When the relief valve works, it is the use of spring pressure to regulate and control the size of the hydraulic fluid pressure. Hydraulic station manufacturers introduce specific hydraulic station pressure adjustment as follows:
1. The relief valve screws all loose, the equipment running, slowly tighten the screws, look at the pressure gauge, boost a few megapascals after stopping, so that the equipment at this pressure to run steadily for a few minutes, and then repeat the process of boosting, running, until adjusted to the set pressure.
2. Each hydraulic station pump outlet will have a relief valve, some times because of some reasons, the pump outlet pressure may be greater than the system required pressure, this time the need for a relief valve will be the excess pressure off, the oil will be discharged back to the tank.
According to different structures, relief valves can be divided into direct-acting and pilot-operated two types. Direct-acting relief valves are relief valves in which the main line pressure acting on the spool is directly balanced with the regulating spring force. According to the valve port and pressure measurement surface structure of different forms, the formation of three basic structures. Regardless of the structure, direct-acting relief valves are composed of three parts: the regulating spring and the regulating handle, the relief port, and the pressure measurement surface.
Pilot-type relief valve: the main valve spring is mainly used to overcome the spool friction, less elastic. Overflow caused by the main valve spring compression deformation of the change, the spring force of the change in the magnitude of the smaller, thus reducing the main valve inlet pressure changes. The pressure adjustment precision is high, widely used in high-pressure high-flow system. Because the spool of the relief valve is subject to friction in the movement process, the valve opening and closing when the friction hydraulic system in the opposite direction, so there is a difference between the opening and closing of the relief valve.
Comparison of direct type relief valve and pilot operated relief valve: direct type relief valve structure is simple, high sensitivity, but the pressure is greatly affected by the change of overflow flow, adjusting the pressure deviation is large, is not suitable for high pressure and large flow rate work, usually used as a safety valve or used to regulate the pressure precision is not high. In the case of normal operation of the system, the valve is closed. When the load exceeds the specified limit (the system pressure exceeds the regulation pressure), the relief valve is opened for overload protection so that the system pressure does not increase (usually the adjustment pressure of the relief valve is 10% to 20% higher than the system working pressure).
