approximately 90 psi. The transfer tank pressure
During filling, LOX flow to the storage tank of the
servicing trailer is through the fill-drain filter (LF-1)
buildup valve (GV-5) regulates pressure in the transfer
and the fill-drain shutoff valve (LV-1). (See fig. 10-7.)
tank. The goal is to maintain pressure in the transfer
The fill-drain relief valve (RV-3) prevents excessive
tank as high as possible, without exceeding 90 psi.
pressure if the fill-drain line shutoff valve (LV-1) and
LOX is now able to flow from the transfer tank into the
the service valve on the supply tank are closed with
converter because the pressure in the transfer tank is
cold gas or liquid trapped within the supply line.
now greater than in the converter.
The fill-drain relief valve (RV-3) is connected to
If the rate of pressure buildup in the transfer tank
the vent line for safe discharge overboard. The storage
begins to look like it will exceed 90 psig, the transfer
tank vent line shutoff valve (GV-6) is left open during
tank vent valve (GV-3) is opened to relieve excess
filling and normal storage, when it is safe to discharge
pressure into the storage tank. This keeps the relief
vapors overboard. Use the storage tank liquid level
valve (RV-2) from opening and discharging gaseous
gauge (LG-1) and the storage tank pressure gauge
oxygen from the vent line.
(P-1) to monitor storage tank conditions. If excessive
pressure builds in the storage tank, the storage tank
The converter full indicator gauge (F-1) will
inner shell relief valve (RV-1) and the storage tank
indicate when the aircraft's LOX converter is full. At
inner shell rupture disc (SD-1) vent excess gas and
that point, any overflow is automatically returned to
liquid.
the storage tank, bypassing through the converter vent
The time required to fill the servicing trailer varies
line shutoff valve (GV-4).
with each supply tank and supply line system. Under
Refer to figure 10-6 for the flow of LOX and gas in
normal conditions of 30 psi transfer pressure, the
the system, and to figure 10-7 for the locations of the
storage tank should fill in 5 to 10 minutes. If it should
controls and indicators. The step-by-step procedures
take significantly longer to fill the tank, check for bad
for transferring LOX to an aircraft converter are as
valves, a clogged filter, or a faulty transfer hose.
follows:
Transferring LOX to the Aircraft
NOTE: Before starting this procedure, be sure to
don all of the appropriate safety clothing.
Once filled with LOX, the servicing trailer is used
1. Ensure that all control valves are closed, except
to fill the aircraft's LOX converter. Use figure 10-6 to
for the storage tank vent valve (GV-6).
trace the flow of LOX from the storage tank to the
transfer tank of the servicing trailer, and subsequently
LV-1: The fill-drain line shutoff valve
to the LOX converter on the aircraft.
LV-2: The transfer tank fill line shutoff valve
In the servicing trailer, LOX flows from the
GV-3: The transfer tank vent line shutoff valve
storage tank to the transfer tank by gravity. It first
passes through the transfer fill line shutoff valve
GV-4: The converter vent line shutoff valve
(LV-2). During this process, the gaseous oxygen
GV-5: The transfer tank pressure buildup valve
produced by cool down of the tank is vented back to the
storage tank through the vent valve (GV-3). The
2. Ensure that the trailer is level, the caster is
transfer tank pressure gauge (P-2) and the transfer tank
down and locked, and that the parking brake is set.
liquid level gauge (LG-2) can be used to monitor the
NOTE: Monitor the storage tank liquid level
condition of the transfer tank. When the transfer tank is
gauge (LG-1) and the storage tank pressure gauge
filled to the desired level, as indicated by the liquid
(P-1) to ensure a sufficient LOX supply and a safe
level gauge, valves LV-2 and GV-3 are closed.
operating pressure.
To service an aircraft LOX converter, the converter
3. Open the transfer tank fill line shutoff valve
is placed on the tray at the piping end of the storage
(LV-2) and the transfer tank vent line shutoff valve
tank, and both the vent line connector (C-3) and the
(GV-3), allowing LOX to flow into the transfer tank.
filler valve (C-2) are connected to the converter. The
filler valve is then opened to allow the pressures in the
4. When the transfer tank liquid level gauge
transfer tank and the aircraft's LOX converter to
(LG-2) indicates that the transfer tank is full, close the
equalize. Then, the transfer tank pressure buildup coil
transfer tank vent line shutoff valve (GV-3) and the
transfer tank fill line shutoff valve (LV-2).
is used to increase the pressure in the transfer tank to
10-10
