3.背压阀(1)结构变幅卷扬背压阀装在马达油路中。在操作过程中,当控制阀在中位时,背压阀提供背压以调节油压并停止马达的转动。在吊臂下降操作中,马达由负荷重量或其惯性力驱动。此时,背压阀提供背压以防止马达超速。背压阀装有一个单向阀和溢流阀,在中位时将关闭油 3 back pressure valve (1) structural luffing hoist back pressure valve installed in the motor oil. During operation, when the control valve is in the neutral position, the backpressure valve provides back pressure to regulate oil pressure and stop the motor from rotating. In boom-down operation, the motor is driven by the load weight or its inertial force. At this point, the back pressure valve provides back pressure to prevent the motor from overspeeding. The backpressure valve is fitted with a check valve and relief valve that will shut off the oil when in the neutral position