IEC 61508

Functional Safety - Electronic Safety-Related Systems

IEC 61508 is an overarching technical safety standard developed by the International Electrochemical Commission (IEC) that covers all aspects of the safety lifecycle. Originating in the process industry, and then further developing related sub-standards for particular industries, IEC 61508 has seven parts. Parts 1-3 contain the requirements of the standard, while Parts 4-7 are guidelines and examples for development of electronic safety systems.

 

IEC 61508 is a generic functional safety standard that sets the standard for safety-related system design of hardware and software. Sector-specific standards have been released using the IEC 61508 framework, including IEC 61511 (process), IEC 61513 (nuclear) and IEC 62061 (machinery).

 

Impact

IEC 61508 covers the requirements for ensuring that systems are designed, implemented, operated and maintained to provide the required safety integrity level (SIL). Four SILs are defined according to the risks involved in the system application, with SIL4 being used to protect against the highest risks.

 

There are three major components to compliance with the standard:

 

  1. Conducting a Target Safety Integrity Level (SIL) assessment to determine what level SIL the safety system should be
  2. Designing, building and implementing the safety system
  3. Verifying that the safety system is as designed and can safely meet the target SIL

 

Typically, the process facility will conduct a Process Hazard Analysis study to assess potential risk, determine the Target SIL in one of a number of ways (Layer of Protection Analysis, Risk Matrix, Risk Graph, Hazard and Operability Analysis with SIL), design the safety system, and then verify that the built system really does correspond with the required SIL level.

 

Challenge

Determining the target SIL can be complex and time-consuming, but it is essential to get it right. Many facilities mistakenly assume that a safety system that can handle a SIL4 is inherently the safest and thus the most likely to not fail when needed. However, this can be overkill in certain situations. The higher SIL a safety system can handle, the more expensive and complex it is. In addition to viewing all potential risk and determining where more complex safety systems are needed, compliance with IEC 61508 requires looking carefully at all systems and analysing the target SIL level that best fits with that particular process.

 

The Dyadem Solution

In order to effectively comply with IEC 61508 and ensure safety systems are designed, built and implemented properly, facilities need tools that can assist in both the initial risk assessment, the target SIL and the verification of the safety system. Organizations are typically looking for a tool that:

 

  • can help in determining how good the safety system should be (target SIL);
  • can utilize multiple ways to determine that target SIL (Risk Matrix, Risk Graph, LOPA); and
  • can help them determine this in conjunction with a HAZOP

 

The Stature enterprise risk management solution has modules that can assist with all aspects of IEC 61508 and related standards. Industry-leading templates for LOPA, SIL and HAZOP can help determine what type of safety system is needed. With the addition of an FTA (Fault Tree Analysis) application, Stature can aid in SIL verification after a system has been implemented. Its Risk Assessment, Management of Change and Incident Management modules support multiple workflows that can be configured to any corporate standard and provide a global risk register of all hazards across the organization. By allowing you to view risk holistically from the start, Stature can help ensure potential risk is addressed efficiently and effectively.