Architecture, FMEDA, PFD/PFH calculation, cybersecurity per IEC 61511 Cl.11-12
Phase 4 takes the SRS and produces the as-designed SIS — architecture selection (1oo1, 1oo2, 2oo3), FMEDA-grade component selection, PFD/PFH verification per IEC 61508-6, cybersecurity zone-and-conduit per IEC 62443, and full design documentation per IEC 61511 Cl.11-12.
Design quality determines the SIS's lifecycle behaviour — its actual integrity, spurious-trip frequency, proof-test cost, and ageing pathway. Poor design choices cost the site for the 20-25 year lifecycle of the asset.
Phase 4 produces the as-designed SIS that Phase 5 commissions and Phase 6 operates. The Safety Manual it produces (per Cl.16) is the master document for the entire SIS lifecycle.
A focused 6-step methodology calibrated to deliver sis design and engineering as a working capability — not a documented compliance artefact.
Select architecture (1oo1 / 1oo1D / 1oo2 / 2oo3) per SIL target, MTTFS budget, CCF mitigation, and prior-use evidence.
Choose TÜV / exida / SIRA-certified sensors, logic solvers, final elements; verify FMEDA data sheets (λDD, λDU, SFF, DC).
Calculate per IEC 61508-6 Annex B using fault tree or Markov; include β-factor common-cause per Annex D; verify SIL target met.
Per Cl.11 — Route 1H (HFT + SFF) vs Route 2H (reliability data); document compliance with constraints.
IEC 62443 zone-and-conduit; segregation from BPCS / corporate; access control; align with NIST SP 800-82.
Issue design report, hardware specs, software specs, cause-and-effect, Safety Manual per Cl.16.
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.