Valve application: ball valve seat structure principle

1 Overview

The main function of the ball valve is to cut or close the fluid passage in the pipe. The working principle of the ball valve is to transmit a certain torque to the ball at the upper end of the valve stem by means of the driving device, and rotate it to 90° to complete the action of opening or closing the valve. The sealing principle of the ball valve seat varies according to its structure. The valve seat structure commonly used by Hongfeng Valve can be divided into two types: fixed valve seat floating ball and floating valve seat fixed ball. When the valve seat fixed sphere floats, the ball is displaced in the direction of fluid flow under the action of fluid pressure, so that it is tightly in contact with the valve seat, that is, the specific pressure on the sealing surface is increased to form a single side. Sealing, at the same time, the specific pressure on the sealing surface of the valve seat before the valve is correspondingly reduced, and the sealing is often not guaranteed. When the floating ball of the valve seat is fixed, the fluid pressure cannot cause the ball to be displaced, but the valve seat is pressed against the ball by the spring or the fluid thrust to establish the sealing specific pressure.

2, structure

2.1, soft sealing seat

(1) Ordinary

The common valve seat is characterized in that the valve seat and the ball are pressed under the pre-tightening force or the fluid pressure, and the valve seat material is elastically plastically deformed to achieve the sealing, and the sealing effect depends on the valve seat in the fluid pressure or the pre-tightening force. The ability to compensate for the roundness of the sphere and the microscopic unevenness of the surface under action. Therefore, there must be a sufficiently large seal specific pressure between the valve seat and the ball.

(2) Flexible

The elastic valve seat is elastically deformed under pre-tightening force or fluid pressure by means of elastic elements, such as metal spring frame and spring, to compensate for the influence of external conditions such as temperature difference, pressure and wear on the sealing performance of the ball.

Seat and seal are key components of the ball valve. Hongfeng Valve believes that the sealing ring should have excellent stability, small friction coefficient, not easy to aging, and good sealing performance. The valve seat should have a certain strength and rigidity, the clearance is moderate, and it is not easily deformed when pressed. The metal sealing seat should meet the functions of high temperature, high pressure, strong corrosion, ultra low temperature, zero leakage, long life, fire safety and pressure and wear resistance.