IEC 61131-6:2012

Overview

IEC 61131-6:2012 is an international standard published by the International Electrotechnical Commission (IEC) that defines requirements for programmable logic controllers (PLCs) and associated peripherals used in safety-related electrical/electronic/programmable electronic (E/E/PE) systems. This standard specifies the criteria that these devices must meet to be classified as Functional Safety Programmable Logic Controllers (FS-PLCs). An FS-PLC integrates hardware and software components designed to ensure reliable and safe operation within safety systems.

This standard is essential for engineers, manufacturers, and safety professionals aiming to develop or utilize PLC systems in environments where functional safety is paramount. It supports compliance with safety integrity levels (SIL) and provides guidelines for validation, verification, maintenance, and lifecycle management of FS-PLCs.

Key Topics

• Scope and Conformance
  IEC 61131-6:2012 outlines the applicability of the standard to PLCs functioning as logic subsystems in E/E/PE safety-related systems. It defines conformance requirements ensuring that PLCs meet safety performance and functional criteria.

• Safety Lifecycle Management
  The standard details the FS-PLC safety lifecycle covering design, development, validation, and operational phases. It emphasizes objectives such as managing safety requirements, data security, and quality management systems throughout the lifecycle.

• Design and Architecture Requirements
  It specifies detailed requirements for hardware (HW) and software (SW) design including failure rates, fault classifications, and architecture of FS-PLCs and their subsystems. The document includes design validation tools and methods such as fault insertion testing and safety validation plans.

• Hardware and Software Development
  The standard mandates rigorous planning, development, and validation processes for both hardware and embedded software components. It addresses systematic and random failures, test procedures for climatic, mechanical, and electromagnetic compatibility (EMC) conditions.

• Verification and Validation
  A comprehensive suite of verification and validation procedures is prescribed, including type testing, fault insertion tests, EMC compliance tests, and assessment of safety integrity performance.

• Maintenance and Modification Procedures
  Guidelines for FS-PLC operation, maintenance, and modification ensure continued compliance to safety requirements during the product lifecycle.

• Safety Information for Users
  Manufacturers must provide detailed documentation such as safety manuals, conformance evidence, and catalogues that guide users in the safe application of the FS-PLC.

Applications

IEC 61131-6:2012 is critically applied in industries where programmable controllers are integral to safety-related control systems. These include:

• Industrial Automation
  Ensuring FS-PLCs meet safety integrity standards in manufacturing lines, robotic controls, and process automation.

• Energy and Power Plants
  Protecting critical infrastructure with safety-certified PLCs managing emergency shutdowns and control logic.

• Transportation Systems
  Application in signaling and control systems where fault-tolerant controllers are essential for passenger and operational safety.

• Chemical and Petrochemical Plants
  Utilizing FS-PLCs to monitor and control hazardous operations, minimizing risks of system failures leading to loss or injury.

• Building Automation and Safety Systems
  Integration in fire detection, evacuation controls, and access security systems requiring certified functional safety.

Related Standards

IEC 61131-6:2012 is part of the broader IEC 61131 series and integrates with other functional safety standards, including:

• IEC 61508 - Functional safety of electrical/electronic/programmable electronic safety-related systems; serves as the fundamental reference for SIL definitions and lifecycle processes.

• IEC 61131-3 - Programming languages for PLCs; defining programming models complementary to the hardware and safety requirements of IEC 61131-6.

• IEC 61511 - Functional safety for the process industry sector, which often employs FS-PLCs complying with IEC 61131-6.

• ISO 13849 and IEC 62061 - Safety of machinery standards that align with FS-PLC functionalities in machine automation contexts.

Integrating IEC 61131-6 with these standards ensures comprehensive safety management, consistent risk reduction, and compliance in control system engineering.

Keywords: IEC 61131-6, functional safety, programmable logic controller, FS-PLC, safety-related systems, hardware design, software validation, SIL, safety lifecycle, verification, validation, safety standards, E/E/PE systems.