English
Tips for valve Gaskets and Packings
Created on 2024.08.06
There are seven main factors affecting the sealing of gaskets and packings:
1. The nature of the fluid: the viscosity of the liquid has a great impact on the tightness of the packing and gasket, and the viscosity of the fluid is easy to seal due to its poor fluidity. The viscosity of liquids is much greater than that of gases, so liquids are easier to seal than gases. Saturated steam is easier to seal than superheated steam because it condenses droplets and blocks the leakage channel between the sealing faces. The larger the molecular volume of a fluid, the more likely it is to be blocked by narrow sealing gaps, making it easier to seal. The wettability of the liquid to the seal material also has an effect on the seal. Liquids that are easy to infiltrate are prone to permeation leakage due to the capillary action of the micropores inside the gasket and filler.
2. The surface condition of the sealing surface: the shape and surface roughness of the sealing surface have a certain impact on the sealing, and the smooth surface is conducive to sealing. Soft gaskets are insensitive to surface conditions due to their ease of deformation, whereas for hard gaskets, surface conditions are extremely influential.
3. The material of the gasket and packing: the soft material is easy to produce elastic or plastic deformation under the action of preload, thus blocking the channel of fluid leakage, so it is conducive to sealing; However, soft materials generally cannot withstand the action of high-pressure fluids. The corrosion resistance, heat resistance, compactness, and hydrophilicity of the sealing material have a certain impact on the sealing.
4. The contact width of the sealing surface: the larger the contact width between the sealing surface and the gasket or packing, the longer the path that the fluid leakage needs to pass through, and the greater the flow resistance loss, which is conducive to sealing. However, the greater the contact width at the same pressing force, the specific pressure of the seal will decrease. Therefore, it is necessary to find the appropriate contact width according to the material of the seal.
5. The temperature of the fluid
6. Specific pressure of sealing surface: The normal force on the unit contact surface between sealing surfaces is called sealing specific pressure, and the size of the specific pressure of the sealing surface is an important factor affecting the sealing of gasket or packing. Usually, a certain specific pressure is generated on the sealing surface by applying preload, so that the seal is deformed to reduce or eliminate the gap between the sealing contact surfaces, prevent the fluid from passing through, and achieve the purpose of sealing. It should be noted that the effect of fluid pressure can cause a change in the specific pressure of the sealing surface. Although the increase of the specific pressure of the sealing surface is conducive to sealing, it is limited by the extrusion strength of the sealing material. For dynamic seals, the increase in the specific pressure of the sealing surface will also cause a corresponding increase in frictional resistance.
7. Influence of external conditions: the vibration of the pipeline system, the deformation of the connecting components, the deviation of the installation position and other reasons will produce additional force on the seal, which will have an adverse impact on the seal. In particular, vibration will cause periodic changes in the compression force between the sealing surfaces, causing the connecting bolts to relax, resulting in seal failure. The cause of the vibration can be external or due to fluid movement inside the system. All of these factors must be carefully considered for a reliable seal, and the manufacture and selection of gaskets and packing materials is critical.
Contact
Leave your information and we will contact you.