Theory of Operation
BOOM MANUAL LOWER NEEDLE VALVE OPERATION
to flow through the needle valve, into the warm-up and
The function of the boom manual lower needle valve
air bleed circuit in the pilot cap, and then to the
(I) is to release the pressure oil from the head end of
hydraulic oil tank (B).
boom cylinders to the hydraulic oil tank to lower the
boom to the ground as needed. (See Lower Boom with
For operation of the boom reduced leakage valve, see
Engine Stopped procedure in Group 9025-25.)
Arm Rod End and Boom Reduced Leakage Valves
Operation in this group.
Opening the needle valve opens a passage for
pressure oil from the head end of boom cylinders (F)
Continued on next page