Diver one of sixteen to die using high-tech gear

[FMT]

Here's a take home message for you. It came in a fortune cookie with my dinner (I shit you not). It said
"Skill comes from diligence."

T ;D

Hi bob! I'm back!

[FMT]

That should read "I sh*t you not."
T

[FMT]

Want to know what my other fortune cookie said?
I was two for two in the relevance department tonight.
My second fortune also applies to this thread and MANY other things in life.
T

[DRE]

Please enlighten us Todd - don't tell me Mouth made onto a fortune cookie... (sorry y'all, inside joke)

[FMT]

Mouth? Does he write for the Shang Pin fortune cookie company?
T

[JNitrox]

Jason, you saw the true nature of my earlier remarks. Thank you. Contrary to what may have been read between the lines, I share the opinion that nothing underwater is worth dying for. At the same time nothing is perfect. As an example, a Space Shuttle was recently lost and I am sure they thought they had prepared for every possibility. I was simply saying that we need to prepare as best we can for our dives, but still admit that no system is perfect.

DRE, no personal attack was intended and I hope you didn't take it that way. I am just expressing what I have learned taking a critical look at diving styles (while doing this type of diving for a decade or so). You were correct in pointing out that testosterone should not factor into the dive plan. At the end of the day, my only goal is to be able to go home again.

I just didn't want anyone to start to get the impression that a specific kit or training style can guarentee their safety. We always need to remember that not everyone that reads these conversations has the same level of training and experience.
Safe diving

[DiverMole]

This is going to be a long reply (in several pieces as there may be a max message length) to address many of the misunderstandings and bad information in this thread

I will use the Inspiration as the example as thats the unit I'm most familiar with, but this applies to almost all other CCR's

On the Inspiration when you exhale the gas goes to the right counter lung/ water trap, it then flows over your shoulder into the base of the CO2 scrubber where it is warmed and cleaned of CO2, there is a water thrap at the base of this to. The gas then goes into the mixing head where O2 is injected if needed. It then flows past triple redundant O2 cells and up to the left counter lung/water trap and to the mouthpiece

The Sensors HAVE to be in the breathing loop as thats what you want to measure. They also HAVE to be between the injection point an the divers lungs as you want to measure what you are going to breath, not what you exhale

The 3 sensors HAVE Hyrophobic (teflon) membranes fitted, Water positively runs off of them, They are all at 90 degreeas to each other so it is impossible for water drops to land on all 3 at the same time. Water on the sensors of the Inspiration is NOT an issue at all (there were some early problems with non hydrophobic cells). Cendensation does occur in the head area (fresh water) but not on the cell face (mainly on the cold metal fixings)

The cells are monitored by the handsets (double redundant with instant failover) and use a voting logic system, where the nearest reading 2 cells are averaged. Alarm conditions arise in the following situations

1) Any cell deviates more than .1 bar from another
2) The reading is deemed to be below .4 bar
3) The reading is deemed to be above 1.6 bar
4) Any cell fails to produce output
5) Battery Low (double redundant)

The alarm is VERY loud and gets louder at depth (its painfully loud below 40m) and is sounded as part of the initialisation routine to verify its use, Its also flashed on the handsets

The cells are calibrated in the machine. The calibration routine requires the user to enter the ambient pressure, the % O2 in the O2 bottle (not always 100%) and to open the mouthpiece. The unit then constantly injects O2 and watches the cells readings rise. When all 3 cells are stabilised and as high as they go these are calibrated to the %O2 you entered. Sensible divers do an O2 flush at 4m to veryfy 1.4 bar is reached before diving (normal dive PO2 is 1.3 so this proves the cells are able to reach the needed values)

There is a good predive routine to follow that checks the loop integrity (both positive and negative) and the function of all mechanicals. You also prebreath the scrubber to activate it and to check for CO2 bypass

I and many others also fit a VR3 with a 4th O2 cell as a separate and independant monitor. This can be calibrated in air or O2 or in the unit.

