Flowserve Twin Screw Rotary - Manual (Page 40)

TWIN SCREW PUMPS. ORIGINAL USER INSTRUCTIONS. ENGLISH. 71569243 – 07/10
Page 37 of 53
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6.6 Renewal clearances
Twin screw pumps are used in a variety of
applications handling materials with a wide range of
viscosities. As such, it is difficult to predict at exactly
what point screw clearances are too large and the
screws should be repaired or replaced. In low
viscosity, or higher pressure applications increased
screw clearances may result in an unacceptable loss
in hydraulic performance. On the other hand, in a high
viscosity, or lower pressure, application the same
change in screw clearance may result in very little
change in pump hydraulic performance. However,
since increased clearance can result in higher shaft
deflection and misalignment with the bearings, pump
performance should be re-evaluated when the screw
to body bore clearance reaches twice the value shown
in the Engineering Data section of this manual.
6.7 Disassembly
Note that replacements materials should be available
prior to disassembly to limit downtime. Refer to
sectional drawing shown in Figure 10 of this manual.
Note that the numbers in parenthesis following part
names refer to items on the sectional drawing.
6.7.1
Disassembly of external bearing pump-
Rear Timing Gear Configuration
a) Ensure that the driver is locked out and
cannot be accidentally started.
b) Ensure that the pump is isolated from the
system by closing off all primary and auxiliary
piping valves associated with the pump.
c) Flush the pump body [1110] and piping
system if necessary.
d) Disconnect bearing cooling water piping.
e) Drain the pump body & lube oil cavities.
f) Remove coupling guard and uncouple the
pump from the driver.
g) Remove the pump half coupling. If a spacer
coupling is not used, it will be necessary to
remove either the pump or the driver from the
baseplate to do this.
h) Remove rear caps [3510] from gear housing
[1600]. Mark to facilitate reassembly.
i) Bend up locking tang on the bearing
lockwashers and remove the bearing locknuts
[5260] and lockwashers.
j) Remove gear housing from the rear bracket
[6160].
k) Before removing timing gears [2810] and
spacers [2164.3] from the shafts, note that
those on the drive shaft are stamped L (long)
and those on the driven shaft are stamped
S(short) and that the stamped letters on the
hubs of the timing gears are facing outboard.
This is important when reassembling the
pump. Remove the timing gears and spacers.
l) Remove the body to rear bracket nuts
[6580.2] and dowel pins [6510.3]. Note that if
the pump is fitted with split brackets the
bearing and seal housing halves can be
separated at this point to facilitate seal
maintenance. Note the markings on the
halves for reassembly.
m) Remove the rear bracket [6160].
n) Remove front cover [1510] from front bracket
[6160].
o) Remove front bracket from body. Mark the
top of the bracket to facilitate reassembly.
Note that if the pump is fitted with split
brackets the seal and bearing housing halves
can be separated at this point to facilitate seal
maintenance. Note the markings on the
halves for reassembly.
p) If mechanical seals [4200] are fitted and the
rotating heads are to be replaced, the shafts
should be marked at the rear of the heads to
facilitate reassembly, before removing from
the shafts.
q) Refer to the INSPECTION AND OVERHAUL
section of this manual.
6.7.2
Disassembly of external bearing pump-
Front Timing Gear Configuration
a) Ensure that the driver is locked out and
cannot be accidentally started.
b) Ensure that the pump is isolated from the
system by closing off all primary and auxiliary
piping valves associated with the pump.
c) Flush the pump body and piping system if
necessary.
d) Disconnect bearing cooling water piping.
e) Drain the pump body [1110] & lube oil
cavities.
f) Remove coupling guard and uncouple the
pump from the driver.
g) Remove the pump half coupling. If a spacer
coupling is not used, it will be necessary to
remove either the pump or the driver from the
baseplate to do this.
h) Remove the gear housing [1600] exposing the
timing gears.
i) Remove the inner race [3014.2] of the gear
housing bearing from the shaft by applying
heat or splitting. Note: In either case it will be
necessary to replace the inner race.
j) Before removing the timing gears [2810] (and
spacers [2164.1, 2164.2, 2164.3] if equipped),
note that those on the drive shaft are stamped