COMPONENT OPERATION / Swing Device VALVE UNIT The valve unit consists of make-up valve and relief valve. The make-up valve prevents cavitation in the circuit and the relief valve prevents surge pressure and overloads in the circuit. Make-Up Valve During swing stopping operation, the swing motor is driven by the inertial force of swing frame. The swing motor is turned forcibly in excess of oil pressure from the pump, so that cavitation may be generated in the motor. In order to avoid this cavitation, when pressure in the swing circuit becomes lower than that in the return circuit (port M), the poppet opens to draw hydraulic oil and compensates the lack of oil feed.
T1J1-03-02-001 Control Valve Poppet Make-Up Valve Make-Up Valve Port M T178-03-02-004 Relief Valve T3-2-6 Relief Make Po Control Valve valve Make -Up Valve rt M Relief valve Po rt M