Fourteen principles for selecting safety valves 1. Boiler steam safety valve, generally adopts open spring full-open safety valve S10 series; 2, safety valve for liquid medium, generally use spring micro-opening safety valve S10 series;
3. For safety valves for air or other gaseous media, a closed full spring safety valve is generally used;
4. Safety valves for LPG tankers or LPG rail tankers, generally with built-in spring full-open safety valves;
5. Safety valves for the exit of oil production wells, generally adopting pilot-operated safety valves;
6. High-pressure bypass safety valve for steam power generation equipment, generally adopts pilot-operated safety valve with dual functions of safety and control.
7. If the safety valve is to be periodically opened to the safety valve during the calibration cycle, the safety valve calibration procedure should be followed. A safety valve with a lifting wrench should be used. When the medium pressure reaches more than 75% of the opening pressure, the lifting valve can be used to lift the valve flap slightly from the valve seat to check the flexibility of the safety valve opening;
8. If the temperature of the medium is high, in order to reduce the temperature of the spring chamber, when the temperature of the closed safety valve exceeds 300 °C and the use temperature of the open safety valve exceeds 350 °C, a safety valve with a radiator should be selected;
9. If the back pressure of the safety valve outlet is fluctuating, and the amount of change exceeds 10% of the opening pressure, the bellows safety valve should be selected;
10. If the medium is corrosive, a bellows safety valve should be used to prevent important parts from failing due to corrosion of the medium.
11. Safety valve installation and maintenance should pay attention to the following matters: construction and installation points
1) The installation position, height, and inlet and outlet direction must meet the design requirements. Note that the direction of the medium flow should be consistent with the direction of the arrow marked on the valve body, and the connection should be firm and tight.
2) The visual inspection must be carried out before the valve is installed. The nameplate of the valve should comply with the current national standard "General Valve Mark" GB 12220. For valves with a working pressure greater than 1.0 MPa and a shut-off function on the main pipe, the strength and tight performance tests shall be carried out before installation, and shall be used after passing the test. In the strength test, the test pressure is 1.5 times the nominal pressure, the duration is not less than 5 min, and the valve casing and the packing should be free of leakage. In the rigorous test, the test pressure is 1.1 times the nominal pressure; the duration of the test complies with the requirements of GB 50243; all safety valves should be installed vertically.
12. There should be no resistance at the exit of the safety valve to avoid pressure.
13. The safety valve should be specially tested before installation and checked for its official seal.
14. The safety valve in use should be checked regularly and the safety valve verification work should be completed. Tag: Double spring safety valve |