packed with a powder-type insulating material. The
(called vacuum-jacketed), with point-contact space
space is evacuated to a high degree to minimize heat
rings to prevent the inner liquid-bearing line from
transfer and to hold evaporation losses to a minimum.
touching the outer jacket wall. To keep the heat influx
as low as possible, low thermal conductivity materials
Transfer Lines
are used for insulation, and the spacer design provides
for as small an area of contact between the inner and
Other than large, fixed-facility piping, most liquid
outer walls as possible.
oxygen systems consists of segmented flexible transfer
Flexible hose is more vulnerable to damage than its
lines. The lines are segmented for ease of demounting,
rigid counterpart. To strengthen flexible hoses, they
so that one transfer system can service different types
are built with braided metallic coverings or tough
of equipment. The most common type of line used in
plastic sheaths over the external corrugations.
the field is corrugated, flexible, metal hose (fig. 10-3),
Although such protection provides a degree of
which is constructed of bronze, stainless steel, or
reinforcement, it cannot entirely overcome the effects
aluminum. The bayonet coupling shown in figure 10-3
o f r o u g h h a n d l i n g . H o s e s a r e t o u g h , bu t n o t
is used to connect the service line to an aircraft LOX
indestructible.
converter.
Over pressurization of oxygen hoses is another
On a typical day lines are cooled and warmed many
condition to be avoided. Over pressurization may
times as LOX is drawn from the tanks. The waste of
produce a bellows-like effect if the covering is not
LOX due to cool down losses can be significant. For
securely fastened at the end connections. This may
this reason, transfer lines, like storage tanks, are as
cause separation of the outer cover at the hose collar,
well insulated as possible. Hoses are double-walled
PUMP-OUT
POINT-CONTACT
EVACUATED CONNECTION
SPACE RING
ANNULUS
6
5
3
BRAND-REINFORCED
BRAID-REINFORCED
INNER HOSE
7
OUTER HOSE
8
2
1
1.
FILLER VALVE AND CAP
2.
LIQUID HOSE AND END FITTINGS
4
3.
DUST PLUG AND CHAIN
4.
DUST CAP AND CHAIN
5.
TRANSFER HOSE AND ADAPTER
6.
CONNECTOR AND FILTER
7.
COUPLING WING NUT
8.
CONNECTOR
ASf10003
Figure 10-3.--Corrugated flexible metal hose.
10-3