Analysis of Gate Valve Leakage: Causes & Solutions

In industrial production, gate valves, as a common type of valve, are widely used in various fluid pipeline systems to control the flow of fluids. However, during their use, gate valves may experience leakage issues, which not only affect production efficiency but can also lead to safety hazards. This article will delve into the causes of gate valve leakage and provide corresponding solutions to help readers better understand and address this problem.

Gate valve leakage is a relatively common issue in industrial applications, and understanding its causes is crucial for prevention and resolution. Here is an analysis of the main causes of gate valve leakage.

The wedge-shaped sealing ring is one of the key components of a gate valve, and its sealing performance directly affects the reliability of the valve. There are two types of wedge-shaped sealing rings: hard seals (metallic wedge rings) and soft seals (composite graphite wedge rings). If the machining precision of the wedge-shaped sealing ring is low, such as non-compliant surface roughness or dimensional accuracy, it can easily lead to internal leakage of the gate valve. This is because the fit between the sealing ring and the valve body is not tight enough to effectively prevent fluid leakage.

During the operation of valves, pressure and ambient temperature may change significantly. These changes can subject the sealing ring to considerable impact pressure, erosion, and deformation. Over time, the gap between the sealing ring and the valve body will gradually increase, eventually causing internal leakage of the valve. For example, in high-temperature and high-pressure environments, the sealing ring may deform due to thermal expansion, while in low-temperature environments, the sealing ring may become brittle and prone to cracking.

When maintaining valves, if the staff do not clean the sealing surface thoroughly, residual fine particles and impurities may scratch the sealing surface during valve operation. Once the sealing surface has through-scratches, it will cause internal leakage of the valve. In addition, if the position of the wedge-shaped sealing ring is not correctly adjusted during installation, it may also lead to poor sealing.

When designing wedge-shaped sealing rings, it is necessary to consider factors such as the strength, corrosion resistance, and surface hardness of the sealing ring. The surface hardness of the sealing ring should be lower than that of the valve cover sealing surface so that it can undergo plastic deformation under external force, thereby better fitting the valve body. If the surface hardness of the sealing ring is too high, it may scratch the valve body during operation, causing leakage. Moreover, the medium running for a long time may corrode the wedge-shaped sealing ring, leading to gate valve leakage.

The opening and closing of gate valves are controlled by actuators, which convert liquid, gas, electricity, or other types of power into driving actions to move the valve to the fully open or fully closed position. If the actuator does not open or close properly, or if its sensitivity is insufficient, it will cause the gate valve to fail to open or close completely, thereby causing internal leakage. For example, if the zero position setting of the actuator is inaccurate and does not reach the fully closed position of the valve, the valve will not be able to close completely.

During the production process of cast valve bodies, defects such as porosity, slag inclusion, cracks, and sand holes may occur. If these defects are not detected before leaving the factory, or if they are detected but not properly repaired, they will cause external leakage of the valve during use. For example, through-cracks and penetrating defects are irreparable and the valve body must be replaced.

Although the problem of gate valve leakage is complex, it can be effectively reduced by adopting scientific and rational solutions to ensure the reliable operation of the valve. Here are some targeted solutions.

Improving the machining precision of wedge-shaped sealing rings is key to solving the problem of gate valve leakage. Manufacturers should strictly control the machining process of the sealing rings to ensure that their surface roughness, dimensional accuracy, and other indicators meet the design requirements. For example, using high-precision machining equipment and advanced detection methods to conduct strict quality inspections on the sealing rings, ensuring that each product meets high-quality standards.

During the operation of valves, it is important to maintain stable pressure and temperature. Operators should strictly follow the operating procedures to avoid unnecessary impact and deformation on the sealing rings. For example, in high-temperature and high-pressure environments, appropriate cooling measures should be taken to prevent the sealing rings from deforming due to thermal expansion. At the same time, regular maintenance and inspection of the valves should be carried out to detect and address potential problems in a timely manner.

When maintaining valves, staff should carefully clean the sealing surface to ensure that there are no residual particles and impurities. When installing the wedge-shaped sealing ring, the position of the sealing ring should be correctly adjusted to ensure a tight fit with the valve body. For example, professional cleaning tools and detection equipment can be used to thoroughly clean and inspect the sealing surface, ensuring that it is smooth and free of scratches.

