PSA: drill your internal booms

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Does anyone know how the Shrader valve in the ISC Meg/Tiburon ADV reacts to increased IP? It's basically an upstream valve where the Shrader pin is depresed by the counterlung. It's not a downstream second stage kind of design, and also has no diaphragm. I guess it should not leak just because of IP creep in the first stage?

I seem to remember threads where overbalanced diaphragm regs caused k-style inflators to leak into the wing, but I am not sure which part failed in those inflators. The shrader valve in the hose seems to hold up against increased IP once the inflator hose is unclipped.
 
Does anyone know how the Shrader vlave in the ISC Meg/Tiburon ADV reacts to increased IP? It's basically an upstream valve where the Shrader pin is depresed by the counterlung. It's not a second stage kind of design, and also has no diaphragm. I guess it should not leak just because of IP creep in the first stage?

I seem to remember threads where overbalanced diaphragm regs caused k-style inflators to leak into the wing, but I am not sure which part failed in those inflators. The shrader valve in the hose seems to hold up against increased IP once the inflator hose is unclipped.
I'm guessing Leon used a similar design to the Mk15 type ADV. It's the same, basically a tyre valve and the stem gets depressed if you bottom out the lung.

I've never tested it for real but I'm told it can take the full cylinder pressure being dumped down the line. I remember Kevin Juergensen saying he'd done a service on a Mk15 where the dil reg had failed and the ADV was seeing high pressure. Apparently the owner had been diving that way for a very long time without ever noticing it.

In saying that, it's a braided steel hose from the 1st stage which connects into rigid stainless steel pipework (if I remember right the 15.5 & 16 has rigid SS pipe all the way from the 1st stage). It's not LP hose. So either the hose will burst or (assuming there is one) the OPV will blow if it is being fed by low pressure rated plumbing. I don't know how the Meg is set up.

The original KISS classic also has an upstream valve. It's a tilt valve connected to a rubber plug. When you inhale the ADV diaphragm pushes the long pin sideways which tilts the plug which breaks the seal. Kind of like a very simple Poseidon Jetstream 2nd stage. I never had any issue with the old brass tophat + oring (unless the oring needs replaced in which case it's so frustrating to fix that you might as well just give up diving). The newer solid rubber version leaked like a retired pornstar.
 
Does anyone know how the Shrader vlave in the ISC Meg/Tiburon ADV reacts to increased IP? It's basically an upstream valve where the Shrader pin is depresed by the counterlung. It's not a second stage kind of design, and also has no diaphragm. I guess it should not leak just because of IP creep in the first stage?

I seem to remember threads where overbalanced diaphragm regs caused k-style inflators to leak into the wing, but I am not sure which part failed in those inflators. The shrader valve in the hose seems to hold up against increased IP once the inflator hose is unclipped.
If you’re using a standard MEG setup with an OTSCL and a shut-off valve on the DIL MAV, the shut-off valve will stop unwanted diluent flow*.

Even if there isn’t a boom, you should still be able to hear DIL trickling into the lung if the shut-off valve isn’t sealing properly. You can cycle the shut-off valve on and off to reseat the O-rings. If the DIL still leaks after this, use a feathering technique on the DIL valve to add gas only when needed.

*Tip: Make sure your CCR regulators have an OPV to prevent unwanted gas dumps. The inexpensive $5 OPVs are disposable and will eventually fail. You may want to upgrade to a rebuildable OPV — or go all-in and use a Poseidon MK3 first stage, which has a built-in OPV.
 
If you’re using a standard MEG setup with an OTSCL and a shut-off valve on the DIL MAV, the shut-off valve will stop unwanted diluent flow*.

Even if there isn’t a boom, you should still be able to hear DIL trickling into the lung if the shut-off valve isn’t sealing properly. You can cycle the shut-off valve on and off to reseat the O-rings. If the DIL still leaks after this, use a feathering technique on the DIL valve to add gas only when needed.

*Tip: Make sure your CCR regulators have an OPV to prevent unwanted gas dumps. The inexpensive $5 OPVs are disposable and will eventually fail. You may want to upgrade to a rebuildable OPV — or go all-in and use a Poseidon MK3 first stage, which has a built-in OPV.
Thanks! Great thread, I hope we are not drifting too far off topic. Yup, I am gonna replace my OPVs with stainless steel ones that are adjustable...
 