During the dive you are not task loaded at all and you check your handsets as often as you should be checking your deco computer and SPG on a normal dive. NOTHING EVER HAPPENS FAST ON A REBREATHER!!, even if the O2 failed you would have 2-3 mins to notice and fix and the alarms would also remind you if you failed to look at the guages. Fastest failure is O2 solenoid jammed open. You can hear this and feel the excess bouyancy immediately as well as the alarm would sound

Cont next message

[FMT]

The second fortune said "You are never bitter, deceptive, or petty."
The take home message of this fortune is that personal attacks have no place on this forum. And no JohnnyN, I'm not talking about you. I think your points 3 (the fun in diving and sharing info) and 4 (research and more research) are spot on. A critical look at different diving styles is the best thing (in my view) that can happen on this forum. In that way things (both good and bad) can be learned.
T

[DRE]

Divermole: "I will use the Inspiration as the example as thats the unit I'm most familiar with, but this applies to almost all other CCR's"

"Fine, then I'll keep my replies focused on the Buddy as it comes from the factory - there are plenty of aftermarket options available for the unit, all trying to fix inherent problems idiomatic to the unit. I honestly believe that if you have to resort to an array of aftermarket options to make a $6000 piece of kit safer it already is a moot point. Funny thing, I don't need anything aftermarket for my tanks, regs and backplate..."

Divermole: "On the Inspiration when you exhale the gas goes to the right counter lung/ water trap, it then flows over your shoulder into the base of the CO2 scrubber where it is warmed and cleaned of CO2, there is a water thrap at the base of this to. The gas then goes into the mixing head where O2 is injected if needed. It then flows past triple redundant O2 cells and up to the left counter lung/water trap and to the mouthpiece

The Sensors HAVE to be in the breathing loop as thats what you want to measure. They also HAVE to be between the injection point an the divers lungs as you want to measure what you are going to breath, not what you exhale

The 3 sensors HAVE Hyrophobic (teflon) membranes fitted, Water positively runs off of them, They are all at 90 degreeas to each other so it is impossible for water drops to land on all 3 at the same time. Water on the sensors of the Inspiration is NOT an issue at all (there were some early problems with non hydrophobic cells). Cendensation does occur in the head area (fresh water) but not on the cell face (mainly on the cold metal fixings)"


"There is a small metal screw inside the oxygen sensor compartment, it is located directly across from sensor number two. Condensation often forms on this metal screw and will allow droplets to fall onto the oxygen sensors. This will happen particularly if the diver moves from side to side as in dumping gas from a drysuit or if they invert from horizontal for any reason.
Condensation is inherently found within this area and will form on the oxygen sensors even without this metal catalyst. The O2 sensors are located on the inhalation side of the breathing loop, so you have warm gas that just went through the scrubbing process meeting with cooler gas that you will inhale thus the condensation forming on the cell faces. This condensation causes discrepancies/inaccuracies within the cell readings and they begin to VOTE trying to figure out which one is more than .2 bar out of line with the other. Cell warnings will manifest within this period of time and the diver will begin to get audible and visual alarms ...task loading increases."


Divermole: "The cells are monitored by the handsets (double redundant with instant failover) and use a voting logic system, where the nearest reading 2 cells are averaged. Alarm conditions arise in the following situations

1) Any cell deviates more than .1 bar from another
2) The reading is deemed to be below .4 bar
3) The reading is deemed to be above 1.6 bar
4) Any cell fails to produce output
5) Battery Low (double redundant)

The alarm is VERY loud and gets louder at depth (its painfully loud below 40m) and is sounded as part of the initialisation routine to verify its use, Its also flashed on the handsets"


"The unit alarms if it senses a PO2 over 1.6, which is a good thing. Problem with this is that many of the divers will run 100% oxygen at 20 ft which is a PO2 of 1.6, if they drop below the 20 ft they get an alarm, fair enough. If you have several Inspiration divers in close proximity with cell warning alarms, and high PO2 alarms it becomes very difficult to know if the alarm is coming from your unit or from another diver. Some will be able to assimilate this to being in an area where several cellular phones begin to ring and everyone pulls out their phone to see if it was theirs. Mix this with CCR divers using wrist computers that alarm and you really have an orchestra playing down there, so much for the peace and tranquility of "no bubbles".


Divermole: "The cells are calibrated in the machine. The calibration routine requires the user to enter the ambient pressure, the % O2 in the O2 bottle (not always 100%) and to open the mouthpiece. The unit then constantly injects O2 and watches the cells readings rise. When all 3 cells are stabilised and as high as they go these are calibrated to the %O2 you entered. Sensible divers do an O2 flush at 4m to veryfy 1.4 bar is reached before diving (normal dive PO2 is 1.3 so this proves the cells are able to reach the needed values)

There is a good predive routine to follow that checks the loop integrity (both positive and negative) and the function of all mechanicals. You also prebreath the scrubber to activate it and to check for CO2 bypass

I and many others also fit a VR3 with a 4th O2 cell as a separate and independant monitor. This can be calibrated in air or O2 or in the unit.

