<html><head></head><body><p dir="ltr">I am skeptical of the utility of the colour indicating absorbent. The reaction front in an axial scrubber is unlikely to be planar (unless perfectly diffused), but rather conical, so you could have breakthrough in the center before the indicating edge approaches the end of the canister, for example. I think actually measuring the CO2 accurately and using the rise in level as the indicator of scrubber breakthrough is the better course of action. One thing to note is that the colour change in the indicating absorbent is usually subtle, and submarine interiors are usually subdued light environments. In some media, the colour is readily apparent immediately after reaction, but the colour fades when left to stand for some time. Also, even if you have an acrylic or polycarbonate canister, dust from the scrubber media can accumulate on the inner wall and make visual inspection difficult.</p>
<p dir="ltr">If I were me, I'd be inclined to design a scrubber that would permit relatively easy media or canister changes in situ, with a designed capacity equal to the mission time + reserve time (or split between multiple scrubbers), and then keep one or two additional sealed canisters or media changes tucked away on board. That way, you can make effective use of the media by exhausting it right to breakthrough. If you make short dives, you can do several on the same canister, and if you reach breakthrough (arbitrarily set but below the permissible limit), you change it out. I would choose a radial flow design, with airflow from outside to inside for maximum efficiency, and consider addressing the operating humidity of the sub to keep it between 30% and 70% RH. Some moisture is actually required for the scrubber to function, as the chemical reaction actually occurs in aqueous solution on the surface of the media granules. I would definitely make a point of keeping a
partially used scrubber sealed off from atmospheric air when not in use. In the absence of a sealed container, simply keeping your hatch closed would suffice, as once the CO2 in the cabin is all reacted it is inert. Atmospheric air has 400 ppm CO2 in it, which will consume a scrubber over time if left exposed.</p>
<p dir="ltr">Sean<br>
</p>
<br><br><div class="gmail_quote">On February 4, 2017 5:45:26 PM MST, Brian Cox via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<div style="font-family:Arial, sans-serif; font-size:10pt;"><div>I'd like to do a radial scrubber design but I also would like to use the indicating SodaSorb, so I can see the color change. Being able to see the color change with a radial design would be a challenge !</div><div> </div><div>Brian<br /><br />--- personal_submersibles@psubs.org wrote:<br /><br />From: "Sean T. Stevenson via Personal_Submersibles" <personal_submersibles@psubs.org><br />To: Personal Submersibles General Discussion <personal_submersibles@psubs.org><br />Subject: Re: [PSUBS-MAILIST] co2 scrubber<br />Date: Sat, 04 Feb 2017 14:53:27 -0700<br /><br /></div><p dir="ltr">Yes. For the chemical reaction to work properly, the air needs some dwell time against the scrubber media. This may be specified in the media datasheets. Regardless, if your fan is too strong and you're blowing tons of air through it, you may just dry it out while scrubbing really inefficiently. If you slow it
down, you give the CO2 time to react and the bed gets more efficient. This is one of the reasons why radial flow scrubbers have an advantage - the surface area is huge, so the actual flow velocity through the bed is minimal in comparison to an axial flow design. You only need enough airflow to remove CO2 faster than you produce it, and ideally to process the entire air volume in your cabin a few times an hour. Slow, large diameter fans will be more effective than a high speed but small fan, and probably easier on your batteries too.</p></div>
<p dir="ltr">Sean
<br /><br /></p><div>On February 4, 2017 2:38:32 PM MST, Brian Cox via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<blockquote style="margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex; border-left-color: rgb(204, 204, 204); border-left-width: 1px; border-left-style: solid;">
<div style="font-family: Arial, sans-serif; font-size: 10pt;"><div>Is there such a thing as to TOO much air flow through a scrubber ??</div><div> </div><div> </div><div>Brian<br /><br />--- personal_submersibles@psubs.org wrote:<br /><br />From: Cliff Redus via Personal_Submersibles <personal_submersibles@psubs.org><br />To: Personal Submersibles General Discussion <personal_submersibles@psubs.org><br />Subject: Re: [PSUBS-MAILIST] co2 scrubber<br />Date: Fri, 3 Feb 2017 09:34:40 -0600<br /><br /></div><div dir="ltr"><div>Brian, see <a href="http://www.ntz-filter.com/Radial_Filtration_versus_Axial_Filtration">http://www.ntz-filter.com/Radial_Filtration_versus_Axial_Filtration</a> for picture which is worth at least a hundred words.</div><div><br /></div><div>Cliff</div><div><br /></div><div><br /></div></div><div><br /><div>On Thu, Feb 2, 2017 at 11:36 PM, Brian Cox via Personal_Submersibles <span dir="ltr"><<a
href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>></span> wrote:<br /><blockquote style="margin: 0px 0px 0px 0.8ex; padding-left: 1ex; border-left-color: rgb(204, 204, 204); border-left-width: 1px; border-left-style: solid;"><div style="font-family: Arial,sans-serif; font-size: 10pt;"><div>What is the difference between a Axial scrubber and a radial ?</div><div> </div><div>Brian<br /><br />--- <a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a> wrote:<br /><br />From: via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br />To: Personal Submersibles General Discussion <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br />Subject: Re: [PSUBS-MAILIST] co2 scrubber<br />Date: Thu, 2 Feb 2017 16:29:34 -0600<br /><br /></div><div>Started life with axial scrubber but now use radial design. Has !
worked
much better for me.</div><div><br /></div><div>Cliff<br /><br />Sent from my iPad</div><div><br />On Feb 2, 2017, at 1:06 PM, hank pronk via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> wrote:<br /><br /></div><blockquote><div><div style="color: rgb(0, 0, 0); font-family: HelveticaNeue,Helvetica Neue,Helvetica,Arial,Lucida Grande,sans-serif; font-size: 12px; background-color: rgb(255, 255, 255);"><div>Thanks' guys, that helps. </div><div>Cliff, I assume you have an axial scrubber</div><div>Hank</div></div></div></blockquote><blockquote><div><span>_______________________________________________</span><br /><span>Personal_Submersibles mailing list</span><br /><span><a href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs.org</a></span><br /><span><a
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