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|  MIL-P-21343(SHIPS)
During submerged operation with 15 degrees permanent list to either
side of the vertical or when pitching 10 degrees up or down, period
for complete pitch cycle 4 seconds.
For surface operations with ship rolling 60 degrees from vertical to
(3)
either side.
(4)
For snorkel operation with ship rolling 30 degrees from vertical to
either side.
(5)
During surface or snorkel operation with 15 degrees permanent list
to either side of the vertical plane and permanently inclined up or
down 7 degrees from the horizontal plane. The time for a complete
roll cycle shall be considered as 8 seconds on the surface and
12 seconds when snorkeling.
(6)
During continuous snorkel or surface operation when ship is pitching
10 degrees up or down from the horizontal plane at a period of
6 seconds for surface and 4 seconds for snorkel operation.
3.2.2 The pump units shall be designed to obtain the quietest possible operation consistent with the
requirements specified in 3.2.1. Noise and vibration standards as specified in the Addendum to Purchase
Specifications for Machinery - Noise and Vibration shall be complied with. (Copies may be obtained
through the Bureau of Ships, Code 549.)
3.2.3 Pumps shall have constantly rising head-capacity characteristic curves. Unless otherwise
specified in the. contract or order, pumps shall be designed to operate satisfactorily with a maxim urn
suction lift of 25 feet.
3.2.4 Pumps shall be capable of operating at any speed between those required to obtain the mini-
m urn and maximum rating points specified (see 6.1).
3.2.5 The pumps shall be multi-stage with single suction impellers designed to give a minimum
hydraulic unbalance.
3.2.6 Pumps shall be designed for series operation through the entire range of pressure,
3.2.7 Pumps shall be vertically mounted with the motor at the top, A mounting ring or table shall
be provided which will support the unit as near to the center of gravity as practicable.
3.2.8
Shockproofness.
-
3.2.8.1 The design of all complete pumping units shall be such that they are capable of passing the
ciass HI (hign-impact) shock test specified in Specification MIL-S-901.
3.2.8.2 Pumps shall be designed for vertical mounting by means of a bracket to which the motor
and pump casing are attached by rigidly bolted flanges. The entire assembly shall be attached to the
bulkhead or other vertical support by means of resilient mountings. Brackets and resilient mountings
shall be furnished by the pump manufacturer. Bracket dimensions and data on resilient mountings shall
be furnished to the manufacturer by the shipbuilder.
3.2.8.3 The determination of stresses resulting from the shock tests is accomplished by the appli-
cation of the usual methods of analytical mechanics. The allowable stress in components due to shock
shall be the yield strength (0. 2 percent offset) of the material. Normal stresses in parts, such as the
tensile stress in a boil due to initial pull-up, shall not be added to the shock stresses. It is of para-
mount importance that the maximum accelerations possible under the shock tests be utilized in the design
of holding down bolts, supporting feet or lugs, and main structural members of the equipment, and that
no failure or permanent deformation occur as a result of shock.
3.28.4 Bolts designed to be stressed in shear shall be installed in holes with a minimum of
clearance, as experience indicates that large clearances allow impacting and subsequent failure.
3
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