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August 19, 2021
Gasket is an important component of flange seal
The gasket is used to seal the gap between the two French sealing surfaces and prevent fluid leakage.
Suitable flange gasket material requires that the gasket can produce necessary elastic deformation without being crushed or extruded under the action of appropriate preload; During operation, the distance between the stainless steel flange sealing surface is enlarged, and the gasket material shall have sufficient resilience to make the gasket surface in close contact with the flange surface, so as to continue to maintain good sealing performance;
When selecting flange gasket materials, the working medium and working temperature shall also be considered. The width of the gasket is also an important factor affecting the sealing. The wider the gasket, the greater the preload required, and the larger the size of the bolt and flange.
1. Non metallic gaskets such as rubber, asbestos rubber and PTEF are commonly used on medium and low pressure equipment and pipeline flanges. They have good corrosion resistance and flexibility, but poor strength and temperature resistance.
In order to improve the strength and heat resistance of the gasket, the spiral wound gasket is made of thin steel tape and asbestos tape, or the metal clad gasket is made of metal sheet wrapped with asbestos or other non-metallic materials. It has multi-channel sealing effect and good resilience. It can be used in a high temperature and pressure range, and can maintain a good seal under the conditions of pressure and temperature fluctuation, Therefore, it is widely used.
3. The metal clad gasket is composed of asbestos rubber plate as the inner core and 0.2 ~ 0.5mm thick thin metal plate (as shown in the figure below),
The material of metal plate can be aluminum, steel and its alloy, or stainless steel or high-quality carbon steel. Metal clad gaskets are also only used for type B flat welding and long neck butt welding flanges.
4. Metal gaskets are commonly used on the flanges of high-pressure equipment and pipelines, including soft aluminum, copper, mild steel and stainless steel. When the operating pressure is very high or the leakage rate is very strict, and the temperature is very high or highly corrosive, metal gaskets can be used. The specific pressure value of metal gasket is very large. In order to reduce the bolt force, the compression surface must be very narrow. Relying on the extremely narrow compression surface to maintain good sealing, it must have small surface roughness