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|  MIL-P-17840C(SH)
3.3.7.2 Pumps in salt water-service with a total head of 30 lb/in2 or
more shall be fitted with cyclone separators. The separator shall be integrally
mounted on the pump (preferably by means of a bracket mounted at the suction
head parting flange) and shall be completely connected to the suction and
discharge by means of tubing and fittings.
3.3.7.3 Cyclone separators shall be constructed of nickel-copper alloy.
Fittings for abrasive separators and pump casings shall be of the straight
thread type adapter with O-ring seals and shall be constructed of nickel-copper
alloy. Tubing shall be copper-nickel (70-30) in accordance with MIL-T-16420.
Multiple springs for sea water service pumps shall be constructed from UNS
N06625 (inconel 625) in accordance with ASTM B 446 Or UNS N10002 (Hasteloy C)
in accordance with ASTM A 494.
3.3.7.4 Each seal shall be provided with a solid gland plate capable of
accommodating two or more rings of packing in accordance with MILP-24337 for
use in the event of a mechanical seal failure. The gland seal shall also be
provided with a flush connection to ensure positive liquid pressure is supplied
to the seal faces under all operating conditions and that there is adequate
circulation of the liquid at the seal faces to minimize deposits of foreign
matter in the seal parts.
3.3.7.5 Metal seal internals shall be nickel-copper alloy or highly
alloyed steel in accordance with ASTM A 744, grade CN-7M or CN-7MS. The
mechanical shaft seal for the pumps shall be a solid tungsten carbide against
a solid carbon face seal.
3.3.7.6 Mechanical shaft seals shall be positioned on the shaft by means
of stub or step sleeves. Mechanical shaft seals shall not be positioned by use
of set screws.
3.3.7.7 Stuffing box glands shall be set up by nuts threaded on studs
secured in the casings or seal gland plate.
3.3.7.8 Pump certification data shall contain certification by the seal
manufacturer that there will be adequate circulation of liquid and adequate
lubrication of the seal faces when the seal is installed as shown on the
sectional assembly drawing (see 3.6.1.2.4.2(m)).
3.3.8 Material. The materials of the pump shall conform to the materials
specified in table V. However, this specification is not intended to be
restrictive provided proposed alternative materials will give equal or better
service than the material specified. Proposed alternative materials shall be
subject to approval by the design review agency. Components of the pump for
which the specific materials are not specified shall be materials best suited
for the intended service. Materials which can be sensitized and are subjected
to heat treatment in the sensitization range during fabrication shall be capable
of passing the intergranular corrosion tests of the base material specifications.
Particular attention should be given to avoiding sensitization of materials during
hard facing, stress-relieving, or repair welding. Use of cadmium-plated parts
and fasteners, including washers, is prohibited.
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