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