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Valve in the operation of the installation should pay attention to several issues
Control valves are among the most commonly used and critical control devices in industrial production. Their proper functioning directly affects the safe and efficient operation of the entire system. With the rapid advancement in control valve technology, a wide variety of manufacturers and types of valves now exist, each with unique functions and specifications. This text focuses on the key issues that should be addressed before installation and during operation to ensure optimal performance.
Before installation, a thorough incoming inspection is essential to confirm that the control valve meets the design requirements. The inspection should focus on several critical aspects:
2.1 **Body/Trim Specifications**
This includes checking the valve type, nominal diameter, seat size, plug configuration, flow characteristics, leakage class, materials (valve body, plug, seat), CV value, flange standards, and sealing surface type. Any deviation from the design must be identified and resolved.
2.2 **Actuator Part**
Verify the actuator type, action mode, spring range, and supply pressure. These factors are crucial for ensuring the correct operation of the valve.
2.3 **Positioner**
Check the input signal, air pressure, electrical and gas interface sizes, and explosion-proof rating. The explosion-proof rating must meet or exceed the design requirements.
2.4 **Accessories**
Ensure all accessories such as filters, position switches, solenoid valves, hand wheels, and special tools are present and match the technical specifications. Use nameplate verification, measuring instruments, and spectroscopy where necessary to confirm material compliance.
3. **Hydraulic Testing**
Valve body pressure testing is essential, especially when the design pressure exceeds 10 MPa. The test should include both body pressure and full closure leak testing.
3.1 **Pressure Test Considerations**
- Use a manual hydraulic pump only; electric pumps are strictly prohibited.
- Test medium should be clean water.
- Test pressure is 1.25 times the design pressure.
- Pressure gauge must be calibrated with an accuracy of at least 1.5 and a scale 1.5 to 2 times the test pressure.
- For air-to-open valves, the plug should be open by at least 20% during testing to avoid overpressure damage.
3.2 **Leakage Test Considerations**
- Manual pump is required for Class VI leakage tests.
- Clean water is used for most tests, while clean air may be used for specific cases.
- Test pressure is set to the maximum differential pressure specified in the design.
- Gauge accuracy and range must also meet the same standards as above.
4. **Single-Unit Adjustment**
After installation, perform single-unit adjustments to meet performance criteria: basic error ±1.5%, return error 1.5%, and deadband 0.6%. Adjustments vary by manufacturer and type, so follow specific guidelines accordingly.
5. **Installation Guidelines**
Proper installation is crucial for reliable operation. Key considerations include:
- Clean the valve thoroughly before installation to prevent dirt from damaging internal components.
- Ensure the valve arrow aligns with the flow direction.
- Avoid stress from pipe deformation by ensuring accurate alignment and proper support.
- Handle welding carefully to prevent heat distortion and contamination from slag.
- Remove the valve during pressure testing to protect it from debris.
6. **Linkage Testing**
Before commissioning, perform linkage tests to verify proper function. Ensure pipelines are purged and free of contaminants. Check butterfly valves for blockage, and ensure handwheel mechanisms are in the "release" position.
7. **Conclusion**
The installation and commissioning of control valves are complex and prone to errors. Close coordination between instrumentation and piping teams is essential to address issues promptly and ensure high-quality execution. Following strict procedures and guidelines is vital to the success of the entire project and the smooth operation of the industrial plant.