These types of valves are used for opening and closing. They are commonly installed at the inlet and outlet of cold and heat sources, equipment inlet and outlet, and pipeline branches (including risers). They can also be used as drain valves and vent valves. Common shut-off valves include gate valves, globe valves, ball valves, and butterfly valves.
Gate valves can be classified as rising stem or non-rising stem, single gate or double gate, wedge gate or parallel gate, etc. Gate valves have poor sealing tightness, and large-diameter gate valves are difficult to open; the valve body size is small along the water flow direction, resulting in low flow resistance, and the nominal diameter range of gate valves is large.
Globe valves are classified into three types according to the medium flow direction: straight-through, right-angle, and direct-flow, and are further divided into rising stem and non-rising stem types. Globe valves have better sealing tightness than gate valves, but the valve body is longer, resulting in higher flow resistance. The maximum nominal diameter is DN200.
The valve core of a ball valve is an orifice ball. Moving the valve stem so that the orifice of the ball is directly aligned with the pipeline axis results in a fully open valve; rotating it 90° results in a fully closed valve. Ball valves offer some regulating capability and provide a tighter seal when closed.
Butterfly valves have a circular valve core that rotates along a vertical axis perpendicular to the pipe axis. When the valve core plane is aligned with the pipe axis, it is fully open; when the valve core plane is perpendicular to the pipe axis, it is fully closed. Butterfly valves have a shorter valve body and lower flow resistance, but are more expensive than gate valves and globe valves.
