The hydraulic system works by changing the pressure to increase the force. A complete hydraulic system consists of five parts, including power component, executive component, control component, auxiliary component (accessories) and hydraulic oil. Hydraulic system can be divided into two categories: hydraulic transmission system and hydraulic control system. Hydraulic transmission system transfers power and motion as the main function. The hydraulic control system should make the output of the hydraulic system meet specific performance requirements (especially dynamic performance). Generally speaking, the hydraulic system mainly refers to the hydraulic transmission system. Power element. The action of the power element is to convert the mechanical energy of the prime mover into the pressure energy of the liquid. The structure of hydraulic pump generally has gear pump, vane pump, plunger pump and screw pump.

Actuating element. The actuator (such as a hydraulic cylinder and a hydraulic motor) is used to convert the pressure energy of the liquid into mechanical energy, driving the load to reciprocate or rotate in a straight line.

Control element. Control elements (various hydraulic valves) control and regulate the pressure, flow and direction of the liquid in a hydraulic system. According to different control functions, hydraulic valves can be divided into pressure control valves, flow control valves and direction control valves. Pressure control valve includes overflow valve (safety valve), pressure reducing valve, sequence valve, pressure relay, etc. The flow control valve includes the throttle valve, the adjustment valve, the shunt collector valve and so on. Direction control valve includes one-way valve, liquid control one-way valve, shuttle valve, reversing valve, etc. According to different control modes, hydraulic valves can be divided into switch type control valves, fixed value control valves and proportional control valves.

Auxiliary components. Auxiliary components include oil tank, oil filter, cooler, heater, energy storage, tubing and pipe joint, seal ring, quick change joint, high-pressure ball valve, rubber tube assembly, pressure gauge joint, pressure gauge, oil level gauge, oil temperature gauge, etc.

The hydraulic oil. Hydraulic oil is the working medium of energy transfer in hydraulic system. There are several kinds of mineral oil, emulsifying liquid and forming hydraulic oil.