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Concentric butterfly valves
Butterfly valve is also part of the quarter turn valve family. What makes butterfly valve distinct from the other valves is the flat to a concave disc that attaches to the valve stem. Positioned in the middle of the valve with the stem bored into it or attached at one side, the disc blocks media flow when the valve is closed. The stem adds support to the disc. This design allows butterfly valve to throttle when there is incremental opening of the valve.