The Sealing Principle of Floating Ball Valve

There are two valve seat rings in the valve body of the floating ball valve, and a ball is clamped between them. There is a through hole on the ball. The diameter of the through hole is equal to the inner diameter of the pipe, which is called a full bore ball valve; the diameter of the through hole is smaller than the inner diameter is called a reduced bore ball valve. With the help of the valve stem, the ball can rotate freely in the valve seat seal. When opening, the ball hole is aligned with the pipe diameter to ensure the minimum resistance of the pipe working medium. When the valve stem rotates 1/4 turn, the ball hole is perpendicular to the channel of the valve, and the ball is tightly pressed on the valve sealing ring at the outlet end by the pre-tightening force and medium pressure applied to the two valve sealing rings, so as to ensure the valve completely sealed. This ball valve is a single-sided forced seal.

The floating ball valve should also focus on whether the seat material can withstand the load of the sphere, because the sphere, in addition to its own weight, also bears the full load of the working medium and transmits it to the valve seat. In addition, it should also be considered that large-diameter float valves require large forces during operation.

In order to ensure the sealing and reliability of the floating ball valve during operation, the following requirements must be met:

1. In order to obtain a seal, there should be a high enough sealing specific pressure on the contact surface of the ball and the valve seat, but it should not exceed the allowable specific pressure of the valve seat material.

2. The fit of the valve seat in the groove should be tight, otherwise even if the valve seat seals against the ball well, the medium will leak along the end face of the groove. In order to meet this requirement, it is recommended to open several triangular concentric grooves with a apex angle of 60^o and a depth of 0.5 ~ 1mm on the end face of the groove. ,

3. The sphere should have the correct geometry and a low surface roughness value. Usually the sphere is manufactured with h8 or h9 precision, and its surface roughness value is not greater than Ra0.4um. In order to improve the surface hardness and wear resistance of the sphere, the surface of the sphere should be hardened.

4. The sealing valve seat can be made of plastic, and should ensure a tight fit, without damaging the sealing surface of the sphere. At the same time, the material should have sufficient strength to withstand high sealing specific pressure. PTFE is one of the most commonly used materials for valve seats.

                              

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