[PSUBS-MAILIST] Co2 scrubbers

Thu Apr 27 12:15:39 EDT 2017

Hi Brian

I just made it as per the plans.  It fits through a stainless insert welded
into the hull.   I hadnt put the threads on in this pic.  Have a look at
the drawing, you can see where they will go.  one each end for the valve
fittings and a thread on the main body for the nut to hold it in.  probably
makes it look longer than it is.

I didn't have an issue getting the material.  I just ordered from a
standard metal supplier in UK.
Was quite expensive though.

On 27 April 2017 at 16:51, Brian Cox via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> James,   that seems like a very elongated fitting, why does it need to be
> so long?  Was it hard to locate the "phosphor bronze"  I have a piece of
> bronze lying around but I'm have no idea the grade.
>
> Brian
>
> --- personal_submersibles at psubs.org wrote:
>
> From: James Frankland 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: Thu, 27 Apr 2017 10:05:29 +0100
>
> 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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> > <image.png>
> >
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