How to test Sodalime ?

shil

Is there a simple test for the effectiveness/ quality/ performance of sodalime?
I would like to make an O2 rig for my studies of shallow reef marine life, as no such rigs are readily availble in India, am planning to make a simple one like a Seahawk.
As for sodalime , some companies manufacture it and so the question.

Shil

abowie

Not really off the top of my head. You need some method of measuring PCO2 in the inhaled limb of your Rebreather and that's going to be complex no matter how you do it.

Most commercially available sorb will be rated at about 140l of CO2 absorbed per kilo of fresh sorb so you could just do some rough calculations based on an assumed CO2 production rate and known amount of sorb. Not very safe though as it assumes a number of (uncontrollable) things.

Or you could just copy an existing unit and use its recommended sorb duration but the same caveat as above would apply.

Sitting on your lounge and breathing on your Rebreather until you get profoundly short of breath is pretty silly too and won't help you that much either.

Maybe someone else has a brilliant idea?

PS what a magnificently simple deathtrap!http://www.teknosofen.com/seahawk_pic.htm

__________________
Andrew Bowie

Rebreather-friendly Buddy

AD_ward9

1. With such a simple horizontal scrubber, tunnelling is likely to bite sooner or later. Better to take a commercial scrubber, or copy a commercial scrubber, keep it in the orientation it is designed for. That way, you also know the scrubber life. OR, use an Extend Air cartridge, that way you do not need a scrubber canister at all in your design (just clamp the tube to it).

2. That bayonet fitting, if it comes loose will kill you quite quickly. Again, using a commercial scrubber avoids this. It is surprising what boats can make come loose. Better still, the Extend Air canister.

3. If you use an inner tube, put it in something. The sun does a lot of damage to rubber, and wrecks/coral even more so. Breathing from an inner tube does not sound wonderful either. Silicone water containers are much better. Remember, what grows on the inside of that inner tube, can find a way of getting to your lungs one way or the other, no matter how you clean the unit (apart from an autoclave, which for rubber would not be too good).

4. How are you going to measure the PPO2? There are some nice 4x sensor boxes on this forum.

Cheers,
Alex

GKAM

Hi AD_ward9, I think our friend here is trying to build an O2 rig. ppO2 monitoring is not an issue I would guess. But you are right about channeling.

I was diving an O2 homebuilt some years back based on a bike inner tube and PVC pipe. To prevent channeling I improvised a system to keep the scrubber material tighly packed. Some pics are still up at http://www.kamarinos.com/rebreather/DIY_CCR_EN.html

btw, inner tubes are extremely duarable and fairly inexpensive. You can easily build a couple of sets for next to nothing. However, you must first do several thorough washes with hot soapy watter to get rid of the rubbery taste and smell


Cheers,
GKAM

AD_ward9

Sorry, after starting I had an interruption for an hour, and when I got back forgot it is an O2 Rebreather. You are right of course.

Your unit looks very neat and tidy. The screw clamp you use to compress the lime is the thing to use, rather than the bayonet linked earlier in this thread.

Makes one think what is the minimum possible config. Probably a tube, clamped to an Extendair cartridge, the breathing hoses with their mushrooms, and an injector valve. It would be under $70 even if one bought everything. All the cost is the breathing tubes and mouthpiece.

I still don't like car inner tubes: black plastics are usually UV tolerant, but inner tubes are not: I use them for holding a holding net on the surface when spear fishing (using a snorkel) and have been through a few. This is in Scotland where the UV is pretty low. Put a cordroy sleeve over it and it would last much longer. Silicone is also more hygenic all around.

Cheers,

Alex