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Liquefied natural gas (LNG) plays an increasingly important role in the energy industry. Its storage, transportation, and delivery all involve high pressure, low temperatures, and flammable and explosive environments, making safety management a top priority. Among numerous safety control measures, valve interlock systems are increasingly becoming a key technical tool for ensuring the safety of LNG operations. They not only prevent misoperation but also automatically shut down hazardous sources in emergencies, serving as the "last line of defense" for LNG operations. This article will delve into the role, operating principles, application cases, and future development trends of valve interlock systems in LNG operations, providing a reference for industry practitioners.

1. Safety Challenges of LNG Operations

The characteristics of LNG (liquefied natural gas) create high risks in its production, storage, transportation, and distribution:

Low-temperature Environment Risks: LNG can reach temperatures as low as -162°C during storage and delivery. Improper handling can lead to equipment brittle fractures or liquid leaks.

High-pressure Operation Risks: LNG storage tanks and pipelines are often high-pressure systems. Uncontrolled pressure can cause explosions or leaks. Flammability and Explosiveness: Liquefied natural gas (LNG) is highly flammable. Once its concentration in the air reaches a certain level, exposure to open flames or sparks can cause serious accidents.

Complex Operational Process: From tank filling to pipeline transportation and final distribution, the process involves numerous operational steps, posing a significant risk of human error.

Thus, LNG operational safety management relies not only on standardized operations but also on automated safety control systems to mitigate the risk of human error. Valve interlock systems are widely adopted in this context, becoming a core technology for ensuring safety.

2. The Role of Valve Interlock Systems

Valve interlock systems are safety process management and control devices that manage the opening and closing states of valves through logical control, ensuring correct operating sequences, preventing misoperation, and promptly shutting off hazardous sources in emergencies. Their core functions include:

Preventing Misoperation: By mandatorily controlling the valve operating sequence, they prevent operator errors due to negligence or inexperience.

Ensuring System Safety: During the LNG storage and transportation process, if an abnormality occurs, such as excessive pressure or leakage, the valve interlock system logically closes the relevant valves to prevent the spread of the accident. Remote Control and Monitoring: Modern valve interlock systems can be integrated with PLCs, DCSs, or SCADA systems to enable remote monitoring and operation, improving safety management efficiency.

Operation History: The system records valve operation history, facilitating post-event analysis and accountability, and providing data support for enterprise safety management.

In short, valve interlock systems minimize safety risks in LNG operations through a three-step mechanism: "Prevention – Control – Response."

3. Working Principle of the Valve Interlock System

Valve interlock systems typically consist of a control logic unit, sensors, actuators, and valves. Their working principles can be summarized as follows:

Logical Control: The system uses preset logic to determine the valve operation sequence. For example, before filling LNG, the exhaust valve must be closed first. The valve interlock system prevents operators from directly opening the tank valve to prevent liquid leakage or pressure runaway.

Signal Acquisition and Feedback: Sensors collect real-time valve open and close status and provide feedback to the control unit.

Alarm and Recording: Valve interlock systems are typically equipped with alarms to alert operators when abnormal conditions occur. Operation history records are also stored in a database for subsequent analysis and auditing. Through this series of safety process management and control, the valve interlock system can form a multi-layered protection mechanism in LNG operations.

4. Application of the Valve Interlock System in LNG Operations

Tank Filling Process: During the LNG tank filling process, the valve interlock system ensures that the filling valve opens when the tank pressure and temperature are normal. It also prevents filling without the exhaust valve closed, thus preventing liquid leakage or abnormal pressure.

Pipeline Transportation: LNG pipelines typically operate at high pressure and low temperatures. The valve interlock system, through safety process management and control, enables the sequential opening and closing of valves in segmented pipelines to prevent overpressure or backflow accidents.

Terminal Distribution and Filling Stations: At filling stations, the valve interlock system can be linked with liquid level sensors and pressure sensors to ensure the correct fuel distribution sequence. It can also cut off the supply in the event of an abnormality to prevent fuel leakage or operational errors.

Emergency Safety Protection: In the event of a fire, pipeline leak, or equipment failure, the valve interlock system can close critical valves based on logic settings, creating an automatic isolation zone, minimizing risks and fulfilling a "last line of defense" function.

5. Advantages of Valve Interlock Systems

Compared to traditional manual operations, valve interlock systems offer significant advantages in LNG operations:

Reduced Risk of Human Error: Safety process management and control reduce reliance on operator experience, significantly reducing the risk of accidents caused by operational errors.

Improved Operational Efficiency: The system can quickly execute valve operations according to preset logic, reducing operator wait time and improving production efficiency.

Enhanced Safety: A multi-level protection mechanism ensures immediate shutdown of hazardous sources in abnormal situations, providing a reliable safety barrier for LNG operations.

Facilitated Remote Management and Data Analysis: Combined with intelligent control systems, it enables remote monitoring, remote operation, and data logging, providing strong support for safety management.

6. Valve Interlock System Selection and Implementation Recommendations

When selecting and implementing a valve interlock system, companies should consider the following aspects:

Matching Process Requirements: The valve interlock system should be selected based on the process parameters of LNG storage and transportation to ensure reliable operation.

Compatible with Automation Platforms: The system should support integration with automation control platforms such as PLC, DCS, and SCADA to facilitate unified management and remote monitoring. Multiple safety features: A high-quality valve interlock system should include protection against misoperation, emergency shutoff, alarm notifications, and operation logging, forming a complete safety closed loop.

Maintenance and training: Regular maintenance and operator training are crucial to ensuring the long-term reliable operation of valve interlock systems. A comprehensive training and maintenance system should be established.

In the LNG industry, safety always comes first. Valve interlock systems, through scientific logic control and real-time monitoring, serve as the last line of defense for LNG operations. They not only reduce the risk of human error but also enable rapid isolation of hazardous sources in emergencies, ensuring operational safety. With the continuous advancement of technology, intelligent and integrated valve interlock systems will become a key standard for future LNG safety management.

As companies advance their LNG business, they should prioritize the selection, installation, and maintenance of valve interlock systems, building a comprehensive safety management system to truly achieve a safe, efficient, and reliable LNG operating environment.

As a professional LNG safety equipment supplier, Nudango is committed to providing industrial users with high-quality valve interlock systems and safety process management solutions. Nudango's valve interlock system not only effectively prevents operational errors but also rapidly shuts off hazardous sources in emergencies, ensuring safety in LNG storage, transportation, pipeline delivery, and bunkering. Leveraging its extensive industry experience and technological advantages, Nudango helps companies build reliable safety systems, minimize risks in LNG operations, and provide users with a safe, efficient, and intelligent operating environment.

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