With a BUTTERFLY VALVESof the type just described, it is desirable to provide features that will optimize the sealing effectiveness of the valve, yet minimize certain disadvantages apparent in prior art Butterfly Valves. For example, it is advantageous for a butterfly valve to provide a tight seal regardless of the direction of fluid flow, and continue to do so despite continuous reversal of pressure differentials across the valve. Further, pressure up to and including the full valve pressure rating should be appliable from either direction without leakage across the valve.

Butterfly valves are frequently subjected to a wide range of temperatures, both from the ambient environment in which they operate and from the flowing media being controlled. Further, the temperature will frequently cycle over a relatively wide range and it is advantageous for a butterfly valve to withstand these temperature variations without adverse effects on its sealing capabilities.

When a butterfly valve is installed for operation, it is generally bolted between pipe flanges on the fluid supply pipes. Gaskets are provided between each flange and the flange-facing side of the valve body. When the bolts are tightened, the above mentioned valve insert is compressed flush with the face of the valve body, thereby compressing the portion of the annular seat that is gripped in the recess formed between insert and body. This compression of a portion of the seat can cause distortions in the seat configuration that adversely affect the sealing contact between seat and disc edge if the disc is not fully closed during installation and can increase the force necessary to overcome the torque of the valve during opening and closing of the valve. Accordingly, it is advantageous for a Butterfly Valves to have a seat that is insensitive to disc position upon installation and to have torque and sealing characteristics that are not affected by flange and gasket compression.

MORE NEWS