The stop valve is a mandatory sealing valve. When the valve is closed, pressure must be applied to the disc to force the sealing surface not to leak. When the medium enters the valve from below the disc, the resistance that the operating force needs to overcome is the frictional force of the valve stem and the packing and the thrust generated by the pressure of the medium. The force to close the valve is greater than the force to open the valve, so the valve stem The diameter of the valve must be large, otherwise the valve stem will bend failure
