Causes and Solutions for Low-Temperature Valve Sticking

Low-temperature valves are typically installed at normal temperatures but operate in very cold environments. Due to the significant temperature variations, these valves are prone to sticking, which can severely affect their performance and the overall safety of the system. To ensure the stable operation of low-temperature valves, it's essential to understand the causes of sticking and implement appropriate solutions. This article discusses the sticking issues associated with low-temperature valves.

Main Causes of Low-Temperature Valve Sticking

Low-temperature valves often face sticking problems during use, which not only disrupts their normal operation but can also lead to system failures. Here are the main causes of sticking in low-temperature valves.

1. Stress and Deformation from Temperature Changes

Thermal Stress Impact: Low-temperature valves are usually installed in a normal temperature environment, but their working environment may be extremely cold. The thermal stress caused by temperature changes can deform the valve materials. In severe cases, this deformation can affect the valve's sealing and fluid control capabilities. This stress is particularly significant during startup and shutdown, making sticking more likely.

Improper Installation Configuration: If the connection between the valve and the pipeline is not well-designed, it may create additional pre-stress on the valve or lead to a change in valve position due to inadequate thermal compensation from the pipeline. This not only impacts the valve's function but can also cause deformation at extreme temperatures, further increasing the risk of sticking.

2. Sticking Due to Material Differences

Mismatch in Coefficient of Linear Expansion: Differences in the coefficients of linear expansion of various materials can also lead to sticking in low-temperature valves. For example, the linear expansion coefficient of stainless steel valve stems is significantly lower than that of brass used for the valve body. In a cold environment, brass contracts more than stainless steel, which can cause the threads to bind, especially in designs using a blind stem structure and fine threads. The stress from temperature changes can reduce the gap between threads, resulting in sticking.

3. Failures Due to Improper Operation

Errors During Maintenance: During routine maintenance and operation, there are often risks of improper handling. For instance, using the valve before it has been thoroughly warmed or allowing water to enter the valve packing can lead to freezing under cryogenic conditions. Additionally, if the valve is overly tightened at normal temperatures, it can damage the threads and hinder the valve's normal operation.

Solutions to Low-Temperature Valve Sticking

To address the issue of sticking in low-temperature valves, implementing appropriate solutions is crucial for ensuring their normal operation. Here are several effective strategies.

1. Optimize Valve Design

Use of Open Stem Structures and Coarse Threads: When designing low-temperature valves, it is recommended to use open stem designs and coarse trapezoidal threads. These features help reduce the impact of temperature variations on valve performance. Open stem designs provide better operational stability, while coarse threads minimize the risk of sticking due to temperature changes, enhancing the valve's durability.

2. Strengthen Valve Installation

Secure Brackets and Flexible Connections: During installation, it is essential to ensure that the valve is securely mounted to prevent deformation of the stem due to movement with the pipeline. Flexible connections can be used to keep the valve stem and body aligned, ensuring that no additional stress is introduced during operation due to environmental changes.

3. Pay Attention to Operational Details

Thorough Heating and Moderate Closing: Before starting the valve, make sure it is adequately heated. When closing the valve, avoid excessive force to prevent damage. Additionally, regular training for operators on the proper use and maintenance of cryogenic valves can help reduce errors caused by improper handling.

Inspection and Maintenance of Low-Temperature Valves

After installing low-temperature valves, comprehensive testing is necessary to ensure correct installation and proper opening and closing of the valves. The valves should only be put into service once their status is confirmed to be good. Moreover, the operation and maintenance of cryogenic valves should be overseen by dedicated personnel to ensure regular upkeep and operation, thus extending the lifespan of the valves.

1. Regular Maintenance

Regardless of the type of low-temperature valve, regular maintenance is essential. It is recommended to perform 1-2 inspections per year to ensure the valves' longevity. During these inspections, special attention should be paid to signs of wear and whether seals show signs of oxidation. If any faults or damaged components are detected, immediate maintenance is necessary to prevent further deterioration.

2. Basic Testing Before Startup

For low-temperature valves that have not been used for an extended period, a basic test is required before startup. This includes allowing the medium to flow through the valve to check for smooth operation and ensure the valve can function correctly. Only after confirming that the low-temperature valve is operational should it be put into actual use. Regular maintenance helps ensure the valve's performance and effectiveness.

Conclusion

The issue of sticking in low-temperature valves not only affects their normal operation but also poses significant safety risks to the entire system. By thoroughly analyzing the main causes of sticking and implementing effective design, installation, and maintenance measures, the risk of sticking can be significantly reduced, enhancing the reliability and efficiency of the valves. Properly configuring valves, selecting appropriate materials and structures, and strengthening maintenance and operational protocols will provide a solid foundation for the safe and stable operation of low-temperature valves.