Resilient butterfly valve

A resilient butterfly valve offers low cost and low weight. A disk is moimted on a one or two-piece shaft that rotates the disk parallel with the pipe when the valve is open or perpendicular to the pipe when the valve is closed. When the valve is open the disk does provide an obstruction to the flow. 

The seats are typically elastomer which is sometimes reinforced with plastic or phenolic backings. They are often available with plastic coating of disks and seats for chemical resistance. Resilient butterfly valves are typically available for lower pressures (up to 250 psig). 

Resilient Butterfly Valve, clean service Open to trip 63.6%... 

Butterfly Valves These valves (Fig. 10-155) occupy less space in the line than any other valves. Relatively tight sealing without excessive operating torque and seat wear is accomphshed by a variety of methods, such as resilient seats, piston rings on the disk, and inclining the stem to limit contact between the portions of disk closest to the stem and the body seat to a few degrees of curvature. 

Chemical compatibility is another important factor to reckon with in material selection as in the case of butterfly valves which are frequently used in industrial fluid flow systems where the valves are operated to load and unload different kinds of fluids for shipment or storage. These applications include tank trailers for transportation of fluids from one location to another as well as fluid flow pipelines. A typical butterfly valve usually incorporates a resilient rubber seal component which the valve pivots to seal off the flow lines and when opened allows the fluid to be conveyed to the flow line. The chemicals transported in tanks using butterfly valves are often caustic or acidic. These chemicals corrode the pivot area of the valve making its function ineffective. The rubber gasket material prevents leakage while the valve chamber is protected by a chemically resistant rubber material. 

For cooling tower water lines butterfly valves with a resilient rubber lining which serves as both the seat and the flange gasket have proved to be very economical. These valves will fit between a standard 125-poimd or 150-pound flange. They are limited to 180° F and 150 psi applications but give good service in 8-inch and 10-inch valve sizes. 

The butterfly valve has a disk-shaped element that rotates about a central shaft or stem. When the valve is closed, the disk face is across the pipe and blocks the flow. Depending upon the type of butterfly valve, the seat may consist of a bonded resilient liner, a mechanically fastened resilient liner, an insert-type reinforced resilient liner, or an integral metal seat with an O-ring inserted around the edge of the disk. 

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