Use this Control Valve Symbols Legend CAD reference when preparing or reviewing P&ID drawings and process schematics. The DWG groups valve bodies, actuation methods, positioners, and fail-action notation in one reusable reference resource.
For drafting teams, the legend provides a practical bridge between a CAD symbol library and the project drawing convention. Always compare the symbols with the applicable project legend and drawing notes before issuing design or construction documents.
This Control Valve Symbols Legend CAD sheet helps standardize valve notation on P&ID and process schematics. It covers common control valve bodies, actuator types, and fail-action symbols so reviewers, operators, and contractors can interpret your drawings quickly and consistently.
Symbols included (typical)
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Control valve (generic)
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Globe control valve
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Diaphragm control valve
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Butterfly control valve
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Angle control valve (common variants)
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Three-way control valve
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Deluge control valve
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Wing valve
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Double Block & Bleed (DBB) valve
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Float valve
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Self-contained pressure regulator
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Back pressure regulator
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Motor operated valve (MOV)
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Hand control valve (without motor)
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Cylinder / piston actuator and actuated valve types
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Control valve with positioner
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Fail action symbols: Fail Close (FC) and Fail Open (FO)
Why this legend is useful
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Keeps valve symbols consistent across multiple P&ID sheets
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Reduces miscommunication between design, construction, and operations
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Speeds up drafting by reusing a clean symbol set
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Improves QA/QC because fail-action and actuation are clearly shown
How to read the control valve legend
The symbol normally communicates several related items: the valve body arrangement, the actuator or operator, any positioner, and the intended fail action. Reading these elements together is more reliable than identifying a valve from its body symbol alone.
Valve body and service function
- Generic, globe, diaphragm, butterfly, and angle symbols: identify common control-valve body arrangements used on process drawings.
- Three-way control valve: indicates a valve with three connected flow paths. The drawing and line connections should be checked to determine whether the service uses mixing or diverting behavior.
- Special-purpose symbols: deluge, wing, double block and bleed, float, self-contained pressure regulator, and back pressure regulator symbols should be read with the associated line, equipment, and control notes.
Actuation, position indication, and fail action
- MOV and hand control valve: distinguish motor-operated control from manual operation without a motor.
- Cylinder or piston actuator: identifies an actuated valve arrangement; the associated instrument and project notes provide the operating context.
- Positioner: shows that a position-control device is included with the valve representation.
- FO and FC: Fail Open and Fail Close identify the intended valve response when the specified actuating condition is lost. Confirm whether the project defines that condition as loss of air, power, signal, or another initiating event.
Drafting and review tips
- Use one approved symbol convention across related P&ID sheets.
- Check the valve tag, line number, actuator annotation, and instrument connection against the symbol.
- Do not infer process safety, isolation capability, or control performance from the symbol alone; verify the design basis and valve specification.
- Keep the DWG with the project’s other P&ID symbols, piping terminology, and CAD/DWG reference resources for easier review and reuse.
Frequently asked questions
What does FO mean on a control valve symbol?
FO means Fail Open. It indicates the intended valve position associated with the defined failure condition. The project documentation should identify the initiating failure condition and confirm the final design.
What does FC mean on a control valve symbol?
FC means Fail Close. It indicates that the valve is intended to move toward the closed position under the defined failure condition. The actuator, accessories, and control philosophy should be checked before relying on the notation.
What does a three-way control valve symbol show?
A three-way symbol represents a control valve with three flow connections. Its actual mixing or diverting role is determined by the connected piping, flow arrows, valve details, and project control narrative.
Can this DWG replace the project P&ID legend?
No. It is a reusable CAD reference and should be coordinated with the project’s approved symbol legend, drafting standards, valve schedule, and instrument documentation before use.
Why are actuators and positioners shown separately?
They communicate different parts of the valve assembly. The body identifies the valve arrangement, while the actuator identifies how it is operated and the positioner indicates an associated positioning function.