How to adjust the power station safety valve after overhaul?

Time：2021/9/11 22:20:50 Category：TECHNICAL ARTICLE Source： Click：

How to adjust the power station safety valve after overhaul?

Power station boilers or large and medium-sized power boilers have superheaters, so safety valves that are adjusted according to the saturated steam pressure and the superheated steam pressure are usually installed.

Due to the pressure difference in the superheater, the saturated steam pressure is always higher than the superheated steam pressure, and the difference increases with the increase of the boiler working pressure level. For example, the difference in the medium pressure furnace is 0.5 MPa, and the difference in the high pressure furnace is 1.0 MPa. Due to the operating pressure of the superheated steam safety valve, the medium pressure furnace is 1.04 times the superheated steam pressure, and the high pressure and above pressure boilers are 1.05 times the superheated steam pressure. The operating pressure of the saturated steam safety valve is 1.06 times the drum pressure for medium-pressure furnaces, and 1.08 times the drum pressure for high-pressure and above pressure boilers. Therefore, the operating pressure of the saturated steam safety valve is higher than that of the superheated steam safety valve.

When adjusting the safety valve on site, whether to adjust the safety valve with high operating pressure first or adjust the safety valve with low operating pressure first, in the "Steam Boiler Safety Technical Supervision Regulations" or "Power Industry Technical Management Regulations" issued by the Ministry of Labor and Human Resources There are no regulations. According to the boiler operation practice, it is reasonable to adjust the safety valve with high operating pressure first, and then adjust the safety valve with low operating pressure. Whether it is the most commonly used heavy hammer safety valve or spring safety valve for boilers, when the boiler needs to be adjusted after installation, overhaul or safety valve overhaul, the heavy hammer is usually placed at the back position first, and the nut for adjusting the spring force will be adjusted. Placed in a position with greater tightening force, so that the operating pressure of the safety valve is significantly higher than the required operating pressure.

During the adjustment of the safety valve, move the position of the heavy hammer forward or loosen the nut to make the operating pressure of the safety valve meet the requirements. If the safety valve with high operating pressure is adjusted first, the safety valve can be put into use after the adjustment of the safety valve is completed and the boiler pressure is reduced. In the process of adjusting the safety valve with low operating pressure, the safety valve with high operating pressure will not operate . If the safety valve with a low operating pressure is adjusted first, after the adjustment of the safety valve is completed, it must be unloaded or other measures must be taken to prevent its operation, and then the pressure can be increased to adjust the safety valve with a high operating pressure. The safety valve with high operating pressure can only be put into normal use after the boiler steam pressure is reduced to normal pressure after the adjustment of the safety valve with high operating pressure is completed. The operating workload increases and the safety is not as good as the former.