Meg Radial Scrubber Test report

RonMicjan

even through moisture is a component of the reaction, heat is also, so the temperature is climbing, therefore no condensation because as the moisture is released by the reaction, the temperature climbs too and until that gas hits a cooler surface it will not condense.

I think you may have some nomenclature confused, the plenum is the aluminum housing surrounding the scrubber, which also the cylinders are mounted to, otherwise known as the "CAN". When the gas travels up the center tube of the radial scrubber canister, the next thing it encounters is the sensor carriage, then the inhale hose heading to the inhale counterlung.

there is no drain in the bottom of the scrubber, there is in older units a one way valve and drain tube in the sensor carriage, that has been eliminated in the newest units however.

High humidity actually produces less dense gas, strange as it may seem, but the difference is minor for this application, in aviation it must be taken into account for takeoffs as warm moist air can add to your takeoff roll.

I believe I need to write a detailed gas flow chart to clarify how this works.

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trob09

Way off topic here, but I miss the one-way valve. There seems to be a lot more moisture on the sensor carriage and sensor faces since Steve 'upgraded' this for me.

Back to your regularly scheduled discussion...

silent running

Hi Stuart, yes of course the amount of sorb is the main factor. But to suppose that all scrubber designs make equal use of the sorb that's there seems a bit too simple.

My own experience with pushing the Prism 6lb radial is the result of several hundred hours getting consistant results, working my way up to the 10hr mark over an additional 100 or so hours. My "testing" was certainly not scientific, but did achieve consistant results. I am fit, not too heavy. All of my diving during that time was done in warm water-68F to 80F-mostly with air dil to max depths of 160ft, limited deco-10-20min-which usually went away on ascent-fairly typical recreational CCR profiles. My impetus to push the scrubber came from diving in remote places for weeks at a time where I had to bring my own sorb and need to make the most of my limited supply. Most days I found myself diving in stiff current with periods of very high exertion, the nature of diving in remote places. There were plenty of times where I found myself working max hard in the 8-9th hr of the scrubber. Others have pushed the scrubber to 11hrs in colder water, with normal exertion. But of all the Prism users I know, I probably have the most experience pushing the scrubber, due to my travel habits.

Of course none of this is meant to encourage others to do the same and you are right that comparison is hard without a formal test regimen, but with the details mentioned above, some type of comparison is possible. -Andy

silent running

Hi Ron, thanks for the further details. On the Prism, the plenum is the part of the head where the gas enters and leaves and where the sensors are. We call the scrubber housing the "bucket". I think that's where the confusion in nomenclature lies... -Andy

schford

Is it really?

Now I do believe that scrubber design affects how break through occurs,but I honestly am not convinced that other than that sensible scrubber design makes a whole lot of difference......

Love to be shown testing that educates me though!

Stuart

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silent running

Hello all, after reading the Prism scrubber post, it looks like I misunderstood something when talking to Peter Ready. It was when they ran the Prism loop backwards with out to in flow, even with a plastic scrubber bucket, that in 65F water or colder the gas was cooled before hitting the scrubbber material and less efficeint. So I imagine that an aly plenum/bucket would make that cooling problem even worse with an out to in flow... -Andy

mverick

Some have reversed the flow of the Meg. It's Easy to do. Takes about 2 minutes if using a standard DSV.

Problem solved. I like it running the way it is, maybe less efficient. But, better in case of flood going into the scrubber. Which if that happens then what?

I know, it's almost impossible to happen. But, what if it does?

In to out. Bailout.
Out to in. You've got a greater chance to save it.

Which option do you prefer if your deep?

silent running

Hi mverick, for me that wold be the one which gives me the most efficeint scrubbing and lowest WOB everyday, especially important down deep...in to out.
As for floods, I seem to recall hearing that somebody has partially flooded a Prism scrubber and there was no serious impact on the performance. If you're talking about a total flood, then it doesn't matter which way the flow is, you're off the loop. -Andy

mverick

Not total. Just enough to fill the center tube of the scrubber. The outside bucket can handle a lot more water then the Inside tube.

And on the Prism, you can purge the water out of the bucket can't you?

silent running

Yes, you could if you rolled it into the lung and blew it out the drain on the bottom. Both CLs have a drain at the bottom.

As for flooding the center tube, it's not very likely. If you had a leak in either of the exhale side hoses, water would most likely wind up in the bottom of the ex CL due to the design and even a slightly horizontal body position. I had a good sized leak at the top of my ex CL, about 3 cups of water after a 3 hr dive. Didn't have any idea that much was there until I got out of the water. The ex CL/head connection is a screw on and is protected in the top of the head. I have trimmed these hoses to a very short length way below my head and cowling, I don't think I could rip them if I tried. If there was a rip in one, I could direct the water into the ex CL and blow it out the bottom simply by staying more horizontal. Also, the head to CL hoses are made of thicker rubber which is supposed to be semi self-sealing, don't know if it's true. As has been said by Decoweenie and others, a small mirror is very imporant to have when diving CCR.

Any leak on the Prism that would let water into the scrubber would be much more likely to come from pinched scrubber seals and would only let water into the outside of the scrubber, where there is a larger volume of gas, including room at the bottom, under the scrubber where the moisture pads are. I have done this and with the help of my buddy figured it out 5 minutes into the dive, ascended, took off the scrubber, replaced the o-ring and was back in the water in 10 minutes. No wetness on the outside of the scrubber as the water went under it into the moisture pads. I have also had a much worse scrubber flood on a Drager with a loose p-port on the scruber inlet, almost total flood, but I stayed on the loop all the way up and was able to breathe reasonably well despite all the gurgling.

It seems to me that most bigger scrubber floods happen early in a dive and would probably not keep you fom returning to the surface, even if it meant going to OC bailout. -Andy