Divided by the use of relief valve? Pressure relief valve and sequence valve. (1) relief valve: can control the hydraulic system to maintain a constant state when the set pressure. The relief valve used for overload protection is called safety valve. When the system fails, the pressure rises to a limit value that may cause damage, the valve will open and overflow to ensure the safety of the system. (2) pressure reducing valve: can control the branch circuit to get lower than the main circuit oil pressure stable. Pressure relief valve according to its control of the different pressure functions, and can be divided into fixed value pressure relief valve (output pressure is constant)? Fixed differential pressure relief valve (input and output pressure differential for the fixed value) and the proportional pressure relief valve (Input and output pressure to maintain a certain ratio). (3) sequence valve: can make an actuator (such as hydraulic cylinder? Hydraulic motor, etc.) action, then the order of the other actuator action. The pressure generated by the oil pump first promote the movement of the hydraulic cylinder 1, at the same time through the inlet port of the sequence valve on the area A, when the hydraulic cylinder 1 movement is completed, the pressure rises, the upward thrust acting on the area A is greater than the spring setting Value, the spool so that the inlet and the oil port connected to the hydraulic cylinder 2 movement. More Keyword Search: Control Valve