What is safety lifecycle

Safety lifecycle

The safety lifecycle describes a safety instrumented system’s (SIS) life and the activities around it from conception through retirement (Decommissioning).

The safety lifecycle is covered in the IEC (International Electrotechnical Commission) standard, and adopted in process safety for high risk processes.

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The IEC 61511 uses the safety lifecycle as a framework and define in phases. To draw out a good safety lifecycle, another important standard is the IEC 61508; which is a functional safety standard that provides the framework for building industry-specific functional standards.

Safety lifecycle


Read AlsoWhat is Safety Instrumented System

The safety lifecycle is divided into three (3) phases:

  1. Analysis Phases: Here the situation is analysed and the safety requirement documented. It covers concept, overall scope definition, hazard and risk analysis, overall safety requirements, and safety requirements allocation.
  2. Design and implementation Phases: Here the safety requirements is translated  into a documented safety system design, using appropriate software and hardware subsystems and design methodology. It covers – Operation and maintenance planning, validation planning, installation and commissioning planning, safety-related systems: E/E/PES implementation, safety-related systems: other technology implementation, external risk reduction facilities implementation, overall installation and commissioning, and overall safety validation.
  3. Operation Phase: System is operated and maintain according to accepted procedures. It covers – Overall operation and maintenance, overall modification and retrofit, and de-commissioning.

NOTE: After the implementation/Realization phase, the system is evaluated against the required integrity and reliability specifications and modification is done if needed. This is ascertained before the operation phase.

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This trend of event is called a cycle “Safety lifecycle” because it does not terminate after decommissioning. From the flow diagram, you will notice “Hazard and risk analysis” immediately after the decommissioning, and this will take you back to the analysis phase. This is important because no system is perfect, it goes through constant review and improvement base on need.

Benefits of drawing out a good process safety lifecycle: 

  • Avoid Safety integrity function over-engineered / under-engineered.
  • Will help improved safety
  • Reduce downtime
  • Ensure cost-effective systems and maintenance processes
  • It will build compliance with safety authorities’ regulations.

Read AlsoHAZOP study | Steps to carry out a HAZOP study


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