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(2)
Internal oil leakage
Oil leaks from a place under higher
pressure to a place under lower pressure,
provided that a gap or a clearance exists
in between.
In the gear pump, small clearances are
provided between the gear and the case
and between the gear and the side plate
to allow the oil to leak out and to serve as
a lubricant so that the pump will be
protected from seizure and binding.
The drawing at right shows how the
leaked oil flows in the pump. As such,
there is always oil leakage in the pump
from the discharge side(under higher
pressure) to the suction side. The
delivery of the pump is reduced by an
amount equal to the pump discharge.
In addition, the delivery of the pump will
also decrease as the amount of oil
leakage increases because of expanded
radial clearance resulting from the wear of
pump parts, the lower oil viscosity
resulting from increases in the oil
temperature, and the initial use of low
(770-3ATM) 4-10
viscosity oil.
4-10
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