[PSUBS-MAILIST] Co2 scrubbers

Thu Apr 27 05:05:29 EDT 2017

Hi Brian
I only have 1 O2 tank mounted outside.  Pic here of the bronze through
hull.  Kittredge design but I changed the threads to match my valve
fittings.  The valve is phosphor bronze as specified on the plans.
Even though its low pressure O2, I used tungem (whatever that is)
tubing inside for the O2 with is specially for O2 applications.  I
like it to be super safe.

http://www.guernseysubmarine.com/extended_files/Page647.htm

On 27 April 2017 at 06:26, Brian Cox via Personal_Submersibles
<personal_submersibles at psubs.org> wrote:
> Alec,   So on that bronze fitting, if I was using HP  O2 coming into the
> cabin I would go from the O2 tank outside with SS tubing , then go to a
> bronze thru hull fitting ?  Then a shut off valve on the inside ( a needle
> valve type) and then to my flow meter.
>
> Brian C
>
> --- personal_submersibles at psubs.org wrote:
>
> From: Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org>
> To: Personal Submersibles General Discussion
> <personal_submersibles at psubs.org>
> Subject: Re: [PSUBS-MAILIST] Co2 scrubbers
> Date: Wed, 26 Apr 2017 21:08:08 -0400
>
> I understand Kittredge used bronze, which is good because it's a material
> that is very unlikely to initiate an O2 fire. However, in my case we're
> already dealing with low pressure at that point, so SS should be fine.
>
> Best,
>
> Alec
>
> On Wed, Apr 26, 2017 at 10:22 AM, Brian Cox via Personal_Submersibles
> <personal_submersibles at psubs.org> wrote:
>
> Alec,         When you transition your O2 thru the hull don't you have to
> have a bronze fitting as a thru hull fitting?
>
> Brian C
>
> --- personal_submersibles at psubs.org wrote:
>
> From: Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org>
> To: Personal Submersibles General Discussion
> <personal_submersibles at psubs.org>
> Subject: Re: [PSUBS-MAILIST] Co2 scrubbers
> Date: Tue, 25 Apr 2017 22:25:36 -0400
>
> Yep, I did that on both Snoopy and Shackleton. On Snoopy there is one O2
> tank outside, which leads to a 1st stage. From there through the hull and on
> the inside a pediatric flow regulator. Shackleton has the same thing, except
> two of everything. Same exact setup as Snoopy except one port and one
> starboard, for redundancy. Good news, I have run both of them several times
> already and they did not turn into flamethrowers. But I'm quite particular
> about the cleaning. For instance I got a pair of little O2 pressure gauges
> but decided not to install them because they didn't arrive bagged. I did my
> own cleaning (twice) on the LP components per Oxygen Hackers Companion
> instructions. The HP side (really just a regulator and a 1st stage) were
> purchased O2 clean.
>
>
> Thanks,
>
> Alec
>
> On Tue, Apr 25, 2017 at 10:03 PM, Rick Patton via Personal_Submersibles
> <personal_submersibles at psubs.org> wrote:
>
> Hank,
>
> Yeah I think your situation would be different than what I would be
> experiencing. I personally just don't believe that there should be any HP
> plumbing inside a one atmosphere vessel but that's just my opinion. Is there
> anyone else out there that is using a first stage reg on a HP exterior tank,
> 02 or air?
>
> Rick
>
> On Tue, Apr 25, 2017 at 1:48 PM, hank pronk via Personal_Submersibles
> <personal_submersibles at psubs.org> wrote:
>
> Rick,
> I know this may not apply, but, Elementary 3000 has  external O2 with a HP
> line to the hull penetrator and inside the hull there is a tower valve with
> medical O2 regulator  mounted directly  to that penetrator.  There is no
> internal HP O2 line.  I am not sure why you want to reduce the O2 pressure
> before the hull.  Gamma also had the identical system for auxiliary O2 when
> I first got it.
> Hank
>
>
> On Tuesday, April 25, 2017 5:38 PM, Rick Patton via Personal_Submersibles
> <personal_submersibles at psubs.org> wrote:
>
>
> I sent out an email regarding balance verses unbalanced 1st stage regs for
> an 02 tank that would be on the outside of a sub but didn't get a response
> so not sure it went so decided to attach to Alan's last email to see.
> Would love to hear from those who have their HP tanks on the outside of
> there sub and knock down the HP to LP at the tank valve to keep HP from
> entering the sub and weather you have an unbalanced or balanced 1at stage.
>
> Thanks
>
> Rick
>
> On Sun, Apr 23, 2017 at 3:29 PM, Alan via Personal_Submersibles
> <personal_submersibles at psubs.org> wrote:
>
> Cliff,
> forget the rumours of sheep everywhere in N.Z..
> We have a very sophisticated coffee culture down here! Translating that
> knowledge over to scrubbers will make for a safer unit.
> Am enjoying this thread as I need to make up a scrubber at some time.
> Am going with 2 scrubbers. Once I know my hull size more accurately I'll
> be contacting Molecular Products tech help, as they have a computer to
