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|  MIL-D-18641F(SH)
3.11.13 Prohibited material. The following material shall not be used for service, manufacture,
test or inspection of distilling units:
a. Mercury (except fluorescent or mercury vapor lighting)
b. Carcinogenic materials
c. Cadmium, magnesium, lead (except for thread lubricant for bolting in joints involving
seawater submarine submergence pressure tightness), or asbestos.
3.12 Operation.
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3.12.1 Types I, II, and III. The distillation unit shall use steam at a pressure of 15 (lb/in )
gage or less, to distill to a final vacuum at the air ejector suction of 7-1/2 inches of mercury (Hg)
absolute pressure, or less (see 6.2), and shall deliver the distillate at a temperature not exceeding
95 `F with an initial temperature of seawater of 85 `F. For single effect units, the evaporator shell
shall operate at a pressure of 11 to 14 inches of mercury absolute to distill seawater.
3.12.2 Type IV. The heat from hot fresh water at specified temperature (see 6.2) shall be
transferred to seawater in a feedwater heater. The heated seawater shall then be injected into a
flash chamber (or chambers in series) in which part of the seawater is flashed to vapor under a
vacuum. The vapor shall then be condensed in a condenser.
3.123 Type V. Hot fresh water at specified temperature (see 6.2) shall be circulated through
a tube bundle. The tube bundle shall be enclosed in a shell and surrounded by the seawater which
is to be evaporated by transfer of heat from the fresh water. The vapor formal shall be condensed
in a distiller condenser.
3.12.4 Types lV and V. Types IV and V shall distill to a final vacuum as required and shall
deliver the distillate at a temperature not exceeding 95 `F with an initial seawater temperature of
85 `F.
In some cases, a higher distillate temperature than 95 `F may be
3.12.5 Temperature
accepted (see 6.2).
3.13 Rating. The average production rate shall be not less than the rated capacity of the unit
(see 6.2) for 24 hours of continuous operation when supplied with seawater between 28 and 85 "F
and with designed brine density as indicated on the heat balance drawing and related technical data
after 90 days of normal operation. The 90 days of operation shall be as nearly continuous as
practicable. Scale preventive treatment in accordance with DOD-D-24577 may be used during
capacity tests.
3.13.1 Condition of operation. Unless otherwise specified (see 6.2), the distillation unit shall
produce distillate having a salinity content not exceeding 0.0325 equivalents per million of chlorides
(0.125 grain of sea salts per gallon) under all conditions of operation, when evaporating seawater
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