Working principle of hydraulic sequence valve from wonepart The sequence valve is a pressure valve used when a hydraulic pump needs to supply two or more hydraulic actuators to operate in a certain sequence. The control pressure can be its own pressure or external oil pressure. Its structure and operating principle are very similar to the relief valve, and the difference is that the outlet of the sequence valve is directly connected to the actuator, and there is a special drain port. Any hydraulic pump parts or hydraulic valve we have, but we focus on kawasaki pump and parts and valves.