Steam & mining industries manufactures butterfly valves. These are designed with plate shaped disc rotated on its axis to open or close the valve as well as to control the flow. Compared with other types of valves, it is of simple construction, compact, light in weight and has less flow resistance. It is also low in cost and with quick valve operation. The seat combination is made of metal-to-metal contact, or metal-to-resin or rubber, or with a teflon or synthetic rubber ring fitted round the disc or resilient material embodied in the body seat. The valve is manually operated [lever-handle or gearing method] or by mechanical actuators [electric motor, or hydraulic-motor or cylinder, or air-cylinder, or air-diaphragm].
