PLATE AS 2825323 - Caterpillar

Illustration 1 g03424144
Partial schematic
(1) Boom cylinders
(2) Boom lowering control valves
(3) Main control valve
(4) Pilot control valve BOOM RAISE Operation
Illustration 2 g02796296
Boom lowering control valve
(1) Port (boom cylinder head end)
(2) Passage
(4) Check valve
(5) Spring
(6) Passage
(7) Line relief valve
(8) Port
(10) Port (pilot)
(11) Spool
(12) Passage
(13) Orifice
(23) Valve When the operator moves the joystick to the BOOM RAISE position, oil from the main control valve flows through port (8) in the boom lowering control valve. As the oil pressure increases, check valve (4) shifts against the force of spring (5). This shift allows oil to flow through passage (6), passage (2), and port (1) to the head end of the boom cylinders. The rod is extended and the boom raises.BOOM LOWER Operation
Illustration 3 g03666223
Boom lowering control valve
(1) Port (boom cylinder head end)
(2) Passage
(7) Line relief valve
(8) Port
(10) Port (pilot)
(11) Spool
(12) Passage
(13) Orifice
(23) Valve When the operator moves the joystick to the BOOM LOWER position, pilot oil flows from the pilot control valve to port (10) of the boom lowering control valve. The pilot pressure moves spool (11) to the left. Orifice (13) opens allowing oil to flow to passage (12).As the joystick is moved further to the BOOM LOWER position, the pilot pressure in port (10) increases. Spool (11) shifts further to the left which allows more oil from passage (2) to flow to passage (12). Oil from the head end of the boom cylinder flows through port (1), to port (8), and then to the main control valve. The boom cylinder rod retracts and the boom lowers.Manual Boom Lower
Illustration 4 g01213309
(1) Port
(15) Port
(21) Seat
(22) Locknut
(23) Valve
(24) Ball As seat (21) is turned counterclockwise, ball (24) will shift. As ball (24) is shifted, oil is allowed to flow through port (1) and valve (23) to port (15). Oil from the head end of the boom cylinder flows through port (15) to the hydraulic tank. This action will allow the boom to lower.