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| MIL-D-18641F(SH)
of not less than 1/32 density (that is: 32 pounds of seawater containing 1 pound of dissolved solids)
under the ship motion conditions given in section 301 of DOD-STD-1399 (see 6.2).
3.13.1.1 Orientation. The contractor shall advise the contracting activity if limitations of his
design require orientation different from that specified for the distilling unit to meet the require-
ments specified herein (see 6.2).
3.13.2 Brine concentration. The distillation unit shall operate with a brine concentration of
one and one-half thirty seconds density or less in the shell of the last evaporator effect or stage.
This equates to a minimum seawater feed to distillate produced ratio of 3 to 1.
3.13.3 First stage. In type H distillation units the temperature of the feedwater entering the
first stage feed inlet compartment shall be limited to between 165 and 175 "F.
3.13.4 Bacteriologically potable distillate. In type I, HI, IV, and V distillation units, provision
shall be made for raising the temperature of the feedwater or distillate to at least 165 "F at some
point in the cycle to ensure that the distillate is bacteriologically potable when the unit is operated
with seawater feed considered contaminated, or with brackish feed which may be contaminated, and
carry over of which would not register on the salinity indicators. Water shall not enter the unit at
a lower temperature than 165 `F subsequent to the point at which the feed has been raised and
held for not less than 7 seconds at that temperature.
3.14 Design. General design shall be as follows (see 6.3 and appendix A):
a.
Distillation units shall be of the lightest and most compact construction consistent with
reliability.
b. Distillation units shall be constructed and furnished as complete package type units to
the extent that the shipbuilder need only to make external water supply and discharge
connections, and external steam, air and electrical connections. Pumps, motors and
controllers, steam pressure reducing valve (if required for proper operation of the unit),
water meter, three way dump valve, and salinity indicating equipment shall be
conveniently mounted on the unit and piped and wired by the distilling unit manufac-
turer. Motor controllers and salinity indicating equipment shall be mounted on a steel
panel or panels l/4-inch minimum thickness. The distiller feed, brine, condensate drain,
and distillate pumps may be located separately from the unit in order to permit ready
accessibility for maintenance and to provide a better net positive suction head (NPSH)
on the pumps pumping from a vacuum.
.
c.
On units with mounted electrical equipment, the appropriate components shall be
completely wired in accordance with MIL-E-917 and MIL-C-24643. When required by
.
suction water level conditions, circulating and feed pumps shall be furnished by the
distilling unit manufacturer for separate mounting by the shipbuilder (see 6.2).
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