What Affect the Sealing Performance of Industrial Valves

  
The sealing performance of industrial valves is crucial for their operational reliability and safety, ensuring that these valves effectively prevent medium leakage under various operating conditions. A variety of factors influence the sealing performance of industrial valves, including the quality of the sealing surface, the width of the sealing surface, the sealing material and its condition, the properties of the medium, and the presence of a lubricating film between the sealing surfaces. Here is a detailed discussion of these factors.

Quality of the Sealing Surface

 
The quality of the sealing surface directly affects the sealing effect of industrial valves. The processing precision and surface roughness are particularly important under low pressure conditions, and the processing technology must be strictly controlled to ensure effective sealing.

1. Processing Precision

 
The processing precision of the sealing surface is one of the key factors to ensure sealing performance. High-precision processing can reduce the gap between the sealing surfaces, thereby reducing the possibility of leakage. Generally, when the pressure on the sealing surface is below 40 MPa, the processing precision has a significant impact on the leakage amount. Studies have shown that under low pressure conditions, an increase in the roughness of the sealing surface will significantly increase the leakage amount. However, under high pressure conditions, the impact of surface roughness on the leakage amount is relatively reduced, indicating that under high pressure conditions, the sealing surface can be better flattened, reducing the impact of surface roughness on sealing performance.

2. Surface Roughness

 
Control of the surface roughness of the sealing surface is also an important factor in ensuring good sealing. Under low pressure conditions, an increase in surface roughness will lead to a decrease in sealing performance, so it is necessary to accurately control the processing technology to achieve a low-roughness sealing surface. Under high pressure conditions, although the impact of surface roughness is reduced, the processing quality still needs to be ensured to maintain a long-term sealing effect.

Width of the Sealing Surface

 
The width of the sealing surface determines the flow distance of the medium in the capillary pores. An increase in width may lead to an increase in the leakage path, thereby affecting the sealing performance. Therefore, when designing industrial valves, it is necessary to balance the relationship between the width of the sealing surface and leakage control.

1. Capillary Length

 
The width of the sealing surface affects the movement of the medium in the capillary pores. An increase in width will extend the movement distance of the medium in the capillary pores, thereby increasing the resistance to movement. Although widening the sealing surface can reduce erosion and wear in high-pressure industrial valves, a wide sealing surface may lead to a proportional increase in the length of the leakage path, and the actual leakage amount may not be reduced proportionally. This is because the processing flatness of a wide sealing surface is often not as good as that of a narrow sealing surface, and deformation of the valve parts may also lead to uneven sealing performance.

2. Leakage Amount and Sealing Surface Width

 
In practical applications, the width of the sealing surface should be optimized according to specific working conditions. An overly wide sealing surface may cause uneven processing and sealing problems, while an overly narrow sealing surface may not effectively prevent medium leakage. Therefore, when designing industrial valves, it is necessary to comprehensively consider the impact of the width of the sealing surface on sealing performance to achieve the best sealing effect.

Material and Condition of the Sealing Surface

 
The material and condition of the sealing surface are crucial for the sealing effect. The hardness of the material and surface treatment will directly affect the sealing performance, and choosing the right material and ensuring its good surface condition are essential for achieving a reliable seal.

1. Material Hardness

 
The hardness of the sealing surface material has an important impact on sealing performance. Materials with higher hardness (such as steel) usually require greater pressure to achieve the same sealing effect as softer materials (such as brass). Therefore, choosing the right material and performing appropriate surface treatment are key to ensuring sealing performance.

2. Surface Treatment Condition

 
The surface treatment condition of the sealing surface, such as deformation of the peaks, gap size, and changes in geometric shape, also affects sealing performance. Surface changes caused by mechanical processing may affect the sealing effect because the performance of the surface metal is different from that of the base material. For example, the grinding process may cause the surface metal structure to be different from the base metal structure, thereby affecting the sealing performance. Therefore, special attention should be paid to the selection of materials and processing technology in the manufacturing process to ensure the stability of sealing performance.

Properties of the Medium

 
The properties of the medium, such as viscosity and hydrophilicity, significantly affect the sealing performance of industrial valves. Different media have different effects on leakage, so understanding the characteristics of the medium helps to optimize the design and sealing effect of industrial valves.

1. The Impact of Viscosity

 
The viscosity of the medium has a significant impact on the leakage amount. The leakage amount of liquid media mainly depends on its viscosity, and the leakage amount of liquid media with high viscosity is significantly less than that of liquid media with low viscosity. The leakage situation of gas media is more obvious, but the situation of saturated steam is different. When saturated steam passes through capillary pores, droplets may block the capillary pores, thereby improving the sealing effect.

2. The Impact of Hydrophilicity

 
The hydrophilicity of the sealing surface also affects the leakage amount. The characteristics of the capillary pores make the presence of a lubricating film increase the pressure of water passing through the gap. Good hydrophilicity of the metal surface allows kerosene to easily penetrate the gaps of castings and sealing surfaces, making kerosene an effective medium for sealing performance testing.

Presence of a Lubricating Film Between the Sealing Surfaces

 
The presence of a lubricating film between the sealing surfaces can significantly improve sealing performance. The lubricating film reduces medium leakage by enhancing the barrier effect of the sealing surfaces and also protects the sealing surfaces from wear. Regular inspection and replenishment of sealing grease are key to maintaining long-term effective sealing.

1. The Role of the Lubricating Film

 
The presence of a lubricating film between the sealing surfaces has a significant impact on sealing performance. The existence of a lubricating film can improve sealing performance because it disrupts the hydrophilicity of the sealing surface, requiring a greater pressure difference for the medium to pass through the capillary pores. At the same time, a dense sealing lubricating film can block the capillary pores through which the medium passes, improving the sealing effect.

2. The Use of Sealing Grease

 
In plug valves, ball valves, and other types of industrial valves, the use of sealing grease can significantly improve sealing performance and extend service life. When using sealing grease, it is important to replenish it regularly to restore the thickness of the lubricating film. At the same time, the grease used should ensure that it does not melt, harden, or undergo other chemical changes at working temperatures to ensure long-term stable sealing performance.
 
The sealing performance of industrial valves is affected by various factors, including the quality of the sealing surface, the width of the sealing surface, the material and its condition, the properties of the medium, and the presence of a lubricating film between the sealing surfaces. Considering these factors comprehensively and optimizing them in the design and maintenance of industrial valves can significantly improve the sealing performance of industrial valves, ensuring the reliable operation and safety of the equipment. By accurately controlling these factors, it is possible to effectively reduce medium leakage, improve the operating efficiency of the equipment, and reduce maintenance costs.