VALVE-RELIEF 1170765 - Caterpillar

Pilot Hydraulic Schematic
Illustration 1 g06053543
Pilot connections for upper main control valve
(1) Reverse fan solenoid valve
(2) Swivel
(3) Stick cylinders
(4) Main boom cylinders
(5) Fan motor
(6) Lower hydraulic shutoff valve
(7) Hydraulic lockout valve
(8) Electronic proportional reducing valves (EPRV)
(9) Main hydraulic oil pump
(10) Swing control valve
(11) Pilot pressure sensor
(12) Control valve - stick (extend)
(13) Control valve - cab (raise/lower)
(14) Control valve - cab (fore/aft)
(15) Control valve - work tool (rotate)
(16) Pilot valve
(17) Control valve - main boom master (extend/retract)
(18) Control valve - stick master (extend/retract)
(19) Control valve - work tool (open/close)
(20) Control valve - main boom slave (extend/retract)
(21) Swing pump
(22) Swing motor
Illustration 2 g03644522
Pilot connections for the lower main control valve
(2) Swivel
(8) Electronic proportional reducing valves (EPRV)
(16) Pilot valve
(23) Travel motor
(24) Manifold and solenoid valve for travel displacement, service brakes, and hydraulic oil warming
(25) Transmission control manifold
(26) Control valve - travel motor slave
(27) Control valve - travel motor
(28) Control valve - right rear stabilizer
(29) Control valve - left rear stabilizer
(30) Control valve - left front stabilizer
(31) Control valve - right front stabilizer
(32) Control valve - steeringThe pilot system provides pilot hydraulic oil to the following components, reverse fan (1), stick lowering control valves (3), boom lowering control valves (4), hydraulic lockout solenoid valve (7), Electronic Proportional Reducing Valves (EPRV) (8), swing control valve (10) and manifold and solenoid valve (24). The pilot oil in these control circuits physically moves the spools in the main control valves to initiate the desired function.An electronically actuated solenoid valve is used to direct pilot oil to the end of a spool within a control valve section. The pilot oil shifts the spool located inside the valve section resulting in a flow of main pump hydraulic oil through the port of the valve.Pilot Oil Circuits
The pilot circuit is part of the following systems:
Cylinder lowering control valves (boom and stick)
Swing parking brake
Swing system
Travel system
Upper and lower main control valveThe pilot circuit pressure is created from the main pump pressure by the pilot valves within both the upper and lower main control valves. The pilot valve is a proportional reducing valve (PRV) that reduces the main pump oil pressure to a pilot pressure.Pilot Control Valve Circuits
Illustration 3 g03646429
Partial schematic
(16) Pilot valve
(33) Upper main control valve
(34) Lower main control valve
(35) Filter (pilot oil)
(36) Pilot relief valve
(37) Load sense valve
(38) Load sense relief valve
(39) Main relief valveSystem pressure hydraulic oil is reduced to pilot oil within upper main control valve (33) and lower main control valve (34).System pressure oil is passed through pilot valve (16) that is set to a pressure of 3503 kPa (508 psi). The pilot oil is then passed through filter (35). In the upper main control valve, pilot oil then flows to the hydraulic lockout solenoid valve (upper main control valve only). The hydraulic lockout valve receives a signal from the IQAN and the control module to stop pilot oil to tank and build pressure in the upper main control valve. The pilot oil flows to each of the electronic proportional reducing valves (EPRV) (8). The EPRV solenoid valves are