Ball valve seat structure principle

1, Overview The main function of the ball valve is to cut off or connect the fluid passage in the pipe. The working principle of the ball valve is to apply a certain amount of torque to the ball body by the driving device at the upper end of the valve stem so as to rotate it by 90 ° to complete the action of opening or closing the valve. Ball valve seat sealing principle varies according to their structure, Hong Feng valve commonly used seat structure can be divided into fixed seat floating ball and floating seat fixed ball two categories. When the valve seat is fixed to float, the sphere displaces in the direction of fluid flow under fluid pressure to make it more closely contact with the seat behind the valve, ie, the specific pressure on the sealing surface increases to form a single side Sealed, at the same time, the valve seat sealing surface of the corresponding reduction in pressure, often do not guarantee the seal. When the valve seat floating ball is fixed, the fluid pressure can not make the ball displacement, but the valve seat by means of spring or fluid pressure to the ball, the establishment of the seal than the pressure. 2, the structure 2.1, soft-sealed seat (1) ordinary ordinary seat is characterized by pre-tightening force or fluid pressure under the seat and the ball compacting, and the seat material elastoplastic deformation to achieve the seal, which The sealing effect depends on the ability of the valve seat to compensate for the roundness of the sphere and the microscopic unevenness of the surface under fluid pressure or preload. Therefore, there must be a large enough seal pressure between the seat and the ball. (2) Elastic elastic seat With elastic elements, such as metal spring frame and spring, elastic deformation under the pre-tightening force or fluid pressure to compensate for the influence of external conditions such as temperature difference, pressure and wear on the sealing performance of the ball . 4, the conclusion Seat and seal are the key components of the ball valve. Hongfeng Valve believes that the seal should have excellent stability, a smaller coefficient of friction, aging is not easy, good sealing performance. Valve seat should have a certain strength and stiffness, the gap is moderate, not easily deformed when pressed. Metal seal valve seat should meet the high temperature, high pressure, strong corrosion, low temperature, zero leakage, long life, fire safety and pressure and wear resistance and other functions.