Parker Hannifin Corporation
Gear Pump Division
Kings Mountain, North Carolina USA
12
Seals and Gaskets
Replace all rubber and polymer seals,
including all “0” rings, thrust block channel
seals, shaft seal and gasket seals.
Checks
Examine the checks, if unit has them, in the
mounting flange to make sure that they are
tight, and free of contamination.
Gear Housing
Wear in excess of .005” cut-out necessitates
replacement of the body. Place a straight-edge
across bore. If you can slip a .005 feeler gage under
the straight-edge in the cut-out area, re-
place the body.
Pressure pushes the gears against the
housing on the low pressure side. As
the hubs and bushings wear, the cut-out
becomes more pronounced. Excessive
cut-out in a short period of time indicates excessive
pressure or oil contamination. If the relief valve settings
are within prescribed limits, check for shock pressures
or tampering.
When the cut-out is moderate, 005” or less, the gear
housing is in good condition and may be reused.
Gears
Any scoring on gear hubs necessitates
replacement. Scoring, grooving, or burr-
ing of the outside diameter of the teeth
requires replacement. Nicking, grooving,
or fretting of teeth surfaces also
necessitates replacement.
Drive Shafts
Replace if there is any wear
detectable by touch in the seal
area or at the drive coupling. The
maximum allowable wear is .002”.
Wear in the shaft seal area indicates oil
contamination. Wear or damage to splines, keys,
or keyways necessitates replacement.
Bushing Blocks
The bushing blocks seal the gear section
at the sides of the gears. Wear here will
allow internal slippage, that is, oil will
bypass within the pump.
A maximum of .002” wear is allowable.
Replace bushing blocks if they are scored, eroded
or pitted. Check center of bushing blocks where the
gears mesh. Erosion here indicates oil contamination.
Pitted bushing blocks indicate cavitation or oil aeration.
Discolored balance plates indicate overheating, likely
due to insufficient oil.
505
1 piece
511
2 pieces
Guideline for acceptable wear
Catalog HY09-SM500/US
Wear Guideline
PGP/PGM500 Series
Service Manual
