CONTACTOR 1708374 - Caterpillar

Illustration 1 g01403301
(1) Tilt cylinder (2) Lift cylinders (3) Load control valves (4) Manual lowering control valve (6) Internal passage (7) Relief valve (8) Pilot operated check valve (9) Internal passage (10) Internal passage (11) Check valve (A) Line from tilt control valve DUMP (B) Line from tilt control valve for TILT BACK (C) Line from pilot valve for DUMP (D) Line from lift control valve for RAISE (E) Line from lift control valve for LOWER (F) Line from pilot valve for LOWER (G) Port from the head end of the lift cylinder or of the tilt cylinder (H) Port from the lowering control valve or from the pilot valve for DUMP (J) Port from the lift control valve for RAISE or for TILT BACKLoad control valves (3) are sometimes known as load check valves or lock valves. Load control valves prevent the work tool from moving if the engine fails or if the hose bursts. The load control valves also prevent cylinder drift. The load control valves are pilot operated check valves.Load Control Valve
Illustration 2 g01403385
There is a load control valve (3) on each of the two lift cylinders and on the tilt cylinder. The load control valves prevent the work tool from moving if the engine fails or if the hose bursts. The load control valves also prevent cylinder drift. The load control valves are pilot operated check valves.Load Control Valve (RAISE or TILT BACK Position)
When the operator raises the implement or the operator racks back the implement, the load control valve allows oil to flow freely to the head end of the lift cylinder or to the head end of the tilt cylinder. High pressure oil flows in port (J). The pressure unseats check valve (8). Oil flows through the passage to port (G) .Load Control Valve (LOWER or DUMP Position)
When the operator lowers the implement or the operator dumps the implement, pilot oil from the pilot valve flows to port (H). Pilot pressure unseats check valve (11) and the pressure acts on pilot operated check valve (8). The pilot operated check valve (8) will unseat. The bank valve directs high pressure oil to the rod end of the lift cylinder or to the rod end of the tilt cylinder. Oil from the head end of the lift cylinder or from the head end of the tilt cylinder flows in port (G), through the passage, and to port (J) .When the Operation and Maintenance Manual, SEBU8028, "Equipment Lowering with Engine Stopped" is performed, the operator uses the lowering control valve (4) in order to pressurize port (H) on the load control valves (3) for the lift cylinders with oil.Load Control Valve (Engine Failure or Hose Failure)
If the engine fails, oil from port (J) will drain to the tank. If a hose bursts, oil from port (J) will be open to the atmosphere. In both cases, pressure at port (G) will be higher than pressure at port (J). The pressure at port (G) will not be sufficient to