12
Section VI – Overhaul
NOTE
Complete cartridges are available in service kits for
rebuilding these pumps. Refer to catalogs listed in
Table 1 for part numbers.
A. General
Plug all removed units and cap all lines to prevent the entry
of dirt into the system. During disassembly, pay particular
attention to identification of the parts, especially the
cartridges, for correct assembly.
Pump bearings are pressed in the bodies or on the shafts
and should not be removed unless defective. Figure 7 is an
exploded view which shows the proper relationship of the
parts for disassembly and assembly. Refer to Figure 1 and
Figure 7 for the correct assembled relationship of the parts.
B. Disassembly
1. Disassembly of Basic Pump – See Figure 7. If a foot
bracket is used, remove before dismantling the pump. Clamp
the pump body in a vise (not too tightly), cover end up, and
remove the four cover screws. Note the position of the cover
port with respect to the body port before lifting off the cover
and “O” ring. (See paragraph 2 for disassembly of flow
control covers).
Remove the pressure plate and spring. Note the position of
the ring for correct reassembly. Lift off the ring and remove
the locating pins. Separate the vanes from the rotor and
remove the rotor from the shaft.
Turn the pump body over, then remove the shaft key and the
snap ring which retains the bearing. Tap with a soft hammer on
the splined end of the shaft to force the shaft out of the body.
Support the bearing inner race and press the shaft out of the
bearing. Pull the shaft seal out of the body with a suitable
hooked tool and press out the inner bearing.
2. Disassembly of Flow Control and Relief Valve
Covers – See Figure 7. If a screen is used in the cover,
remove the plug and pull out the screen. Do not remove the
orifice plug unless it is necessary. Check whether there is a
plug at each end of the relief valve bore. If the bore is blind,
remove the plug and the snap ring to release the valve and
spring as shown in the inset view, Figure 7. If the bore is
through the cover, remove only the one plug to release the
spring and valve. Leave the snap ring and the other plug in
the cover.
C. Inspection and Repair
1. Discard the used shaft seal and all “O” rings. Wash the
metal parts in mineral oil solvent, blow them dry with filtered
compressed air and place them on a clean surface for
inspection.
2. Check the wearing surfaces of the body, pressure
plate, ring and rotor for scoring and excessive wear. Remove
light score marks by lapping. Replace any heavily scored or
badly worn parts.
3. Inspect the vanes for burrs, wear and excessive play
in the rotor slots. Replace the rotor if the slots are worn.
4. Check the bearings for wear and looseness. Rotate
the bearings while applying pressure to check for pitted or
cracked races.
5. Inspect the oil seal mating surface on the shaft for
scoring or wear. If marks on the shaft cannot be removed by
light polishing, replace the shaft.
6. Check the relief valve sub-assembly for free
movement in the cover bore. Remove burrs from the valve
by polishing, but do not round off the corners of the lands. Do
not attempt to rework the valve bore. If the bore is damaged,
replace the cover.
D. Assembly
Coat all parts with hydraulic fluid to facilitate assembly and
provide initial lubrication. Use small amounts of petroleum
jelly to hold “O” rings in place during assembly.
IMPORTANT
During handling and shipping of the precision
machined cartridge parts, it is possible to raise burrs
on the sharp edges. All sharp edges on the parts of a
new cartridge kit should be stoned, prior to installation.
1. Assembly of Flow Control Cover – See Figure 7. If the
cover has a through bore, insert the valve in the bore, small
land first. Then install the spring and pipe plug. For models with
the blind bore, first install the spring, then the valve, with the
hexagon head end first. Follow this with the snap ring (being
certain it is firmly seated in the groove) and the pipe plug. Install
the screen and the plug which retains it.
2. Assembly of Priority Valve Cover – See Figure 8. If the
relief valve seat was removed, a new seat must be pressed
into the body. Lubricate and insert the new seat chamfered end
first into the cover opening. Align square and press into place.
Use a short length of brass rod as a pressing tool, to prevent
seat damage. Clean the relief valve bore to remove chips and
filings. Insert the poppet into the bore, align square and lightly
tap the stem of the poppet to mate the poppet and seat. Install
the spring, shims and plug into the cover. Be sure to check the
pressure setting of the relief valve against the model code. If
the setting is out of tolerance, readjust by removing or adding
shims. (Removing shims reduces pressure while adding shims
increases pressure.)
Priority Valve – Install the snap ring within the priority
valve cover bore; make sure the snap ring is seated within its
groove. Insert the priority valve spool, small land first, into the
bore. Install plugs at each end of the bore and secure. Refer
to Figure 7 for spool orientation.