How did my NERD/AI setup make me VERY glad to have it?

[Bierstadt]

Thanks for sharing.

 

[Heat Miser]

In a tight environment and your O2 gets rolled off? A HUD that alerts you before your ppO2 even begins to drop noticeably seems nice.

You must have one hell of a back kick if you can get the revo O2 cylinder to roll off.

Did at anytime you see bubbles coming from the DSV. I'm just wondering why you didn't plumb offboard and run it manually? Perhaps not thumb the dive.

But with that thing about loop leaking on the surface it sounds like you made the right call. And I wonder whether it was a problem with the DSV and not the BOV per se.

 

[Wibble]

Knowing your gas pressures on CCR is normally one of those low priority pieces of information which is perfectly suited to the Nerd's mini-display in the third cell position. During any normal dive gas levels change very slowly and there's plenty in reserve.

However, when gas starts leaking, gas pressures become critical information, certainly in the fault finding phase. It's also nice that the Nerd will throw up the "T2 Reserve Pressure" warning message when the gas gets to 60bar (had this over the weekend when in a poor visibility shallow lake doing loads of drills and using a 2 litre diluent -- constantly filling the wing uses a lot of diluent)

One thing that's great about the Nerd's AI is where you can switch the bottom row to the larger pressure display thus easily read the numbers.

I had a leak on my unit during a descent which I could hear behind me and see the bubbles reflected in the Petrel's screen, but I couldn't determine where the leak was coming from. Being able to accurately know the exact O2+Dil pressures (even if it's not accurate, digital clearly shows changes in pressure) meant that I could determine the leak was not from my unit, but from the bailout; turning off the bailout stopped the leak (if I needed to bail out I'd use the standard regulator and turn the bailout back on). Thus I could descend and resolve the issue on the bottom. It turned out that the BOV LP hose connection had come undone by 3 turns, bubbles leaking up the loop cover and exiting behind my head. Tightening that regulator connector by hand sorted that out and the dive was saved. I now have that bolt properly tightened, marked, and check it on every dive.

I have my BOV LP hose routed down behind my shoulder and through a bungee loop just below my shoulder blade; this has a QC6 connector which can be disconnected under pressure and under water. This is connected to my deep bailout. For the problem above, I could have just disconnected the QC6 and stopped the LP leak, falling back to the normal regulator as a bailout.

Am happy with my decision to connect the BOV to offboard bailout with QC6s.

My guiding principle for most of my modifications has been redundancy. This means keeping systems separated such that a failure of one thing can't affect another. Example would be cell splitters which effectively connect the two systems together and, however unlikely, could be a single point of failure of both monitoring systems. Bailout is the same: my BOV is where the loop meets the bailout, so should, say, the mouthpiece come away then I can bail out to an independent regulator.


Great lessons learned for all of us.

 

[kensuf]

Just curious what BOV you were using and any idea what caused the o-ring to pop out.

 

[rob.mwpropane]

I don't trust myself to be so aware. It has not happened (yet). But, I don't believe that I am SO aware that it could never happen that I would be losing gas somewhere, somehow where I didn't notice it happening. I *wish* I felt so on top of things at all times that I had confidence that would never happen.. but I don't. I think I do pretty good, but I know I don't always know EVERYTHING that is going on around me.

^^^ This is me... I try to be aware but the best I can do sometimes is be be honest with myself that I'm unaware. I joke all the time that one day I will get eaten by a shark looking at a small starfish or urchin in between the cracks!!

I'm not ccr, just agree with knowing that I'm unaware.

 

[rddvet]

Huds save lives whether they’re a nerd or a regular hud. I personally didn’t like the nerd at all when I tried it. But I’m a proponent of every single ccr having a secondary output. Obviously a regular hud wouldn’t have told you about the dil pressure, but I think your main point is having info in front of your face is helpful and I fully agree. If somebody can’t afford or doesn’t like the nerd, then at least have some other secondary monitor. Because I don’t have a nerd I’ve gotten it into my brain as second nature to start checking my computer a lot if I’m having an issue.

 

[Tracy]

I have to admit I’m amused by your attempted use of your tongue as an O ring pusher.

I’m still in training but diving with a O2 bottle transmitter as well as one for dilout bottle. I had a SPG on dilout reg, but then I noticed at home after the first day of training that it was stuck at 1000 psi. I’ve not used a SPG in two years. Took one of my SM reg transmitters and added it to dilout reg. I have both on my Perdix on right arm. Prefer to keep that separate from Petrel 3 monitoring po2 on left arm.

You can program the transmitters to both computers. You don't have to put them on the main screen. When your right arm computer battery dies, if you needed to, you could scroll right three times and view the pressures on your left arm. The petrel 3 is a nice upgrade. I especially love the idea of haptic feedback for po2 warning. My first rebreather had a haptic feedback hud, while annoying on the surface and during setup, it was amazing when things went wrong.

 

[Marie13]

You can program the transmitters to both computers. You don't have to put them on the main screen. When your right arm computer battery dies, if you needed to, you could scroll right three times and view the pressures on your left arm. The petrel 3 is a nice upgrade. I especially love the idea of haptic feedback for po2 warning. My first rebreather had a haptic feedback hud, while annoying on the surface and during setup, it was amazing when things went wrong.

Have both transmitters going to both Perdix for SM, just really haven’t bothered to set them up on Petrel 3 yet.

 

[tbone1004]

Kudos to you for your vigilance. I don't trust myself to be so aware. It has not happened (yet). But, I don't believe that I am SO aware that it could never happen that I would be losing gas somewhere, somehow where I didn't notice it happening. I *wish* I felt so on top of things at all times that I had confidence that would never happen.. but I don't. I think I do pretty good, but I know I don't always know EVERYTHING that is going on around me.

Fortunately, as you said - and in what happened to me in Pompano - I could have lost either (or both) 3L cylinder and still been fine. But, I am glad I became aware BEFORE I lost all my dil.

I will actually concede that if I did have a monitor that had AI then I would put transmitters on there because I find them infinitely better than button gauges and if I change my kisskat over to a Petrel 3 then I'll put a transmitter on the O2 side and transfer that with its mate to the O2/inflation bottle on my rack for those dives but it's simply for convenience and certainly wouldn't get me to run long SPG's from those bottles

 

[cathal]

I think the course of action around removing the BOV is for another thread. Equally experienced divers will disagree with you removing the BOV. Personally, I have a BOV and I keep it serviced and connected to an offboard cylinder. If I am wrong about having one I figure I have misspent €1,000 or so, but as a life safety mechanism, better to have it and not want it as opposed to wanting it and not having it etc...