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What is the design of trunnion mounted ball valve

Author:Site Editor     Publish Time: 2018-11-06      Origin:Site

The trunnion mounted ball valve body consists of a main valve body, two left and right sub-valves. The ball is a ball with a journal at the upper end and a shaft hole at the lower end. The upper part of the valve body has a stuffing box and is connected to the spherical journal. There is a sliding bearing, the shaft has a shaft hole at the lower end, and a sliding shaft bearing sleeve is arranged. What is the design of trunnion mounted ball valve?

 

A bearing at the bottom of the valve body is inserted into the shaft hole of the lower end of the ball. This way the ball is held on the center line of the swivel and there is no offset when it is rotated. The ball has two floating seat assemblies symmetrically on both sides. This seat assembly consists of a metal race, a PTFE seal ring embedded in the race, a rubber O-ring on the outer edge and a back coil spring. When the valves are closed, the medium force acts on the components of the seal seat, causing the valve seat to contact the ball, creating contact stress and obtaining an effective seal. The stem and packing housing are sealed by a braided rubber ring.

 

The structure of the trunnion ball valve is much more complicated than that of the floating ball valve. The principle is that the medium pressure pushes the valve seat assembly to act on the ball to generate the contact stress to obtain the seal. The center axis of the ball rotation does not shift, and the components of the valve seat are floating. So it is called a trunnion type ball-floating seat structure. 


Since the medium force acts on a ring-shaped area, the medium thrust is much smaller than the force of the floating ball valve medium, so the trunnion mounted ball valve structure is suitable for high-pressure large-diameter, and its applicable range pressure level is Classl50~2500, valve diameter For NPS 2~60. For the structure using PTFE, reinforced PTFE, nylon, PEEK and other polymer materials as the sealing ring, the design must still meet the sealing specific pressure q greater than the required sealing specific pressure qb, which is smaller than the allowable specific pressure of the material.

 

Trunnion mounted ball valve design principle is double seal seat

The design of the double-sealed valve seat can be double-sealed by adjusting the relative position of the sealing ring and the 0-shaped rubber sealing ring, or changing the size of the sealing seat tail, which is also called "double piston effect".

 

When the pressure at the inlet end is higher than the pressure in the valve chamber, the pressure of the medium acting on the inlet valve seat forms a pressure difference. The pressure difference multiplied by the annular area F=0.785 is the sealing force of the valve seat. Push the valve seat to seal the ball valve and cut off the media at the inlet end.

 

When the pressure at the outlet end valve seat in the valve chamber is greater than the pressure at the outlet end, the pressure of the medium acting on the outlet end valve seat forms a pressure difference Af, which is multiplied by the annular area F=0.785 (*2—A2). The force acting on the outlet end seat also pushes the valve seat to seal the ball valve, and the pressure of the cut-off chamber flows toward the outlet end, that is, the front stage seal is also sealed.

 

The two seat seats of the double-sealed valve seat have the function of cutting off the fluid in both the positive and negative directions, which is called the isolated valve seat, and the self-discharge valve seat design is a one-way seal for the valve seat itself.


The above is the design of trunnion type ball valve. We are a manufacturer of trunnion mounted ball valve and ball valve related products. If you are interested, you can consult us on the official website.

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