1 Working principle: According to the working principle and structure, the sequence valve is divided into direct acting and pilot type; according to the pressure control mode, the sequence valve has internal control and external control points. In the sequence valve is equipped with one-way valve, through the reverse flow of composite valve called the one-way sequence valve. In general, this valve to use more. 2 Functions and Applications: The basic function of sequence valve is to control the sequence of multiple actuators, according to their different functions are called sequence valve, back pressure valve, unloading valve and balance valve. Sequence valve performance and relief valve is basically the same, but due to different functions, the sequence valve has its special requirements: (1) in order to achieve the precise implementation of the sequential operation of the order element, the order valve pressure regulator requires high precision, small deviation ; (2) In order to order the accuracy of the operation, the valve is required to close the internal leakage is small; (3) For one-way sequence valve, the required reverse pressure loss and the value of the forward pressure loss should be small. The main functions of the sequence valve are: (1) control the sequential operation of a plurality of components; (2) for the packing pressure circuit; (3) prevent the piston of the cylinder from falling due to its own weight to be used as a balancing valve; (4) Sequence valve to do the unloading valve, the pump unloading; (5) with internal control valve for back pressure valve. 3 Production Sequence Valve Products manufacturers: China mainly Yuci Hydraulic Group Co., Ltd., Beijing Huade Hydraulic Group Co., Ltd., Shanghai Li new hydraulic plant and so on. Foreign countries such as the United States Vickers, Germany Rexroth and other manufacturers. 4 Sequence valve selection: Sequence valve according to the different assembly structure, can achieve different circuit functions, such as relief valve, valve sequence valve and the balance valve function. Sequence valve opening and closing characteristics if poor, the flow rate is too high when the pressure is too high, the circuit efficiency decreases. Opening and closing characteristics with hysteresis, opening pressure is lower than the closing pressure, should be noted when the load flow changes. Open the valve is too low pressure, then the pressure is lower than the set pressure leakage occurred before, causing the actuator malfunction. Vibration or other instability occurs when the flow through the valve is much less than the rated flow. At this point to take measures to return to the road.
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