Working principle of pilot-operated safety valve: Pilot-operated safety valve is composed of main valve, pilot valve, relief valve, joints and conduits. Under normal operating conditions, the medium pressure of the system acts both below and above the main valve disc. Since the media action area of ??the air chamber above the main valve disc is larger than the media action area below, the main valve disc is in a closed state under the action of the pressure difference. As the pipeline medium pressure rises, the sealing specific pressure obtained by the sealing pair will also rise. This is exactly the opposite of the spring directly loaded safety valve, that is, the higher the medium pressure, the more reliable the sealing.
When the pipeline medium pressure is abnormal and reaches or exceeds the set pressure, the upper valve disc of the pilot valve (Figure 2) quickly opens, and the medium in the air chamber above the main valve disc is quickly discharged through the exhaust joint of the pilot valve. , the main valve disc opens instantly under the strong effect of the medium pressure below, and the medium is quickly discharged from the outlet of the main valve in large quantities, so that the medium pressure in the pipeline returns to the normal working pressure, ensuring the safety of the system. When the pressure of the pipeline medium drops to about 90% of the set pressure set by the system, the valve disc on the pilot valve closes, and the pipeline medium enters the air chamber above the main valve disc through the pilot valve. Under the action of pressure difference, the main valve is closed, ensuring the normal operation of the system.
Calibration method of pilot-operated safety valve:
1. Cut off the switch valve upstream of the safety valve to avoid danger during the debugging process of the safety valve;
2. Remove the stainless steel pipe connecting the safety valve pilot valve to the main valve;
3. Connect the pressure test air source to the inlet of the safety valve pilot valve;
4. Adjust the safety valve pilot valve Adjust the adjusting screw of the valve to tighten (or loosen) the spring, and observe the pressure gauge to make the pilot valve reach the specified set pressure;
5. Connect the stainless steel pipe of the safety valve pilot valve and main valve ;
6. Reopen the switch valve upstream of the safety valve;
7. Apply fresh soapy water to each connection part of the safety valve to check the sealing of the safety valve;
8. Control the pressure in front of the safety valve to make the safety valve jump, discharge, and return to its seat. Repeat the test several times, observe and record each pressure value, and control the pressure within the specified accuracy;
9. After debugging, fix the adjusting nut and install the lead seal.