What items are included in the online calibration of safety valves?

Time：2021/9/24 22:47:37 Category：TECHNICAL ARTICLE Source： Click：

What items are included in safety valve online verification?

1. The safety valve should be cleaned and visually inspected first, and then the safety valve should be disassembled to inspect all parts. It is found that the valve body, spring, valve stem, and sealing surface are damaged'; cracks; safety valves with defects such as corrosion and deformation should be repaired, adjusted, and replaced. Safety valves with cracks in the valve body, sticking of the valve core and the seat, severely corroded and deformed springs, severely damaged parts and unrepairable safety valves should be scrapped.

When checking the safety valve online, first clean the valve body properly and remove rust. Check the pressure part of the safety valve body for rust and cracks. If there are cracks, the valve should be replaced immediately.

Safety valves produced by manufacturers without manufacturing licenses or safety valves without nameplates or calibration records should be rejected.

2. Set pressure calibration

Slowly increase the inlet pressure of the safety valve. When it reaches 90% of the set pressure, the pressure increase speed should not be higher than O. OllVlPa/s. When it is detected that the valve disc is opened or the continuous discharge of the test medium is seen and heard, the inlet pressure of the safety valve

The force is regarded as the set pressure of this safety valve. When the setting pressure is less than 0.5MPa, the allowable error between the actual setting value and the required setting value is ±0~014MPa; when the setting pressure is greater than or equal to 0.5MPa, it is ±3% of the setting pressure.

3. Sealing performance test

After the set pressure is qualified, the inlet pressure of the safety valve should be reduced and adjusted to conduct a sealing performance test. When the set pressure is less than 0.3MPa, the sealing performance test pressure should be 0.03MPa lower than the set pressure; when the set pressure is greater than or equal to 0.3MPa, the sealing performance test pressure is 90% of the set pressure.

When the sealing performance test uses gas as the test medium, for closed safety valves, the number of leaking bubbles can be used to indicate the leakage rate. The test device and test method can be in accordance with C. The requirements of B/T12242 "Safety Valve Performance Test Method", the eligibility standard sees GB/T12243 "Spring Direct Loaded Safety Valve" or other relevant regulations and standards; for non-closed safety valves, leakage can be based on closed safety valves The relationship between the bubble and the pressure drop value of the pressure gauge is judged by the corresponding pressure drop value.

When the bubble and pressure drop value cannot be used for judgment, it can be judged by sight and hearing. If no gas leakage sound is heard for a certain period of time or there is no liquid bead on the sealing surface of the valve clack and the valve seat, the sealing test is considered qualified.

4. The calibration of the safety valve should continuously perform the setting pressure calibration and the sealing performance test, generally no less than 2 times. For equipment containing flammable, explosive or moderately toxic media that does not allow trace leakage, the safety valve sealing performance test shall not be less than three times and shall meet the requirements each time.

Knowledge contributor: Shanghai Wuyue Safety Valve