Hydraulic systems can be divided into two categories: hydraulic drive systems and hydraulic control systems. The main function of hydraulic transmission system is to transmit power and movement. The hydraulic control system must make the output of the hydraulic system meet specific performance requirements, especially dynamic performance.

　　A complete hydraulic system consists of five parts, namely power components, executive components, control components, auxiliary components and hydraulic oil.

　　 1. The function of the power element is to convert the mechanical energy of the prime mover into liquid pressure energy, which refers to the oil pump in the hydraulic system, which provides power to the entire hydraulic system.

　　2. The function of the actuator is to convert the pressure energy of the liquid into mechanical energy and drive the load for linear reciprocating or rotary motion.

　　3. The control element controls and regulates the pressure, flow and direction of the liquid in the hydraulic system. According to different control functions, hydraulic valves can be divided into pressure control valves, flow control valves and directional control valves.

　　4. Auxiliary components include fuel tanks, oil filters, coolers, heaters, accumulators, oil pipes and pipe joints, high-pressure ball valves, pressure gauges, oil level gauges, oil temperature gauges, etc.

　　5. Hydraulic oil is the working medium that transmits energy in the hydraulic system. There are various types of mineral oil, emulsion and synthetic hydraulic oil.

　　Hydraulic systems are mainly used in large and medium-sized industrial production machinery and equipment in electric power, building materials, petrochemical, metallurgical and other industries.