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|  MIL-P-17639F(SH)
(g) Any other design features which the manufacturer considers of
significant interest to describe the proposed unit.
(h) Whether the specified rated capacity and range of capacity (see
6.2.1) will result in shipboard operation at capacities that
will cause pump internal recirculation (suction or discharge)
sufficient to degrade pump life, performance, or reliability.
3.8.3 Part materials. The materials proposed for all parts shall be
justified as follows, both for proposals that use the materials in table I and
proposals that do not:
(a)
For all threaded parts, galling compatibility between mating
parts must be justified with technical substantiation.
(b)
For all parts that form a close running clearance between
rotating and stationary parts, the galling and wear com-
patibility between the mating parts must be justified with
technical substantiation. A close running clearance is
defined as one that will or might close during operation
(including during inclined operation or shock or the combina-
tion of the two) and in any event every running clearance with
less than 40 roils radial clearance.
For all parts exposed to sea water, the part must be shown to
(c)
be galvanically compatible with the material proposed for each
nearby part. The justification must identify and take into
account the relative area ratios of the galvanically coupled
parts. To facilitate design review activity review, the
justification shall include a copy of the sectional assembly
drawing with each part colored in accordance with a color coding
scheme picked by the manufacturer to permit visual distinction
between parts of different materials.
(d)
For parts that are both exposed to sea water and form a close
running clearance, the justification for galling and wear as
required in 3.8.3(b) and for galvanic acceptability as required
in 3.8.3(c) must be based on successful actual experience in
similar applications. The justification must state the basis
for thinking the two applications similar and for thinking the
past application successful. The justification must include a
copy of the sectional assembly drawing for the past application
showing the geometry and showing, by markup if necessary, the
minimum and maximum clearance, the running speed, and the
materials.
(e)
If the material proposed for a given part is not one of the
materials allowed in table I for that part (as defined by part
function, even if the part name is different), then additionally
justify with technical substantiation why the proposed material
is more in the Navy's interest than the material specified in
table I and why the latter material cannot be used.
(f)
If the part is one for which table I does not specify a material,
the proposed material must be justified with technical substan-
tiation.
36
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