What is a shut-off valve?
A sanitary shut-off valve is a kind of mandatory sealed valve. When the valve is closed, pressure must be applied to the valve gate to ensure the sealing surface doesn’t leak. When the medium enters the valve from below the valve gate, the resistance the operating force needs to overcome is the friction between the valve stem and stuffing as well as the propulsion produced by the pressure of the medium. The force used to close the valve is bigger than the force used to open the valve, so the diameter of the valve needs to be big, otherwise, the valve stem will be bent.
There’re three types of connection methods: flange connection, threaded connection, welded connection. Since the appearance of self-sealing valves, the flow direction of the medium of shut-off valves is changed to entering from above the valve gate. In this case, under the pressure of the medium, the force used to close the valve is small while the force used to open the valve is big, so the diameter of the valve stem can be reduced accordingly. Meanwhile, under the influence of the medium, this type of valve is also more compact.
The opening and closing member of the shut-off valve is a plug-shaped sanitary valve gate. Its sealing surface is flat or sea-coned. The valve gate shuttles along the centerline of the valve seat. The movement of the valve stem includes up-and-down rotating rod type, used for controlling the flow of various fluids like air, water, steam, corrosive media, mud, oil, liquid metal and radioactive media. Thus, this type of shut-off valve is very suitable for cutting off or regulating or throttling. This type of valve is very suitable for regulating the flow because the opening and closing distance of the valve stem is relatively short and has very reliable cutting-off functions and because the change in the valve seat is proportional to the distance of the valve gate.