Does anyone know how the Shrader valve in the ISC Meg/Tiburon ADV reacts to increased IP? It's basically an upstream valve where the Shrader pin is depresed by the counterlung. It's not a downstream second stage kind of design, and also has no diaphragm. I guess it should not leak just because of IP creep in the first stage?

I seem to remember threads where overbalanced diaphragm regs caused k-style inflators to leak into the wing, but I am not sure which part failed in those inflators. The shrader valve in the hose seems to hold up against increased IP once the inflator hose is unclipped.
As mentioned, the OPV on the 1st stage is there for a reason. The schraeder valve won't leak. If your power inflator is on the diluent that will be the point of leakage if the OPV doesn't bubble first.
 
This happened to me today, as a new JJ diver with probably 50 hours in the unit. It was pretty much completely my fault due to skipped check lists and poor equipment config.

Yesterday I did two dives on the unit (about 50ish metres each) and was having issues both times. Struggling to get down, high dil usage. On the second dive, my buddy noted that my OPV on my dil first stage was leaking.

Because I'm an idiot, I 'solved the problem' by replacing the misbehaving OPV with a port plug. Just until I could get a replacement OPV, I told myself.

On the boat at 5am this morning the unit was misbehaving. It kept blowing the wing LPI off. I replaced the inflator on the boat and jumped in.

At 60ish metres 25 minutes into the dive the ADV free-flowed and very rapidly filled my CLs. I thought it was the misbehaving inflator and quickly removed the LPI. Then thought it might be a stuck solenoid but the PO2 was constant (the solenoid was firing to maintain PO2 as the dill rushed in, making the problem worse).

It took me a while to find the dil valve and shutdown. I was sufficiently flustered by that stage that I bailed out and we ended the dive uneventfully. It was a scary experience, and I felt fortunate I was with good dive buddies. Hitting the flow stop (which I initially forgot, going straight for the valve) wouldn't have helped, for reasons we diagnosed on the surface.

It turns out that the seat on the dil first stage was damaged, and the IP was high, and climbed once the valve was opened. This is why the LPI was popping off, and this is why I'd been burning through Dil the day before.

If I had not removed the OPV, this would have been a leaky dil reg, not a 'boom'. Dive likely would have ended, but under far better conditions.

If I had followed the checklist, which requires using an IP gauge to check the IP pressure before each day's diving. The problem would have been fixed before I got in the water.

In the end, we had about 45mins of deco and my first real life bailout went ok. I'll be re-drilling my shutdowns (including more aggressive venting or even releasing the loop to let the gas escape in an emergency situation) in future so that I'm better prepared in the unfortunate event this happens again.
 
Then thought it might be a stuck solenoid but the PO2 was constant (the solenoid was firing to maintain PO2 as the dill rushed in, making the problem worse).
I found the above interesting, as I dive a manual unit. I knew an eCCR can complicate buoyancy on ascent, but I hadn't connected the dots to this scenario. Thanks for sharing, and I'm glad you were able to get it sorted!

<off to check my IPs right now. It's been... too long. 🫤>
 
I respectfully disagree. If eCCRs complicate buoyancy on ascent, you're dealing with skills issues.
Less disagreement than you might think, since I only said, "can complicate", not "must complicate" or similar. (Although no one is perfect -- I suspect everyone gets surprised by the solenoid firing on occasion.) That said, things can get heated when the rig malfunctions, and I view drilling reactions & process refinement as skill improvement. It's also a good test to see if your skills are where you want them to be.
 
I respectfully disagree. If eCCRs complicate buoyancy on ascent, you're dealing with skills issues.
When your dil in bleeding into the loop through an IP driven ADV leak, you're trying to ascend, <and> your solenoid is trying to maintain setpoint, blaming the diver for a "challenging" ascent is really in poor taste buddy. Not that it would be that much easier on mCCR since someone or something needs to keep the loop at least marginally breathable. And if you bail in frustration or fear, you still have the IP problem screwing with your 4th airspace. (Lungs, wing, drysuit, CL = 4)
 
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