Standby; Oxygen Flow - CAIRE COMPANION 1000 Technical Manual

2.3.3
Companion T
2.3.4
2-8 Theory of Operation

Standby

With the vent valve and flow control valve closed and liquid oxygen in the Companion
1000/T Portable (Figure 2-12), the pressure in the inner container soon stabilizes at the
primary relief valve set point, approximately 22 psig (152 kPa). The liquid oxygen
maintains saturation at this pressure due to the normal evaporation rate (NER) of the
system.
The NER is a function of the rate at which ambient heat "leaks" into and warms the
liquid oxygen in the inner container. Once the liquid oxygen is at saturation
temperature, continued heat infiltration readily vaporizes some of the liquid oxygen into
gas. This gas builds pressure in the headspace above the liquid until the relief valve
opens. Once open, the relief valve vents excess vaporized gas to maintain the system
pressure at a constant 22 psig (152 kPa). The vented gas represents the system's NER
loss.
Flow
Control
Valve
Companion 1000
Vacuum
Gas Molecules
Liquid Oxygen
Gaseous Oxygen
Figure 2-12: Standby

Oxygen Flow

The primary relief valve on the Companion 1000/T establishes both the maximum
system pressure and the operating pressure. Internal system pressure increases until the
cracking pressure of the primary relief valve is reached at 22 psig (152 kPa). The
primary relief valve vents gas to maintain the system pressure at the primary relief valve
set point (Figure 2-13). The rate at which gas vents through the primary relief valve is
determined by the NER of the system.
With the flow control valve set to the desired flow, pressure drops to atmosphere across
the flow control valve. System pressure forces liquid up the liquid withdrawal tube into
the warming coils, where it vaporizes and warms to near ambient temperatures.
Gaseous oxygen enters the flow control valve at approximately 22 psig (152 kPa).
If the Companion 1000/T is accidentally tipped over, the primary relief valve circuit
delays liquid oxygen leakage from the primary relief valve for approximately 60
seconds. The relief valve tube length, along with the relief valve silencer, enables liquid
entering the tube to vaporize into gas before reaching the relief valve.
Companion 1000/T Liquid Oxygen System Technical Manual
Warming Manifold
Coils
30 PSI
(207 kPa)
Vent Tube
Pressure
22 PSI
(152 kPa)
Secondary
Relief Valve
22 PSI
(152 kPa)
Primary
Relief
Valve
Fill
Tube
Liquid
Withdrawal
Tube
Female
Quick Connect
Molecular Sieve
B-701964-00 Rev. C