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What is fixed ball valve?

1. Fixed ball valve ,ball body:

The most important feature of the fixed ball valve is that the ball does not deviate from the center of rotation of the ball during the switching process.

Three types of structure:

①As shown in the figure, the upper part of the ball has a shaft shank, and the lower part is a shaft hole for a fixed shaft to be inserted, the structure of the ball is a shaft and a hole structure.

② As shown in figures (a) and (b), the sphere is two upper and lower shaft holes, respectively inserted by the upper and lower shafts. The structure shown in figure (a) is suitable for small diameter, the insertion depth of the shaft hole in the sphere is short and can only withstand a small-medium force, the structure shown in figure (b) is suitable for large diameter and can withstand a larger medium force, and the support journal and drive shaft are separated, the drive shaft only withstands the action of torque.

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③ As shown in Figure (c), the ball is two outreach shafts, vertical upper and lower two support plates, the media force through the journal and support plate

transferred to the valve body, and again, the drive shaft is only subjected to a single torque action, separating the medium force and the operating torque.

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2. Fixed ball valve,valve body:

Since the valve body is a forged simplified form, there is no usual valve neck, the valve neck is replaced by a stuffing box, the stuffing box body is bolted to the platform of the valve body, the shaft seal is an O-shaped rubber ring, the external connection with the actuator support plate, also through the body of the stuffing box, fixed on the valve body, it can be seen that this cylindrical structure valve body, in the journal part, the strength of the valve body is greatly weakened.

As for the structure of the valve body, like the floating ball valve, there are two types of side-mounted and top-mounted.

The side-mounted type can be divided into a two-part structure with one main body and one sub-body, or a three-part structure with one main body and two sub-bodies.

The top-mounted valve body is an integral structure, the upper valve cover is bolted to the valve body to form a complete pressure boundary, the ball is a ball with upper and lower support shafts, the lower support bearing is embedded in the valve body, the upper support bearing is placed in the valve cover, the upper shaft end is machined with a groove connected to the flange of the shaft head, which is used to transfer torque, the medium force acts on the bearing, the drive shaft only transfers torque, and is designed to prevent blow-out structure, the valve seat The design of the valve seat is difficult to assemble or disassemble, that is, when the ball is installed in the valve cavity seat to move to both sides This is designed to slide the back of the seat, the seat in advance to shrink the left and right channels, to be loaded into the ball, through the flange on the back valve, the seat pushed to the center of the ball, and then with a ring, stuck in the groove of the back of the seat, disassembly, then remove the ring, and then the seat pushed into the left and right channels of the valve cavity, the ball can be removed from the upper. Therefore, the top-mounted structure ball has the advantage of online maintenance.

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3.Temperature rating:

As with floating ball valves, the body material has a pressure-temperature rating in use, which is given by the standard ANSI B16.34. In addition, different seal materials, set in metal seats, also have a pressure-temperature rating. This is because the pressure-temperature rating of the seal material in use is related not only to pressure and temperature, but also to the passage diameter and inlay or construction of the seal material. So this value is different from the floating ball ball valve, and the data provided by each manufacturer is not the same. Should be provided by the valve manufacturer. The chart below shows the pressure-temperature ratings for the valve body and seal material.


4.Range of Application:

Floating ball valves are available in Class 600 and below, with a passage diameter of NPS8 or less. The range of application of fixed ball valves is not so controlled because the ratio of the seal material on the seat can be controlled in the design, and therefore it is suitable for all sizes up to Class 2500 and through diameters up to NPS 60.

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