What are Resilient-seated Gate Valves?

In industrial and domestic water supply and drainage systems, valves play a crucial role in controlling fluid flow, and their performance and reliability are of utmost importance. The resilient-seated gate valve, widely used for its unique sealing performance and structural advantages, has become the preferred choice for many engineering projects. This article will delve into the working principle, structural features, sealing performance, and practical application advantages of the resilient-seated gate valve, helping readers gain a comprehensive understanding of this vital fluid control device.

Resilient-seated gate valves are widely used in water supply and drainage pipelines, with a working pressure generally below 1.6 MPa and a working temperature not exceeding 80°C. The sealing pair of this valve consists of a rubber-coated gate and a cast iron valve body sealing surface coated with electrostatic spray. The rubber coating on the gate is made of nitrile rubber with a hardness of 70A, while the shell surface, including the sealing surface, is coated with epoxy resin. This combination of materials not only ensures the valve's sealing performance but also provides excellent corrosion and wear resistance.

Nitrile rubber has a low elastic modulus, which allows it to undergo significant elastic and plastic deformation under a small sealing force, thereby effectively filling and sealing any leakage gaps. However, this material also has a low permissible specific pressure. If excessive sealing force is applied, the rubber may become over-compressed, leading to permanent deformation and loss of sealing capability. Therefore, selecting an appropriate rubber compression rate and coordinating the structural parameters of the sealing pair are crucial for the valve's sealing performance and service life.

The sealing principle of resilient-seated gate valves primarily relies on the elastic deformation between the gate and the valve body sealing surface. The gate's sealing surface is typically covered with a layer of rubber, which deforms elastically under pressure to fill the minute gaps between the sealing surfaces, achieving a seal. To enhance sealing performance, the resilient-seated gate valve employs a three-dimensional sealing design, which synchronously achieves sealing through the wedge surface in the Z-axis direction, the inclined surface in the X-axis direction, and the arc surface in the Y-axis direction.

This three-dimensional sealing design changes the traditional wedge gate valve's reliance on a single wedge surface for sealing. By applying pressure from multiple directions, it ensures tight contact of the sealing surfaces in all directions. For example, the wedge surfaces, due to their wedge angle, have a longer downward displacement during sealing. To reduce wear on the rubber coating during movement, a larger wedge angle is usually chosen, or the wedge surface is inclined at a small angle to both sides, with the compression amount decreasing progressively. The inclined surface is selected at a 40° angle, which is closest to the direction of the arc surface. The combination of the inclined plane and edge completes the transition from wedge surface to arc surface sealing.

Next, let's explore the key factors that influence the sealing performance of resilient-seated gate valves. These factors not only determine the valve's sealing effectiveness but also directly affect its service life and reliability.

The compression rate of rubber seals is one of the key factors affecting sealing performance. The recommended compression rate range is 8% to 40%, with a gate rubber hardness of 65 to 70A being ideal. By selecting an appropriate rubber compression rate, it ensures that the rubber can deform sufficiently to fill gaps during sealing while avoiding permanent deformation caused by over-compression.

The structural parameters of the sealing surface, such as the wedge angle and inclined angle, also significantly impact sealing performance. Different slopes and structures result in diverse widths of the sealing surfaces, with varying minimum compression rates and downward displacement amounts required. If the structural parameters of the sealing surface are not properly set, synchronous sealing cannot be achieved, leading to compression rates outside the normal range for certain sections of the sealing surface. Too low a compression rate will fail to seal, while too high a rate will cause excessive compression.

The choice of materials for the valve body and gate also directly affects sealing performance. The valve body is cast from ductile iron, reducing the weight by about 20% to 30% compared to traditional gate valves while offering higher strength and toughness. The gate is fully coated with high-quality rubber inside and out. Domestic first-class rubber vulcanization technology ensures precise geometric dimensions of the vulcanized gate plate, with a secure bond between the rubber and the ductile iron gate, preventing detachment.

After understanding the key factors affecting the sealing performance of resilient-seated gate valves, let's further explore the structural advantages of this type of valve. These design features not only enhance the overall performance of the valve but also make it excel in practical applications, making it the preferred choice for many engineering projects.

The resilient-seated wedge gate valve features a straight-through design with no recesses at the bottom of the valve body flow path. This design not only reduces fluid resistance within the valve body but also prevents debris accumulation in the valve bottom recesses, ensuring smooth fluid flow. Traditional gate valves often fail to close tightly after water flushing due to debris accumulation in the valve bottom recesses, leading to leakage. The flat-bottom design of the resilient-seated gate valve effectively solves this problem.

The valve stem is sealed with three "O" rings, which reduces friction resistance during operation and significantly minimizes leakage. This design also allows for the replacement of the sealing rings without shutting off the water supply, greatly enhancing the valve's maintenance convenience.

The valve body is coated with powder epoxy resin to prevent corrosion and rust, making it suitable for sewage systems. The gate's inner and outer surfaces are fully covered with rubber, preventing rust water or corrosion and ensuring the cleanliness of the fluid, making it suitable for drinking water systems.

Resilient-seated gate valves are widely used in water supply and drainage pipelines, including municipal water supply systems, sewage treatment plants, and industrial water systems. Their excellent sealing performance and corrosion resistance enable stable operation under various complex working conditions. For example, in municipal water supply systems, resilient-seated gate valves can effectively prevent water wastage and ensure reliable water supply. In sewage treatment plants, their corrosion resistance protects against sewage erosion and ensures the normal operation of sewage treatment processes.

Choosing the right resilient-seated gate valve not only ensures the valve's performance and reliability but also extends its service life and reduces maintenance costs.

The quality of the sealing surface is a key factor affecting the valve's sealing performance. High-quality sealing surfaces can maintain good sealing effects over long-term use. When selecting resilient-seated gate valves, priority should be given to products with high-quality rubber and advanced vulcanization technology.

When selecting the valve, attention should also be paid to the physical properties of the fluid, including viscosity, temperature, and hydrophilicity. Generally, the greater the fluid viscosity, the lower its permeability. The viscosity of gases is dozens of times lower than that of liquids, so their permeability is stronger than that of liquids, and compressed gases are more likely to leak than liquids. However, saturated steam is an exception, with relatively weak permeability, making it easier to ensure sealing.

Choosing a reliable manufacturer and high-quality products is key to ensuring valve performance. When purchasing, select manufacturers with a good reputation and rich experience, and request detailed product manuals and technical parameters to ensure accurate selection and installation.

The resilient-seated gate valve, with its unique sealing principle, structural advantages, and excellent sealing performance, has become an ideal choice for water supply and drainage pipelines. By selecting an appropriate rubber compression rate, optimizing the structural parameters of the sealing surface, and using high-quality materials and advanced manufacturing processes, the resilient-seated gate valve can operate stably under various working conditions, effectively prevent leakage, and ensure the normal operation of fluid systems. When selecting and using resilient-seated gate valves, it is essential to consider the quality of the sealing surface, the physical properties of the fluid, and the reliability of the manufacturer to ensure the long-term stable operation and efficient sealing performance of the valve.