Flowserve MNV - Manual (Page 37)

MNV & MNZ USER INSTRUCTIONS ENGLISH 71569188 11/04
Page 37 of 47
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6.7 Disassembly
Refer to section 1.6, Safety , before dismantling
the pump.
Before dismantling the pump for
overhaul, ensure genuine Flowserve replacement
parts are available. Refer to sectional drawings for
part numbers and their identification.
6.7.1 Preliminary dismantling procedure
a) Isolate motor and lock off electrical supply in
accordance with local regulations.
b) Isolate suction and discharge valves.
c) Remove coupling guards and disconnect the U
shaft.
d) Drain pump casing. Remove any auxiliary piping
if applicable.
6.7.2 Pump dismantling procedure
Care must be exercised in the dismantling operation.
Close the suction and discharge valves and drain
liquid from the casing. For convenience at re-
assembly, lay out all parts in the order in which they
are removed. Protect all machined faces against
metal to metal contact and corrosion. Proceed as
follows referencing the pump sectional drawing.
a) Disconnect the intermediate shaft section closest
to the pump. If possible, swing the shaft section
out to the side and secure.
b) Unbolt the stuffing box head from the casing.
c) Draw out the rotating assembly complete with the
stuffing box head, bearing housing, impeller, etc.
Exercised care in slinging and handling the unit.
d) Remove the impeller nut set screw and the
impeller nut. The set screw was mounted using
Loctite 271 or equivalent and may require
heating to 200 o C (400 o F) for removal. A
standard square bar will fit the square hole
provided in the impeller nut.
e) Remove the impeller and impeller key.
f) Remove the packing gland. If the pump is
equipped with a mechanical seal unbolt the
gland.
g) Unbolt and remove the bearing frame from
stuffing box head. The packing and seal cage
halves may be removed at this time. Remove
the mechanical seal if so equipped.
h) Remove the shaft sleeve only if necessary; see
Maintenance of Shaft and Shaft Sleeve.
i) Remove pump coupling half. Do not hammer to
remove.
j) Remove the upper and lower outside seal rings.
k) Remove the upper and lower bearing housing
covers with their respective seals. If a bent shaft
is suspected, the shaft should be checked for
runout at this time. The maximum permissible
runout is 0.002" (0.051mm) TIR at the bearing,
coupling, sleeve, and impeller turns.
l) Disengage the thrust bearing lock washer tab
from its locknut. Unscrew the thrust bearing
locknut and remove the lock washer and bearing
washer.
m) Remove the shaft toward the impeller end. The
thrust bearing will be pushed off the shaft by this
movement.
n) For further removal of bearings refer to
Maintenance of Bearings.
Carefully examine all individual parts, important
joints, and all wearing surfaces as the pump and
rotor are dismantled. As a general rule, regardless of
the performance of the unit, bearings and parts
appreciably worn should be renewed if it is not
intended to examine the pump again until the next
overhaul period.
6.7.3 Bearing installation and removal
Anti-friction bearing cones (inner race) are usually
pressed or shrunk onto the shaft. The cups (outer
races) are usually pressed or shrunk into the bearing
housing. When mounting bearings it is important that
the proper fit is maintained.
When a pulling device is used to remove bearings
from the shaft, the pulling jaws or fingers should be
located on the bearing cone. When other parts do
not interfere, the bearing cone may be supported by
a split ring and the shaft pressed out using an arbor
press. The bearing cups can similarly be pulled out
of the housing.
There are two methods for mounting a bearing on the
pump shaft:
a) Heating the bearing to expand the cone and
shrinking it on the shaft.
b) Pressing the bearing onto the shaft.
The method (a) is preferred over the method (b).
Heat the bearing in an oil bath or electric oven to a
uniform temperature of 120 o C (250 o F). When
heated, quickly mount it on the shaft. If the alternate
method is used, apply force by means of an arbor
press; see detail below. Use a tubular sleeve, ring,
or small blocks of equal thickness to apply the force
to the cone (inner race).