Decommissioning
We deliver safe removal from service with hazard mitigation to IEC 61511 clause 18
What this element is and why it matters
Phase 8 closes the lifecycle of the safety instrumented system through safe removal from service, hazard mitigation during the transition and the retention of documentation. To clause 18 decommissioning must be planned so that protection of personnel and the environment is maintained throughout the transition, with a hazard analysis driven by process hazard analysis wherever the unit keeps operating without the safety instrumented system.
Individual significance for organisations
Decommissioning is the phase that is often overlooked, yet the partial protection that exists during the transition creates the highest residual risk. Facilities that plan Phase 8 properly keep their people safe through plant retirement or major restructuring, and our team plans it with the same rigour as the build.
Contribution to Functional Safety Lifecycle Implementation
Phase 8 closes the audit trail for the lifecycle of the safety instrumented system. The documentation it produces, including the final functional safety assessment and the decommissioning record, supports any post event investigation or liability defence for your legacy operations.
What compliant execution looks like
How we implement this element
A focused six step methodology calibrated to deliver decommissioning as a working capability rather than a documented compliance artefact.
We catalogue the affected functions, units and dependencies and identify the duration and the phasing requirements.
To clause 18.2 we assess the hazards during the shutdown transition, identify any operation without the safety instrumented system and specify the compensating controls.
We build a sequenced shutdown, specify the temporary protections and align with utility isolation, process inerting and residual fluid removal.
We execute to the plan, monitor against the predictions of the hazard analysis and trigger management of change if a deviation is required.
We carry out the physical removal or isolation, the cybersecurity decommissioning and the documentation of the final configuration.
We complete the final functional safety assessment and retain the documentation to paragraph m subparagraph 6 of OSHA PSM and your corporate requirements.
Element implementation flow chart
A decision gated workflow that shows the actual sequence of activities from initiation through steady state operation, with key decision points highlighted.
What we produce
- A decommissioning plan with a hazard analysis
- A phased shutdown record
- A final functional safety assessment report with a retained documentation pack
- A management of change pack governing the decommissioning
- A compensating controls register for the transition operation
- A final as isolated configuration and de energisation record
Where execution fails
- Transition operation run without compensating controls
- Cybersecurity decommissioning skipped, leaving a legacy attack surface
- Documentation retention shorter than the statutory requirement
- The system isolated while interconnected units still rely on its trip outputs
Codes this element is built on
Explore related elements in this framework
Functional Safety Lifecycle Implementation full element index
Talk to us about implementing Decommissioning
We can scope this element implementation against your facility, regulatory context, and existing management system maturity, then integrate it with the other Functional Safety Lifecycle Implementation elements you already operate.