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Service (cont'd)
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 19.3 Bar (280 psi).
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
.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).
COVERPLATE
36.17 mm (1.424")
37.29 mm (1.468")
69
70
71
Figure A5
4
Greenlee Textron / Subsidiary of Textron Inc.
976-22, 980-22 Hydraulic Power Pump
42
47
43
44
45
46
Figure A4
3
7
49
48
8 mm (5/16") Ø BALL
(used to make measurement)
High-Pressure Inlet Check Ball Travel
The amount of allowable ball travel is critical to the
optimum high pressure output (flow rate). Refer to
Figure A5-1. Carefully and accurately measure (depth
"mike") the "A" dimension (top of pump block to seated
ball) and "B" dimension (top of pump block to head of
plug—at center). Carefully and accurately set the "C"
dimension (overall length of assembled plug and pin)
of a new plug and pin equal to "A" minus "B" minus
.305 ± .050 mm (.012 ± .002 inches).
42
Low Pressure Pump Drive Pin
Assemble with cone point end in half-round keyway.
20
4455 Boeing Dr., Rockford, IL 61109-2988 815/397-7070
TOP OF
79
105
PUMP BLOCK
B
A
C
TRAVEL
.305 mm
(.012 inch)
Figure A3-1
Figure A6
78
5
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