Poseidon Upstream Valve

[Beau640]

Calling @tbone1004 since he is the Poseidon Master...

I've been diving a pair of poseidon xstreams for the last year on my doubles and love them. They breathe like a dream no matter how deep I am, and I've shared air from 150 feet in 34 degree water and came out with a block of ice on the regs - and they still functioned/breathed completely fine. The poseidon "quirks" have never bothered me.

However recently I've begun to read/learn about reg servicing and performance (read through reg savvy, shadowing a reg tech near me, etc) and now that I can finally understand what the jargon in a reg manual actually means, I began reading about my Poseidons.

What's the thinking on the up-stream servo valve? In theory, the way Poseidon describes it, it seems like it would be beneficial to have your "free flow" upstream and not out of the reg mouth piece in your face. Poseidon says in a 1st stage HP seat failure, the release valve upstream will void air upstream from your second stage and you can continue to breathe normally from your 2nd stage at your mouth, as opposed to a downstream valve that will free flow in your face when there's failure. My concern would be that it may be difficult to figure out which post to shut down in a failure without the "in your face" bubbles, although if this is not true and it's still easy to figure out where the bubbles are coming from, having the excess pressure vented near the first stage and being able to breathe still normally from the second would seem to be beneficial.

Anyone dive these and ever had a failure? The old upstream design of a reg failing closed doesn't happen with these Poseidons so that's not my concern (in the past it seems that old poseidon regs were not "DIR" secondary to having a true upstream design in the past which they no longer do/can't fail close and before not having a 2nd stage cover that could be removed to fix exhaust underwater which they now do). I'm more concerned of the upstream pressure release being somewhere that will lead to a longer than usual proper post shut down in an emergency (maybe have to shut the isolator first then one post and then the other until you can figure out what the hell is going on rather than shutting off the correct post first try with a different reg).

Thanks!

Beau

 

[tbone1004]

not the master by any means, especially not on the Xstreams since I don't own any. That said, they are basically just mini Jetstreams as far as the important parts go in the second stage so they are functionally identical.

Now, regarding the failure modes. From a breathing standpoint, I prefer the OPV concept. Initially the Poseidon Jetstreams and Xstreams had a custom hose where the OPV was at the second stage fitting so you could see the bubbles directly. When the new first stages came out, they put the OPV in the first stage which allows you to use a cheap adapter and normal hoses. Great for travelling divers since you can use any hose that the shop has in the event of a failure.

Regarding the true upstream design. No Poseidon to my knowledge was every a true upstream design that would lock closed. The 2nd stage insert *condom looking thing, usually blue* will actually extrude through the second stage and provide air to the diver if the IP gets much above 180 ish. The OPV should go long before then.

The 2nd stage cover is an issue on the Jetstreams, but not on the cyklon or the Xstream. I still dive the Jetstreams with no issue and they've been through some pretty nasty silt with no issues. Flood the second stage and one good purge will flush it out. They have the advantage of one diaphragm for inhale and exhale which means it can push debris through the mouthpiece or out of the diaphragm if it gets really buried. In OW this is a nonissue, and in most caves it's a nonissue. Forrest Wilson does a lot of sump diving, and will switch to his Cyklons for that from his Xstreams. Cyklons are a normal downstream design and were actually the first single hose regulator for scuba when they came out in 1958.

My valve shutdown procedure is VERY different than what the DIR guys subscribe.
If diving solo, or in a position where my buddy can't tell me where the bubbles are coming from.
If I hear something bubbling, I take a normal breath and shut down both posts at the same time and leave my hand on my right valve *quick ability to turn it back on if you need a breath*. You will either see your SPG start to drop, or you won't. If you see your SPG start to drop, open your right valve again and start breathing as normal. You will still hear bubbles until it purges all the way down and then your second stage will freeflow and purge the rest of the gas out when the IP drops below about 100psi. You can purge the second stage to expedite that process if you want. Whole process should take about 15-20 seconds
If the SPG holds steady, then clip your SPG off, turn the left post on, and switch second stages. If after the second stage purges itself you still hear bubbles, you can isolate.

This prevents the violent freeflow that happens when the Poseidons pressurize which is a bit shocking if you do the valve drill by the DIR method. Nothing wrong with theirs, I just don't like getting that excited

 

[Caveeagle]

Beau, I had a HP seat go bad on one of my early 2960 Jetstream regs. This version has the OPV on the hose end and not the first stage. In my case, the OPV(hose end) did not really "free flow". it just sort of made a loud-short 'PTSHHH' sound about every 15-30 seconds, and did not seem to do it al all while I was breathing it. I would assume that a HP seat failure leak could be much worse and cause a longer venting.

