Flow characteristic of control valve

Flow characteristic of control valves are normally called according to “percentage of flow vs percentage of stroke”.
When the valve stem moves, such as 50% down, aka 50%Stroke, not necessary mean that the flow is 50% of it maximum flow. The output flow is according to it’s characteristic.

There are three main types of flow characteristics:

1. Linear
2. Non-linear, quick opening (aka quick opening)
3. Non-linear, equal percentage (aka equal percentage)

Flow characteristic and it’s application of various type of valves:

1. Butterfly valve:
   • Quick opening
   • Shu-off (or service) application
2. Ball valve:
   • Varies, according to it’s design
   • Shut-off (quick opening), Modulate (equal percentage)
3. Globe valve:
   • Varies, according to it’s design, usually modulate application
   • Modulate (equal percentage) –> chilled water control valve

Related notes:

Chilled water cooling coil characteristic