Valve Sealing Quality: Key Factor for Ensuring Valve Safety

In industrial production and daily life, valves play a critically important role. Whether in chemical, petroleum, natural gas, or ordinary household plumbing systems, the sealing performance of valves is the key factor in evaluating their quality. A high-quality valve must have a tight sealing performance to prevent internal or external leakage, avoid potentially serious safety accidents, and ensure safe production or daily life. This article will explore the importance of valve sealing quality, analyze the various factors affecting sealing performance, and provide some practical maintenance and repair methods to help you better understand and manage valve sealing performance.

The main function of a valve is to control the flow of fluid, and sealing performance is the foundation for achieving this function. If a valve's sealing performance is poor, it may lead to fluid leakage, which can not only waste resources but also cause environmental pollution, equipment damage, and even personal injury. For example, in chemical production, if a valve is not tightly sealed, toxic or harmful gases may leak, posing serious threats to the health of operators. In a household environment, sealing problems in water pipe valves may lead to water leaks, causing flooding and property damage. Therefore, ensuring the sealing performance of valves is key to guaranteeing safety and efficiency.

The degree of valve sealing is closely related to multiple factors; any problem in one link can affect its sealing performance.

The materials of a valve are the foundation affecting sealing performance. High-quality materials can provide better corrosion resistance and wear resistance, thus extending the service life of the valve. For example, stainless steel, copper alloys, and polytetrafluoroethylene (PTFE) are widely used in valve manufacturing due to their excellent performance. Stainless steel has good corrosion resistance and strength, suitable for various media; copper alloys are often used in water and steam systems due to good thermal conductivity and corrosion resistance; PTFE is used in soft sealing gaskets for its excellent chemical stability and low friction coefficient.

The manufacturing process of a valve is equally important. Advanced manufacturing processes can ensure high precision and tight fit of each valve component, thereby improving sealing performance. For example, precision casting and CNC machining can produce valve components with minimal shape tolerance, reducing the possibility of leakage. In addition, welding technology also has an important impact on sealing performance. For example, the welding quality between the valve bonnet and valve body must be strictly controlled to prevent leakage caused by welding defects.

The equipment and tools used in valve manufacturing also affect sealing performance. High-precision lathes, milling machines, and grinders can ensure the machining accuracy of valve components, while advanced testing equipment can detect and correct deviations during manufacturing. For example, using a coordinate measuring machine can accurately measure the dimensions and shape tolerances of valve components to ensure they meet design requirements.

The shape tolerance and machining accuracy of a valve directly affect sealing performance. For example, the sealing surfaces of the valve stem and valve bonnet must achieve extremely high flatness and roughness requirements to ensure sealing effectiveness. Even slight irregularities on the sealing surface may cause leakage. Therefore, machining accuracy must be strictly controlled during manufacturing to ensure that every component meets design standards.

According to scientific design standards, valve sealing structures are usually designed as conical or spherical bodies. This structure can provide good sealing performance but also has some disadvantages. For example, conical or spherical sealing structures require extremely high manufacturing precision, and even minor deviations may lead to sealing failure. Additionally, this structure is relatively complex during machining and assembly, increasing cost and difficulty.

In contrast, planar sealing structures have many advantages. Planar sealing structures are simple, easy to machine, and less restricted by external conditions. For example, the sealing surfaces of the valve stem and bonnet can be changed from the original conical shape to a flat contact style, making machining and assembly simpler. After overlay welding on the sealing area of the valve bonnet, precise turning can achieve the design requirements. In addition, valves with planar sealing structures are easier to maintain and repair during use.

Valve sealing testing is an important step to ensure sealing performance. Generally, a single sealing test can meet standard pass rates. During testing, pressure testing and sealing checks are performed to ensure that the valve does not leak under working pressure. If any problems are found during testing, they should be repaired or replaced promptly.

Valve maintenance is also key to ensuring sealing performance. Regularly inspecting the sealing surface and addressing potential problems promptly can effectively extend the valve's service life. For example, if minor wear is found on the sealing surface, grinding with a stone or sandpaper can repair it. If wear is severe, the sealing gasket needs to be replaced or undergo deep repair processing.

