CASE 2031174 - Caterpillar

Illustration 1 g06332702
SWING RIGHT partial schematic
(1) Passage
(2) Relief valve
(3) Check valve
(4) Makeup port
(5) Passage (supply oil)
(6) Swing motor
(7) Motor rotary group
(8) Passage (return oil)
(9) Check valve
(10) Relief valve
(11) Passage
(12) Main control valve
(13) Port (return oil)
(14) Hydraulic oil cooler
(15) Makeup line
(16) Port (supply oil)
(17) Check valve
(18) Slow return check valve
(19) Return line
Illustration 2 g06244109
Swing motor
(2) Relief valve
(4) Makeup port
(6) Swing motor
(10) Relief valve
Illustration 3 g06198316
Swing relief valve
(8) Passage
(11) Return passage
(20) Orifice
(21) Spring
(22) Stem
(23) Piston chamber
(24) Passage
(25) Piston
(26) Passage
(27) Piston chamber
(28) Orifice
(29) Passage
(30) Adjustment plugRelief valves (2) and (10) are located in the head of swing motor (6). These relief valves limit the pressure in the left and right swing circuits to the swing relief valve setting. This pressure limit provides a cushion effect at the start or stop of a swing.When the swing joystick is returned to the NEUTRAL position during a swing right, the swing control valve shifts to the NEUTRAL position. Since the swing control valve is in the NEUTRAL position, the oil flow through port (16) to motor rotary group (7) is now blocked at the swing control valve. The return oil from the motor rotary group through port (13) is also blocked at the swing control valve.The mass (weight and size) of the upper structure causes the upper structure to attempt to continue to rotate after the swing joystick is returned to the NEUTRAL position. The motor rotary group is also attempting to continue to rotate. The motor rotary group attempts to draw oil through port (16) and attempts to displace the oil through port (13).The oil supply to motor rotary group is insufficient. A vacuum condition occurs in passage (5). Return oil is supplied to the motor rotary group as makeup oil to prevent the vacuum condition. For more information concerning the makeup oil operation, refer to Systems Operation, "Oil Makeup (Swing System)".Since the flow of return oil from the motor rotary group through port (13) is blocked at the swing control valve, the pressure of the blocked oil in passage (8) increases. The increased oil pressure in passage (8) acts on swing relief valve (10). The increased pressure oil forces stem (22) of relief valve (10) to the right (open position) against the force of spring (21). When stem (22) shifts, oil flows through passage (11), check valve (3), and passage (5) to the motor rotary group. The shock load is absorbed at the stop of a swing movement.At swing relief valve (10), the increased oil pressure in passage (8)