What is the hard seal butterfly valve?The hard seal butterfly valve is also called metal hard sealing butterfly valve, which is the butterfly valve with metal material on both sides of the seal.The metal hard sealing butterfly valve has the advantages of high temperature, high pressure environment, erosion and corrosion resistance, long service life.The defect is the sealing problem, because the sealing pair is metal on both sides, there will still be a certain amount of leakage after the butterfly valve is completely closed , poor sealing performance.
The common hard seal butterfly valve structure is double eccentric and three eccentric.The double-eccentric hard-sealing butterfly valve is characterized by the fact that the shaft of the valve stem has two eccentricities. The first one is offset from the center of the butterfly plate, and the second is off center of the valve body. This double eccentricity effect makes the butterfly valve open when it is opened. The butterfly plate can quickly leave the valve seat, substantially eliminating friction and scraping between the butterfly plate and the valve seat, which not only reduces the opening and closing resistance of the butterfly valve, but also improves the service life of the valve seat.
Double eccentric butterfly valve seat material can be used to prevent corrosion by using ptfe material.Metal seal seats can also be used in high temperature working conditions.However, the double eccentric butterfly valve with metal seat can not be used in high pressure environment.
If used in high pressure condition, the double eccentric butterfly valve will produce a lot of leakage.Therefore, in a high-pressure operating environment or in a piping system with requirements for sealing performance, the metal seat double eccentric hard seal butterfly valve does not apply.
Because the double eccentric butterfly valve can not exist at the same time between high temperature resistance and good sealing performance, in order to overcome this contradiction, the butterfly valve has a third eccentric design, which is now the performance of the three eccentric hard seal butterfly valve. The appearance of the triple eccentric butterfly valve not only solves the problem that the traditional butterfly valve cannot achieve the seal between the sealing performance and the high temperature and high pressure, but also further expands the use of the hard seal butterfly valve.