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Page Title:
Calculations shall be submitted to cover the following - Cont'd |
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|  MIL-P-17639F(SH)
At 140 percent
rated flow
At rated flow
At shutoff
Casing type
0.36
0.10
0.00024Ns for Ns
Single volute
less than 1500
0.36 for Ns of
1500 or greater
.05
.10
0.11
Double volute
.15
.15
.15
Concentric and
modified concentric
.15
.07
.15
Varied diffuser in volute
.03
.15
.07
Vaned diffuser in concentric
Where:
NS = specific speed at the best efficiency point.
(2) Effects of thrust reversal where conditions which might
cause thrust reversal exist.
(3) Effects of roll, pitch, list and trim of the ship (including
gyroscopic effects) shall be considered in the bearing
design.
(4) Bearing clearance ratios, L/D ratio and characteristic
numbers, lubricant flow, and temperature rise (water-
lubricated bearings).
(5) Minimum film thickness required and calculated under maximum
radial and axial load conditions over the range of specified
pump operating conditions (water-lubricated bearings).
Analysis of driver bearings for close-coupled or rigidly coupled
(c)
units.
Calculations of the worst case cumulative effect of dimensions
(d)
and tolerances for parts and locations. These calculations
shall demonstrate:
(1) There will no interferences between rotating and stationary
parts as assembled.
(2) There will be no interference between rotating and station-
ary parts and hence no reduction in life of wearing parts,
when these worst case cumulative effects are combined
with operational, environmental, and thermal loading.
Casing design (submarine sea water pumps only). In the design
(e)
of submergence pressure boundaries in sea connected pumps for
submarine application, full consideration shall be given to
the cyclic nature of the submergence pressure, external nozzle
loading, and liquid temperature. The design of the pressure
containing parts shall be in accordance with the following:
(1) Attached system piping size and material shall be as
specified (see 6.2.1).
(2) Pressure and temperature transients as specified (see
6.2.1).
(3) The average flow velocity in the casing shall be calculated
in feet per second at rated flow. This velocity shall be
shown for the narrowest and widest sections of the casing.
38
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