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H-Series
Reassembly
Figure 1
NOTE:
During and between each
reassembly step, manually turn the meter-
ing gears to ensure that they are free turn-
ing. If binding occurs at any time, deter-
mine the cause and correct it immediately.
A tiny nick, burr, or foreign particle can
extensively damage a valuable pump
component. Never use force in reassem-
bling or turning a Zenith pump. If properly
aligned, the pieces will fit easily into
place, and the pump will turn freely.
The HMB has a press fit arbor in the
rear plate. As such, some of these instruc-
tions may need reversal of the front and
rear plates.
NOTE:
Replace all fasteners, packings or
seal plates with new parts prior to assembly.
Reassemble the pump as follows:
1) After all worn parts have been
refinished or replaced, all parts should be
thoroughly cleaned in a solvent and dried.
2) Using the driven gear (7) as an
up-righting fixture, carefully locate the
arbor (5) over its press fit hole in either
the front or rear plate. Smoothly drive the
arbor into its hole with the help of an
appropriate arbor press.
3) Place the front side plate (1) with
the arbor in position in a soft-jaw vise or
holding fixture.
4) Slip together the driving metering
gear (6), drive shaft (4) and key (8). Position
in the front of the side plate by installing the
drive shaft through the bearing (49).
5) Place the driven metering gear on
its arbor and carefully mesh with the driving
metering gear.
6) Carefully lower the center plate (2)
over the gears.
7) Position the rear side plate (3).
8) Rotate the gears to ensure free
rotation.
9) Press the dowels (10) into place
moving in the direction of the shortest
press distance. (Usually from the rear side
of the pump.)
10) Lubricate the binder screws (47,
48) with DAG dispersion #154 or a similar
heat re-sistant lubricant and install. Torque
the screws in even increments, using a
crossing pattern, to the manufacturer’s
recommended limit. It is especially impor-
tant to rotate the gears frequently during
this operation.
See Table 2 on page 10 for
screw torque specifications.
11) Reassemble the seal arrange-
ment, making sure the sealing surfaces
are perfectly clean and free of scratches,
nicks,or burrs. When a carbon seal plate
is used, always use a new carbon seal
that has been lightly polished on 400/600
grit paper. When using a carbon seal, the
coupling housing screws (27) should be
torqued to the manufacturer’s recom-
mended limit. For pumps with a compres-
sion packing seal, be sure all old packing
is removed from the packing housing.
12) Inspect the drive shaft at the seal
area making sure that it is not scored,
shouldered or worn. Worn shafts will result
in premature seal leakage and should be
replaced.
13) Dip the packing rings into high-
temperature oil and graphite. This aids in
assembly and running-in of the packing.
14) Place the first packing over the
shaft and force it firmly and evenly to the
bottom of the packing housing. Tap it firmly
into place.
15) Rotate the drive shaft by hand
after each ring is installed to aid in seat-
ing the packing. Continue to install the
rings in this manner until the proper num-
ber of rings have been installed.
16) Firmly compress the packing by
alternating and evenly tightening up the
gland screws, then back off 1/2 turn. Be
sure to adjust the gland evenly. The pump
should not turn now.
17) In pumps with a universal seal
coupling, the seal area should be lubricat-
ed with a high- temperature lubricant prior
to installation.
18) Make sure that the rotating seal
coupling is positioned with the shallow slot
towards the internal pump shaft. Scoring on
the seal faces is detrimental to pump per-
formance. Lapping should only be done on
the seal plate and not on the rotating cou-
pling. Lapping the rotating coupling will
increase the end play of the seal resulting in
possible leakage and/or shaft misalignment.
9
