Poseidon Xstream barks like a seal

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

IslandKraut

Registered
Messages
67
Reaction score
16
Location
Hawaii
# of dives
100 - 199
Aloha all,

I just realized one of my Xstreams has a weird resonance when I press the purge button. No sound in normal breathing, but when I pressurize from empty or press the purge button it "barks" like a seal and it seems the sound echoes in the tank. I suspect the first stage, as it does it with two different seconds, who themselves are find on a different first stage.

Any ideas? @rsingler ?

Mahalo!
 
@IslandKraut , when pressurizing from tank off, that disconcerting honk is completely normal for every Jetstream or Xstream. The valve insert (the blue umbrella) is completely depressurized.
When you open to tank pressure, air rushes out of the system at full volume until the servo tube pressurizes through the little filter at the top of the valve insert. Once the servo tube and valve insert are pressurized, the sides of the insert bulge out and seal the multiple holes in the valve. In the meantime, the sides of the valve insert are fluttering in the breeze, creating that resonant noise.
If you open the tank valve slowly, it's worse, as the restriction at the tank valve makes it take longer to reach IP in the servo. It's another reason why there's that second o-ring in the 3960 first stage - it's all an effort to pressurize the servo mechanism quickly. That's why you really need to "slam open" Xstream tanks. With the Duration, of course, and 100% O2 for accelerated deco, you shouldn't do that, and just need to accept the longer honk.

As for it happening with a purge, that must be a fairly vigorous purge! The Xstream second stage gas delivery is huge, and gas expansion at the surface is similarly large: 123 --> 14.7 psi is a more than 8:1 expansion. Because the valve is so capable, it allows downstream IP in the servo tube to fall off precipitously, making it much like tank opening. Even though the Xstream first is capable of large flow, all that expansion at the surface means a bigger drop in hose pressure downstream near the second stage.

All completely normal, albeit different than other designs. At depth, gas expansion is much less (e.g., at 99 feet it's 183 --> 59 psi, or only 3x), so the flow is relatively less abrupt, and since the first stage is able to maintain dynamic IP, downstream IP is maintained and the honking should have no equivalent vibration at depth.

I've noticed a little chatter with a lightly tuned XStream near the surface during heavy breathing, but it disappears below 20 feet.

A fault for one reg design might be a plus for another reg that's certified to 600ft Norsok standards. You can help minimize it for recreational diving by running your IP at the low end of limit (116-123 psi).
 
Thank you, Rob - Time to dial down the pressure... As an old Cyklon fan, I usually tend to the higher end...
Much appreciate the fast response!!
 
@IslandKraut , when pressurizing from tank off, that disconcerting honk is completely normal for every Jetstream or Xstream. The valve insert (the blue umbrella) is completely depressurized.
When you open to tank pressure, air rushes out of the system at full volume until the servo tube pressurizes through the little filter at the top of the valve insert. Once the servo tube and valve insert are pressurized, the sides of the insert bulge out and seal the multiple holes in the valve. In the meantime, the sides of the valve insert are fluttering in the breeze, creating that resonant noise.
If you open the tank valve slowly, it's worse, as the restriction at the tank valve makes it take longer to reach IP in the servo. It's another reason why there's that second o-ring in the 3960 first stage - it's all an effort to pressurize the servo mechanism quickly. That's why you really need to "slam open" Xstream tanks. With the Duration, of course, and 100% O2 for accelerated deco, you shouldn't do that, and just need to accept the longer honk.

As for it happening with a purge, that must be a fairly vigorous purge! The Xstream second stage gas delivery is huge, and gas expansion at the surface is similarly large: 123 --> 14.7 psi is a more than 8:1 expansion. Because the valve is so capable, it allows downstream IP in the servo tube to fall off precipitously, making it much like tank opening. Even though the Xstream first is capable of large flow, all that expansion at the surface means a bigger drop in hose pressure downstream near the second stage.

All completely normal, albeit different than other designs. At depth, gas expansion is much less (e.g., at 99 feet it's 183 --> 59 psi, or only 3x), so the flow is relatively less abrupt, and since the first stage is able to maintain dynamic IP, downstream IP is maintained and the honking should have no equivalent vibration at depth.

I've noticed a little chatter with a lightly tuned XStream near the surface during heavy breathing, but it disappears below 20 feet.

A fault for one reg design might be a plus for another reg that's certified to 600ft Norsok standards. You can help minimize it for recreational diving by running your IP at the low end of limit (116-123 psi).
The lovelly Poseidon woosh!
Did i need to say they are my favorite regs since 2005?
 

Back
Top Bottom