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MIL-P-17881D(SHIPS) For mechanical shaft seals, the design shall insure that positive liquid
pressure is supplied to the seal faces under all conditions of operation and that there is
adequate circulation of the liquid at the seal faces to minimize the deposit of foreign
matter on the seal parts.  The pump certification data shall contain certification by the
seal manufacture that there will be adequate circulation of liquid and adequate lubrication
at the seal faces when the seal is installed as shown on the drawing. The design shall insure that any Leakage cannot reach the bearings or be thrown
over bearing housings and driving unit.  Drip pockets and drains shall be provided.
3.3.8 Bearings.
# Radial bearings. Radial bearings may be of the hydrodynamic or rolling contact type (see 3.3.9).
If specifically approved by the design review agency hydrostatic bearings may be used (see Hydrodynamic radial bearings may be of the
fixed or self-aligning type and
shall be designed to operate under full fluid film (stable
lubrication) operation over the
entire range of the characteristic curve as defined by the
operating conditions.  Where the
requirement for full fluid film operation cannot be met, a
hydrostatic bearing may be re-
commended by the vendor (see Water lubricated hydrodynamic radial bearings shall not be provided with
lubrication grooves unless specifically requested by the vendor and approved by the design
review agency.  If a hydrodynamic bearing design having axial grooves is recommended by the
vendor, the actual direction of radial loadin must be established.  The orientation of the
bearing shall be such that the effective bearing arc will not be reduced to less than 120
degrees at any operating condition of the pump.  The effective arc is defined herein as the
continuous load carrying surface which is symmetrical with respect to the load vector. Re-
lease for manufacture shall be subject to the verification of the applied load direction
either by a method approved by the design review agency or by l xperimental data approved by
the design review agency l nd derived from tests of manufacturer's own similar designs. Where the requirements.for full fluid film operation (see of a
hydrodynamic bearing cannot be met, as an alternative the vendor may recommend a hydrostatic
bearing for approval of the design review agency.  The hydrostatic bearing shall operate
without metal-to-metal contact over the entire operating range.
# The hydrodynamic and hydrostatic bearing surface and the journal shall be
finished to 32 roughness height rating (RHR) or better. A radial bearing shall consist of a housing, shell and liner. The housing
shall be of a split design consisting of a cap bolted to a base and shall contain the bear-
ing shell and liner.  The liner may be l ither cast in the shell or may be a removable insert.
3.3.8,1.7 Each bearing housing shall be supported by a bracket that is either cast in-
tegral with the casing, securely bolted to the casing on a machined shoulder, or held in
alignment with the casing by at least two heavy dowels and securely bolted thereto.  The
use of bolts alone for scouring brackets is prohibited. Hydrodynamic radial bearing shells shall he split along the axis and so
arranged as to permit renewal or refitting without removal of pump rotor from the casing.
They shall be neatly fitted in their seatings to prevent axial play. Shells and their
seatings shall be finish machined. Internal water lubricated hydrodynamic radial bearings, for vertical pumps
only, shall be of the one piece sleeve type. Thrust bearings. A thrust bearing shall be installed on l ach pump to counteract any unbalanced
hydraulic or mechanical thrust in either direction.  In this connection, consideration shall
be given to the fact that rolling,  itching, or list of a ship at sea may introduce thrust
loads in a unit which is in hydraulic balance.

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