MANIFOLD 1242966 - Caterpillar

The pilot oil flow from port (11) shifts spool (49) of boom I control valve (16) against the force of spring (17). The oil delivery from the drive pump in parallel feeder passage (10) flows through load check valve (27), passage (52), passage (48) and port (53) to boom drift reduction valve (14). The oil delivery from the drive pump shifts valve (21) in boom drift reduction valve (14) downward. The oil delivery from the drive pump then flows through line (4) to the head end of boom cylinders (2).Note: For more information on the boom drift reduction valve, refer to Systems Operation, "Boom Drift Reduction Valve".The pilot oil flow in port (13) of boom II control valve (23) shifts spool (45) against the force of spring (24). The oil delivery from the idler pump in parallel feeder passage (25) now flows through check valve (18), passage (46), and passage (47). From passage (47) the oil flows out of port (53). The oil delivery from the idler pump combines with the oil delivery from the drive pump at passages (47) and (48). The combined pump oil flows through port (53) and line (4) to the head end of boom cylinders (2).Return oil from the rod end of boom cylinders (2) flows through line (3) to port (51). The oil then flows through boom I control valve (16), return passage (28), and return line (6) to the hydraulic tank.Boom Raise (Low Speed)
When the joystick for the boom is moved less than half of the travel distance for BOOM RAISE, low pilot oil pressure