Layer responsibilities

• PLC handles equipment logic, interlocks, alarms and permissives.
• HMI supports local operation, manual controls and operator actions.
• SCADA supports wider monitoring, trends, reports and supervision.

Good practice

• Keep critical logic in the PLC.
• Keep HMI screens close to the process flow.
• Use SCADA for visibility, not as a replacement for control logic.

Practical review checklist

• Confirm the note against the actual process sequence, not only the electrical drawing.
• Check that the operator screen, alarm text and field device tag use the same naming logic.
• Verify that manual operation, automatic operation and maintenance access are all covered.
• Record any commissioning observation that changes a setpoint, interlock or operator instruction.
• Keep the final note short enough for the operation team to use during startup and troubleshooting.

How ECCT applies this on projects

ECCT uses this type of engineering note as a bridge between panel wiring, PLC logic, HMI screens and site commissioning. The goal is to make every control decision traceable from the process requirement to the operator action.

• Panel details are reviewed together with I/O and field signal requirements.
• PLC/HMI behavior is checked against real startup, shutdown and fault scenarios.
• Commissioning notes are kept as a practical handover reference, not only as internal engineering comments.