Commonly used flange gaskets are divided into non-metallic gaskets, semi-metallic gaskets and metal gaskets according to their constituent materials.
(1) Non-metallic gasket
Non-metallic gaskets, also known as soft gaskets, mainly including asbestos rubber sheet gaskets, PTFE-coated gaskets. Gasket type is mostly flat gasket, the use of pressure is not high, should not be higher than 5.0MPa, the use of temperature depends on the gasket material.
(2) Semi-metallic gasket
Semi-metallic gasket by the metal and non-metallic two materials together into a combination, including winding gaskets and metal-coated gaskets. This gasket has good sealing performance and good pressure resistance. Winding gasket can be used in the highest 25.0MPa and 600 ℃ harsh conditions.
(3) Metal gasket
Metal gaskets are made of metal (or alloy) materials by mechanical processing. Gasket type has flat gasket, oval-shaped gasket and octagonal gasket. Metal gasket material according to the corrosive nature of the medium and temperature selection, specifically soft iron, alloy steel, copper, aluminium and so on. Generally used in high-pressure situations, the use of temperature is based on the choice of materials.
Two gasket selection principles
(1) Gasket selection should be based on the sealing performance of the gasket, operating pressure, operating temperature, operating medium characteristics and sealing requirements and other factors.
(2) Gasket material performance requirements
Gasket material performance should meet the following requirements.
① have good physical and mechanical properties;
② not contaminated by the sealing medium, do not corrode the sealing surface, corrosion resistance of the working medium;
③ has good compression, resilience;
④ have a small stress relaxation rate;
⑤ low leakage rate.
(2) Flexible graphite composite gasket
① The maximum working pressure of flexible graphite composite gasket is 10.0MPa. The maximum working temperature depends on the metal core plate material. According to the core plate material material, can be selected between -196 ℃ ~ 650 ℃. Flexible graphite composite gasket is suitable for water, oil, solvents, acids, alkalis, hydrogen, oil and gas, high-temperature flue gas, steam and other strong corrosive, permeable media.
② gaskets should be in line with the current chemical industry standard "steel pipe flange with flexible graphite composite gasket" HG 20608 (European system), HG 20629 (American system), etc. or its equivalent standards.
(3) Metal ring gasket
① Metal ring gaskets are suitable for high temperature and high pressure pipelines, and the maximum temperature is shown in Table 10-7-13 according to the different materials used;
② gasket should be in line with the current petrochemical industry standards "pipe flange with metal ring gasket" SH 3403, the chemical industry standard "steel pipe flange with metal ring gasket" HG 20612 (European system), HG 20633 (American system) and the mechanical industry standard "pipe flange with metal ring gasket," JB / T 89, etc., or its equivalent standards;
③ The hardness value of the metal ring gasket material shall be lower than that of the flange material by 30～40HB.
(4) Metal clad gasket
① Metal clad gasket has good sealing performance and is suitable for higher temperature media. Metal clad gaskets can be made into gaskets with complex shapes. Widely used is flat metal clad gasket;
The maximum operating temperature of the gasket is shown in Table 10-7-14;
③ Gaskets should comply with the current chemical industry standard "steel pipe flanges with metal clad gaskets" HG 20609 (European system), and HG 20630 (American system) or its equivalent standards.
