<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div>Cliff,</div><div>forget the rumours of sheep everywhere in N.Z.. </div><div>We have a very sophisticated coffee culture down here! Translating that </div><div>knowledge over to scrubbers will make for a safer unit.</div><div>Am enjoying this thread as I need to make up a scrubber at some time.</div><div>Am going with 2 scrubbers. Once I know my hull size more accurately I'll</div><div>be contacting Molecular Products tech help, as they have a computer to</div><div>calculate flow rate needed to keep you within your required limits.</div><div>Cheers Alan</div><div><br><div>Sent from my iPad</div></div><div><br>On 24/04/2017, at 1:11 PM, Cliff Redus via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> wrote:<br><br></div><blockquote type="cite"><div><div dir="ltr"><div>Yes I like it, Psub Baristas with one small difference, if you get your DIY coffee machine wrong, you get a bad cup of Joe; if you get your DIY CO2 scrubber wrong you die!</div><div><br></div><div>Cliff</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Sun, Apr 23, 2017 at 5:37 PM, Alan via Personal_Submersibles <span dir="ltr"><<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="auto"><div>Some great thoughts thanks.</div><div>This all seems very much like the art of coffee making!</div><div>You have the type of bean ( absorbent choice). There is the grind ( granule size)</div><div>Moisture has an effect on coffee extraction. There is the amount of coffee grind</div><div>in the shot! If you have differing volumes of absorbant in the scrubber this would </div><div>have an effect. There is the tamping of the grind that effects the speed water flows through the ground coffee, which is equivalent to how the absorbent is compacted. There is a set perfect time that it should take for the water to flow through the grind </div><div>to get the maximum desired extraction, this relates to the previous factors & the pressure of the pump. With a scrubber the pump is replaced by the fan & the flow</div><div>rate is what is required to keep CO2 levels below required levels & this is dictated </div><div>by the size of the hull & number of passengers.</div><div>Baristas can spend ages fine tuning their coffee machines every day & during</div><div>the day. </div><div>Not saying we should be this fussy; but there are a lot of factors to balance if</div><div>you want it perfect!</div><div>Alan </div><div><br></div><div><br></div><div> <br><br><div>Sent from my iPad</div></div><div><br>On 24/04/2017, at 9:33 AM, james cottrell via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.<wbr>org</a>> wrote:<br><br></div><blockquote type="cite"><div><div style="color:rgb(0,0,0);font-family:verdana,helvetica,sans-serif;font-size:13px;background-color:rgb(255,255,255)"><div id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_11336"><span id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_11363">Hi Cliff,</span></div><div id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_11336"><span id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_11491">Thanks for the excellent info. Great research. If I could add a couple of things they would be-</span></div><div id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_11336"><span><br></span></div><div id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_11336" dir="ltr">Pushing air through absorbent vs pulling air has different effects too. </div><div id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_11336" dir="ltr">Pushing air through with a blower has the benefit of slightly higher pressure in the media which can yield more efficiency compared to drawing air through which lowers pressure.</div><div id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_11336" dir="ltr">However, too much airflow can cause the the media to dry out and lose effectiveness. Humidity may have to be controlled within limits.</div><div id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_11336" dir="ltr">Pushing air through can also cause uneven distribution and poor performance depending on scrubber design.</div><div id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_11336" dir="ltr"><br></div><div class="m_2651918275972479902qtdSeparateBR" id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_12008">So the challenges are to keep humidity within limits, air flow sufficient with even distribution all without exceeding available power over duration of dive (especially in an emergency).</div><div class="m_2651918275972479902qtdSeparateBR" id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_12008"><br>For these reasons, lung powered devices are great as a back up. The lungs provide the airflow and the humidity. If the unit is made from clear acrylic, it is possible to use color changing media.</div><div class="m_2651918275972479902qtdSeparateBR" id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_12008">One last thought- Absorbent cartridges (like micro-pore re-breather cartridges) can make it easier to change used up media in the sub during an emergency than trying to empty and replace granules. Just pull out the old cartridge, insert the new one and continue breathing.