Radial Scrubbers

[apitkin]

Originally Posted by ewan

Look at the independent tests on the Ouroborus and Inspiration - they both get close to 100% efficiency based on Molecular Products' figures and that's difficult to improve on.

I'd certainly like to see those tests. Where are they?

Originally Posted by Drmike

I believe radial scrubbers have a more sudden breakthrough when expired whereas axial tends to have a slower breakthrough. Also radial need more care packing. But I could be talking bollocs

I don't think so (about talking bollocks I mean). The question is, is it better to have a longer duration without any breakthrough, or do you think that slow breakthrough is a useful phenomenon in terms of warning the diver? I would prefer to avoid it altogether. All the CO2 episodes I've heard about scare me quite a lot. I personally think any CO2 in the inhaled gas is very dangerous indeed. But that's just my opinion. And Nigel's hit the nail on the head again, as usual.

Andy

[ewan]

Originally Posted by apitkin

I'd certainly like to see those tests. Where are they?

The results are in the users' manuals.

They're presented in a similar fashion and I'm pretty sure they were undertaken by the same testing facility following the same procedure to gain the CE stamp.

[Needlebender]

I'm pretty sure it goes anticlockwise

[iain/hsm]

Originally Posted by apitkin

I'd certainly like to see those tests. Where are they?
Andy

I too would like to see these independent tests on canister duration published. After all informed choice can only be made from reliable information. However it is up to the manufacturers to publish the information first.
With testing there is a magnitude of difference between an independent EN14143 test and sucking and blowing on your bike with your set in the fridge, puffing till the lights go out. However in the UK EN14143 does give reassurance of at least the minimum standard being achieved.

To help this along I enclose copy of a wrist controller download showing C02 break out with depth, time, and water temp. Perhaps with the absense of test results being published we could arrange to test and compare the results from a list of rebreathers you would like to see tested. Iain Middlebrook

[Drmike]

Originally Posted by iain/hsm

Perhaps with the absense of test results being published we could arrange to test and compare the results from a list of rebreathers you would like to see tested. Iain Middlebrook

Or you can just tell me where to buy a real time PPCO2 monitor and I can do it myself.

I know I know not available yet/only to military...sigh

[wreckweasel]

Originally Posted by iain/hsm

To help this along I enclose copy of a wrist controller download showing C02 break out with depth, time, and water temp. Perhaps with the absense of test results being published we could arrange to test and compare the results from a list of rebreathers you would like to see tested. Iain Middlebrook

Iain,

Are you saying you could arrange this? If so.... Im happy to chuck you my lump to play with (Classic KISS)

I guess people would be interested in;

Kato (ten a penny!)
Evolution
KISS
Sports KISS (Just to see how that double scrubbing breakthrough occurs)
Megalodon (Decodiver on here has one)
PRISM (Apitkin has one on here)
CCR converted drager (now that'll be an eye opener, I can source one)
MK 15?
Ouroboros

Im guessing thats a whole bundle of work

oh well... worth a try!

[ewan]

Originally Posted by Drmike

Or you can just tell me where to buy a real time PPCO2 monitor and I can do it myself.
I know I know not available yet/only to military...sigh

There are CO2 monitors available if you want one for a test rig.

CO2 analysers are regularly used to monitor bell and chamber atmosphere and to warn of scrubber breakthrough. Possibly because the scrubber designs used in this application (invariably radial BTW) are so efficient, breakthrough is very fast when it happens.

Personally I'd prefer to know about any impending breakthrough well in advance, which is why I'm not sure that a CO2 monitor in my RB would be that much of a blessing.

[Duncan Price]

Originally Posted by wreckweasel

Iain,

Are you saying you could arrange this? If so.... Im happy to chuck you my lump to play with (Classic KISS)

I guess people would be interested in;

<snip>

and a D5! In fact I'll bring it around on my bike.

Onre thing I would like to know though is the test a continous flow through the loop or does the gas go in pulses like normal breathing. If the latter then there is a dwell in the scrubber between pulses.

[Drmike]

Originally Posted by ewan

There are CO2 monitors available if you want one for a test rig.
.

I want one in my diving rig - those arent available - I wish they were.

CO2 monitors are availiable yes but none that will work inside a loop with 100% humidity....I would be very happy to be proved wrong but CO2 monitors for RBs are just vapourware if you cant physically buy one - and I cant.

[iain/hsm]

In reply to the points made:
1. At present the (military version) of the unit is suitable pretty much only for the LARV shallow water pure oxygen rebreather monitoring both PP02 and PPC02. With the added ability to activate two solenoids that in turn fill a Secumar divers jacket and to flush the bag (O2) in the event of a gas trend change, a high C02 spike, or an increase in depth deeper than MOD. The other is an accent control that operates a dump solenoid to slow the divers accent near the surface. On surfacing the fill solenoid keeps the bag full. Power on accent is directed to fire up EPIRBS and a strobe light for diver recovery. This product we call a SRD or self rescue device. A manual delay or reset is also fitted in the event the diver has switched breathing from UBA to a plug in submarine set.

2. Far from being “vapour ware” The second version proposed for the CCR variants was shown to selected parties at DEMA last year and is more suited for sport or commercial diving in so far as the circuit variants allow control of diluent gas for PPO2 and is suitable for 200MSW depth. In addition the system logs 16 events every 0.1 min including run time, depth, oxygen average (3 off K1 cells) PP02, PPC02, battery, alarms, RTS. However the VVAL 21 deco program may require changing to say DECAP with standard values. PPC02 accuacy is +/- 0.2kPa with resolution to 0.01% with a reaction time of 5 seconds.

3. IMHO It is difficult to see that a stand alone PPC02 monitor is of any great value when its greatest effect is being able to control. Further the nature of a C02 breakout or spike may incapacitate the diver so at the very least provision to activate a flush was anticipated and for that you need PP02, and for that you need depth, and for that time, and deco etc. etc. etc. so you may as well go for the whole hog control.

4. The controller is not the same as the Analox Bell Diving or saturation gas analysis system. (Here I disclose an interest. Alan Harbottle managing Director of Analox and myself did have a 25% partnership in a gas analysis company some 20 years ago but we have had no commercial links since then)

5. The proposed test with various commercial rebreathers would be part of an engineering data submission. It would also require to ventilate each rig up to 90 RMV and bleed in 1.6 SLM of C02 to simulate the diver breathing under a heavy load. The breathing cycle is a sinusoidal cyclic test to mimic actual diver breathing per EN250 EN 14143 but with an optional 0-7 litres variable swept volume per stroke option to suit Mil spec and USN.