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|  MIL-P-17639F(SH)
3.3.8.2 Surface ship sea water pumps with total head of 30
or
more shall also be fitted with cyclone separators. Submarine sea water pumps
regardless of pressure shall be furnished with cyclone separators. A cyclone
separator is required for each stuffing box. The separator shall be integrally
mounted on the pump (preferably by means of a bracket on the casing parting
flange) and shall be connected to the suction and discharge piping by means of
tubing and fittings.
3.3.8.3 Each seal installed on surface ships shall be provided with a
solid gland plate designed to house two or more rings of packing for use in the
event of a mechanical seal failure. The stuffing box of all pumps installed in
submarine service shall be designed to house a minimum of four rings of packing
for use in the event of mechanical seal failure. The packing shall. be in
accordance with MIL-P-24377. The gland design shall be such that the packing
can be installed without removing the mechanical shaft seal. The gland shall
also be provided with a flush connection to insure 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.
3.3.8.4 Metal seal internal parts for sea water service pumps (except fire
pumps) shall be constructed of nickel-copper alloy in accordance with QQ-N-281
or Ni-Cr-No-Cb alloy in accordance with ASTM B 446, or B 443. For sea water
pumps where the mechanical seal is in close proximity to the impeller, the
mechanical seal internal parts shall be made of Ni-Cr-Mo-Cb alloy in accordance
with ASTM B 446, or B 443. Fire pump mechanical seal body and internals,
except springs, shall be made of titanium in accordance with ASTM B 367.
Metal seal internal parts for fresh water service pumps shall be constructed
of 304 or 316 corrosion resisting steel or nickelcopper alloy in accordance
with QQ-N-281 or highly alloyed corrosion resisting steel in accordance with
ASTM A 744, grade CN-7M or CN-7MS or Ni-Cr-Mo-Cb alloy in accordance with ASTM
B 446 or B 443. Mechanical seal springs for all pumps shall be made from
Ni-Cr-Mo-Cb alloy in accordance with ASTM B 446 or B 443. The mechanical
shaft seal for both fresh and sea water service shall have a solid tungsten
carbide or silicon carbide against carbon sealing surface.
3.3.8.5 On sea water pumps only, the mechanical seal O-ring and other
elastomers shall not be mounted or come in contact with the impeller.
3.3.8.6 Cyclone separators shall be constructed of nickel-copper alloy
in accordance with QQ-N-281. Fittings for abrasive separators and pump casings
shall be straight thread type adapter with Oring 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 con-
structed of Ni-Cr-Mo-Cb alloy in accordance with ASTM B 446 or B 443.
3.3.8.7 Stuffing box glands shall be set up by nuts threaded on studs
secured in the casings. The emergency packing gland shall be set up by nuts
threaded on studs. Space shall be provided between bearing and stuffing boxes
to permit easy examination of mechanical seals and bearings. Mechanical shaft
20
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