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XLB-4319
4-10
Check and adjust the hydraulic bypass pressure for the basket or ground station boom
controls as follows:
1. Connect a hydraulic pressure gage to the pressure test port.
2. Start the gasoline engine or DC motor. Run the engine or motor for at least five
minutes to warm the hydraulic oil to the normal operating temperature.
3. Extend the outriggers to fully support and level the boom lift.
4. Turn the ground control station key switch to basket or ground position, accord-
ing to which bypass pressure (basket or ground control) is to be adjusted.
NOTE: When adjusting the bypass pressure for the basket station boom controls,
the basket station boom controls must be used. When adjusting the by-
pass pressure for the ground station boom controls, the ground station
boom controls must be used.
5. Push down the lower beam control lever at the basket or ground station and read
the pressure gage. If the pressure gage reading is 2750 psig [190 bar (19 000
kPa)] nominal, no adjustment is required. If an adjustment is required, proceed
with step 6.
6. Press the emergency stop pushbutton to turn off the hydraulic pump.
NOTE: Removing the adjust screw cap while the hydraulic pump is running will
cause oil to leak from the bypass valve. It is recommended that you shut
the engine off before removing the adjust screw cap.
7. Locate the bypass valve for the selected boom control valve bank. Remove the
adjust screw cap.
8. Use screwdriver to turn the adjust screw. Turning the adjust screw 1/4 turn to
the right will increase the pressure about 150 psig [10,4 bar (1 037 kPa gage)].
9. Reinstall and tighten the adjust screw cap. Do not over tighten the cap.
10. Reset the emergency stop pushbutton and restart the engine or motor.
11. Push the upper or lower beam control lever down at the basket or ground station
controls and read the pressure gage. If the bypass pressure is still too high or too
low, repeat the adjustment starting with step 6.
12. If no other hydraulic pressures are to be checked, shut down the engine or motor
and remove the pressure gage.
Hydraulic Cylinder Replacement
WARNING
Hydraulic cylinders are heavy and may have hydraulic oil on the surface. Hydrau-
lic cylinders must be secured with lifting straps or tie-downs when removing, in-
stalling, and handling. Failure to heed this warning can result in serious injury.