On several of my 37XX series Jetsreams, there is a OPV on both the 1st stage and the Hose end. It would be interesting to find out what the burst pressure is for the 1st stage integral and the one on the hose end. and see which would blow first etc.

If diving sidemount, the venting would be easier to spot from the 1st stage.

I dive mostly backmount doubles, and have also wondered if I would notice the leaking OPV if it was going on behind my head.

In the FWIW category.. They do make the Poseidon hose swivel adapters that still have the OPV built in. They aren't cheap, but what I plan to add to my 2960/Jetstream backmount set at some point so that I can maintain the OPV near my line of sight.

I think you could also do this with your Xstreams.. but I would want to confirm which OPV would blow first.. ie the 1st stage, or hose end.

I think its relevant to point out that some early Xstream first stages also came without the integral OPV. I don't doubt Tbone's assertion that a "fail-closed" scenario is unlikely, but I would be very careful not to mix early and late components so that you end up without any OPV in place.

The closest thing I have had to a "fail-closed" scenario was when that little Jetstream servo valve seal fell apart causing the servo valve 'pin' to wedge off center and not allow the valve insert (condom) to open on. That was really my fault because it was an old used 2nd stage and I had checked out everything BUT the condition of that servo valve. (FYI)

 

[tbone1004]

@Caveeagle poseidon was nice to us. If you go with the OPV's on the hose end

they are omni's btw
Omni Swivel Poseidon Xtreme Swivel | Dive Right In Scuba - Plainfield, IL - Dive Right in Scuba

the OPV can be plugged with a regulator port plug on the 39xx series first stages. Should be the same on the MK3 first stages as well

 

[Beau640]

Hm maybe I'll have to plug the first stage opv and go back to using a hose opv.

Is it not obvious which 1st stage opv is popping when diving back mount? I would imagine you would feel some difference in the breathing of the 2nd stage or I guess you'd feel bubbles if you put your hand behind you near that post.

 

[tbone1004]

Hm maybe I'll have to plug the first stage opv and go back to using a hose opv.

Is it not obvious which 1st stage opv is popping when diving back mount? I would imagine you would feel some difference in the breathing of the 2nd stage or I guess you'd feel bubbles if you put your hand behind you near that post.

if you have a hood and gloves on it is all but impossible to feel or hear bubbles. They are VERY small and will look almost like the Sherwood dry bleed. It's not a big gushing volume of air that comes out of there. One of mine that started to fail had a bubble that would come out every 5-10 seconds. You MAY notice a slightly increased cracking pressure, but it depends on what you're doing if you're going to notice it at all. If you have an attentive buddy they should see it.

IP checks are also your friend though, you should be doing them on a regular basis, basically before every dive trip. I.e. if you are diving for 3 days over a weekend, check it when you do your pre-trip checks on Thursday night before you leave. If you're diving for 2 weeks in a row, I usually check them in the middle of the trip. Takes 10 seconds to check during your predive checks so it isn't a major thing. When I do it, I will usually set one tank up, put the IP gauge on and verify that's hanging out and stable. I'll leave it on there while I put the next regulator on. Once that is on and pressurized I will go back and make sure it is stable and then switch the gauge over to reg 2. I'll leave it there for a few minutes while I do whatever the next step is and verify that. Not a big time killer, but if it isn't creeping at the surface, odds are it won't go at depth.

 

[rhwestfall]

if you want "belts and suspenders", there is an adjustable OPV which Piranha Dive sells for the first stage....

 

[Blue Quaker]

When the OPV goes on a first stage seat failure it makes a "sewing machine" type noise as the valve continuously opens then closes as the pressure builds up and drops. If it is a slow/steady IP creep you only get bubbles and no real noise other than bubbling once the OPV cracks open.

 

[Beau640]

I'm thinking more catastrophic failure rather than slow IP creep. I'd imagine if you had a seat failure your opv will almost be constantly open rather than every 5-10 seconds no?

Thanks for all your time

 

[tbone1004]

I'm thinking more catastrophic failure rather than slow IP creep. I'd imagine if you had a seat failure your opv will almost be constantly open rather than every 5-10 seconds no?

Thanks for all your time

catastrophic failure you should notice quickly, but in that case I will do the shutdown drill as prescribed above if I can't feel which side has gone