Types and functions of flange gasket
Commonly used flange gaskets are generally divided into three categories:
1. Non metallic gasket
a. Asbestos rubber gasket
Features: good elasticity, high strength, good oil resistance, high temperature resistance, easy to obtain. But asbestos products can cause cancer
Scope of application: t ≤ 260 ℃, PN ≤ 2.0MPa (sh3401), t ≤ 400 ℃, PN ≤ 4.0Mpa (GB / t539); used in water, air, nitrogen, acid, alkali, oil and other media conditions.
b. PTFE coated gasket
Scope of application: T = - 180 ~ 200 ℃, PN ≤ 4.0Mpa, often used in low temperature or clean situation.
2. Semi metallic gasket
There are spiral wound gasket, metal coated gasket and flexible graphite gasket
a. Spiral wound gasket
Features: it is the most ideal and widely used semi-metallic gasket. It has good compression resilience, high strength, and can adapt to the changes of pressure and temperature. It can maintain good sealing performance under high temperature, low temperature, impact, vibration and variable load. Material: winding steel strip: 20, 1Cr13, 0Cr18Ni10Ti, 0Cr17Ni12Mo2, etc
Non metallic winding tape: special asbestos, flexible graphite tape, polytetrafluoroethylene tape
b. Iron clad gasket
The sealing performance of spiral wound gasket is not as good as that of spiral wound gasket, so it is rarely used in pipelines. It is often used in large diameter flange connection such as heat exchanger head
c. Flexible graphite composite gasket
Suitable for raised face, concave convex face and mortise face flange
3. Metal gasket
It is often used on high pressure flange to bear high sealing pressure. There are three kinds of commonly used metal gaskets: flat gasket, octagonal gasket and oval gasket
Metal flat gasket: often used with raised, concave and mortise face flange
Octagonal gasket and oval gasket: often used with ring groove face flange. Compared with the two, octagonal gasket processing is easy, so use more
In general, the material of metal gasket should be selected with flange material, and the hardness of gasket should be lower than that of flange sealing surface (not less than 30hb).
Selection standard of pipe flange, gasket and fastener
Flange gasket selection guide free download