IEC PAS 63131:2017

Overview

IEC PAS 63131:2017 - System control diagram (SCD) is a publicly available pre-standard from the IEC that defines a structured set of operational control functions (objects) and a logical diagramming method called the System Control Diagram (SCD) for the continuous control process industry (for example, oil & gas). The PAS was developed to enable efficient engineering, implementation, commissioning and reuse of control applications across different control system suppliers. It also supports machine-readable, data-transfer friendly logical representations and documents sequence logic and its interaction with control objects.

Key topics and technical requirements

• SCD approach and framework: Conceptual definition, lifecycle considerations, basic design and application design for process control systems.
• Function templates: Standardized control templates and terminal codes for reuse (examples in the document include CA - PID controller, CS - step control, MA/MAS - analogue monitoring/acquisition, MB - binary monitoring, QA - totalizer, SBE/SBV - equipment control, and sequence logic templates).
• SCD drawing standard: Rules for layout, symbols, tagging, signal/process lines, layers, colors, legends and title blocks to ensure consistent, readable diagrams.
• Terminal and tagging conventions: Standard terminal codes and signal-type classifications to enable unambiguous data exchange and mapping between diagrams and control system implementations.
• Sequence documentation: Method to document sequences (sequential function charts) and interaction with control objects.
• Alarm management and HMI considerations: Guidance on alarm presentation and positive-logic conventions for operator interfaces.
• Project execution & commissioning: Informative guidance on project implementation, verification, commissioning procedures and operational modification handling.

Practical applications and who uses it

IEC PAS 63131 is intended for organizations and roles involved in process automation and control engineering, including:

• Process control engineers and automation designers who create control logic and SCDs.
• System integrators and control system suppliers seeking interoperable, reusable control applications.
• Commissioning engineers and project managers implementing and validating control systems.
• HMI/SCADA designers and alarm managers aligning operator displays with standardized logic.
• Plant operators and safety engineers needing clear documentation of sequences and safety interfaces.

Typical uses:

• Creating standardized SCDs that map P&ID/D&ID information into logic-ready diagrams.
• Reusing function templates to reduce engineering time and vendor lock-in.
• Enabling data transfer between engineering tools and different control platforms.
• Documenting sequence interactions, alarm behavior and safety system interfaces.

Related standards

• IEC PAS 63131 complements other IEC publications on automation and control system documentation and should be used alongside applicable IEC process-control standards and organizational drawing conventions. See IEC webstore and Electropedia for related IEC documents and terminology.