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|  MIL-P-18682D(SH)
3.3.3.5 Fitted bolts or dowel pins shall be provided to insure main-
tenance of alinement in assembly. Dowel pins shall be corrosion-resistant,
shall have a threaded end and nut design, and shall be secured against coming
adrift under shock loading.
3.3.3.6 Forcing bolts shall be provided for breaking joints.
3.3.3.7 Casings of horizontal and vertical surface ship pumps shall be
fitted with drain and vent connections. Drain connections shall be in accor-
dance with MS16142 and MS18229 and shall permit complete drainage of the pump
without disassembly of the pump. For vertical, bottom suction pumps, the pump
suction may serve as the drain. Threaded drain connections are prohibited in
the pressure boundary of submarine pumps.
3.3.3.8 For type I pump, the casing shall be fitted with a removable
casing liner in way of propeller.
3.3.3.9 For type II and type III pumps, the casings shall be fitted with
removable casing wearing rings. The casing wearing rings shall be located and
shaped in such a manner that leakage through wearing ring clearances shall not
be allowed to impinge directly on the casing.
3.3.3.9.1 Spare casing wearing rings (see table 11) shall be machined
undersize by at least 0.050 inch on the diameter in order to permit finish
machining during overhaul installation to mate with machined-down used impellers.
3.3.3.10 Pump casing joints shall be made up using compressed asbestos
sheet gaskets. O-rings may be used to seal casing joints in the sea water pumps
for submarines. O-rings and gaskets are prohibited from being in contact with
highly-alloyed corrosion resistant steel parts.
3.3.3.11 Venting. Pump casing shall be self-venting or be provided with
casing vents. Those portions of the casings which might trap air, but are not
vented, when the pump is secured, shall be rapidly cleared of air by flow during
pump operation. Special attention shall be paid to the vent location so that
the seal lubrication requirements of 3.3.8.5 are met during pump start-up and
operation.
3.3.3.12 For pumps with suction and discharge connections which are pre-
pared for welding to the system piping, the vent connections shall be located
on parts of the pump which do not need to be removed for repair or maintenance
and shall be configured for welding the system venting piping directly to the
pump. If, in order to perform its intended function, the vent connection must
be located on a removable part of the pump, then the vent connection shall be
flanged for mating with flanges.
3.3.3.13 Casing thickness shall include an allowance for fabrication
deviations and for erosion and corrosion in service. For submarine pumps,
areas subject to fluid velocity in excess of 15 feet per second at rated flow
shall be readily renewable or shall be protected by replaceable erosion shields.
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