HOUSING-YM 4162141 - Caterpillar

Illustration 1 g00480078
(1) Angle Cylinders (2) Lift Cylinders (3) Tilt Cylinder (4) Ripper Cylinders (5) Hydraulic Tank and Filter (6) Pump Compensator Valve (7) Pump (8) Signal Line (9) Control Valves (A) Inlet Manifold (B) Bulldozer Lift Control Section (C) Bulldozer Tilt Control Section (D) Bulldozer Angle Control Section (E) Ripper Lift Control Section (F) End CoverThe hydraulic system controls the operation of the bulldozer and the ripper. The hydraulic system can be different from one machine to the next machine according to the blade configuration and optional equipment that is on the machine.The basic hydraulic system consists of the following components:
return filter (5)
variable displacement axial piston pump (7)
control valves (9)
one to four pressure compensated control valves (B) , (C) , (D) and (E)
hydraulic cylinders (1) , (2) , (3) and (4) See the following tables.
Table 1
Hydraulic System Components    
Options     (B)     (C)     (D)     (E)    
5 VPAT Bulldozer     X     X     X        
5 VPAT Bulldozer with Ripper     X     X     X     X    
Table 2
Hydraulic System Components    
Options     (1)     (2)     (3)     (4)    
5 VPAT Bulldozer     X     X     X        
5 VPAT Bulldozer with Ripper     X     X     X     X    The hydraulic system is a closed centered, load sensing system. A load sensing system keeps a constant flow for a given directional control spool position. A constant flow is achieved by maintaining a constant pressure difference across the orifice of the directional control spool.
Illustration 2 g00480114
Pump (7) has pump compensator valve (6) that automatically keeps pump pressure and flow at a level needed in order to fulfill the system load and flow needs. When none of the hydraulic circuits are being used, the pump is at low pressure standby, or about 1725 kPa (250.2 psi). If one or more of the circuits is being used, a resolver network compares the control valve work port pressures. The highest pressure goes through signal line (8) to pump compensator valve (6) .This valve now keeps the pump flow at a level needed in order to fulfill system flow and pressure requirements. The actual system pressure will usually be about 1380 kPa (200.2 psi) above the highest work port pressure requirement unless the pump is at full stroke. The difference between the highest work port pressure requirement and the higher supply pressure is called margin pressure.The compensator valve also limits pressure in order to prevent overloading of the pump and the system. When a work port pressure goes above 20700 350 kPa (3002.3 50.8 psi), the compensator will lower the pump output. This action starts at approximately 690 kPa (100.1 psi) below the maximum pressure setting. The hydraulic system is now protected from high pressures that