Online calibration of safety valves is a method of safety valve calibration that can ensure the safe operation of safety valves in industrial equipment and pipeline systems. Compared to traditional offline verification methods, online verification can be performed during equipment operation without the need for shutdown or disassembly, ensuring that the safety valve of the equipment is in good working condition under actual operating conditions. The following is a more detailed introduction to online calibration of safety valves:
A safety valve is a crucial safety device in equipment such as pressure vessels, boilers, and pipeline systems. When the pressure inside the system exceeds the set value, the safety valve will automatically open, releasing some medium to reduce pressure and prevent destructive failures of the equipment. Therefore, regular calibration of safety valves is crucial for industrial safety. The principle of online verification is to use externally applied force or pressure to simulate the pressure rise process of the system, test the opening and closing performance of the safety valve, and record its key parameters, such as opening pressure, reseating pressure (closing pressure), discharge volume, etc., to ensure that it meets the design standards.
There are various methods for online verification of safety valves, including common ones.
1. External force loading method
Apply an appropriate amount of force to the safety valve using a calibration tool (such as a hydraulic puller), gradually increase the external force to the open position of the safety valve, and simulate the pressure rise process inside the system. This method does not affect the production process under normal operating pressure.
This method uses external force to lift the valve core of the safety valve. When the external force reaches the force value corresponding to the set pressure of the safety valve, the valve core should automatically rise. The verification system will record the force value at this time and convert it into the opening pressure of the valve.
2. System boosting method
Gradually increase the pressure of the internal medium in the equipment or pipeline system until the safety valve is activated, and record the opening and closing pressures of the safety valve. This method is suitable for systems that allow for a short-term increase in pressure.
The system boosting method can use a slow boosting method to verify the opening performance of the safety valve during normal operation, ensuring more accurate data.
3. Pneumatic or hydraulic calibration method
Using gas or liquid as the medium, apply pressure to the safety valve through a calibration device to simulate the working pressure. When the safety valve reaches the set pressure, the valve should open and record the pressure at this time.
Online verification usually requires specific verification devices and tools. Common equipment includes hydraulic pullers, which simulate the action of valve cores by applying hydraulic pressure and monitor the opening pressure of valves. Pneumatic calibration device, which simulates the internal pressure of the system by compressing gas, is suitable for some systems with relatively low pressure. The online monitoring system integrates pressure sensors, displacement sensors, and data recording devices, which can monitor the action process of the safety valve in real time and record relevant data.
Before conducting formal calibration, check the surrounding environment of the safety valve and the status of the calibration equipment to ensure safety. Connect the hydraulic or pneumatic calibration equipment correctly to the safety valve and check the system's sealing. Gradually apply external force or increase system pressure to the operating point of the safety valve through the verification device. Record the opening pressure and reseating pressure of the safety valve, and compare them with the set values required by the equipment. Analyze the verification data, determine whether the safety valve meets the set requirements, and generate a verification report.
Compared to traditional offline verification methods, online verification has the following obvious advantages:
No impact on production: Online verification can be performed during equipment operation without the need for downtime, greatly reducing production losses.
Real working condition testing: Online verification is conducted in the actual operating environment of the equipment, and the test results are closer to the performance of the safety valve under actual working conditions.
Cost saving: No need to stop production and dismantle safety valves for calibration, saving maintenance costs and downtime losses.
Timeliness: Able to promptly identify potential issues with safety valves, make quick adjustments and repairs, and avoid serious accidents caused by safety valve failures.
Although online verification has many advantages, it is important to strictly follow safety operating procedures during the implementation process, especially when applying high voltage, to prevent dangers caused by misoperation or equipment damage. Online calibration equipment must be regularly calibrated to ensure the accuracy of measurement results. Some devices are not suitable for online calibration under full load or high-risk conditions, and appropriate operating conditions should be selected to ensure the safety and effectiveness of the calibration process. Special protective measures are required for certain hazardous media equipment during calibration to prevent leakage or explosion.