Precautions for Control Valve Installation & Interlock Testing

Control valves serve as critical actuating devices in industrial automation systems. They have a significant impact on the operational quality, performance metrics, and safety of production processes. The correct installation, adjustment, and quality of control valves directly affect the system's commissioning and the safety of the production process. Therefore, ensuring that the valve is properly installed, accurately adjusted, and thoroughly tested in interlock with the control system is essential for stable system operation.

Installation Requirements for Control Valves

The installation of a control valve is not just a mechanical task; it also involves system-wide adjustments and safety considerations. After installation, interlock testing with instrumentation and control systems (e.g., DCS, PLC) must be carried out to ensure that the valve can properly respond to control signals and adjust parameters such as flow, pressure, and temperature. Interlock testing is a critical step before the valve can be put into normal operation. Only after passing these tests can the commissioning or startup procedure proceed.

Preparation for Control Valve Installation

Before installation and interlock testing, a series of preparatory steps must be completed. These steps directly impact the success of the tests and the operational reliability of the equipment.

1. Pipe Flushing and Inspection

Before installing the control valve, the process pipes must undergo strict flushing and inspection to ensure they are free from debris, oil, or other contaminants that may affect the valve's performance. Flushing and acceptance of the pipes is fundamental to ensuring the proper functioning of the control valve. Only after the pipes have been cleaned and certified can the valve installation proceed.

2. Avoiding Improper Practices

In some cases, construction personnel may skip the flushing process to save time and proceed directly to pressure testing or valve installation. This is a serious mistake, as it can cause valve jamming, blockages, inaccurate travel, damaged sealing surfaces, or even lead to severe equipment failures. If problems arise, the valve may need to be reworked or replaced, wasting time and potentially delaying the entire project.

3. Control Valve Classification and Installation

Different types of control valves require different installation approaches. Proper classification helps avoid equipment malfunctions and operational issues.
Precision Control Valves: For valves with complex internal structures or passages that are prone to blockages or debris buildup (e.g., high-precision control valves), installation should only proceed after pipe flushing and pressure testing are completed. These valves have delicate internal components, so cleanliness is particularly important to prevent debris from causing damage or malfunction.
Simple Structure Valves: For valves with straightforward designs or those less prone to accumulating debris (e.g., standard butterfly valves, straight-through ball valves, diaphragm valves), flushing and pressure testing can be done with the valve in the fully open position, without needing to disassemble it. However, for valves with protruding seats or areas where debris may accumulate, disassembly is required for cleaning to ensure no foreign material is left inside the valve.

4. Connection and Labeling Inspection

After the control valve installation, it is essential to check the valve control lines, connections, attachments, and labels to ensure all components are properly installed and functional.
Removal of Temporary Facilities: Temporary facilities used during installation should be removed once the valve installation is complete to avoid interfering with subsequent tests and operations.
Wiring Verification: Ensure that all wiring, including signal lines, power supply lines, and feedback signal lines, is correctly installed. For shielded signal lines, confirm that the shielding is grounded at only one end to avoid ground loop issues, ensuring stable and reliable signal transmission.

Implementation of Control Valve Interlock Testing

Interlock testing is a crucial step before the control valve is officially put into service. The purpose of interlock testing is to ensure that the control valve operates in sync with other systems (e.g., DCS, PLC) and can accurately adjust process parameters in response to control signals.

1. Single-Device Operation Verification

Before conducting interlock tests, the control valve must undergo a standalone operation verification. This step ensures that the valve's basic functions—such as opening and closing flexibility, accurate travel, and reliable sealing—are working correctly. During this verification, it is important to check the functionality of the valve's electrical control system, pneumatic control system, actuator, and other components.
Power and Air Supply Verification: Ensure that the power supply voltage and air pressure meet the required specifications to avoid operational failures due to electrical or air supply issues.
Control and Feedback Signal Matching: Verify that the control signals are correctly matched with the feedback signals to ensure proper transmission and system feedback, enabling real-time adjustment of the valve's operation.

2. Manual and Automatic Mode Adjustments

During interlock testing, if the control valve is equipped with a manual mechanism (e.g., a handwheel), the manual mechanism must be switched to the automatic position to release manual control, allowing the valve to operate automatically according to control signals.
Electric Control Valve Operation: When testing electric control valves, manual operation is not allowed while the valve is in the “automatic” mode. Manual operation could damage the actuator motor or interfere with the automatic control system's functioning. Therefore, electric control valves should only be switched to manual mode when necessary.

Post-Interlock Testing Actions

After completing interlock testing, necessary adjustments and optimizations should be carried out based on the test results. If any issues are detected, such as inaccurate valve response or other malfunctions, immediate checks and adjustments are needed to ensure the control valve performs as expected.

1. Performance Optimization

For any issues identified during the testing phase, adjustments should be made to optimize valve performance, ensuring the valve is in optimal operating condition before being put into production.

2. Documentation and Records

All test procedures and results should be thoroughly documented to ensure that each step of the process has been inspected and verified. This documentation will provide a basis for future operations and maintenance.

Conclusion

The installation and interlock testing of control valves are essential steps to ensure the proper functioning of automation systems. By adhering to strict installation, adjustment, and testing procedures, equipment failures can be minimized, and the safety and efficiency of the production process can be guaranteed. Therefore, operators must pay close attention to every detail of the control valve installation and commissioning, ensuring the equipment meets standards, passes testing, and lays a solid foundation for long-term system stability.