The main function is to cut off the ball valve or pipe connected to the fluid channel.

Valve drive device works with the top of the stem to exert torque passed ball to make it rotate 90 °, to complete the action open or close

the valve. Valve seat sealing principle varies according to its structure, the valve seat structure commonly used floating ball valve seat

can be divided into fixed and floating valve seat fixed ball two categories.
When the fixed ball float valve seat when the ball under

pressure in the fluid flow direction is in the displacement, so that it seals with the valve seat closer contact, that is, in the sealing

surface pressure increases, the formation of single-sided sealed at the same time, the valve seat sealing surface before the pressure is

reduced, often do not ensure the seal. When the floating ball valve seat is fixed, the fluid pressure can not produce a shift in the ball,

but push the seat by means of a spring or fluid beat to the ball, the establishment than the pressure seal.
Structure
Soft seal

seat
(1) Ordinary type
Is characteristic of an ordinary seat preload or fluid pressure valve seat and ball compression, and to

produce plastic deformation of the valve seat material to achieve sealing, the sealing effect depends on the gate valve seat in fluid pressure or preload Compensation under the action of micro-ball roundness and surface roughness

of the capacity. Thus, between the valve seat and ball must be large enough to seal than the pressure.
(2) Flexible type
With

flexible seating flexible components, such as metal spring frame and springs, preload or fluid in the elastic deformation under pressure to

compensate for temperature, pressure and wear and tear and other external conditions change on the sealing performance of the sphere.
Conclusion
Valve seat and seals are a key component. Hilltop valve that seals should have good stability, low coefficient of

friction, no aging, good sealing performance. Seat should have a certain strength and stiffness, the gap is moderate, the compression

deformation. Metal seal ball valve seat should meet the high temperature, high pressure,

highly corrosive, ultra-low temperature, zero leakage, long life, fire safety and pressure wear and so on.