Greenlee 980 - Pressure Relief and Bypass Valve Adjustments

Greenlee / A Textron Company 22 4455 Boeing Dr. • Rockford, IL 61109-2988 USA • 815-397-7070
980 Hydraulic Power Pump
Low-Pressure Bypass Check Pressure Adjustment
When properly set to the dimension shown in Figure A5,
the high pressure stage operation of the pump will be
delayed approximately one (1) second after the motor
starts. This delay is created by the closing time of the
pilot-operated valve.
Note: This dimension must be increased if ball seat
depth is increased by more than 0.4 mm (1/64 inch).
Increasing the bypass pressure (CW rotation of adjusting
screw—increase of set dimension) will shorten delay. If
delay becomes too short, the motor will not restart when
high pressure is held in the line. The motor should restart
with a maximum required off time of 1/2 to 1 second.
Decreasing the bypass pressure (CCW rotation of
adjusting screw) will increase delay. The pilot-operated
valve will not close if pressure is set too low.
Changes in oil temperature (viscosity) will affect the
amount of delay. The pumping delay will increase with
rising oil temperature (thinner oil).
Low Pressure Relief Setting
Refer to Figure A4. Lightly bottom the stem (44) on the
ball (46). Then, back out the stem 3-1/2 turns. Tighten
nut (43). The resulting pressure setting should be
approximately 19 bar (280 psi).
Repairs (cont’d)
44
3
Figure A4
7
42
47
43
45
46
49
48
COVERPLATE
36.17 mm (1.424")
8 mm (5/16") Ø BALL
(used to make measurement)
37.29 mm (1.468")
69
70
71
4
Figure A5