</div><div class="m_2651918275972479902qtdSeparateBR" id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_12008"><br></div><div class="m_2651918275972479902qtdSeparateBR" id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_12008">Greg C</div><div class="m_2651918275972479902yahoo_quoted" id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_14394" style="display:block"> <div id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_14393" style="font-family:verdana,helvetica,sans-serif;font-size:13px"> <div id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_14392" style="font-family:HelveticaNeue,Helvetica Neue,Helvetica,Arial,Lucida Grande,sans-serif;font-size:16px"> <div id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_14391" dir="ltr"> <font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_14390" face="Arial" size="2"> <hr size="1" id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_14389"> <b><span style="font-weight:bold">From:</span></b> Cliff Redus via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.<wbr>org</a>><br> <b><span style="font-weight:bold">To:</span></b> Personal Submersibles General Discussion <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.<wbr>org</a>> <br> <b><span style="font-weight:bold">Sent:</span></b> Sunday, April 23, 2017 1:17 PM<br> <b><span style="font-weight:bold">Subject:</span></b> Re: [PSUBS-MAILIST] Co2 scrubbers on eBay<br> </font> </div> <div class="m_2651918275972479902y_msg_container" id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18270"><br><div id="m_2651918275972479902yiv7311172270"><div id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18276"><div id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18275" dir="ltr"><div id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18274"><font color="#000000" face="Times New Roman" size="3">
</font><div id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18273" style="margin:0in 0in 10pt"><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18272" face="Calibri"><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18306" size="3"><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18305" color="#000000">To elaborate a bit on Alec's comments, a few years back I did some work the scrubber for my one-man
boat and came away with some conclusions.<span>
</span></font></font><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18271" color="#000000" size="3">The first was that a radial design was better than an axial design for
air flow throws the absorbent and the second was that the goldilocks rule applies
for fan/blower associated with the scrubber.</font><span><font color="#000000" size="3">
</font></span><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18529" color="#000000" size="3">Engineers make a distinction on equipment used to compress air.</font><span><font color="#000000" size="3"> </font></span><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18277" color="#000000" size="3">They define a parameter known as the specific
ratio which is defined as the discharge pressure divided by the supply pressure
where each pressure is in terms of absolute pressure rather than gage
pressure.</font><span><font color="#000000" size="3"> </font></span><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18530" color="#000000" size="3">If the device has a specific
ratio less than 1.1, they call it fan, if it has a specific ratio greater than
1.2 they call it compressor and if it has a specific ration between 1.11 and
1.2, it is a blower.</font><span><font color="#000000" size="3"> </font></span><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18278" color="#000000" size="3">What I found from my
testing on the scrubber was that fans like you would typically see on PC are
axial flow and these are designed for high flow rates but low head. When you
try and use them to push air through the CO2 absorbent, they just don't have
enough head and the resulting flowrate is very low.</font><span><font color="#000000" size="3"> </font></span><font color="#000000" size="3">In this case they are not operating anywhere
near their best efficiency point (BEP).</font><span><font color="#000000" size="3">
</font></span><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18279" color="#000000" size="3">What I found worked better were squirrel cage blowers. These are
designed for lower flow rates than PC axial fans but with more head.</font><span><font color="#000000" size="3"> </font></span><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18531" color="#000000" size="3">I am sure there are many models of squirrel
blade blowers that would work but the model I use is from Papst, model
RL90-18/24.</font><span><font color="#000000" size="3"> </font></span><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18280" color="#000000" size="3">This blower operates off
24VDC and has a power rating of 7.5 W which translates to 0.31 amps.</font><span><font color="#000000" size="3"> </font></span><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18532" color="#000000" size="3">If you look on ebay, these blowers come up
