The valve is mainly composed of valve body, valve disc, sealing ring, valve stem, bracket, valve gland, hand wheel, flange, nut, positioning screw and other parts. See the figure below for details. When the hand wheel rotates clockwise, the valve is closed and the valve stem moves upward. This valve is an upward expansion type; when the hand wheel rotates clockwise, the valve is closed and the valve stem moves downward. This valve is a downward expansion type.