Rebreather error!

[Depth-junkie]

Glad all ended safely Mark, but i for 1 would not have dived the unit with a known fault at the surface.

If the unit went faulty whilst underwater then that is a different scenario, you fix the probelm and finish the dive manulay as you started the dive. But to dive it like that from the start is asking for trouble IMHO.

Not trying to make you suck eggs m8, far from it. But too many good divers have been lost diving units with known faluts before they enterd the water.

I know you were shallow, hence why you dived it as you said if it was deeper you would not have gone in.

But if the water is deep enough not to be able to stand up in, it's deep enough to drown in. Dont take unnecessarily risks.

it either all works or i dont dive it, if it brakes underwater i fix/manage the problem but i would never ever dive my unit with a known major fault before i roll in.



ATB
Gareth

[dublinbay]

Good post Mark. As I was told and told others, if it`s not right above water ,it can get worse very quickly underwater, so don`t dive. Sounds to me like you are acknowledging what you already knew on a public forum. Nice one mate, green incoming.

[NotDeadYet]

Originally Posted by Depth-junkie

Glad all ended safely Mark, but i for 1 would not have dived the unit with a known fault at the surface.

I have to agree. Diving a broken rebreather is a bailout option, if you already start off on a broken rebreather then you're essentially getting in the water already on bailout. I've binned a couple of dives because I had my doubts about the calibration, it's not worth it. But then hindsight is great...

[Okeanos]

Originally Posted by Depth-junkie

i would never ever dive my unit with a known major fault before i roll in.

Cheers Gareth.

I wouldn't dive it with a major fault, the solenoid not working just turns it into a manual CCR. I already drive the dil manually so driving the oxygen manually is just another skill we should all practice and this seemed a good time to try it.

What I would like to know, was that the unit calibrated incorrectly, how on earth did it do that?

Originally Posted by dublinbay

As I was told and told others, if it`s not right above water ,it can get worse very quickly underwater, so don`t dive. Sounds to me like you are acknowledging what you already knew on a public forum.

Thanks Jack, I was. I am not ashamed to show that I make mistakes and to tell people I can be a muppet. I was told that after 50 hours it bites you in the ass, then again at 150 hours, luckily my 50 hours didn't happen, my 150 hours was only a gentle nibble. Still enough to make me sit up and think though.

Now, for my next trick!

Who was it said? "What doesn't kill you makes you stronger?"

[turbanator]

Hi Mark,

Originally Posted by Okeanos

I wouldn't dive it with a major fault, the solenoid not working just turns it into a manual CCR. I already drive the dil manually so driving the oxygen manually is just another skill we should all practice and this seemed a good time to try it.

Yep, that's SOP for us poor ol' Kiss divers

Originally Posted by Okeanos

My main point was that the unit calibrated incorrectly, how on earth did it do that?

Thanks Jack, I was. I am not ashamed to show that I make mistakes and tell people.

The thing that I'm having trouble with, assuming that I understand the scenario that you describe, and also not being an Inspo diver, is that you (fortunately correctly) went for gut feel, and belived the VR3 single cell over the Inspo's 3 cells.

For me speed of calibration if it was a lot faster (speaking as someone who has to tweak his displays with a screwdriver) should have just made you want to run the calibration process again.

Glad it finished ok.
Best
P

[Depth-junkie]

Cheers Gareth.

I wouldn't dive it with a major fault, the solenoid not working just turns it into a manual CCR. I already drive the dil manually so driving the oxygen manually is just another skill we should all practice and this seemed a good time to try it.

A solaniod is a major part of an ECCR IMHO, you are not diving a manual CCR. So a core feature of that particular unit was faulty. Manualy running a unit is good practice for the reason you stated (if the solanoid packed up whilst diving) but i would not go in knowing before hand that the problem excisted, as you are already on plan B

My main point was that the unit calibrated incorrectly, how on earth did it do that?

