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The valve disc and the shape of the valve’s passage give the valve certain flow characteristics. This must be taken into account when selecting valves. 1. Valves for connecting and shutting off the medium are usually chosen to have low flow resistance and a straight-through design. Such valves include gate valves, globe valves, and plunger valves. Downward-closing valves have a higher flow resistance due to the tortuous path, so they are less commonly used compared to other types of valves. However, in situations where a higher flow resistance is acceptable, closed-type valves can also be used. 2. Valves used for controlling flow rate: It is advisable to choose valves that are easy to adjust for flow control, such as control valves, throttle valves, and plunger valves, as there is a direct proportional relationship between the size of their valve seats and the stroke of the moving parts. Rotary types (such as plug valves, ball valves, butterfly valves) and wedge-shaped body types (clamped tube valves, diaphragm valves) can also be used for throttling control, but they are typically suitable only for a limited range of valve sizes. In most cases, people usually change the shape of the valve disc of the globe valve for throttling purposes. It should be noted that using changes in the opening height of gate valves or stop valves to achieve throttling is highly unreasonable, as the flow velocity of the fluid in the pipeline under throttling conditions is very high, which can easily cause erosion and wear of the sealing surfaces, resulting in a loss of their ability to cut off flow and provide sealing. Similarly, using a throttle valve as a shut-off device is also unreasonable. 3. Valve for reversing and shunting flow: Depending on the requirements for reversing and shunting flow, such valves can have three or more channels; plug valves and ball valves are suitable choices. Most valves used for commutation and shunting are of this type. Under certain circumstances, other types of valves, when properly connected to two or more others, can also be used for reversing and diverting the flow of the medium. 4. Valves for media containing suspended particles: If the medium contains suspended particles, valves in which the closing element slides along the sealing surface while performing a wiping action, such as gate valves, are the most suitable.