my orings are either to big or to small. O rings look good in this one but still be nice to change them out. I am in the process of assembling an overhaul set of o-rings for my AK. Happy to share as there is usually 50 of each size in every order. The HP diaphragm and the LP seat are easy to find. Hey Luis, what durometer are the o-rings in the AK diagram? M |
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Post by luis on Jul 20, 2023 4:44:38 GMT -8
For the kraken owners, has anyone had luck finding orings or a kit that you can rebuild the kraken with? Seems like my orings are either to big or to small. O rings look good in this one but still be nice to change them out. I am in the process of assembling an overhaul set of o-rings for my AK. Happy to share as there is usually 50 of each size in every order. The HP diaphragm and the LP seat are easy to find. Hey Luis, what durometer are the o-rings in the AK diagram? M 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. The 70 durometer O-ring is compliant enough to normally create a good seal. The only time I go to a 90 durometer is if there is a concern with extrusion and pinching, like the high pressure piston shaft in a Scubapro Mk-5. There has been a trend to use 90 durometer for high pressure O-rings. I don't subscribe to that, if the O-ring is properly captured, like for example, the tank neck O-ring. I always use 70 durometer for tank neck and I always check that there is proper metal to metal contact (closure). This O-ring closure is designed to have no gap that could allow O-ring extrusion. On rare occasions I felt the need to used 50 durometer O-ring to create a seal with a particularly irregular surface. When I felt the need to use the softer O-ring, I normally also needed an oversize O-ring (a fatter one). |
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Post by nikeajax on Jul 20, 2023 8:03:53 GMT -8
There has been a trend to use 90 durometer for high pressure O-rings. I don't subscribe to that, if the O-ring is properly captured, like for example, the tank neck O-ring. I always use 70 durometer for tank neck and I always check that there is proper metal to metal contact (closure). This O-ring closure is designed to have no gap that could allow O-ring extrusion. Yep, this is what my friend Jim Steele said too: 90 for the most part is... He said it was the industries way of trying to cover their behinds as there had been some very petty law suits that had ruined people's livelihoods. JB |
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Post by luis on Jul 20, 2023 8:42:39 GMT -8
Hi JB,
My preference for 70 durometer over 90 durometer O-rings (when applicable, in most situations) is because the 70 durometer is more flexible and compliant, therefore it actually tend to seal better, if it encounters any imperfections on the sealing surface.
The 90 durometer is stiffer, which helps it against extruding when faced with small gap, like in a dynamic gland seal (like the piston shaft). But being stiffer it is also less forgiving to small surface imperfections.
I hope this helps.
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Post by nikeajax on Jul 20, 2023 10:06:19 GMT -8
I'm hip, daddy-o!  JB
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Post by antique diver on Jul 20, 2023 12:38:48 GMT -8
Hi JB, My preference for 70 durometer over 90 durometer O-rings (when applicable, in most situations) is because the 70 durometer is more flexible and compliant, therefore it actually tend to seal better, if it encounters any imperfections on the sealing surface. The 90 durometer is stiffer, which helps it against extruding when faced with small gap, like in a dynamic gland seal (like the piston shaft). But being stiffer it is also less forgiving to small surface imperfections. I hope this helps. I agree, and add another reason I like the 70 in the valve face. Any type used in that application seems (to me) to wear out and begin to leak more often than orings in other applications, and the 70 is much easier to dig out for changing than a 90 or the urethane orings. |
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Post by duramax on Jul 25, 2023 20:43:46 GMT -8
Hi All,
Just curious what is the preferred material. EPDM, Burna, Viton?
RK
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Post by luis on Jul 26, 2023 3:44:34 GMT -8
Buna has been the go-to O-ring material for a very long time and there is really no reason to change.
Viton and EPDM are both good O-ring material and for very high temperatures (over 200 F) in industrial applications they are better than Buna. The only reason they have become popular for scuba is because of their durability with oxygen. But, even a deco regulator exposed to 100% oxygen only has a limited time exposure (as opposed to an industrial application of weeks or months of exposure).
Most divers would never use a double hose regulator as their deco 100% oxygen regulator, so the maximum O2 exposure should be less 40% (normally 32% or 36%). Therefore, there I don’t see any reason to use anything but Buna O-rings on a double hose.
I also always use silicone grease, which is far superior to any of the oxygen compatible grease. The oxygen compatible grease tends to separate in little time. I have encountered many regulators that have not been serviced in over 40 years and the silicone grease was still performing as good as new.
My deco regulator (for 100% O2) is the only one that get special treatment and I only use an unbalanced piston first stage for that application. It is the most oxygen friendly first stage, for several reasons. One of the reasons is because there are no dynamic O-rings exposed to high pressure.
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Post by nikeajax on Jul 26, 2023 8:23:53 GMT -8
Luis, again, always good info from you  So, what pray tell, constitutes a dynamic o-ring? JB |
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Post by SeaRat on Jul 26, 2023 8:35:24 GMT -8
Luis, again, always good info from you So, what pray tell, constitutes a dynamic o-ring? JB JB, My understanding, subject to change by Luis, is that a dynamic O-ring is one where the O-ring seals a sliding piece, such as is found in both balanced first and second stages. Luis may have a better definition. John |
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Post by luis on Jul 26, 2023 9:41:12 GMT -8
Correct, a dynamic O-ring is one that slides or rotates (actually the O-ring doesn't rotate, but a shaft in it may). Examples of dynamic O-rings are shaft seals on camera housing and most common in Scuba are the piston seals in a first stage (balanced or unbalanced) and the balance chamber seal in a Conshelf first stage. Most dynamic O-rings are gland seals (as opposed to face seals). Dynamic O-rings need some clearance to function, but too much clearance and they can get extruded. There is a balancing act and it can involve the O-ring durometer and designed pressure differential. Also, a back-up ring (like in a Conshelf) normally takes care of the gap extrusion issue. Note: I have been asked if you can just use two O-rings instead of the back-up ring and the answer is: absolutely “not”. The back-up ring has a separate function. It is to keep the O-ring from extruding or pinching (it is not for sealing). The typical flow through balanced piston 1st stage has one HP dynamic O-ring and one LP dynamic O-ring. Versus a typical flow-by unbalanced piston has two LP dynamic O-rings. Static O-rings can be: gland, face, or crush (the corner O-rings on the port plugs or valve to tank seal are crush design). The valve to regulator O-ring are face seals and they are classified as static, even though you can rotate the regulator just a bit (it can slide a little), but the motion is minimal and it is not designed into the joint. Static O-ring seal can often be designed with no gap that would allow extrusion (like the LP and HP ports or the valve to tank O-ring seal). In those three examples, there should be metal to metal contact with no gap that would allow the O-ring to extrude. A static gland seal only requires the clearance needed for assembly, which is normally less than needed for moving parts. The best resource for seals and specifically O-ring design is the Parker O-ring Handbook. It is a great resource. There is more to O-ring design than what is obvious to the casual observer. www.parker.com/content/dam/Parker-com/Literature/O-Ring-Division-Literature/ORD-5700.pdfI hope that helps. |
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Post by nikeajax on Jul 26, 2023 14:02:17 GMT -8
I agree, and add another reason I like the 70 in the valve face. Any type used in that application seems (to me) to wear out and begin to leak more often than orings in other applications, and the 70 is much easier to dig out for changing than a 90 or the urethane orings. What/where is the/a valve-face?  JB |
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