The shut-off valve is designed for low inlet and high outlet, with the aim of reducing flow resistance and saving effort when opening the valve. When the valve is closed at the same time, the gasket between the valve shell and valve cover and the packing around the valve stem are not subjected to force, and will not be subjected to medium pressure and temperature for a long time, which can extend the service life and reduce the probability of leakage. In addition, this can also replace or add packing when the valve is closed, making maintenance easier.
Of course, in addition to the common type of low inlet and high outlet, there are also some special cases where the shut-off valve is high inlet and low outlet.
It is difficult to close the valve when using low inlet and high outlet in general large caliber (8 "or above) and high-pressure conditions. If using low inlet and high outlet in high-pressure large caliber conditions, the driving torque of the valve is relatively large, approximately 1.05-1.08 times that of high inlet and low outlet. The axial force on the valve stem is large, and the valve stem is prone to deformation and bending under long-term water pressure, which affects the safety and sealing of the valve. And using high inlet and low outlet, because the medium pressure will make the valve seal tighter, there is no need for a large reaction force to ensure sealing, and the stress condition of the valve stem is improved.