Determine safety integrity levels for individual safety instrumented functions using layer of protection analysis and risk graphs.
Oil, Gas & Energy
Safety Instrumented Systems and SIL Verification to IEC 61511
Learn to determine SIL targets, verify safety instrumented function designs and run the ongoing functional safety management that keeps an IEC 61511 safety instrumented system valid throughout its operating life.
🗓️Duration5 training days
📚Content4 modules · 8 sessions
🎓On completionAccredited attendance certificate
About the programme
Course Overview
Process plants and offshore facilities rely on safety instrumented systems to shut down safely when normal control fails, yet many organisations struggle to prove that a given system actually delivers the safety integrity level it claims. This course works through the full IEC 61511 safety lifecycle: turning HAZOP and layer of protection analysis findings into safety instrumented functions, writing a safety requirements specification, selecting voting architectures and calculating average probability of failure on demand for the resulting design. Participants verify a worked safety instrumented function from first principles, set realistic proof test intervals, and review the functional safety management arrangements — competence, assessment gates, management of change — that keep an achieved SIL valid over decades of operation. Teaching combines calculation exercises, a case-based verification exercise, and review of real safety requirements specifications and verification reports. Participants leave able to determine SIL targets, verify that a design meets them, and run the ongoing functional safety management a regulator or independent assessor would expect to see.
Expected Learning Outcomes
Draft a safety requirements specification that defines the safety function, process safety time and required response for each SIF.
Calculate average probability of failure on demand for 1oo1, 1oo2 and 2oo3 voting architectures using simplified equations and reliability data.
Select field devices, logic solvers and final elements with certified safety integrity claims that meet the target SIL.
Set proof test intervals and test coverage levels that keep achieved SIL within the specified target over the operating life of the system.
Audit an existing safety instrumented system against IEC 61511 functional safety management requirements and close identified gaps.
Manage modifications to safety instrumented systems through management of change and functional safety assessment gates.
Who Should Attend
Instrumentation and control engineers responsible for specifying or maintaining safety instrumented systems on process plant.
Process safety engineers who run hazard studies and need to translate risk findings into SIL targets.
Functional safety engineers preparing for independent verification and validation assignments.
Maintenance planners who schedule and record proof tests on safety instrumented functions.
Project engineers integrating new safety instrumented systems into brownfield process units.
Technical authorities who approve safety requirements specifications and functional safety assessments.
Course Modules
Select any module to see its sessions and points.
01Risk Basis and SIL Determination for Safety Instrumented Functions
2 sessions · 8 points
Session 1From Hazard Studies to Safety Instrumented Functions
- Trace hazardous scenarios from HAZOP worksheets into candidate safety instrumented functions with defined initiating causes and consequences.
- Apply layer of protection analysis to credit independent protection layers and calculate the residual risk gap a SIF must close.
- Distinguish safety instrumented functions from basic process control and alarm layers to avoid double-counting risk reduction.
- Build a SIF register that links each function to its hazard scenario, consequence severity and required risk reduction factor.
Session 2SIL Determination Methods and Calibration
- Compare risk graph, LOPA and risk matrix methods for assigning target SIL and select the method that fits the facility's risk criteria.
- Calibrate company risk tolerance criteria against IEC 61511 SIL bands so scenario severity maps consistently to SIL targets.
- Facilitate a SIL determination workshop that records assumptions, enabling conditions and conditional modifiers for each scenario.
- Reconcile SIL determination outputs with corporate process safety standards and site-specific risk acceptance criteria.
02Safety Requirements Specification and System Design
2 sessions · 8 points
Session 1Writing the Safety Requirements Specification
- Define the safety function, process safety time, safe state and response time required for each safety instrumented function.
- Specify de-energise-to-trip or energise-to-trip logic and justify the choice against fail-safe behaviour on loss of signal.
- Document bypass, override and manual shutdown provisions with the operational conditions under which they may be used.
- Set diagnostic coverage and proof test requirements the design must achieve to reach the specified SIL.
Session 2Architecture Selection and Reliability Calculation
- Select voting architectures such as 1oo1, 1oo2, 2oo2 and 2oo3 for sensors, logic solvers and final elements based on target SIL and spurious trip tolerance.
- Calculate average probability of failure on demand using simplified equations that combine failure rate, proof test interval and common cause factor.
- Apply beta factor estimates for common cause failure and show their effect on the achieved SIL of redundant architectures.
- Select certified transmitters, logic solvers and valves with SIL capability data from manufacturer safety manuals.
03Verification, Validation and Proof Testing
2 sessions · 8 points
Session 1Independent Verification and Validation
- Run an independent verification check that confirms the as-built safety instrumented function meets its safety requirements specification.
- Prepare a safety validation plan and factory or site acceptance test that exercises trip logic, voting and safe state on demand.
- Review vendor safety manuals for systematic capability, hardware fault tolerance and safe failure fraction claims against the target SIL.
- Record verification evidence in a functional safety file that a third-party assessor or regulator can audit.
Session 2Proof Testing and Maintaining Achieved SIL
- Design partial and full proof test procedures that detect dangerous undetected failures within the assumed proof test interval.
- Calculate the effect of partial stroke testing on valve proof test intervals and overall loop unavailability.
- Track proof test results, deferrals and overdue tests through a computerised maintenance management system.
- Investigate spurious trips and dangerous failures to update failure rate assumptions used in the SIL calculation.
04Functional Safety Management across the Lifecycle
2 sessions · 8 points
Session 1Functional Safety Management System
- Establish roles, competence requirements and assessment gates required by IEC 61511 across the safety lifecycle.
- Run a functional safety assessment at each lifecycle phase and record findings, actions and close-out evidence.
- Build a competence assurance process for engineers and technicians who design, install or maintain safety instrumented systems.
- Maintain a functional safety management plan that assigns ownership for each lifecycle activity on the project.
Session 2Modifications, Decommissioning and Continuous Improvement
- Route safety instrumented system changes through management of change with a functional safety impact assessment.
- Update the SIF register and safety requirements specification whenever process conditions or equipment change.
- Plan decommissioning of safety instrumented functions so interim risk is controlled while permanent protection is removed.
- Benchmark near-miss and demand data across the SIS to identify systems needing design or maintenance improvement.
What the participant receives
4 course modules
A structured syllabus
8 training sessions
across 5 days
32 detailed points
Applied, detailed content
Accredited attendance certificate
On completing the programme
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