SIS Detailed Design and Lifecycle Verification
We deliver IEC 61511 phase six through twelve design covering architecture, FMEDA graded components, factory and site testing, the safety manual and cybersecurity
SIS Detailed Design
and Lifecycle Verification
Safety instrumented system design translates the safety requirements specification into an as built protection system that achieves and sustains the allocated SIL across the lifecycle. Our team integrates sensor selection covering transmitter type, redundancy and partial proof test coverage, logic solver architecture using TÜV and exida certified safety PLCs such as Triconex, HIMA, ABB AC800M HI, Yokogawa ProSafe RS and Siemens S7 410F, final element specification covering block valve actuation, fail safe direction, partial stroke testing capability and fugitive emission tightness per ISO 15848, and the cabling, networking, power supply and operator interface architecture that surrounds them. The 2016 second edition of IEC 61511 tightened design requirements significantly, adding explicit cybersecurity treatment that now mandates IEC 62443 alignment, restricting the sharing of sensors between the control system and the safety system, formalising prior use justification for non certified devices, and requiring a safety manual. Common audit findings now cluster on sensor common cause separation such as transmitter mounting, impulse line geometry and calibration drift, on final element diagnostic coverage and realistic partial stroke testing, on honest beta factor scoring, and on the cybersecurity dimension that safety systems from the 1990s rarely addressed.
SIS Detailed Design and Lifecycle Verification workflow
Review approved SRS for completeness, establish SIS design basis with architecture targets, redundancy strategy, and cybersecurity zone definition, align with IEC 61511 Phase 6 design and engineering requirements.
Select TÜV certified safety logic solver (Triconex, HIMA, ABB AC800M HI, AB GuardLogix), justify prior use per IEC 61511 Cl.11.5.3, specify platform certification (SIL 2 / SIL 3 / SIL 4 capable), align with IEC 62443 cybersecurity requirements.
Specify sensors with FMEDA data, pressure (Rosemount 3051SIS / E+H Cerabar), temperature (RTD/TC with safety transmitter), level (radar/DP), flow (vortex/coriolis), specify final elements, ESD valves (Mokveld, Velan) with API 6FA fire safe, partial stroke capable for SIL ≥2.
Design voting architecture (1oo1D, 1oo2, 2oo3) per SIL target, MTTFS (spurious trip), and CCF mitigation, specify diverse sensors / separated cabinets / independent power for high CCF risk, align with IEC 61508 Route 1H or 2H per design tolerance.
Implement IEC 62443 zone and conduit architecture, SIS zone isolated from BPCS via uni directional data diode or firewall, specify access control, audit log, USB lockdown, align with NIST SP 800 82 OT security guidance.
Develop FAT procedure exercising every SIF cause and effect, SAT with end to end loop testing, produce Safety Manual per IEC 61511 Cl.16 covering operating, proof testing, bypass, MOC procedures, align with FSA Stage 2 / 3 examination.
Every deliverable from basis to handover
Complete SIS Detailed Design and Lifecycle Verification scope covering every calculation, drawing, specification, and construction support activity.
Outcomes of SIS Detailed Design and Lifecycle Verification
- We achieve the target SIL through engineered architecture rather than an optimistic claim
- We eliminate the sharing patterns between control and safety systems that fail the IEC 61511 independence test
- We address the silent partial stroke test coverage gap on critical block valves
- We close the cybersecurity exposure historically ignored in safety systems from the 1990s
- We produce IEC 61511 second edition design that withstands scrutiny, with documented prior use justification
- We give you documentation that withstands TÜV, exida and third party assessment at FSA stage two and three
- We align you with the IEC 62443 cybersecurity zone and conduit requirements
- We support the operational control safety system evidence that COMAH and Seveso require
- We reduce spurious trip frequency through architecture aware of mean time to fail spuriously
- We sharpen proof test design to cover unrevealed failure modes honestly
- We enable online partial stroke testing on critical block valves
- We build safety manual content that survives handover to the operating team
- We right size the SIL and architecture and avoid the SIL three everywhere capital pattern
- We reduce commissioning rework through factory test quality verification
- We cut spurious trip business interruption, typically by fifty to eighty per cent against a legacy safety system
- We trim lifecycle safety system maintenance through diagnostic coverage credit
Codes & standards we work to
Triggers that signal the need
Where SIS Detailed Design and Lifecycle Verification applies
Wellheads, separators, gas compression, FPSO topsides, produced water systems.
Distillation columns, reactors, heat exchangers, storage spheres, LPG handling.
Cryogenic exchangers, liquefaction trains, BOG compressors, storage and sendout.
Reactive systems, batch reactors, solvent handling, runaway reaction scenarios.
Boilers, HRSGs, steam headers, hydrogen systems, ammonia SCR units.
Sterile vessels, CIP/SIP, pressure fermenters, solvent recovery, spray dryers.
Tangible deliverables
- SIS design basis aligned to the safety requirements specification
- Architecture and voting specification for each safety instrumented function
- Sensor and final element datasheets with FMEDA data
- Logic solver configuration and safety application program
- Proof test procedures with coverage analysis
- Partial stroke test specification where applicable
- Cybersecurity zone and conduit drawings per IEC 62443
- Factory and site acceptance test specifications with acceptance criteria
- Safety manual content per IEC 61511
- Management of change procedure for safety system modifications
Ready to start your project?
Speak with our team to scope an engagement tailored to your facility, regulatory context, and lifecycle stage.