Fixed Flow
Dismantling and Assembly
Before removing and dismantling the pump, check flow and
pressure. If either of these are low the pump must be
changed. Renewal of components such as gears, bearings
and housing will not effect a permanent cure. If the pump
output is satisfactory but there is external leakage, the pump
should be removed and dismantled for re-sealing only.
Before removing and dismantling the pump, make sure the
exterior of the pump and working area is thoroughly cleaned
and free of possible sources of contamination.
Dismantling
1 Remove the four bolts 3 and serrated washers 4 which
clamp the units together.
2 Use a soft faced hammer to separate front body 5 and
rear body 6 after first marking them to ensure correct
re-assembly.
3 Remove splined coupling 7 and O-rings 8. Discard the
O-rings.
4 Use a soft faced hammer to separate end cover 9 from
rear body 6, after first marking them to ensure correct
re-assembly.
5 Remove drive gear 10 from its bore. Pushing it out of
the rear body will also remove balance plate 11
complete with seal 12 and seal energiser 13. Discard
the seal and seal energiser. Note the position of the
driveshaft and the balance plate to ensure correct re-
assembly.
6 Remove driven gear 14, followed by balance plate 15
complete with seal 16 and seal energiser 17. Discard
the seal and seal energiser.
7 Discard O-ring 18.
8 Use a soft hammer to separate mounting flange 19 from
front body 5, after first marking them to ensure correct
re-assembly.
9 Remove circlip 21 and shaft seals 22. Note which way
round the seal lips are fitted to ensure correct fitting of
new seals on re-assembly.
10 Remove driveshaft 23 from front body 5. Removal will
also remove balance plate 28 complete with seal 29 and
seal energiser 30. Discard the seal and seal energiser.
11 Remove driven gear 27 followed by balance plate 24,
seal 25 and seal energiser 26. Discard the seal and seal
energiser.
12 Discard O-ring 31.
13 Remove all sealant from the contact faces of the
mounting flange/front body and end cover/rear body
interfaces.
14 Wash all components and immediately apply a coating
of hydraulic oil to prevent corrosion.
Inspection
1 Generally check all pump parts for damage and/or
wear. The O-ring grooves, the seal recess in the
mounting flange and all sealing faces must be free of
burrs and scores which could result in seal damage
and hence hydraulic oil leakage.
2 Renew the pump if any of the following symptoms
exist:
a The PTFE coated bearings in the pump bodies, the
mounting flange and the end cover are worn
through to reveal the bronze backing.
b The gear side faces are scored. Often
contaminated fluid results in a distinct wear step
coincident with the gear root diameter. This can
normally be felt by drawing a sharp point across
the gear side face from the journal towards the tip
of the gear.
c There is a noticeable wear groove on driveshaft 23
where seals 22 run.
d The balance plate faces are scored, particularly in
the area adjacent to the gear root diameter.
e The shaft splines are worn or severely fretted.
f The gear "cut-in" area in the low pressure side of
the pump body is deeper than 0.15 mm (0.006 in)
or has a torn or pitted appearance.
31 - 2
Section E
Hydraulics
9803/3280
Section E
31 - 2
Issue 1
Main Pump
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