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|  MIL-P-17639F(SH)
3.2.7.1.6 The hydrodynamic and hydrostatic bearing surface and the journal
shall be finished to 32 roughness height rating (RHR) or better.
3.2.7. 1.7 Water lubricated hydrodynamic or hydrostatic bearings may be
of the one piece sleeve type. Pumps utilizing water-lubricated bearings shall
use one or more of the following means to minimize radial loading on the shaft:
(a)
Double volute casing.
(b)
Concentric casing.
(c)
Diffusers.
(d)
Modified concentric casing.
For modified concentric casings, the casing shall be circular over at least 270
degrees of the arc beginning at the cut water and proceeding in the direction
of impeller rotation toward the discharge nozzle. For both concentric and
modified concentric casings, the ratio of the casing diameter at the cut water
to the impeller diameter shall be 1.3 or greater.
3.2.7.2 Thrust bearings.
3.2.7.2.1 Thrust bearing shall be installed in each flexible coupled unit
for counteracting the forces resulting from the conditions stated in 3.2.7.
3.2.7.2.1.1 Thrust bearings shall be of the combined radial and thrust
rolling contact type in accordance with 3.2.7.1.2.
3.2.7.2.2 For rigidly coupled units, the thrust bearing for the unit shall
be in the driver and shall comply with 3.2.7.2.1.1. For rigidly coupled units
where the driver is a turbine rated 500 horsepower (hp) or over, the thrust bear-
ing shall be as specified in MIL-T-17523. Thrust bearings of the rolling contact
type shall be type 111, 120 or 134 in accordance with FF-B-171.
3.2.7.2.3 When pivoted segmental type thrust bearings are used, the design
shall permit renewal or refitting of shoes without removal of shafts.
3.2.7.2.4 For vertical flexible-coupled pumps, thrust bearings shall be
installed at the top, external of the pump, between the coupling and stuffing
box. For rigidly-coupled pumps, the thrust bearing shall be located in the
driver and shall comply with all requirements stated herein.
3.2.7.3 Installation.
3.2.7.3.1 Ball or roller bearings, when used, shall be installed in
housings separate from and independent of the stuffing boxes and with adequate
protection from gland leakage. In vertical flexible coupled pumps, rolling
contact bearings, where used, shall be installed external to the pump between
the coupling and gland seal. Means shall be provided to prevent escape of
lubricant around the shaft. All baffles, wipers, and related parts shall be
readily renewable.
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