Flowserve Twin Screw Rotary - Manual (Page 44)

TWIN SCREW PUMPS. ORIGINAL USER INSTRUCTIONS. ENGLISH. 71569243 – 07/10
Page 41 of 53
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and including step d) in section 6.9.1 or step o) in
6.9.2. The following procedure is then to be followed.
a) Using a straightedge, mark the point on the drive
and driven shafts in line with the flange face on
the front end of the body.
b) Remove the thrust bearing bracket to body
capscrews and nuts, and pull the rotating element
partially out from the rear of the pump with the
rear bracket assembly intact.
c) Using a straightedge, mark the point on the shafts
in line with the flange face of the rear bracket.
d) Remove the bracket assembly from the rotating
element.
e) With the datum lines now marked on the shafts,
refer to the applicable mechanical seal drawing for
the required setting dimension.
f) Assemble the seals on the shafts and proceed
with the steps outlined in section 6.9.1 or 6.9.2.
6.10.1.2 Internal bearing pump
If a new rotating element is being installed, the pump
should be assembled without mechanical seals up to
and including step e) in section 6.9.3. The following
procedure is then to be followed.
a) Using a straightedge, mark the point on the drive
shaft in line with the flange face on the front head.
b) Remove the front head.
c) With the datum lines now marked on the shafts,
refer to the applicable mechanical seal drawing for
the required setting dimension.
d) Assemble the seals on the shafts and proceed
with the steps outlined in section 6.9.3.
6.11 Free Movement
If the pump does not turn freely after reassembly, the
following procedure should be observed.
a) Remove front and rear head dowel pins.
b) Loosen all head to body capscrews except for the
four corners at each end.
c) Check location of rotors in the body bores by
reaching into the discharge flange and checking
the radial clearance between the rotors and the
body bores with a feeler gauge.
d) Using a large mallet move the front and rear
heads radially to equalize the clearance between
the outside diameter of the pumping rotors and
the body bores, checking for the pump to turn
freely.
e) Once the pump is turning freely, tighten all head
capscrews.
f) Continue with step s) in section 6.9.1, step m) in
section 6.9.2 or step n) in section 6.9.3.
If the pump does not turn freely after executing this
procedure it is due to incorrectly dimensioned parts or
a timing problem. Contact the nearest Flowserve
Service Representative for assistance. Section Error!
Reference source not found., provides guidance in
verifying the timing of the rotating element.
6.12 Timing Gear Replacement
If new timing gears are to be installed on the rotating
elements, they must be timed before key slotting. The
reason for this is that the timing gear angular position
on the shaft determines, in part, the critical clearance
between the pumping rotors. Since the normal axial
clearance of meshing rotors varies with the size of
pump and viscosity of the fluid that the pump was
designed for, very accurate key slotting is essential for
proper operation. The total rotor side (flank)
clearances should be determined with feeler gauges,
with the shaft sitting in the appropriate timing stands.
This number represents the total clearance. One half
of it is the proper axial distance between the meshing
rotor teeth.
To replace the timing gears, the following procedure
should be used.
a) For optimum results it is highly recommended
that a set of timing stands as shown in Fig. 9
be manufactured.
b) Mount the shafts with the screws intermeshed
onto the timing stands resting the shafts on
the bearing diameters. The bearings are not
mounted on the shafts at this time.
c) Install the driven shaft timing gear key.
d) Slide the driven shaft timing gear partially onto
its' respective shaft diameter, engaging the
key.
e) Slide the drive shaft timing gear partially onto
its' respective shaft diameter with the existing
keyway 180 away from the shaft keyway,
meshing with the driven shaft gear. (Fig. 6 &
7).
f) Place feeler gauges with a thickness equal to
half of the total side clearance on each side of
one screw tooth on the drive shaft. This will
eliminate contact between the drive and
driven pumping screws.
g) Rotate the drive shaft gear in the direction of
rotation of the pump until the teeth of both
gears in contact. (Fig. 8).
h) Place the driver shaft gear key into the
keyway at a right angle to the shaft and
against the time gear face. (Fig. 8).
i) Scribe a line on both sides of the key on the
time gear face. (Fig. 8)
j) Mark the position of the drive gear with
respect to the driven gear with 3 punch marks.
(Fig. 8).