When designing wedge-shaped sealing rings, factors such as strength, corrosion resistance, and surface hardness should be comprehensively considered. The surface hardness of the sealing ring should be lower than that of the valve cover sealing surface so that it can undergo plastic deformation under external force. At the same time, materials with strong corrosion resistance should be selected to extend the service life of the sealing ring. For example, composite materials or coating technologies can be used to enhance the corrosion resistance of the sealing ring.

The reliability of the actuator directly affects the opening and closing performance of the gate valve. Regular maintenance and inspection of the actuator should be carried out to ensure that it can accurately open or close the valve. For example, by manually fully opening and closing the valve, the zero position of the actuator should be adjusted to ensure that it can accurately reach the fully closed position. At the same time, high-quality actuator products should be selected to avoid gate valve leakage caused by actuator failures.

For casting defects in valve bodies, strict quality inspection should be carried out before leaving the factory. If defects are found, appropriate repair measures should be taken. For example, for valve body defects that can be welded, a suitable welding process should be developed, including determining the welding method, electrode material, and post-weld stress relief method, and conducting non-destructive testing on the welding position to ensure that the repair meets the requirements. For irreparable defects, such as through-cracks and penetrating defects, the valve body must be resolutely replaced to avoid leakage during use.

Solving the problem of gate valve leakage not only requires a holistic approach to design and operation but also targeted measures for specific leakage locations.

If there is leakage at the connection between gate valves, first check whether the connecting bolts between the gate valves are tightened. Ensure that the sealing gasket ring is fully combined with the flange sealing groove surface. If leakage has already occurred here, check the bolts and nuts in sequence and tighten them to compress the sealing surface ring. Finally, check the dimensions and precision of the sealing gasket ring and the flange sealing groove surface to see if there are any pitting, sand holes, sand eyes, or impurities, and take corresponding welding, repair, or cleaning actions based on the situation.

Bonnet leakage is usually caused by leakage of the packing seal. First, check the selection of the sealing element to ensure that it matches the sealing groove. If the selection is inappropriate, the problem can be solved by replacing the sealing ring or repairing the sealing groove. At the same time, check whether the sealing element has burrs, crushing, twisting, or other phenomena, and replace it in a timely manner if necessary. In addition, check whether the sealing surfaces of each sealing groove are rough or have other defects, and eliminate or replace the new parts if there are defects. Finally, pay attention to the installation of the packing and the fit of the packing seal surface to ensure correct installation.

Valve body leakage may be caused by casting defects such as sand eyes and sand holes that occur during the casting process. These defects are difficult to detect before pressure testing, but once pressure is applied, leakage will occur. In this case, welding, repair, or replacement should be carried out. When welding, ensure that the welding process meets the requirements to avoid new leaks caused by improper welding.

Sealing surface leakage is one of the common phenomena of gate valve leakage, which is divided into two situations: sealing surface leakage and leakage at the root of the sealing ring. First, check the precision of the sealing surface. If it is too rough, it needs to be removed and reground. Secondly, check whether there are defects such as pitting, indentations, sand eyes, and cracks on the sealing surface. If necessary, replace the valve plate or valve seat. In addition, a valve seat with a spring may leak due to the weakening of the spring's elasticity, which should be replaced in a timely manner. At the same time, pay attention to whether the connection between the valve plate and the lower part of the valve stem is too loose, and make adjustments if necessary.

If foreign matter such as welding slag, iron filings, and impurities enters the valve body, it will also cause the valve plate to not close to the expected depth and cause leakage. In this case, the valve body should be removed and cleaned again to ensure that the inside of the valve body is clean and free of foreign matter.

Gate valve leakage is a complex issue with a variety of causes, including insufficient machining precision of wedge-shaped sealing rings, pressure and temperature variations during operation, substandard maintenance quality, unreasonable sealing ring design, actuator problems, and casting defects in valve bodies. To effectively solve the problem of gate valve leakage, a comprehensive approach is needed. Manufacturers should enhance the machining precision of wedge-shaped sealing rings, optimize the operation process, improve maintenance quality, design sealing rings reasonably, ensure the reliability of actuators, and strictly address casting defects in valve bodies. At the same time, users should pay attention to regular maintenance and inspection during use, promptly detect and address potential problems, and ensure the safe and reliable operation of gate valves. Through these measures, the occurrence of gate valve leakage can be effectively reduced, improving the efficiency and safety of industrial production.