Body, actuator, and live position are separate ideas
The body shape identifies the valve type or drawing convention. The actuator identifies how it is operated. Live position and command agreement belong to the control-system state model.
Fail-open and fail-closed intent is an engineering property, not a substitute for live feedback. A display should not imply current position from design intent alone.
Valve display checks
| Question | Why it matters |
|---|---|
| What does the project legend call this body? | Similar geometry can have different local conventions. |
| Is position measured or inferred? | Commanded state is not always actual state. |
| How are transition and disagreement shown? | Intermediate or failed movement can be operationally important. |
| Where is fail intent documented? | Fail action belongs in approved engineering documentation and detail context. |
Sources and boundaries
KonnectSymbols is independently developed and is not endorsed by ISA, IEC, or ISO. These educational notes do not reproduce or replace current standards, project specifications, regulations, or an approved project legend.
- ANSI/ISA-5.1-2024 Instrumentation Symbols and IdentificationInternational Society of Automation. Official publisher page for the current ISA-5.1 edition and related technical reports.
- ISO 10628-1:2014International Organization for Standardization. Official publisher page for diagrams for the chemical and petrochemical industry.