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| MIL-D-18641F(SH)
not less than 3/16 inch thick with nickel-copper alloy or 70-30 copper-nickel alloy in accordance
with MIL-E-22200 and MIL-E-22200/4 or type MIL-EN67 of MIL-E-21562, or nickel-copper alloy
in accordance with MIL-9N10 of MIL-E-22200 and MIL-E-2200/3 or types MIL-RN60 or
MIL-EN60 of MIL-E-21562. On the face of the flange this protection shall extend from the bore
to at least the inner edge of the bolt holes. The 3/16 inch thickness of the protecting alloy is the
minimum required after final machining of the flange. Inlay thickness shall be verified after
depositing (allowance for machining shall be provided) and, after final machining of the flange.
3.14.8 Waterboxes. Components of the distillation unit which require salt water circulation
through the tubes shall be provided with waterboxes so proportioned as to provide sufficient area
at all points for flow of the circulating water with a minimum of turbulence, and for uniform
distribution of the water to all tubes in each pass. Single pass components shall have an inlet
waterbox depth measured normal to the tube sheet at the center of not less than one-half the
diameter of the tube sheet exposed to circulating water flow. Multi-pass components shall have
waterboxes so constructed that the depth at each inlet pass, at the center thereof, shall be not less
than one-half of the diameter of a circle of area equivalent to that portion of the tube sheet
exposed to inlet circulating water flow. Waterboxes shall be provided with adequate vents, including
vent holes in the partitions between passage and with drains as necessary.
3.14.9 Flow velocity limits. The velocity of flow of circulating water or feed entering the inlet
nozzles of the distillate coder, distiller or stage condensers, air ejector pre-cooler and after-
condenser, and vapor or salt water feed heaters shall not exceed 7.5 feet per second average under
the rated conditions. Salt water feed heaters of type II units using recirculated brine may be
designed for an average velocity through the tubes of 8 feet per second. If divergent nozzles are
provided, this velocity shall not be exceeded at the actual entrance of the water into the waterbox.
3.14.10 Salt water feed beating. In types I and III, provision for heating the salt water feed
shall be made by segregation of a section of the distiller condenser tubes, circulation of the
feedwater through the ejector after condenser, and provision of a vapor feed heater for each
evaporator effect except the last, the feedwater being circuited through these components in
series. The foregoing series may be varied as best suits the design of the unit for operation with
varying water temperatures. In types 11 and IV, provision for heating the sea water feed shall be
made by circulation of the feedwater through the distillate cooler, the stage condensers, the ejector
after condenser, and the salt water feed heater in series.
3.14.11 Installation of salinity cells. Provision shall be made as applicable in the integral
piping or drain regulators for installation of salinity cells in the fresh water drains from each
component of the distillation unit in which salt water leakage may contaminate the condensate or
distillate. The salinity cells shall be so oriented as to be submerged in water under any condition
of operation. Cells associated with dump valve operations shall be located a sufficient distance
upstream of the valve to prevent passage through the valve of any contamination sensed by the
salinity cell.
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