ENGINEMAN 1 & C
auxiliary equipment. Some of the more important
maintenance problems will be discussed in the
AIR LEAKAGE.Since all parts of the
distilling plant are designed to operate under a
vacuum except the circulating, feed, and
freshwater lines, extreme care must be taken to
prevent leakage of air which might seriously
interfere with the proper operation of the plant.
The brine overboard and distillate pumps take
their suction from points of relatively high
vacuum. Air leakage in the piping to these pumps
is particularly objectionable and must be
eliminated. A small amount of air entering these
lines, even though it is insufficient to affect the
distilling plant vacuum, may cause the pump to
lose suction. Leaks in the lines to the pump suc-
tion gages must never be overlooked.
An 8 to 10 psig, low pressure hydrostatic test
should be applied to the entire system in accord-
ance with the PMS, and at any other time when
there is an indication that air leakage may exist.
The saltwater circulating pump can be used to
apply the pressure.
PUMPS.Proper operation of all pumps is
essential for the successful operation of the dis-
tilling plant. The effect of air leakage into the suc-
tion line of the pumps has been discussed in the
preceding paragraph. Proper operation of the
water-sealed gland lines and proper mainte-
nance of the glands themselves are necessary for
dependable operation of the pumps. General in-
formation on the operation and maintenance of
pumps is found in Engineman 3 & 2, NAVED-
TRA 10541 (current edition). However, for details
of any specific pump, consult the manufacturers
SALTWATER LEAKAGE.Saltwater to
distillate or saltwater to condensate leaks at any
of the various tube bundles will be immediately
indicated by an alarm bell and a red light which
shows at which cell a conductivity increase has
occurred. These cells are located downstream
from each tube bundle. Tube leaks usually result
from damaged or corroded tubes or from im-
proper expansion of tubes into the tube sheets.
Faulty tubes may be sealed with plastic tube
plugs or may be removed and replaced in accord-
ance with standard Navy procedures, as given in
chapter 9581 of Naval Ships Technical Manual.
Cleaning Heat Exchangers
The tubes of the distillate cooler, the air ejec-
tor condenser, and the stage condensers operate
with comparatively cool saltwater inside them and
seldom require cleaning. The seawater in the
saltwater heater, on the other hand, is at a higher
temperature and its tubes will occasionally require
cleaning to remove the hard scale on the inside
of the tubes. A special tool is furnished for this
purpose; this cleaning tool is shown in figure 7-6.
Figure 7-6.Tool for removing scale inside tubes.