How does the Poseidon Xstream first stage work?

[tbone1004]

@js47 not all directed at me, but whatever.

Poseidon engineers have come out with the stance that because the lubricant used in machining their regs outside of the duration is not O2 compatible, that it is not possible to ever truly clean their regulators for oxygen service. I don't think any other manufacturers are using O2 clean lubricant during the machining process, so it's up to you to decide whether to do it or not. Me personally? All of my Poseidon first stages are O2 cleaned and I haven't had an issue.
The parts kits are interchangeable for reference, however nitrile orings and silicone grease are certainly more durable than viton/ptfe and both are significantly cheaper as well. Most regulator brands have an O2 service and "regular" parts kit. Also no reason you can't use the deep with normal nitrox mixes out of the box.

If you're buying new ones, just buy the black one and it's fine for whatever else you want to do with it. The Duration can be used deep with no issues as well. I don't necessarily agree with their decision to market it that way, but it is what it is and they're Swedish so they do things a little differently than we do in the US. It's not intentionally handicapping, it's builting for-purpose products and the deep was designed to go deep where fO2 is well below 21%. I don't necessarily agree with that logic which is why all of my first stages are O2 clean, but since the o-rings and lubes are more durable and cheaper, I can see why they did it.

Floating seats are ideal because they will naturally find their happy place and have a higher contact area than a traditional seat design. This when combined with the fewer moving parts and fewer sealing surfaces combine to increase the duration between required service.

On the heat sink, it's all about flow. With those open ports, the water can't sit and cool off like it can inside of the chamber of a MK25, or the older Poseidon first stages. There is always a little water movement in designs like that, but cold pockets can form. When the big cutouts are made, the water can't sit on top of the diaphragm where it will quickly drop below ambient temp and shortly thereafter start to freeze.

 

[Luis H]

Poseidon engineers have come out with the stance that because the lubricant used in machining their regs outside of the duration is not O2 compatible, that it is not possible to ever truly clean their regulators for oxygen service.

Hi @tbone1004

At first I thought that make sense and it would explain it if the metal parts were not plated (like for stainless or titanium parts, etc), but aren’t the Poseidon’s made mostly of plated brass? My background is not in materials engineering, but my understanding is that the chrome plating process involves some very aggressive cleaning acids and two or three layers of plating.

Am I missing something here? I know some oils can be hard to clean, but after plating…



My experience is that silicone grease is superior (lubrication, durability, etc) than any of the O2 compatible grease, with only one exception: the lack of compatibility with high O2. I only use silicone grease for anything up to 40% O2.



About the floating orifice seat I would like to add that it actually is more than a “floating seat”. The orifice seat is actually part of what is technically a pneumatic piston. There is a sealing dynamic (sliding) O-ring on the outside diameter of this piston. On one face of the piston you have full tank pressure acting on it (including the projected pressure area of the ball/seat) and on the other side you have the IP pressure plus a heavy spring force.

The combination of the pneumatic forces are designed to balance (with the springs) and move the point where the valve seat will close, creating a relatively constant IP (independent of tank pressure). The magnitude of the IP should only be affected by the summation of the spring forces (and ambient pressure since it is pressure compensated). If the pneumatic pressure areas were accurately designed, then any change in tank pressure should not affect the IP output.

This is the same balancing design used by Sherwood in their old Blizzard, Magnum and a few other older piston regulator.

So my question, since I don’t have one of this regulators, how well did they do on balancing design? Is the IP truly constant at all tank pressures? Small IP variations are not really that important, I am just curious.

 

[tbone1004]

@Luis H that's what the engineers have said when asked about it in the past. Whether I agree with them or not is another thing, but that's their stance on it. I don't think the Duration or Black is actually any more expensive to buy up front, just more expensive to service.

The MK3 is significantly more balanced than previous Poseidon first stages and only varies a few psi in my testing from 4000psi down to about 200

 

[rsingler]

This is the same balancing design used by Sherwood in their old Blizzard, Magnum and a few other older piston regulator.

Yeah, those Sherwood Bellevue washers remain ahead of their time. Very underrated reg, though the HP air passage diameter is smaller than it might be.
But what pistons were you thinking of, Luis? I'm wracking my brain...

 

[Luis H]

Hi @rsingler

The volcano orifice in the Sherwood are in a moving/ sliding body with a dynamic O-ring sealing the differential pressure. The two pressures acting on this body (piston) are the tank pressure and the IP. Technically that moving body meets the definition of a piston. So you could say that the Sherwood actually had two pistons working together to create a balance system (were the tank pressure changes are canceled out by the balance system).

This is exactly the same principles as in the newer Poseidon first stage. The only difference is that you have a diaphragm and a simplified piston working together.

BTW, the new Sherwood first stages look different and I have not seen them or their diagrams so I don’t know if they work on the same principle.

Did I answer your question?