What is IEC 61508 and 61511 ?

IEC 61508 and IEC 61511 are two important international standards related to functional safety in the process industries. These standards provide guidelines and requirements for the development and implementation of safety instrumented systems (SIS) to prevent hazardous incidents. In this article, we will explore what IEC 61508 and IEC 61511 entail and how they ensure safety in industrial processes.

IEC 61508 is an international standard that provides requirements and guidelines for the management of safety requirements throughout the entire lifecycle of a safety instrumented system (SIS). It follows a goal-based approach and defines Safety Integrity Levels (SILs) to assess the reliability and dependability of overall safety functions. The SIL levels are determined based on the desired risk reduction measures and the probability of hazardous events occurring. IEC 61508 emphasizes the systematic management of safety requirements throughout the entire lifecycle, including specification, design, integration, operation, maintenance, and decommissioning phases.

IEC 61511 is an international standard that provides requirements and guidelines for the management of functional safety requirements throughout the entire lifecycle of a safety instrumented system (SIS). It follows a performance-based approach and evaluates the safety of a control system by analyzing the performance of safety-related parts and components, such as sensors, logic devices, and actuators. The standard provides guidelines for determining the required Performance Level (PL) based on the severity of potential injuries, the frequency and duration of exposure to hazards, and the possibility of avoiding or limiting harm.

In conclusion, while both ISO 13849 and IEC 61508 serve the purpose of ensuring safety in industrial settings, they differ in terms of scope and approach. ISO 13849 targets safety-related parts within machinery, employing a performance-based approach to manage risks. On the other hand, IEC 61508 has a broader application range beyond machinery and adopts a goal-based approach for assessing overall system integrity. Understanding these differences is crucial for professionals involved in the design, implementation, and maintenance of safety systems to choose the appropriate standard for their specific needs.