My GUESS.....It takes a good few fills of the bag and vent to get the unit reading 1.00 @ the surface whilst doing a manual flush to acheive it. As you are adding gas at the bottom of the lung and forcing it all the way through the bags, hoses, slime bed etc etc all the way to the head. So there is a lot of air space to be filled with 02 (flush out any air in the loop) to get a good solid reliable reading whilst then allowing the unit to be at ambeint (i.e opening the mouth peice)

the solanoid fires the 02 directly at the top of the head and 02 sensors. So it only has a small space to fill with 02 to get a reliable stable reading.

So any residual air not flushed out fully whilst allowing the unit to be at ambeint pressure will affect the calibration when doing a manual calibration, Just my thoughts



ATB
Gareth

[turbanator]

Originally Posted by Depth-junkie

My GUESS.....It takes a good few fills of the bag and vent to get the unit reading 1.00 @ the surface whilst doing a manual flush to acheive it. As you are adding gas at the bottom of the lung and forcing it all the way through the bags, hoses, slime bed etc etc all the way to the head. So there is a lot of air space to be filled with 02 (flush out any air in the loop) to get a good solid reliable reading whilst then allowing the unit to be at ambeint (i.e opening the mouth peice)

Sounds feasable, when we calibrate the Kiss, we suck it down to callapse the lungs, then fill it with O2. This is repeated twice more, O2 bled off, then the mouthpice opened and closed to ensure the loop is at ambient, then we calibrate.

However, whether Mark had the loop for of O2 or not, would that explaind the fact that it calibrated faster than normally.

Also, as you rightly say, there problem was there before he entered the water, I would guess that this would normally indicate that the unit should not be dived. If this is the cased, is there a publishe procedure for a 'manual' calibration?

r
P

[NotDeadYet]

Originally Posted by turbanator

Sounds feasable, when we calibrate the Kiss, we suck it down to callapse the lungs, then fill it with O2. This is repeated twice more, O2 bled off, then the mouthpice opened and closed to ensure the loop is at ambient, then we calibrate.

I don't. I take the exhale hose off and breathe through the DSV to draw fresh air into the head then calibrate in air. Once the hose is back on then I verify in O2 but I do the actual calibration in air. I find the loop stabilises at a bit less than 1.00, not much but enough to be significant. I felt I was getting too much error when calibrating in O2.

I do a final check at 6m first on O2 then with a dil flush.

[turbanator]

Originally Posted by NotDeadYet

I don't. I take the exhale hose off and breathe through the DSV to draw fresh air into the head then calibrate in air. Once the hose is back on then I verify in O2 but I do the actual calibration in air. I find the loop stabilises at a bit less than 1.00, not much but enough to be significant. I felt I was getting too much error when calibrating in O2.

I do a final check at 6m first on O2 then with a dil flush.

This assumes linearity, we were taught the other way around as 1 bar is nearer the 1.3 or so you'll be using on the dive. The check in air is a good sanity check and then your O2 and dil flush at 6m verifies the lot.

Like you I get a bit of error, i.e. I seem to need to trim the pots most calibrations, which is not what I thought would happen when the cells were 'run-in'.

I may try it your way tho' as the 21% source is a bit more reliable than 100%

r
P

[Depth-junkie]

There are 2 design features i would like to have seen added to my vision inspo:-

1:- standard slot for a ind-4th cell and the head with a blanking plug, which can be removed to allow the cable for say a VR3/explorer to be fitted with a 4th cell.

2:- Manual 02 addition to be directed straight into the head next to the cells etc, and not at the furthest part of the loop away from the cells I.E the bottom of the counter lung.
Wether this be done via a KISS valve style 02 set up with the injector nozzle in the head or something like that (like a user opperated solaniod so to speak, you push a button to open the solaniod, when you let off it closes). Now that would be a nice redundant feature if the battery opperated solaniod failed.

Leave the 02 add button on the lungs for the addition of offboard 02 to be added, so 3 ways of getting 02 into the loop for redundancy. 2 inboard 1 off board

The 02 add on the lungs is good enough to get the job done, but the above would improve the ease of doing a manual drive of the unit if the onboard 02 is still accesable IMHO.




ATB
Gareth