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Fixed Ball Valve And Floating Ball Valve Sealing Principle
- Oct 23, 2017 -

Fixed ball valve is mainly used in high pressure large diameter ball valve. According to the installation of the valve seat seal, the fixed ball valve has a ball before the seal seat and the ball after the sealed seat two structures. Seal the front of the ball seal principle: and the valve into a whole sphere can be in the upper and lower sliding bearings or rolling bearings in the free rotation, the valve seat seal is installed in the active sleeve, the sleeve in the valve body with 0 Ring seal. The seat seal is pre-pressed by a set of springs mounted in the sleeve. The inlet end of the valve seat, when the ball valve is closed, by acting on the inlet end diameter d and with the valve body with the sleeve diameter D. Of the circumference of the ring surface of the medium pressure on the valve seat pressure to the ball, which played the role of inlet seal, the outlet side of the valve seat can not afford to seal. When the reverse pressure, the role of the seat will change.

 Floating ball valve body has two valve seat seals, between them clamping a sphere, the ball has a through hole, the diameter of the hole is equal to the diameter of the pipeline, said the whole diameter ball valve; through the hole diameter is slightly smaller than the pipe Inner diameter, said reduced diameter ball valve. The ball is free to rotate in the valve seat seal by means of the valve stem. In the open, the ball hole and pipe diameter aligned to ensure that the pipeline working medium resistance to the smallest. When the stem turns 1/4 turn, the ball hole is perpendicular to the channel of the valve, and the ball is tightly pressed against the valve seat seal on the outlet side by the preload and media pressure applied to the two valve seat seals to ensure that the valve Completely sealed. This ball valve is a single-sided forced seal. Floating ball valve should also focus on whether the seat material can withstand the load of the ball, because the ball in addition to its own weight but also bear the full load of the working medium and pass to the seat. In addition, also consider the large diameter of the float valve in the operation requires a greater force.

In order to ensure the sealing and reliability of the floating ball valve, there shall be a high enough seal pressure on the surface of the ball and the seat, but shall not exceed the allowable pressure of the valve seat material. The fit of the valve seat in the groove should be tight, otherwise the media will leak along the end of the groove even if the seat is well sealed against the ball. The sphere should have the correct geometry and low surface roughness values. Usually the h6 or h7 precision manufacturing sphere, the surface roughness value is not greater than R.0.4, in order to improve the surface hardness and wear resistance of the sphere, the surface of the sphere should be hardened. Sealed seat can be made of plastic, and should ensure that close fit, shall not damage the ball sealing surface. At the same time, the material should be of sufficient strength to withstand high sealing pressure. Polytetrafluoroethylene is one of the most commonly used materials for the manufacture of seats.