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|  MIL-P-17881D (SHIPS)
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3.2.3.3 Pumps shall not be damaged or caused to malfunction either by internally
excited vibrations, or by the environmental vibrations specified in MIL-STD-167. Frequen-
ties shall be as specified (see 6.1).
3.2.4 Alignment.
#
3.2.4.1 The design of all pumps shall be such that alignment will not be disturbed or
undue stresses set-up in any part by normal vibration, contraction and expansion of piping
attached thereto in Service; The pump shall be designed to withstand loads imposed by
attached piping as specified (see 6.1).
3.2.4.2 Alignment between separate components of a unit shall be maintained by means
of keyways or other adequate means. All parts manufactured to the same drawings shall be
interchangeable.
3.2.4.3 In no case shall a piece of equipment be rigidly supported from more than
one plane.
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3.2.5 Noise.
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3.2.5.1 The design, construction, and workmanship, of the equipment shall be such that
a minimum practical noise level will result under all operating conditions. Airborne noise,
structureborne vibration and fluidborne noise requirements shall be as specified (see 6.1).
3.3 Detail requirements.
3.3,1 Performance characteristics.
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3.3.1.1 The operating conditions and characteristics of the pumps shall be as specified
(see 6.1).
3.3.1.2 The head-capacity curve of these pumps shall rise continuously from rated
capacity to shut-off so that at constant rated speed the shut-off pressure shall be not
less than 15 percent greater than at rated capacity.
3.3.1.3 At constant rated speed the pumps shall develop 120 percent rated capacity
at a pressure not less than 80 percent of rated discharge, pressure unless otherwise specified
(see 6.1).
3,3.1.4 All feed pumps shall be designed to operate in parallel with other identical
pumps without surging, under all conditions of operation from shut-off to full capacity when
operating under any of the following methods of control of the driving unit:
(a) Unit operating at constant speed under control of speed limiting governor.
(b) Unit operating at variable speed under control of pressure governor.
(c) Unit operating at constant or variable speed with electric motor.
3.3.1.5 The limiting rotative speed for these pumps for a given capacity, suction
pressure and temperature shall be as specified (see 6.1).
3.3.1.6 The steam pressure drop through pump pressure regulating governors shall be
considered when rating turbine driven pumps.
,
"3.3.1.7 Motor driven pumps shall be able to withstand reverse rotation for a period
of one minute at all speeds up to design speed without damage.
#
3.3.2 Casings.
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3.3.2.1 Casings shall be of the double volute, diffuser concentric or modified concen-
tric casing design to minimize radial bearing loads.
3.3.2.2 Stationary (casing) wearing rings shall be fitted to all pumps.
#
3.3.2.3 Casings of horizontal and vertical pumps shall be provided with flanged vent
connections. The vents shall be located to permit release of entrapped air prior to start-up
to ensure complete submergence of the rotor in the process fluid. Drain connections shall be
l ither flanged or threaded in accordance with MS16142 and MS18229 and shall permit complete
drainage of the pump without disassembly of the pump. Vent and drain valves shall be supplied
with the unit unless otherwise specified (see 6.1).
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