Control valve symbol
Also called Pneumatic control valve, Diaphragm actuated valve
A control valve changes its opening continuously to hold a process variable such as flow, pressure, level or temperature at its set point, on a signal from a controller.
What the control valve symbol means
A control valve changes its opening continuously to hold a process variable such as flow, pressure, level or temperature at its set point, on a signal from a controller.
How it is drawn
A valve body with a stem rising to a dome, the pneumatic diaphragm actuator. The tag bubble beside it carries the loop: FV, PV, LV or TV and the loop number.
Variants
- Fail open (FO) or fail closed (FC) marked under the valve
- Positioner shown as a box on the stem
The control valve symbol in each standard
Drawn as ISA 5.1 defines it, as on most US and international legends.
Valve, control type, continuously operated. ISO shows modulation with a diagonal arrow through the body. It draws no actuator: how the valve is moved and controlled is shown with the instrumentation, usually to IEC 62424.
ISO SVG
German (DIN): Stellventil. See DIN P&ID symbols.
Where you see it on a P&ID
In every control loop on the P&ID, usually with block valves either side and a globe-valve bypass.
Tag codes
The control valve is commonly tagged:
- FV
- PV
- LV
- TV
- HV
Tag formats follow the project numbering procedure. For instruments, the letters follow ISA 5.1, explained on the instrument symbols page.
Related symbols
Frequently asked questions
What does the control valve symbol look like on a P&ID?
A valve body with a stem rising to a dome, the pneumatic diaphragm actuator. The tag bubble beside it carries the loop: FV, PV, LV or TV and the loop number.
What is a control valve used for?
A control valve changes its opening continuously to hold a process variable such as flow, pressure, level or temperature at its set point, on a signal from a controller. You will find it in every control loop on the P&ID, usually with block valves either side and a globe-valve bypass.
What tag does a control valve have?
It is commonly tagged FV, PV, LV, TV, HV. The exact tag format comes from the project numbering procedure and the legend sheets.
Is the control valve symbol the same in ISA and ISO?
No. ISO shows modulation with a diagonal arrow through the body. It draws no actuator: how the valve is moved and controlled is shown with the instrumentation, usually to IEC 62424. The ISO 10628-2 registration number is X8087. Always check the legend sheets at the front of the P&ID set.
What is the control valve called in German?
Stellventil. On a German R&I-Fließschema it is drawn to DIN EN ISO 10628-2.
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