all the time.</font><span><font color="#000000" size="3"> </font></span><font color="#000000" size="3">Back to the goldilocks
rule;</font><span><font color="#000000" size="3"> </font></span><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18281" color="#000000" size="3">to meet ABS rules, you have to demonstrate
that your life support system will operate through the the emergency time
period which is 72 hours on the backup battery.</font><span><font color="#000000" size="3">
</font></span><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18282" color="#000000" size="3">The current during this period is known as the “Hotel Load” for obvious
reasons.</font><span><font color="#000000" size="3"> </font></span><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18283" color="#000000" size="3">When I tested axial PC fans,
they were great on battery endurance because they pull a very low current but
they did not work well because they did not have enough head to overcome the
pressure drop through the CO2 absorbent material , SodaSorb HP in my case.</font><span><font color="#000000" size="3"> </font></span><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18284" color="#000000" size="3">This showed up as having erratic CO2 levels
in the boat and not being able to sustain concentrations less than ABS required
maximum of 5000 ppm (1/2%).</font><span><font color="#000000" size="3"> </font></span><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18285" color="#000000" size="3">When I tried
larger axial fans like you would use for a bilge fan, the unit would keep the
CO2 level below the 5000 ppm limit but they pulled way much current and </font><span><font color="#000000" size="3"> </font></span><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18292" color="#000000" size="3">would not last anywhere near the 80 hours.</font><span><font color="#000000" size="3"> </font></span><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18533" color="#000000" size="3">The Papst, model RL90-18/24 squirrel cage
blower turned out to be </font><span><font color="#000000" size="3"> </font></span><font color="#000000" size="3">perfect with
enough head to circulated</font><span><font color="#000000" size="3"> </font></span><font color="#000000" size="3">the cabin
air</font><span><font color="#000000" size="3"> </font></span><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18286" color="#000000" size="3">to keep the CO2 level typically
below 2000 ppm but also because they only pull 0.31 amps.</font><span><font color="#000000" size="3"> </font></span><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18534" color="#000000" size="3">This blower did not let me meet the 72 ABS
endurance limit but got me close.</font><span><font color="#000000" size="3"> </font></span><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18287" color="#000000" size="3">Below
is a graph of hotel load current through my backup battery and the voltage
across the backup battery as a function of time on a life support test in my
boat.</font><span><font color="#000000" size="3"> </font></span><font color="#000000" size="3">You can see from the graph at
about 69 hours into the test the backup battery was exhausted.</font><span><font color="#000000" size="3"> </font></span><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18288" color="#000000" size="3">Also the hotel load started at about 1.6 amps
but slowly climbed to 1.7 amps over the 69 hours.</font><span><font color="#000000" size="3"> </font></span><font color="#000000" size="3">This hotel load was a little higher than the
1.5 amps that I had designed around.</font><span><font color="#000000" size="3"> </font></span><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18289" color="#000000" size="3">I
need to go back and look at the contributors to this hotel load and see if I
can reduce.</font><span><font color="#000000" size="3"> </font></span><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18290" color="#000000" size="3">I am happy with the 69 hours
because during a real emergency like be stranded on the bottom due to entanglement,
I could utilize at least some of the main battery.</font><span><font color="#000000" size="3"> </font></span><font color="#000000" size="3">For reference, the backup battery consist of
two AGM</font><span><font color="#000000" size="3"> </font></span><font color="#000000" size="3">100 Ah battery.</font><span><font color="#000000" size="3"> </font></span><font id="m_2651918275972479902yui_3_16_0_ym19_1_1492981118710_18291" color="#000000" size="3">If you divide the capacity by the hotel load
you get the expected endurance of 100Ahr/1.65A is 61 hours so my 69 hours did better
than expected.</font><span><font color="#000000" size="3"> </font></span></font></div><font color="#000000" face="Times New Roman" size="3">