> calculate flow rate needed to keep you within your required limits.
> Cheers Alan
>
> Sent from my iPad
>
> On 24/04/2017, at 1:11 PM, Cliff Redus via Personal_Submersibles
> <personal_submersibles at psubs. org> wrote:
>
> 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!
>
> Cliff
>
> On Sun, Apr 23, 2017 at 5:37 PM, Alan via Personal_Submersibles
> <personal_submersibles at psubs. org> wrote:
>
> Some great thoughts thanks.
> This all seems very much like the art of coffee making!
> You have the type of bean ( absorbent choice). There is the grind ( granule
> size)
> Moisture has an effect on coffee extraction.  There is the amount of coffee
> grind
> in the shot! If you have differing volumes of absorbant in the scrubber this
> would
> 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
> 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
> rate is what is required to keep CO2 levels below required levels & this is
> dictated
> by the size of the hull & number of passengers.
> Baristas can spend ages fine tuning their coffee machines every day & during
> the day.
> Not saying we should be this fussy; but there are a lot of factors to
> balance if
> you want it perfect!
> Alan
>
>
>
>
> Sent from my iPad
>
> On 24/04/2017, at 9:33 AM, james cottrell via Personal_Submersibles
> <personal_submersibles at psubs.o rg> wrote:
>
> Hi Cliff,
> Thanks for the excellent info. Great research. If I could add a couple of
> things they would be-
>
> Pushing air through absorbent vs pulling air has different effects too.
> 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.
> However, too much airflow can cause the the media to dry out and lose
> effectiveness. Humidity may have to be controlled within limits.
> Pushing air through can also cause uneven distribution and poor performance
> depending on scrubber design.
>
> 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).
>
> 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.
> 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.
>
> Greg C
> ________________________________
> From: Cliff Redus via Personal_Submersibles <personal_submersibles at psubs.o
> rg>
> To: Personal Submersibles General Discussion <personal_submersibles at psubs.o
> rg>
> Sent: Sunday, April 23, 2017 1:17 PM
> Subject: Re: [PSUBS-MAILIST] Co2 scrubbers on eBay
>
> 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.  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.  Engineers make a distinction on
> equipment used to compress air.  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.  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.  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.  In this case they are not operating anywhere near their best
> efficiency point (BEP).  What I found worked better were squirrel cage
> blowers. These are designed for lower flow rates than PC axial fans but with
> more head.  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.  This blower
> operates off 24VDC and has a power rating of 7.5 W which translates to 0.31
> amps.  If you look on ebay, these blowers come up all the time.  Back to the
> goldilocks rule;  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.  The current during this period is known as
> the “Hotel Load” for obvious reasons.  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.
> 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%).
> 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  would not last anywhere near the 80 hours.  The Papst, model
> RL90-18/24 squirrel cage blower turned out to be  perfect with enough head
> to circulated  the cabin air  to keep the CO2 level typically below 2000 ppm
> but also because they only pull 0.31 amps.  This blower did not let me meet
> the 72 ABS endurance limit but got me close.  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.  You can see from
> the graph at about 69 hours into the test the backup battery was exhausted.
> Also the hotel load started at about 1.6 amps but slowly climbed to 1.7 amps
> over the 69 hours.  This hotel load was a little higher than the 1.5 amps
> that I had designed around.  I need to go back and look at the contributors
> to this hotel load and see if I can reduce.  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.  For
> reference, the backup battery consist of two AGM  100 Ah battery.  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.
> .
>
> <image.png>
>
>
> Cliff
>
>
>
>
>
> On Sat, Apr 22, 2017 at 6:07 PM, Alec Smyth via Personal_Submersibles
> <personal_submersibles at psubs.o rg> wrote:
>
> Hi Brian,
>
> 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.
>
> Best,
>
> Alec
>
> On Sat, Apr 22, 2017 at 6:08 PM, Brian Hughes via Personal_Submersibles
> <personal_submersibles at psubs. org> wrote:
>
> Alec,
> 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.
>
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