Re: [PSUBS-MAILIST] o2 control

[Carsten Standfuss <Merlinsub@t-online.de>]

Hi Cliff, how do you run the scrubber in "black ship" condition ? By a
small 24V emergency battery or by a flexible hose conection from the
scrubber to a mouthpiece ? Or both ?

best regards Carsten

> Cliff Redus schrieb:
> 
> In this thread on O2 control, I thought I would outline the system
> that I am using on my boat. I am about a year and a half into the
> fabrication of a one-man, one-atm. submersible rated to 300 ft.  After
> much thought, and with the intent to stay within ABS rules, the
> following is what I ended up using.  The normal mission time is 8
> hours with provisions for additional 72 hours of emergency life
> support.  Components:
> 
> 1 each  Scuba first stage regulator (Aqualung Titan First Stage -
> Setup for 100% O2)
> 2 each Medical "E" size tank, 24 SCF, 2015 psig max
> 2 each Medical "D" size tank, 15 SCF,  2015 psig max
> 1 24VDC solenoid (O2 clean), NC,  controlled by PLC
> 1 each Barometric pressure transducer, 0-5 VDC output , 700-1100 mbar
> 1 each Backup Oxygen Regulator 0-8 LPM H-Style gauge, John Bunn # 106
> JB0150-085
> 8 each Filter Cartridges,  CO2 Scrubbing, "4-8". mesh Sofnolime, 4.5
> lbm/cartridge
> 1 each Flow-Control Needle Valve
> 1 24 VDC blower for circulation of cabin air through the
> filter system
> 1 each CO2 Sensor, 0-2000 ppm
> 1 each Maxtec MAx-250 O2 sensor element
> 
> Normal operation:
> 
> When the hatch is closed, the PLC records the barometric pressure in
> the hull.  When the barometric pressures drop 10 mbar below the last
> hatch closure pressure, PLC signals solenoid valve to open in the
> regulated O2 supply.  Four small external tanks for O2 are manifolded
> and located inside a FRP cowling to minimize drag. The first stage
> regulator is set to deliver 25 psi above ambient water pressure. When
> barometric pressure has been restored to the hatch closure pressure,
> the solenoid is closed.  A needle valve down stream of the solenoid
> valve  is adjusted so that a the surface, it takes 60 seconds to
> restore pressure to 1 atm. Cycle is repeated to maintain cabin
> pressure at 1 atm. The 100% O2 is introduced at the inlet to the
> scrubber.  O2 and CO2 sensor measurements are displayed on a touch
> screen display and are for information only, not control.  PLC will
> issue visual and audible alarms if O2 or CO2 levels go out of range.
> 
> Emergency operation:
> 
> In the event both the main power and backup power fail, the operator
> can manually adjust a medical oxygen regulator with a dial indicator
> from (0-8 lpm) .  For one man, 0.5 lpm is nominal rate.
> 
> All the elements of the life support system have been installed in the
> boat and leak tested.  SS Swaglelok fittings were used for air and O2
> gas lines.  A scuba first stage regulator was used for O2 so that in
> an emergency, I can blow MBT at depth with either air or O2 by opening
> a crossover solenoid valve between the air and O2 systems from the
> touch screen panel.
> 
> In the next several weeks, I will be doing some life support tests in
> my shop so should be able to confirm how both the primary and backup
> systems work.  If the automated system proves to be problematic, I
> will just use the backup system as the primary which is a fixed
> metered flow rate of O2 into cabin and monitor the O2 and CO2 levels.
> 
> Cliff
>



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