Safe removal from service with hazard mitigation per IEC 61511 Cl.18
Phase 8 closes the SIS lifecycle — safe removal from service, hazard mitigation during transition, and documentation retention. Per Cl.18, decommissioning must be planned to maintain protection of personnel and environment throughout the transition, with PHA-driven hazard analysis where the unit continues to operate without the SIS.
Decommissioning is the often-overlooked phase where partial protection during transition creates the highest residual risk. Sites that plan Phase 8 properly maintain personnel safety during plant retirement or major restructuring.
Phase 8 closes the audit trail for the SIS lifecycle. Documentation produced (final FSA, decommissioning record) supports any post-event investigation or liability defence for legacy operations.
A focused 6-step methodology calibrated to deliver decommissioning as a working capability — not a documented compliance artefact.
Catalogue affected SIFs, units, dependencies; identify duration and phasing requirements.
Per Cl.18.2 — assess hazards during shutdown transition; identify any operation without SIS; specify compensating controls.
Build sequenced shutdown; specify temporary protections; align with utility isolation, process inerting, residual fluid removal.
Execute per plan; monitor against hazard analysis predictions; trigger MOC if deviation required.
Physical removal or isolation; cybersecurity de-commissioning; documentation of final configuration.
Final functional safety assessment; retain documentation per OSHA PSM (m)(6) and corporate requirements.
Decision-gated workflow showing the actual sequence of activities — from initiation through steady-state operation — with key decision points highlighted.
We can scope this element implementation against your facility, regulatory context, and existing management-system maturity — and integrate it with the other Functional Safety Lifecycle Implementation elements you already operate.