1. Should first stop cleaning and stop the safety valve, appearance inspection, and then stop the collapse of the safety valve, check the parts. It is found that the body, spring, stem and sealing surface of the valve are damaged; cracks; corrosion, deformation and other defects of the safety valve should stop repairing, adjusting and replacing. Safety valves with cracks in the body, sticking of the spool to the seat, serious corrosion and deformation of the spring, serious damage to the parts and unable to repair should be scrapped.
In the on-line check of safety valve, the valve body should be properly cleaned and rusted first, and the corrosion and cracks in the pressurized part of safety valve body should be inspected with naked eyes. If there are cracks, the valve should be replaced immediately.
Safety valves consumed by manufacturers without manufacturing permits or without nameplates or verification records should be discarded.
2. Setting Pressure Calibration
Slowly raise the inlet pressure of safety valve, when 90% of the setting pressure is reached, the boost speed should not be higher than O.Oll VlPa/s. When the valve disc is opened or continuously discharged from the experimental medium is seen or heard, the inlet pressure of the safety valve is measured.
Force is regarded as the setting pressure of the safety valve. When the setting pressure is less than 0.5 MPa, the allowable error between the practical setting value and the requested setting value is (+0~014 MPa); when the setting pressure is greater than or equal to 0.5 MPa, it is (+3%).
3. Sealing performance test
After qualified adjustment of setting pressure, the inlet pressure of safety valve should be lowered and adjusted to stop sealing performance test. When the setting pressure is less than 0.3 MPa, the experimental pressure of sealing performance should be 0.03 MPa lower than the setting pressure; when the setting pressure is greater than or equal to 0.3 MPa, the experimental pressure of sealing performance is 90% of the setting pressure.
When gas is used as the experimental medium in the sealing performance test, the number of leaking bubbles can be used to express the leaking rate for the sealing safety valve. The experimental installation and method can be according to C. For the request of B/T12242 "Safety Valve Performance Test Method", the eligible specifications can be found in GB/T12243 "Spring Direct Load Safety Valve" or other relevant regulations and rules. For non-blocking safety valves, the corresponding pressure drop can be judged according to the relationship between the leakage bubble of the blocking safety valve and the pressure drop value of the pressure gauge.
When bubbles and pressure drop values can not be used to stop discrimination, visual and auditory stop discrimination can be used. In a certain period of time, no sound of gas leakage or no liquid beads on the sealing surface of disc and seat can qualify the sealing test.
4. The check of safety valve should stop setting pressure check and sealing performance test continuously, usually no less than 2 times. With regard to equipment containing medium with inflammable, explosive or toxic level above moderate, which does not allow trace leakage, its safety valve sealing performance test shall not be less than/3 times and shall meet the requirements each time.