ENGINEMAN 1 & C
of the desuperheating temperature in the steam
The steam supply to the saltwater heater flows
from the auxiliary exhaust line, through the
regulating valve (1-5 psig) and then through an
orifice which provides, within limits, a uniform
flow of steam. It then flows past the desuperheater
nozzle, which reduces the steam temperature in
the shell of the heater. Steam pressure is indicated
by a pressure gage on the operating panel.
The outlet for noncondensables is mounted on
the top of the shell and flanged to the suction
chamber of the first ejector of the two-stage air
ejector system. The two air ejectors produce the
vacuum in the precooler which causes the flow
of steam and noncondensables from the
A thermometer is mounted on the feedwater
inlet of the cooler.
The entering steam is directed along the length
of the tubes by impingement baffles. Steam con-
denses on the tubes and falls to a condensate well
at the bottom of the heater shell. (A drain
regulator of the float type controls the level of
the condensate in the well. A salinity cell, set to
energize at 0.10 epm, controls a shutoff valve
located in the ships piping between the drain
pump and the regulating valve.) The
desuperheater atomizes the heater condensate in
the low pressure steam side of the heater.
Cooling water from the air ejector precooler
flows into the AFTER-CONDENSER, which is
the fifth of the heat exchangers mounted on the
evaporator. The after-condenser completes the
condensation of any air ejector steam not con-
densed in the precooler and cools noncondensable
gases before venting them to the atmosphere. The
after-condenser enables the unit to operate
without emission of steam from the evaporator.
Cooling water enters and leaves the after-
condenser through an inlet pipe in the front and
an outlet pipe in the rear of the condenser.
The function of the saltwater heater is to pro-
vide feedwater to the inlet of the first evaporator
stage flash chamber. Since the amount of heat
from the steam is constant, the feedwater flow
through the heater must be adjusted according to
the inlet temperature so that the feedwater flow
is controlled by a valve on the outlet side of the
Air ejector steam and noncondensable gases
enter the shell side through an inlet in the front
of the unit. Noncondensable gases are vented
through a valve on the rear of the unit. A series
of vertical baffles direct the steam around the
tubes on which it condenses. Condensate is re-
moved through bottom outlets on both ends of
The air ejector PRECOOLER is a gas or
liquid heat exchanger which cools noncon-
densables and condenses steam drawn from the
first three evaporator stages and the saltwater
heater by a two-stage, vacuum-producing air
A salinity cell set to operate at 0.10 epm con-
trols a shutoff valve below the condenser.
The precooler receives its coolant from the
feedwater pumped into the distilling unit. The
flow of coolant is through the heat transfer tubes,
where it makes six passes, entering and leaving
at the front end of the cooler.
Three high-pressure steam-operated vacuum-
producing AIR EJECTORS are mounted on the
precooler side of the evaporator unit. The ejec-
tor system consists of a single-stage (booster) air
ejector and a two-stage air ejector arrangement
in which the steam outlet from one air ejector is
flanged to the suction side of the other.
Steam and noncondensables are drawn into
the cooler at the top near the rear of the cooler.
Impingement baffles at the inlet and seven ver-
tical baffles, through which the transfer tubes run,
direct the flow of hot gases around the tubes for
efficient heat transfer.
The single-stage ejector uses ships steam to
draw vapor and noncondensables from
evaporator stages four and five. Gases are drawn
from the evaporator through a vapor duct in each
distillate collection trough so that a minimum of
steam is withdrawn. Pipes from stages four and
five lead to a bronze tee flanged to the ejector.
Condensate collects on the tubes and drops to
the bottom of the shell. A salinity cell operates
a shutoff valve in the precooler condensate line
to dump to the bilge or drain tank when the salin-
ity is greater than 0.65 epm.
The single-stage ejector steam and entrained
gases leave the ejector outlet tubing, flow through
a check valve, and reenter the evaporator shell
through the top of stage three, from which they
are piped into the bottom of the stage three con-