The shapes of the valve closure member and valve flow path endow the valve with specific flow characteristics. This must be taken into consideration during valve selection.

Valves for Cutting‑off and Connecting Media
Valves with low flow resistance and straight‑through flow paths are generally preferred. Typical types include gate valves, globe valves and plunger valves. Downward‑closing valves have tortuous flow passages and higher flow resistance than other valves, so they are less commonly selected. Nevertheless, closing‑type valves may also be adopted where higher flow resistance is acceptable.
Valves for Flow Control
Valves that facilitate easy flow regulation are normally selected, such as control valves, throttle valves and plunger valves. Their seat size is in direct proportion to the stroke of the closure member. Rotary‑type valves (e.g. plug valves, ball valves, butterfly valves) and flexible‑body valves (pinch valves, diaphragm valves) can also be used for throttling control, yet they are generally applicable only within a limited range of valve nominal diameters. In most practical cases, globe valves with modified disc profiles are used for throttling purposes.
It should be noted that throttling by adjusting the opening height of gate valves or ordinary globe valves is highly inadvisable. Under throttling conditions, the medium flows at high velocity in the pipeline, which easily erodes and wears the sealing surfaces and results in loss of shut‑off sealing performance. Similarly, it is unreasonable to use throttle valves as shut‑off devices.
Valves for Flow Diversion and Switching
For flow diversion and switching requirements, valves with three or more ports are required. Plug valves and ball valves are suitable options and widely adopted for most diversion‑switching applications. Under certain circumstances, two or more valves of other types can be properly interconnected to realize medium diversion and switching.
Valves for Media Containing Suspended Particles
For media carrying suspended particles, valves whose closure member slides along the sealing surface with a wiping effect are most suitable, for example, flat‑plate gate valves.