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Selection principle of safety valve

Time : 2020-04-10

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Selection principle of safety valve

  1. Steam boiler safety valve, generally choose the open full-open spring safety valve 0490 series;

  2. The safety valve for liquid medium, generally choose the micro-start spring safety valve 0485 series;

  3. Safety valve for air or other gas medium, generally choose full-open spring safety valve;

  4. Safety valves for LPG tank trucks or LPG railway tank trucks, generally use full-open internal safety valves;

  5. Safety valve for oil well outlet, generally choose pilot safety valve;

  6. The high-pressure bypass safety valve of steam power generation equipment is generally a pilot safety valve with dual functions of safety and control.

  7. If it is required to conduct regular opening test on the safety valve, the safety valve with a lifting wrench should be selected. When the medium pressure reaches more than 75% of the opening pressure, you can use a lifting wrench 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 ℃ and the temperature of the open safety valve exceeds 350 ℃, a safety valve with a radiator should be selected;

  9. If the back pressure of the outlet of the safety valve is variable, and its variation exceeds 10% of the opening pressure, the bellows safety valve should be selected;

  10. If the medium is corrosive, the bellows safety valve should be selected to prevent the failure of important parts due to the medium corrosion.

  11. The installation and maintenance of safety valves should pay attention to the following points. Construction and installation points

  The installation position, height, and inlet and outlet directions must meet the design requirements. Note that the direction of medium flow should be consistent with the direction of the arrow marked on the valve body, and the connection should be firm and tight.

  The valve must be visually inspected before installation, and the nameplate of the valve should comply with the provisions of the current national standard "General Valve Mark" GB12220. For valves with a working pressure greater than 1.0 MPa and acting as a shut-off on the main pipe, the strength and tightness performance tests should be carried out before installation, and they shall be used after passing the test. During the strength test, the test pressure is 1.5 times the nominal pressure, the duration is not less than 5min, and the valve housing and packing should be qualified for no leakage. During the tightness test, the test pressure is 1.1 times the nominal pressure; the duration of the test meets the requirements of GB 50243.

  12. There should be no resistance at the outlet of the safety valve to avoid pressure.

  13. The safety valve should be specially tested before installation, and check its tightness.

  14. The safety valve in use should be checked regularly.