The seat is a detachable part inside the valve. The main function is to support the valve core to be fully closed or fully closed, and constitute a sealing pair. Normally, the diameter of the seat is the diameter of the valve. The butterfly valve seat is made of a wide range of materials. However, commonly used materials are soft-sealed EPDM, nitrile rubber (NBR), polytetrafluoroethylene (PTFE), and metal hard-sealed carbide. Let us introduce them one by one.
1. EPDM: EPDM has a great advantage over other general rubbers.
First of all, the price is very high. Among the commonly used rubbers, EPDM has the lowest density of green rubber and can do a lot of filling, which reduces the cost of the compound. Secondly, the EPDM material is resistant to aging, sunlight exposure, heat resistance, moisture resistance, radiation resistance, and is suitable for weak acid and weak base media. It has good insulation properties. Finally, it has a temperature range of -40 ° C to 60 ° C and can be used for a long time at 130 ° C.
2. Nitrile rubber (NBR): It is resistant to oil, heat and abrasion, and has good water resistance, air tightness and excellent bonding properties. More applications in oil pipelines. The disadvantage is that it is not resistant to low temperatures. It is not resistant to ozone. The insulation performance is very poor and the elasticity is also general.
3. Polytetrafluoroethylene (PTFE): It is a fluoroplastic. This material has strong resistance to acids and alkalis and resistance to various organic solvents. At the same time, the material is resistant to high temperatures and can be used continuously at 260 °C. The maximum operating temperature can reach 290-320 °C. The emergence of PTFE has successfully solved many problems in the chemical, petroleum, pharmaceutical and other industries.
4. Metal hard seal (hard alloy): The material of the metal hard seal seat has very good resistance to high temperature, high pressure, corrosion resistance and wear resistance, which makes up for the defect that the soft seal material is not resistant to high temperature and high pressure. However, hard sealing materials require a high processing process. The only disadvantage of the metal hard-sealed seat is the poor sealing performance that can leak after prolonged operation.