Service Manual

HY13-1521-M2/US Service Manual
General Information Series HB Hydrostatic Transmission
CAUTION: All fittings and hoses must be securely attached. The test is
accomplished using the vehicle’s high pressure system lines. Failure to secure
connections could result in bodily injury.
5. Completely open the restriction valve.
6. Start the engine and, if required, engage the drive pulley.
7. Slowly bring engine up to maximum operating speed.
8. Move the vehicle’s directional control lever on the pump being tested all the way into the
forward position. Lock the control arm into position to prevent false readings.
9. Continue to operate without any load to allow the system oil temperature to rise.
NOTE: Raising the temperature of the oil will make a difference in your readings. To complete
the test accurately, the oil temperature should fall between 110˚ and 140˚ F.
10. Tighten the restriction valve until the difference between the pressure gauge readings is
300 psi (21 bar). Record the flow reading from the bi-directional flow meter.
11. Tighten the restriction valve until the difference between the pressure gauge readings is
1000 psi (69 bar) and record the flow reading again.
12. The maximum allowable flow rate change is shown below. If the difference exceeds this
level, the pump is unacceptable.
13. When testing is complete, re-install the motor port plugs. Torque to 35 to 50 ft-lb.
Series
Displacement
cc/rev
(nominal)
Max. Allowable Flow Rate
Change* (gpm)
UHT 12 to 16 1.0
* Max. Allowable Flow Rate Change is equal to the flow rate at 300 psi minus the flow rate at 1000 psi.
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Parker Hannifin Corporation
Hydraulic Pump/Motor Division
Greeneville, Tennessee USA