If a valve's sealing surface is damaged, the following methods can be used.

For minor damage to the sealing surface, grinding with a stone or sandpaper and adding an appropriate amount of abrasive can be used. This method is simple and effective in restoring the flatness and smoothness of the sealing surface. During grinding, pressure and direction should be controlled to avoid further damage.

For more serious damage to the sealing surface, turning can be used for repair. However, this method is more complex and requires professional equipment and skilled operators. After turning, the material quality and hardness of the sealing surface may change, so strict inspection and adjustment are required to ensure optimal performance.

For hard sealing surfaces, soft sealing gaskets can be used for repair. For example, a fully threaded small bolt can be welded to the center of the valve disc end, and a gasket made of PTFE or rubber matching the sealing surface of the valve disc can be used. By adjusting the gasket and nut tightening device, the gasket is fixed on the valve core to form a sealed contact surface with the valve seat. This method is inexpensive, easy to replace, and maintain.

When assembling a valve, attention should be paid to the following points.

Bolts welded on the valve disc should not be too long, otherwise they may block the inner flow channel, preventing the sealing surfaces from contacting properly and losing sealing function. Therefore, bolt length must be appropriate in design and assembly.

During assembly, carefully check and adjust the stem extension to ensure the sealing surfaces are closely contacting. Improper stem adjustment may prevent tight contact, affecting sealing performance.

Select shims of appropriate size and thickness; the shim height should be slightly lower than the thickness of the valve disc sealing surface step. This ensures the soft sealing gasket closely contacts and integrates with the valve disc, remaining on the same plane.

When tightening nuts, loosen them appropriately to prevent the clamping nut from falling off. Over-tightening may damage the gasket, affecting sealing performance.

To prevent corrosion or high-temperature deformation from the fluid medium, soft sealing gaskets suitable for the medium must be chosen scientifically. For example, in high-temperature environments, high-temperature-resistant gasket materials like PTFE should be selected.

In special environments such as high temperature or high pressure, valve sealing performance faces greater challenges. In such cases, special measures are needed to ensure safe operation.

In high-temperature and high-pressure environments, valve service life is shortened. Regular replacement is recommended to ensure sealing performance. Continuing to use damaged valves to save costs may lead to more serious consequences.

Adding cooling devices at pressure-relief valves can effectively lower the medium temperature and extend valve life. For example, when high-temperature media pass through the valve, the cooling device can reduce the medium temperature to a safe range, minimizing thermal damage to the valve.

Regular cleaning and filtering of high-pressure media reduce damage to valves caused by impurities. Use filters for liquid filtration and shorten their usage cycle according to the number of uses. Regularly clean tanks and replace old media to maintain good valve operation.

To extend valve life and ensure sealing performance, the following measures are recommended.

Do not operate the valve at very small openings. Small openings reduce the throttle interval, increasing valve wear. Properly increase the screw pitch of the locking mechanism, increase the valve needle opening speed and stroke, enlarge the working opening, and effectively extend valve life.

Medium temperature significantly affects valve life. Excessive temperature shortens service life. Avoid using valves under high-temperature media; if unavoidable, implement proper cooling measures.

Operate the valve gently to avoid excessive force. Gentle operation reduces impact on the sealing gasket and prolongs its life. Mark adjustments clearly for future operations and maintenance.

Regularly maintain and inspect valves to detect and address potential issues. For example, check sealing surface wear, replace damaged gaskets, and clean and filter the medium to maintain valve cleanliness and proper operation.

Valve sealing performance is key to safe operation. Through scientific design, manufacturing, and maintenance, sealing performance can be effectively improved and service life extended. In practice, select appropriate valve materials and sealing structures based on working conditions, and adopt suitable maintenance measures to ensure optimal sealing performance. Only then can valves fully play their role in industrial production and daily life, ensuring safety and efficiency.

In summary, the quality of valve sealing directly affects safety and efficiency in production and daily life. This article aims to help you better understand and manage valve sealing performance, ensuring safe and reliable operation under various conditions.