During the dive you are not task loaded at all and you check your handsets as often as you should be checking your deco computer and SPG on a normal dive. NOTHING EVER HAPPENS FAST ON A REBREATHER!!, even if the O2 failed you would have 2-3 mins to notice and fix and the alarms would also remind you if you failed to look at the guages. Fastest failure is O2 solenoid jammed open. You can hear this and feel the excess bouyancy immediately as well as the alarm would sound"

"As the diver descends they must equalize the counter lungs, if this procedure is not adhered to and they begin an uncontrolled descent the lungs collapse and the diver is not able to breath, an automatic diluent add is an aftermarket product which does combat this. But since we are talking factory here the diver is faced with equalizing counter lungs, ears, sinuses, mask drysuit, BCD, monitoring PO2 on handsets, buddy position (as far as they dive with buddies), light and depth in the water column. Seems to me like this might be a busy time in which things could move very fast, especially when going wrong."

[DRE]

And since we're at it: "weight must be placed on the top of the rebreather in order to balance the trim. If divers put to much gas in the counter lungs the upper body is lifted and trim is then off center. Gas in a counter lung is just another source to administrate, along with drysuit, BCD, PO2 on handsets, pressure in O2 and DIL cylinders.The mouthpiece does not have OC bailout built into it, bailout is a time of increased stress so it is pertinent the transition should be smooth without chance for a mistake. The bailout procedure on the factory unit uses a device called an Auto Air, this duals as a breathing device and BCD inflator. I couldn't imagine this being an effective tool for gas sharing, nor proper bail out for the user either, as the CCR mouthpiece has to be effectively closed before the transition to OC bailout is performed or it will flood the breathing loop making the diver negatively buoyant. Bailout should be in the form of a combination unit on the mouthpiece to facilitate safe transition.
If the O-ring on top of the cartridge lid is dirty or not aligned properly CO2 will take the path of least resistance and bypass the carbon dioxide scrubber therefore breathed back into the loop. Hypercapnia begins and the diver is faced with another problem to solve.
The Inspiration does not have SS backplate and utilizes many plastic fastex clips, which I view as failure points. There are seven quick releases on the soft harness including the crotch strap and handset clips. The clips that hold the yellow casing lid on the unit break frequently so spares are required as well.
Scrubber canister is small (2.45 Kg of 8-12 mesh, 797 diving grade sofnolime) and does not facilitate the use many of the mixed gas Inspiration divers put it through. At depth CO2 breakthrough is rapid even with a resting diver, if breathing resistance is elevated the scrubber is near void. With increased CO2 build up the diver is of course exposing oneself to further malady. Diving high helium concentrations assist with this problem as it is less dense than air, easier to breath therefore less CO2 buildup and the scrubber should last longer but it is playing on the edge. High PPN2 should be ultimately avoided.
If the counter lungs are not situated adequately they will float above the divers shoulders and increase breathing resistance. It is taught in the basic course to watch for this ... But they are clipped down with fastex buckles which as we know do fail on occasion. With the diver already quite
task loaded on the CCR it is easy not to notice the lung has crept up, CO2 will then increase from breathing resistance.
The LP hoses which feed the diluent and the oxygen inlets on the counter lungs use a different end than the BCD inflator. The BCD is inflated with diluent gas, the same which you are adding into the counter lung, there is no sound reason not to have the same end on this for diversity. The reason the end is different on the BCD inflator is to supply a greater amount of gas to the Auto Air regulator used as a bailout/inflation device. This Auto Air is prone to free flow situations and can dump the diluent gas if not tended to quick enough. Most Inspirations divers discard this Auto Air early into their CCR career.
If both handsets shut off in the water the diver is faced with a series of questions in order to "reboot" the system. One of the questions ask if you would like to calibrate "yes or no" if the diver is stressed and chooses "yes" they will effectively be adding 100% oxygen into the breathing loop no matter what depth they are at in the water column.
If the battery is low it will not supply enough EMF for the oxygen solenoid to open the valve and add life sustaining gas.
The control handsets are secured to the canister via rubber hose, the wiring is run through this conduit down to the electronic handsets that are monitoring the dynamics of the oxygen sensors. These rubber conduits enter into the scrubber/O2 sensor compartment where it is humid and if not perfectly sealed will allow condensation to migrate into the hose and wreak havoc with the electronics in the handsets. Many electronic problems with the handsets have involved this scenario."

If anyone feels that there still is misinformation, bad information, unfounded allegations, backstabbing and drive-by-shootings going on, please take it up personally with me.