Theory Of Operation - CAIRE Companion C1000 Technical & Service Manual

V

Theory of Operation

Filling
The C1000/T portable units are designed to be filled from any
top-fill (TF) reservoir with a compatible male QDV. The fol-
lowing CAIRE reservoirs are compatible with the C1000/T for
filling:
• Liberator (TF/DF) 10, 20, 30, 37, 45, 60
• Companion C21, C31, C41
• Low Loss (TF/DF) 31, 42
• HELiOS Universal U36, U46
NOTE: The Companion T moisture cup must be removed from
the unit before filling.
The C1000/T is filled by coupling its female quick disconnect
valve (QDV) with the male QDV on the reservoir and opening
the vent valve.
Once the QDV's have been connected, the vent valve on the port-
able unit must be opened to initiate flow of liquid into the unit.
When the vent valve is opened, it vents the contents of the inner
container to the atmosphere.
Venting the gas inside of the container creates a pressure drop in-
side of the C1000/T. This pressure differential causes liquid oxy-
gen to flow up the reservoir fill tube, through the coupled QDV's,
and into the inner container of the C1000/T
At the beginning of a fill, the liquid oxygen that leaves the res-
ervoir will vaporize into a gas because the inside of the C1000/T
container is relatively warm. This gas is discharged through the
vent valve. After a short time, the container cools and liquid oxy-
gen is contained.
When the unit is full, liquid oxygen is expelled through the vent
valve. The venting sound also changes and the liquid oxygen
creates a dense vapor cloud coming from under the reservoir's
shroud. Closing the vent valve and separating the C1000/T from
the reservoir terminates the fill process.
The saturation pressure (explained in section VII of this manual)
of the liquid oxygen in a reservoir can seriously affect the overall
efficiency and operation of the C1000/T.
Standby/Normal Evaporation Rate
When the C1000/T contains liquid oxygen, the vent valve is
closed, and there is no flow demand, the pressure in the system
will remain at or near its PRV pressure. The liquid oxygen main-
tains 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 in-
ner container.
As with all vacuum-insulated cryogenic containers, the liquid
oxygen in the C1000/T is always evaporating into a gas. The rate
of generation of this gas (called "head gas") is called the normal
evaporation rate (NER). When the flow control knob is in the off
position, this gas will build up pressure in the headspace above
the liquid oxygen. When the pressure reaches the PRV setting,
this gas is released through the primary relief valve into the at-
mosphere. The vented gas represents the system's NER loss.
Oxygen Withdrawal
With oxygen in the unit, and the vent valve closed, the pres-
sure in the inner vessel will remain at or near the primary relief
valve opening pressure. At operating pressure and with the flow
control valve open, pressure forces liquid oxygen up the liquid
withdrawal tube and into the warming coils. In the warming coils,
liquid oxygen absorbs heat and vaporizes, warming to almost am-
bient temperature by the time gas is dispensed by the flow control
valve to the patient.
A moisture collection pad is an internal component of the
C1000, and a moisture collection cup is externally attached to the
C1000T. These collect the additional condensed water that is cre-
ated when the Companion is operated at higher flow-rates.
Liquid Contents/Level Indicator Operation
The C1000/T is equipped with a spring scale liquid level meas-
urement system. The spring scale is incorporated into the strap
assembly of the portable and the display is built in to the top
bezel. Suspending the unit from the carrying strap closest to the
contents indicator activates the weight-scale mechanism. The
needle on the weight scale display moves an amount proportional
to the amount of LOX in the unit.
Companion Portable Technical Service Manual • PN 20562220 Rev B
11