The inherent characteristic is measured with a constant pressure drop across the valve and is set by trim shape: linear, equal percentage or quick opening. The installed characteristic is what happens in the real piping, where pressure drop across the valve falls as flow rises. Picking the characteristic so the installed curve is close to linear gives a loop with steady gain across its range.
Quick-opening is fine on the dump valve, but TCV-210 on the reboiler needs an equal percentage flow characteristic, swap the cage.
Also heard as
- valve characteristic
- trim characteristic
Related terms
Equal percentage
Describes a valve characteristic where each equal step of travel changes flow by the same percentage of current flow.
Cv
Flow coefficient: US gallons per minute of 60 degree F water a valve passes with a 1 psi pressure drop.
Rangeability
The ratio of the largest to the smallest flow a control valve can regulate while keeping its characteristic.
Cage
A slotted or drilled sleeve around a control valve plug that guides it and shapes how flow changes with travel.