During LOX servicing of aircraft converters, a lot
TRANSFER LINES AND PIPING SYS-
of oxygen is lost because of the way the transfer is
TEM.--These lines carry the LOX from the storage
carried out. In addition to the economic loss, a safety
tank to the transfer tank, and then to the aircraft
hazard is created when LOX or oxygen vapors are
converter. They also carry the vented oxygen gas from
released into the atmosphere near operating equipment
the aircraft's converter to the storage tank.
and personnel. The low loss, closed loop system was
The closed loop system of the transfer lines
designed to significantly reduce these losses and
contains the vented oxygen gas during filling
eliminate the safety hazards associated with venting
operations. The interconnected liquid and return gas
oxygen in critical areas.
lines are vacuum-jacketed wherever practical and are a
minimum length to reduce cooldown and heat leak
The TMU-70/M is a completely self-contained unit
The piping system consists of a fill line for storage
with three major components: a 50-gallon Dewar tank,
tank filling, a vent system for overboard venting of
a 15-liter Dewar transfer tank, and a low loss, closed
excess liquid or gas, and a pressure relief valve system
loop (LLCL) system of transfer lines. Separate liquid
connected to the vent system.
level and pressure gauges, as well as pressure relief
devices, are provided for each tank. These components
Controls And Indicators
are permanently mounted on a portable three-wheel
trailer, which is equipped with a manually operated
The controls and indicators of the TMU-70/M are
parking brake and retractable caster wheel.
illustrated in figure 8-2. The functions of the controls
are as follows:
The primary purpose of the TMU-70/M is to
service aircraft LOX converters. The LLCL system is
STORAGE TANK PRESSURE GAUGE.--(Fig.
designed to recycle oxygen vapor caused by heat losses
8-2, item 1). The pressure gauge indicates the pressure
during transfer to the aircraft converter. The oxygen
in the inner storage tank. The gauge is calibrated to read
vapors vented from the transfer tank and aircraft
from 0 to 100 pounds per square inch gauge (psig). A
converter are returned to the storage tank for cooldown
green band on the gauge face indicates safe operating
pressure of 0 to 50 psig; a red band indicates unsafe
operating pressure of 50 to 100 psig.
STORAGE TANK LIQUID LEVEL GAUGE.--
Components include a storage tank, transfer tank,
(Fig. 8-2, item 2). The liquid level gauge directly
and transfer lines and piping system.
indicates the level of liquid oxygen in the inner tank
when the tank is sitting level. The gauge dial is
STORAGE TANK.--The storage tank is a
magnetically and mechanically coupled to a float
50-gallon (U.S.) capacity, double-walled Dewar. The
sensor inside the storage tank. The gauge is calibrated
space between the double walls of the storage tank and
in gallons. Safe operating levels of up to 50 gallons are
transfer tank is evacuated down to 5 microns or lower
indicated in green; unsafe operating levels of more than
and contains a multi-layer, high-vacuum insulation to
50 gallons are indicated in red.
minimize heat gain and boil-off of the LOX.
CONVERTER V E N T L I N E S H U T O F F
TRANSFER TANK.--The 15-liter capacity
VALVE.--(Fig. 8-2, item 3). The vent valve controls
transfer tank is a double-walled, vacuum insulated
the flow of oxygen gas vapors from the converter being
Dewar, permanently attached to the storage tank. It is
filled to the storage tank and prevents the loss of storage
self-contained and gravity-filled from the storage tank.
tank gas when the converter is not being filled.
The transfer tank is equipped with a pressure buildup
coil, relief valve, rupture disc, and controls. The
TRANSFER TANK VENT LINE SHUTOFF
primary function of the transfer tank is to hold small
VALVE.--(Fig. 8-2, item 4). The vent valve controls
volumes of LOX and to utilize cold gas pressure from
the flow of oxygen gas vapors from the transfer tank to
the pressure buildup unit to transfer LOX to the aircraft
the vapor space of the storage tank.