(1) Valves for shutting off and connecting the medium
Usually choose a valve with a small flow resistance and a straight-through flow channel. Such valves include gate valves, globe valves, and plunger valves. The downward closed valve is less used because of the tortuous flow path and higher flow resistance than other valves. However, closed valves can also be used where higher flow resistance is allowed.

(2) Valve for flow control
Usually choose a valve that is easy to adjust the flow. Such as regulating valve, throttle valve, plunger valve, because its valve seat size is proportional to the stroke of the opener. Rotary (such as plug valves, ball valves, butterfly valves) and flexible (pinch valves, diaphragm valves) valves can also be used for throttling control, but usually only within a limited range of valve sizes. In most cases, people usually change the shape of the valve disc of the globe valve for throttling. It should be pointed out that it is extremely unreasonable to change the opening height of the gate valve or globe valve to achieve the throttling effect. Because the medium in the pipeline is in a throttled state, the flow rate is high, the sealing surface is easily washed and worn, and the cutting and sealing effect is lost. Similarly, it is unreasonable to use the throttle valve as the cutting device.

(3) Valve for reversing and diverting flow
According to the needs of reversing and diverting, this valve can have two or more channels, which is suitable for selecting plug valves and ball valves. Most of the Foot Valve used for reversing and diverting are selected for this type of valve. In some cases, other types of valves, properly interconnected with two or more valves, can also be used for reversing the flow of the medium.

(4) Valves for media with suspended particles
If the medium contains suspended particles, it is most suitable to use a valve whose opening and closing member slides along the sealing surface with a wiping effect, such as a flat gate valve.