Valves offset butterfly

There are many different types of valves used in safety instrumented functions. Typical valve t)rpes include ball, butterfly, offset butterfly, gate, globe and other special designs that are not readily categorized into the standard design groups. 

A high-performance butterfly valve has a disc that is offset from the shaft centerline. This eccentricity causes the seating surface to move away from the seal once the disc is out of the closed position, reducing friction and seal wear. It is also known as an eccentric disc valve the advantage of the butterfly valve is improved shutoff while maintaining... 

The high performance butterfly valve operates like aU butterfly valves with a disk mounted in the middle of the valve that is rotated to open and close the valve. The high performance butterfly is designed with a more complex disk assembly often called "double offset." The first offset is done by locating the stem downstream of the centerline of the disk. This allows an unobstructed 360-degree sealing surface. The second offset moves the stem off the vertical axis of the disk. The combination moves the disk quickly away from the seat as the stem is rotated. This is done to reduce operating torque and extend seat life. 

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