Hydraulic supports are supporting equipment in coal mining machinery. They can generally be used underground for five years after major repairs. However, the service life of various hydraulic valves in hydraulic supports is very low. The longest is 3 months and the shortest is only a few weeks. The solution abroad is to increase the filtration accuracy of the system and improve the quality of the emulsion, but it has little effect. Take a British hydraulic valve as an example. Although the machining accuracy and the filtering accuracy of the entire hydraulic system are relatively high, it has been eliminated in my country due to its low service life.

In the early hydraulic supports, there were no other sealing measures between the movement pairs. The metal contacted the seal directly, that is, the contact surfaces of the seal pairs were required to be consistent, with high processing accuracy. Otherwise, the bonding force of the seal pairs must be increased to make the contact surface plastic. Deformation, blocking the leakage channel. A complete hydraulic system consists of five parts, namely power components, executive components, control components, parts and hydraulic oil. The function of the power element is to convert the mechanical energy of the prime mover into the pressure energy of the liquid, which refers to the oil pump in the hydraulic system, which provides power to the entire hydraulic system. The structure of hydraulic pumps generally includes gear pumps, vane pumps and plunger pumps.

The function of the executive components (such as hydraulic cylinders and hydraulic motors) is to convert the pressure energy of the liquid into mechanical energy, and drive the load for linear reciprocating motion or rotary motion.

Control elements (ie various hydraulic valves) control and regulate the pressure, flow and direction of the liquid in the hydraulic system. According to different control functions, hydraulic valves can be divided into village force control valves, flow control valves and directional control valves.

Pressure control valves are further divided into flow control valves (safety valves), pressure reducing valves, sequence valves, pressure relays, etc.; flow control valves include throttle valves, regulating valves, diversion and collector valves, etc.; directional control valves include check valves, Hydraulic control check valve, shuttle valve, reversing valve, etc.

According to different control methods, hydraulic valves can be divided into on-off control valves, fixed value control valves and proportional control valves.

Auxiliary components include oil tank, oil filter, oil pipe and pipe joint, sealing ring, pressure gauge, oil level oil temperature gauge, etc.

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