Head replacement for existing CCR rebreathers

Faceless

Just have read your documents describing technologies you're offer.
http://www.deeplife.co.uk/files/One_...CCR_Safety.pdf
Amazing, i'm literally shattered ...
Right now I'm just an ordinary OC diver, planning to take some Rebreather courses, but reading thru your documents
has seriously impacted my way of thinking about approach to safety & diving procedures applied to rebreathers.
Small question regardind possible implementation:
You have mentioned that easiest way of applying Open Revolution concepts into real world would be issuing new heads
for existing and proven models of rebreathers, such as Megalodon Inspiration or some others.
Do you have plans of dealing with manufacturers on this matter ?

I apologize if this question has been answered earlier.

AD_ward9

We expect the DL Open Revolution submission to be available in different forms, from four sports dive companies, and one commercial diving company. More than this I can't say just now: companies like to announce products when completely finished, without sales of earlier units tapering off beforehand. We are in the verification stage with more than one company right now (i.e. companies that have contracted with us to deliver the Open Revolution safety technology to their users, we have designed the kit and now are doing compliance and verification work). This means it is getting much closer to being a real product you can use.

Incidentally, there are a few more cases we need to add to the doc you reference:

• Case A: falling PPO2 on rapid ascents. There are some fatalities which seem to come down to the system not being able to inject O2 fast enough.
• O2 tox issues.
• CO or Hydrocarbon contamination: more an issue for commercial diving where a diver can be in a hydrocarbon soup.

For Case A above, The situations that give rise to this are:

1. The PPO2 set point is low to begin with, and the user does a fast ascent. On fast ascents, the specified max EU injection rate of 6litres/min of O2 is not enough to keep the O2 above 0.21. That is, EN14143:2003 has a limit in it which can kill people. The solution is to put in multiple injectors where only one works at a time, until the PPO2 is outside the allowed bands. For example, on a Meg if the user sets a PPO2 of 0.4 then goes for the surface quickly, the diver can lose consciousness on the way up.

2. Running out of O2 on an ascent. Going up is not a good time to run out of O2. Period. Only solution we know of is to force bail out using the auto shut off valve.

3. O2 sensors being replaced by a sensor with a slow response, or two of the sensors failing with a slow response. This problem is specific to certain sensor manufacturers and PPO2 controllers. The result is the controlled does not know the PPO2 is falling fast.

Cheers

Alex

NB: Max specified, means that in the EU spec it specifies that the max level used for testing. It gives a minimum O2 injector requirement of 6l/m.

onetime

Hey Alex,

Any estimates on when it might really come on the market? Are we talking a year, two years, etc?

AD_ward9

In service during 2007. Launches may be late on this year from some of the companies going down the O.R. route. The test and verification programme involves some "quite interesting" manned dives. More info after they have been carried out.
Cheers,

Alex

jknights

Presumably this will need to be CE certified.
Will you be able to do this before mid-2007 ?

I certainly hope so.
Do you have any target price ?
Will it be sold as an alternative to the Vision offereing for Inpiration Classic owners ?


Thanks
JK

AD_ward9

CE certification should be complete in a couple of months. There are some small improvements we are discussing with a scrubber material manufacturuer that would change the WOB very slightly, so have to redo some tests when that change is complete.

On what will be available and pricing, one of our clients will be showing at DEMA or Birmingham. Visa and security hassle in going to the USA is a real pain, so I hope it is Birmingham but we shall see.

Cheers,

Alex

jradomski

I guess my response was lost during the upgrade.. The ce is a MIN not max injection rate.. (and with the jaksa solenoid the meg is just above this)

5.7.2 Oxygen partial pressure setpoint maintenance

In apparatus with a fixed oxygen partial pressure setpoint the inspired partial pressure of oxygen shall be
maintained within

at a low setpoint this is insuf***ient, and borderline from a high setpoint with a reasonable ascent (and little work).. Its insufficient with an emergency ascent or a working ascent.. IMHO about 12lpm should be the minimum target..

__________________
Joe Radomski
CCR Trimix Instructor Trainer
ANDI Instructor Trainer Director #10

All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.

AD_ward9

Thanks for Joe for reposting, as quite a bit of this thread seems to have got lost in the upgrade.

We concur on what should be the min figure: 12l/m.

I would suggest that as less than 12l/m presents a lethal risk under what are quite common circumstances, that any equipment that cannot provide 12l/m has failed to carry out a proper FMECA, as is required for a CE certification. That is, though the standard says 6l/m, it also requires and FMECA and requires EN61508 compliance. To meet that, would need 12l/m. Less than that, the CE certification is, IMHO, false.

One other thing to highlight, that seemed to have vanished in upgrading, is that the solenoid should not switch off, ever. The Inspo method of switching off the solenoid for 6 seconds at a time, is dangerous for very fast ascents, as in extreme cases the increase in intermediate pressure that occurs during those 6 seconds is enough for the valve to stick: it works over an very narrow range.

IMHO injectors should ALWAYS be able to provide 12l/m.

Alex

UKSteve

As I understand it - with the Vision software, the software will fire the solenoid continuously if the pO2 is more than 0.1 bar below setpoint. Not sure what the classic's controller software does however...or if AP is upgrading its software in line with the vision algorithm.

Not sure about the statement on intermediate pressure however. During ascent, the interstage pressure would stay the same until either the solenoid fires or until the over-pressure valve which is fitted to the first stage vents some gas. If it stays constant while the diver ascends fast then there would indeed be an increase is the differential pressure across the solenoid. However I am not sure what the lift setting on the over pressure valve is vs the maximum differential pressure that the solenoid will operate at. Anyone know?

Steve

AD_ward9

The Classic does the 6 second O2 injector pause.

The intermediate pressure issue is quite interesting. The "over-pressure valve" is not fitted to most O2 first stages, especially in Europe, and they generally blows at a much higher pressure than the APD solenoid sticks at anyway. This means if the O2 solenoid is programmed not to fire for a period, and the ascent is fast enough (350ft/min is what some divers manage to achieve in uncontrolled ascents), then the intermediate pressure increases relative to ambient. That is, the differential pressure across the solenoid increases.

The APD O2 injector operates over an extremely narrow range for a safety critical system. The increase in differerential pressure across the injector in 6 seconds in an uncontrolled ascent is enough to jam on an APD injector if the intermediate pressure were near the top end of its range to start with.

Just to highlight the differences between a safety critical injector and a modified machine automation injector, attached is the Test Plan for the DL Open Revolution submission O2 Injector (Edit: Upload failed: 1.9MB limit, file is 3MB. Will put it onto the DL web site when I have time next week).

Cheers,

Alex