Scrubber

With Radial Scrubbers you can have In to Out flow or Out to In flow - both have advantages and disadvantages.

On the Meg unless you switch the hoses you have Out to In (same as CIS I believe).

Out to In means that with a hydrophic membrane the scrubber is much much more tolerant to water flooding and can cope with a partially flooded cannister much better.

In to Out flow means that you will get a slightly longer scrubber duration as the gas velocity slows when it gets towards the outer edges of the scrubber giving you a longer dwell time but not much ability to cope with a flood.

Stuart

Axial:[adj] situated on or along or in the direction of an axis (up and down)

Radial:Radiating from or converging to a common center

Hope this helps,
Andy

Stuart,

The Cis was equipped with a membrane to protect the scrubber material and allowing you to clear the flooded scrubber or bail out. A caustic cocktail with liquid hydroxiode is deadly as oppose(please excuse spelling it is late and I am tired) to lime were you will probably recover from a caustic cocktail, the direction of flow pertains to the design of the scrubber, so if you do not rotate the hoses there is no real benefit to a radial scrubber IMO, In fact you are creating an increase in wob. Can you rotate the hoses on the meg and reverse the flow, or will it screw up the electronics?

hey Martin, first of all its not liquid hydroxide, it lithium hydroxide, which is very causetic comapring to normal sofnolime. the you cannot just switch the hoses, cause then you would have to turn the mouthpiece upside down in order to get the mushrooms on the right side too.
As Stuart said above you can use a radial scrubber of the type out to in, which will still give you a performace bennefit over an axial one, you cna also use the hyrophobic one from the cis, if you are able to find one and want to pay the price. I am looking forward to get the prism scrubber for my meg.

/Jonny

Yes you are quite correct a hydrophobic membrane allows the use of lithium hydroxide and the ability to change scrubbers under water! Which the CIS had - however I believe it also had an out to in flow too....

OK let me try and give an example to illustrate an advantage of out to in - for this example we shall assume the volume displaced by the inner tube in a radial scrubber was 10 cm3 or 3 cubic inches or so (no idea if these measurments are correct).

Lets imagine we are using say a PRISM scrubber here without a membrane....

Right then we are swimming merrily along and we get our hoses caught inside a wreck and it gets pulled out of our mouth - we get oh say 15cm3 or say 4 cubic inches of water into the system - we quickly untangle by means of a little roll and backwards swim and stick our DSV back in out mouth.

We now have some water in the system and because of our acrobatics it has worked its way down into the scrubber past any water traps we might have.....

With an In to Out flow the centre space in the scrubber is now completely full of water and our WOB is such that we have to bail and now can not go back on the loop.

With an out to In flow the bottom inch or so of the can / scrubber is now covered with water and we will have a slight increase in WOB but a perfectly usable scrubber still.

The downside to Out to In is that the scrubber will not last as long as an In to Out however it still should last longer that a standard axial as dwell time of the gas is still increased.

As to the other questions you can swap hose direction on the Meg no problems(mushroom valves changed etc) but for me I would prefer the ability to cope with a partially flooded scrubber more valuable than slightly increased run time on scrubber. Horses for Courses etc - no right answer!

In terms of increased WOB with radial scrubber - I had always assumed there would be especially one with a hydrophobic membrane but when I was out with Leon in August I used his CIS scrubber for the week and could tell no difference.

Stuart