Figure 5-3.—Transfer line connector/coupling.
line. The reason is that as the LOX vaporizes, the
vapors will warm, and excessive pressures may
develop that can burst the conduit walls.
For transfer efficiency, vacuum-jacketed lines
with well-designed, low-heat input couplings are
best for most uses. Unthinking use of two or three
transfer sections coupled together where one could
do the job wastes liquid and time. Several times
as much line material has to be cooled down, and
several times more heat transferring line surface
area is contacted by the LOX. Additional heat
influx means additional LOX vaporization;
therefore, more liquid is needed to satisfy a given
transfer demand.
VALVES
Although valves might appear to be of minor
concern in a system, low-temperature valves often
cause more trouble than any other element of the
system. In addition to the general requirements
for any valve, LOX valves must be able to
function properly at extremely low temperatures
without causing excessive boil-off losses to the
liquid flowing through them. Insulation is the best
method to meet these thermal requirements.
Various materials have been used for insulation,
but the best method is to vacuum insulate the
valve. The valve illustrated in figure 5-4 is typical
of this type. The method of operation will vary
by manufacturer.
OXYGEN SERVICING EQUIPMENT
Learning Objective: Describe oxygen
servicing equipment to include safety
precautions, servicing trailers, and system
servicing.
Figure 5-4.—Vacuum-insulated cryogenic valve.
Oxygen servicing equipment for both liquid
and gaseous oxygen systems are discussed in this
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