identified in figure 5-7. The storage tank pressure
gauge (1) indicates the pressure in the inner tank.
The storage tank liquid level gauge (2) indicates
the level of liquid in the inner tank when the tank
is on level ground. The dial is magnetically and
mechanically coupled to a float sensor inside the
storage tank and is calibrated in gallons. The
transfer tank pressure gauge (8) indicates the
pressure in the transfer tank. This pressure must
be more than that in the storage tank for the
liquid to transfer, since the converter is vented into
the storage tank during converter filling. The
transfer tank liquid level gauge (7), which reads
in percent full, is the same type as the storage tank
liquid level gauge that reads in gallons. The
converter full indicator gauge (9) (marked
LIQUID—GAS on the gauge), is a vapor pressure
thermometer that monitors the converter vent line
temperature. During transfer of liquid to a
Figure 5-7.—TMU-70/M liquid oxygen servicing trailer
controls and indicators.
5-6
converter, it indicates “GAS” temperature in the
converter vent line. When the converter is full,
the vent line is filled with LOX. The converter
vent line temperature drops and the gauge
indicator moves to the “LIQUID” position that
indicates a full converter.
With the exception of the converter full
indicator gauge and the transfer tank liquid level
gauge, all gauges have a green band to indicate
safe operating pressures and a red band to indicate
unsafe pressures.
In addition to the indicators covered, there are
several valves in the system. The converter vent
line shutoff valve (3) controls the flow of oxygen
gas vapors from the converter to the storage tank
and prevents loss of storage tank gas when the
converter is not being filled. The transfer tank
vent line shutoff valve (4) controls the flow of
oxygen gas vapors from the transfer tank to the
vapor space of the storage tank.
The valve used to control the gravity flow of
LOX to the transfer tank from the storage tank
is the transfer tank fill line shutoff valve (5).
The transfer tank pressure buildup valve (6)
controls the flow of LOX from the bottom of the
transfer tank to the pressure buildup coil (PBU).
The PBU coil is a heat exchanger that exposes the
LOX to ambient temperatures, converting the
LOX to gas. As this conversion takes place, the
gas expands and the output gas from the PBU is
fed back to the transfer tank vapor space,
providing the pressure to discharge the LOX to
the converter.
The fill drain line shutoff valve (10) is used
during the storage tank filling operation. It
permits the flow of LOX from a central supply
tank to the storage tank. This valve is to be opened
completely during the filling function and closed
after the transfer has been completed.
CAUTION
The fill-drain line shutoff valve is not used
to control flow. Restricting transfer flow
may create a dangerous back pressure on
the supply line used for filling. Control of
transfer flow should be maintained with
the service valve of the central supply
tank.
