1. Valves used to cut off and open the medium.
The flow path is a straight-through vacuum valve with low flow path resistance. It is usually used as a shut-off and open medium valve. The downward closing valve (stop valve, plunger valve) is seldom selected because of the bending of the flow path and the resistance of the flow path being higher than other valves. In the case of allowing high flow resistance, a closed valve can be selected.
2. Valves used to control flow.
Usually choose a valve that is easy to adjust the flow rate as the control flow rate. A downward closing valve (such as a stop valve) is suitable for this purpose because its seat size is proportional to the stroke of the closing part. Rotary valves (cock valves, butterfly valves, ball valves) and flex valves (pinch valves, diaphragm valves) can also be used for throttling control, but they are usually only suitable for a limited valve diameter range. The gate valve uses a disc gate to cut the circular valve seat transversely, and the flow can be better controlled only when it is close to the closed position, so it is usually not used for flow control.
3. Reversing diverter valve.
According to the needs of reversing and shunting, this kind of valve can have three or more channels. Plug valves and ball valves are more suitable for this purpose. Therefore, most of the valves used for reversing and splitting choose one of these valves. However, in some cases, as long as two or more valves are connected to each other, other types of valves can also be used for reversing and shunting.
4. Medium valve with suspended particles.
When the medium contains suspended particles, it is suitable to use a valve with a wiping effect when the closing part slides along the sealing surface. If the back and forth movement of the closing member to the valve seat is vertical, the end may clamp particles, so this valve is only suitable for basic cleaning media unless the sealing surface material allows particles to be embedded. Ball valves and plug valves wipe the sealing surface during opening and closing, so they are suitable for media containing suspended particles.