Butterfly valve is a type of valve which can be used in a variety of chemical services. They are available with small dimensions allowing for use in areas where space is limited, and they allow a high coefficient of flow.

A butterfly valve is composed of body, soft seat or hard seat, disc, stem, packing, notched position plate, and a lever or gear. The seat is under compression when it is mounted in the valve body, thus making a seal around the periphery of the disc both upper and lower points where the stem passes through the seat. Packing is provided forming a positive seal around the stem for added protection in case the seal formed by the seat could become damaged.