When the manual ventilation butterfly valve is in full open position, the thickness of the manual ventilation butterfly plate is the only resistance when the medium flows through the valve body, so the pressure drop generated by the valve is very small, so it has better flow control characteristics. Butterfly valve has elastic seal and metal seal. Elastic sealing valve, sealing ring can be embedded in the valve body or attached to the butterfly plate.
Manual ventilation butterfly valves with metal seals generally have longer service life than those with elastic seals, but it is difficult to achieve complete sealing. Metal seal can adapt to higher working temperature, while elastic seal has the defect of temperature limitation.
A more advanced butterfly valve is a three-eccentric metal hard-sealed butterfly valve. The valve body and seat are connected components. The sealing surface layer of the valve seat is surfacing welded with heat-resistant and corrosion-resistant alloy materials. The multi-layer soft overlapping seal ring is fixed on the valve plate. Compared with the traditional butterfly valve, the butterfly valve has the advantages of high temperature resistance, light operation, no friction in opening and closing. When closing, the seal is compensated with the increase of the torque of the transmission mechanism, which improves the sealing performance and prolongs the service life of the butterfly valve.