Interlock / logic diamond
ISA 5.1-2009 (binary logic)
Drawn as
A diamond with "I" (or an interlock number) inside, with signal lines in and out.
Meaning
Interlock or logic function, defined on the logic diagrams or the cause & effect chart: e.g. LAHH trips a pump and closes an ESDV. Not physical; use it to understand the shutdowns.
Variants
- The number inside refers to the logic or C&E sheet
- ISA logic gates (AND/OR) may be drawn as boxes on the P&ID
- SIS trips are often a diamond with "S" or "SIS"
Tags
I
Not physical hardware. Read it, then skip it in the 3D model.