The commonly used principle of ball valve seat structure

1, summarize the main functions of the ball valve is cut off or connect pipe in the fluid channel. The working principle of ball valve is help drive in applying a certain amount of torque to stem the upper sphere, make its rotating 90 & deg; , by completing the open or close the valve. Ball valve seat seal principle according to its structure, commonly used the seat structure can be divided into fixed and floating seats floating ball seat two types: a fixed sphere. When the seat fixed sphere floating ball in the direction of fluid flow under the action of a fluid pressure produce displacement, making it more closely after the valve seat seal and contact, namely in the sealing surface pressure increase, form a single seal, at the same time, before the valve seat sealing surface of the pressure decreases, often do not guarantee the seal. When the fixed seat floating ball, fluid pressure can't make a sphere to produce displacement, but the seat with the aid of a spring or fluid thrust pressure to a sphere, sealing pressure is established. 2, the structure 2. 1, soft sealing seat ( 1) Ordinary ordinary seat ( FIG. 1) Is the feature of the pre-tightening force or fluid pressure under the action of the seat and the ball pressure, and make the seat material and elastic-plastic deformation to seal, the sealing effect depends on the seat of prestressing force in the fluid pressure or compensation under the action of ball roundness and the micro roughness of the surface. The seat between the sphere and, therefore, must have a large enough sealing pressure. ( 2) Elastic resilient seated ( FIG. 2) By means of elastic element, such as metal spring and spring, prestressing force in produce elastic deformation or fluid pressure, to compensate for temperature, pressure and wear of the outside world affect the performance of ball seal conditions change. 3, in the seat and seal is the key to the ball valve components. Sealing ring should have good stability, smaller friction coefficient, not easy ageing, sealed performance is good. The seat should have a certain strength and stiffness, clearance is moderate, compressive resistance to deformation. Metal sealing seat should meet the high temperature and high pressure, strong corrosion, temperature, zero leakage, long life, fire safety, and compression wear-resisting, etc.