Functional Safety Lifecycle

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Functional Safety Lifecycle is a sequence of steps that provide a logical path to commissioning, operation, maintenance, and, eventually, decommissioning of the EUC.

Fasi del Functional Safety Lifecycle

The standard introduces the concept of a Safety Lifecycle to ensure that all activities, actions, and tests are implemented so as to guarantee the required level of safety.

IEC 61508 indicates 16 phases, specifying for each:

  • Objectives to achieve
  • Requirements to meet
  • Purpose of each phase
  • Inputs and outputs

 

During the safety lifecycle, verification of the previous phases must be planned and carried out.

 

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Concept

Objective Develop a sufficient level of understanding of the EUC and its environment (physical, legislative, etc.) to enable successive safety lifecycle activities to be properly carried out
Scope EUC and its environment (physical, legislative, etc.)
Input All the information necessary to meet the requirements of the sub-clause
Output Information about the EUC, its environment, and hazards

 

Overall scope definition

Objective Determine the boundary between the EUC and the EUC control system; specify the scope of the hazard and risk analysis (e.g. process hazards, environmental hazards, etc.)
Scope EUC and its environment
Input Information about the EUC, its environment and hazards
Output Defined scope of the hazard and risk analysis

 

Hazard and risk analysis

Objective Determine the hazards, hazardous events, and hazardous situations related to the EUC and the EUC control system (in all operating modes) for all reasonably foreseeable circumstances, including fault conditions and reasonably foreseeable misuse; determine the sequences of events leading to hazardous events; determine the EUC risks associated to hazardous events
Scope The scope of application will depend on the stage reached in the overall E/E/PE system and safety software lifecycle (as more than one hazard and risk analysis may be required). For the preliminary hazard and risk analysis, the scope of application will be determined by the definition of the overall scope
Input Defined scope of the hazard and risk analysis
Output Description and information related to the hazard and risk analysis

 

Recommended in-depth study:

 

General safety requirements

Objective Develop the specifications for general safety requirements, in terms of safety function requirements and safety integrity, for E/E/PE safety systems and other risk reduction measures, in order to achieve the required functional safety
Scope As determined by the definition of the overall scope
Input Description and information related to the hazard and risk analysis
Output Specific general safety requirements in terms of safety function requirements and safety integrity requirements

 

Assignment of general safety requirements

Objective Assign safety functions, contained in the general safety requirements specification (both safety function requirements and safety integrity requirements), to the designated E/E/PE safety systems and other risk reduction measures; assign a safety integrity level to each safety function to be performed by an E/E/PE safety system
Scope As determined by the definition of the overall scope
Input Specific general safety requirements in terms of safety function requirements and safety integrity requirements
Output Information on the assignment of the overall safety functions, the planned fault measures, and the associated safety integrity levels. Assumptions made about the risk reduction measures to be managed throughout the EUC lifecycle

 

General planning

Objective Develop a plan for E/E/PE system operation and maintenance to ensure that the required functional safety is maintained during operation and maintenance; develop a plan to validate the overall safety of E/E/PE safety systems; develop a plan to install E/E/PE safety systems in a controlled manner to ensure that the required functional safety is achieved; develop a plan to commission the E/E/PE safety systems in a controlled manner to ensure that the required functional safety is achieved
Scope EUC and the EUC control system; E/E/PE safety systems
Input Information and results of the overall assignment of safety requirements
Output Un piano per l’installazione dei sistemi di sicurezza E/E/PE; un piano per la messa in servizio dei sistemi di sicurezza E/E/PE

 

Realisation

Objective Develop a plan for E/E/PE system operation and maintenance to ensure that the required functional safety is maintained during operation and maintenance; develop a plan to validate the overall safety of E/E/PE safety systems; develop a plan to install E/E/PE safety systems in a controlled manner to ensure that the required functional safety is achieved; develop a plan to commission the E/E/PE safety systems in a controlled manner to ensure that the required functional safety is achieved
Scope EUC and the EUC control system; E/E/PE safety systems
Input Information and results of the overall assignment of safety requirements
Output A plan to install E/E/PE safety systems; a plan to commission E/E/PE safety systems

 

Installation and commissioning

Objective Install E/E/PE safety systems; commission E/E/PE safety systems
Scope EUC and the EUC control system; E/E/PE safety systems
Input A plan to install E/E/PE safety systems; a plan to commission E/E/PE safety systems
Output Fully installed E/E/PE safety systems; fully installed E/E/PE safety systems

 

Recommended in-depth study:

 

Safety validation

Objective Validate that E/E/PE safety systems meet the specifications of the general safety requirements in terms of the general safety function and safety integrity requirements, taking into account the assignment of safety requirements for the developed E/E/PE safety systems
Scope EUC and the EUC control system; E/E/PE safety systems
Input General safety validation plan for E/E/PE safety systems; information and results from the overall safety requirement assignment
Output Confirmation that all E/E/PE safety systems meet the specifications of the general safety requirements, taking into account the safety requirements for E/E/PE safety systems

 

Operation, maintenance and repair

Objective Ensure that the functional safety of E/E/PE safety systems is maintained at the specified level; ensure that the technical requirements necessary for overall E/E/PE safety system operation, maintenance, and repair are specified and provided to those responsible for future E/E/PE safety system operation and maintenance
Scope EUC and the EUC control system; E/E/PE safety systems
Input The general operation and maintenance plan for E/E/PE safety systems
Output Continued achievement of the required functional safety for E/E/PE safety systems; chronological documentation of E/E/PE safety system operation, repair, and maintenance

 

Overall modification and retrofitting

Objective Define the procedures necessary to ensure adequate E/E/PE safety system functional safety, both during and after the modification and retrofitting phase
Scope EUC and the EUC control system; E/E/PE safety systems
Input Request for modification or adaptation according to functional safety management procedures
Output Achieving the necessary functional safety for E/E/PE safety systems, both during and after the modification and retrofitting phase; chronological documentation of E/E/PE safety system modification and retrofitting

 

Decommissioning or disposal

Objective Define the necessary procedures to ensure that the functional safety of the E/E/PE safety systems is appropriate to the circumstances during and after EUC decommissioning or disposal activities
Scope EUC and the EUC control system; E/E/PE safety systems
Input Request for decommissioning or disposal according to functional safety management procedures
Output Achieving the functional safety required for E/E/PE safety systems both during and after decommissioning or disposal activities; chronological documentation of decommissioning or disposal activities

 

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