.</font></div><div><br clear="none"></div><div><image.png></div><div><br clear="none"></div><div><br clear="none"></div><div>Cliff </div><div><br clear="none"></div><div><br clear="none"></div><div><br clear="none"></div><div><br clear="none"></div></div><div class="m_2651918275972479902yiv7311172270gmail_extra"><br clear="none"><div class="m_2651918275972479902yiv7311172270yqt0610476675" id="m_2651918275972479902yiv7311172270yqtfd28439"><div class="m_2651918275972479902yiv7311172270gmail_quote">On Sat, Apr 22, 2017 at 6:07 PM, Alec Smyth via Personal_Submersibles <span dir="ltr"><<a href="mailto:personal_submersibles@psubs.org" target="_blank" rel="nofollow" shape="rect">personal_submersibles@psubs.<wbr>org</a>></span> wrote:<br clear="none"><blockquote class="m_2651918275972479902yiv7311172270gmail_quote" 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 dir="ltr">Hi Brian,<div><br clear="none"></div><div>If by "straight flow fan" you mean the geometry you would see on a computer cooling fan for instance, they are way less efficient for this purpose. I believe the reason is they move good volumes of air but develop very little pressure. I've tested both kinds, and the sort I'm using now has much better performance. Cliff has done similar tests and had the same results.<div><br clear="none"></div><div>Best,</div><div><br clear="none">Alec</div></div></div><div class="m_2651918275972479902yiv7311172270gmail_extra"><br clear="none"><div class="m_2651918275972479902yiv7311172270gmail_quote">On Sat, Apr 22, 2017 at 6:08 PM, Brian Hughes via Personal_Submersibles <span dir="ltr"><<a href="mailto:personal_submersibles@psubs.org" target="_blank" rel="nofollow" shape="rect">personal_submersibles@psubs. org</a>></span> wrote:<br clear="none"><blockquote class="m_2651918275972479902yiv7311172270gmail_quote" 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>
<div style="text-align:left;color:black;font-family:sans-serif;font-size:11pt;margin-top:25px;margin-bottom:25px;background-color:white">
Alec,</div>
<div style="text-align:left;color:black;font-family:sans-serif;font-size:11pt;margin-top:25px;margin-bottom:25px;background-color:white">
Just ordered a tank holder that has two bungies about an inch apart, used to strap tanks down on a boat. I'm thinking I can hang this scrubber from the roof using the aft most reinforcing ring, holding it up in the middle. If it works, straight flow fan.<br clear="none">
</div>
</div>
<br clear="none">______________________________ _________________<br clear="none">
Personal_Submersibles mailing list<br clear="none">
<a href="mailto:Personal_Submersibles@psubs.org" target="_blank" rel="nofollow" shape="rect">Personal_Submersibles@psubs.or g</a><br clear="none">
<a href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" target="_blank" rel="nofollow" shape="rect">http://www.psubs.org/mailman/l istinfo.cgi/personal_submersib les</a><br clear="none">
<br clear="none"></blockquote></div><br clear="none"></div>
<br clear="none">______________________________ _________________<br clear="none">
Personal_Submersibles mailing list<br clear="none">
<a href="mailto:Personal_Submersibles@psubs.org" target="_blank" rel="nofollow" shape="rect">Personal_Submersibles@psubs. org</a><br clear="none">
<a href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" target="_blank" rel="nofollow" shape="rect">http://www.psubs.org/mailman/ listinfo.cgi/personal_ submersibles</a><br clear="none">
<br clear="none"></blockquote></div><br clear="none"></div></div></div></div><div class="m_2651918275972479902yqt0610476675" id="m_2651918275972479902yqtfd78500">______________________________<wbr>_________________<br clear="none">Personal_Submersibles mailing list<br clear="none"><a href="mailto:Personal_Submersibles@psubs.org" target="_blank" shape="rect">Personal_Submersibles@psubs.<wbr>org</a><br clear="none"><a href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" target="_blank" shape="rect">http://www.psubs.org/mailman/<wbr>listinfo.cgi/personal_<wbr>submersibles</a><br clear="none"></div><br><br></div> </div> </div> </div></div></div></blockquote><blockquote type="cite"><div><image.png></div></blockquote><blockquote type="cite"><div><span>______________________________<wbr>_________________</span><br><span>Personal_Submersibles mailing list</span><br><span><a href="mailto:Personal_Submersibles@psubs.org" target="_blank">Personal_Submersibles@psubs.<wbr>org</a></span><br><span><a href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" target="_blank">http://www.psubs.org/mailman/<wbr>listinfo.cgi/personal_<wbr>submersibles</a></span><br></div></blockquote></div><br>______________________________<wbr>_________________<br>
Personal_Submersibles mailing list<br>
<a href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs.<wbr>org</a><br>
<a href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" target="_blank" rel="noreferrer">http://www.psubs.org/mailman/<wbr>listinfo.cgi/personal_<wbr>submersibles</a><br>
<br></blockquote></div><br></div>
</div></blockquote><blockquote type="cite"><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 href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a></span><br></div></blockquote></body></html>