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 of time, it may be necessary to apply leverage to free the rotor. When
restarting a pump, i t is well to have the packing gland finger tight only.
All leakage must flow along the shaft to lubricate the packing and prevent
overheating.
( c ) Mechanical Seals. A mechanical seal consists of two primary parts,
a stationary sealing face and a rotating sealing face attached to the shaft
a n d in contact with the stationary face. The close, lapped clearances between
t h e two faces prevent leakage of liquid out or air in. Mechanical seals are
p r e c i s i o n products and should be treated with care. Follow manufacturer's
instructions for maintenance procedures. I f s p e c i f i c i n f o r m a t i o n i s
u n a v a i l a b l e , perform the following procedure.
( 1 ) Clean each part by washing in a suitable solvent.
( 2 ) Check for defective or damaged seal faces, (nicks, cracks, or
s c r a t c h e s , especially those running transversely across the face). Replace
seal faces, i f required, or relap on a lapping plate.
( 3 ) Replace defective or damaged shaft seal rings. Shaft seal rings
should have a push-fit over the shaft. I f clearance is excessive, leakage
will result.
( 4 ) Replace defective springs.
( 5 ) Replace defective spring retainer, or relocate as required.
( 6 ) Correct seal lubrication, if necessary.
(7) Remove shaft burrs that may damage shaft seal rings.
( d ) Alignment. Check alignment by placing a straight edge over top and
sides of the two halves of the coupling. Also, measure the space between the
two halves with a thickness gauge, at four points 90 apart. All measurements
should be equal. Correct misalignment by using shims under the pump or motor
as required. Alignment must be correct after the foundation bolts have been
t h o r o u g h l y tightened. M i s a l i g n m e n t is often caused by pipe strain. See that
s u c t i o n and discharge piping is properly supported to relieve strains on
pump. Faulty alignment causes excessive wear of bearings, shaft, and packing,
and produces noise and vibration.
( e ) M e t a l l i z i n g . Worn shaft sleeves may be replaced, or they may be
r e b u i l t to size by welding or metallizing. In the metallizing process, new
surface metal in wire form is automatically drawn through a special gun to a
nozzle. In the nozzle, the wire is melted in an oxygen-gas flame and sprayed
by a blast of compressed air which carries the metal to the previously
prepared surface. Particles mesh on this surface to produce a coating. The
air blast keeps the sprayed surface cool, e l i m i n a t i n g risk of warpage or
distortion.
4-27
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