LOPA Analysis
LOPA (Layer of Protection Analysis)
LOPA is a semi-quantitative method used to test whether existing safeguards are sufficient for defined scenarios.
LOPA Analysis Overview
It converts credible events into numbers that can be explained and defended to stakeholders, regulators, and internal assurance.
The work typically starts from selected HAZOP findings or clearly defined hazards. For each scenario, the initiating event frequency is estimated, Independent Protection Layers (IPLs) are identified, and the combined risk is calculated. Results are then compared to your risk tolerability criteria, and Safety Integrity Level (SIL) targets are set where needed.
Workshops are structured, traceable, and easy to follow. With support from our specialists, your team moves from initial scoping to a complete, audit-ready outcome.
Background & Regulatory Context
LOPA is documented and promoted by CCPS as a practical way to evaluate protection layers and make transparent risk decisions across the process industries. CCPS guidance defines the concept and qualification of IPLs, including expectations for independence, effectiveness, and auditability.
IEC 61511 requires a structured safety lifecycle for Safety Instrumented Systems (SIS). LOPA is commonly used within that lifecycle to determine SIL targets that feed into SIS design and verification.
In the United States, OSHA PSM mandates a Process Hazard Analysis (PHA) and five-year revalidation; many organizations use LOPA to strengthen the PHA basis and to prioritize risk reduction. Under COMAH/Seveso and similar frameworks, authorities and auditors recognize LOPA because it links scenarios, safeguards, and decisions in a consistent, defensible way.
How LOPA Works – Step by Step
- Preparation
The engagement begins by aligning LOPA with your objectives and existing studies:
- Defining scope, objectives, and risk criteria.
- Confirming interfaces with HAZOP, QRA, and functional safety work.
- Gathering the basis of design, relevant procedures, alarm philosophy, and proof-test strategies.
- Agreeing roles, agenda, and logistics.
- Finalizing the worksheet template, units, and data sources.
Good preparation ensures that workshop time is spent on analysis rather than clarifying inputs.
- Scenario Selection
Next, the team agrees which scenarios will be taken through LOPA:
- Selecting scenarios from recent HAZOP nodes or from an existing hazard register.
- Grouping duplicates and screening out non-credible paths.
- Defining consequences with clear severity descriptors.
- Documenting all assumptions in an Assumptions Log.
This step focuses the effort on scenarios where LOPA adds the most value.
- Frequency and IPLs
For each selected scenario, initiating frequencies and IPLs are defined:
- Estimating initiating event frequency using plant data, industry databases, or justified generic values.
- Identifying candidate IPLs and testing them against independence, effectiveness, and integrity criteria.
- Crediting only those IPLs that meet the CCPS definition.
- Recording proof-test intervals, response times, and claimed risk reduction.
Our specialists support the team in applying consistent rules so that credits remain robust under scrutiny.
- Risk Evaluation and SIL Targeting
The analysis then moves from inputs to decisions:
- Calculating scenario frequency with credited IPLs.
- Comparing results to your risk tolerability criteria.
- Flagging gaps where additional layers or design changes are required.
- Where instrumented protection is appropriate, setting a target SIL to be carried into the SIS lifecycle under IEC 61511.
- Keeping the calculation path transparent and replicable.
This step creates a clear bridge between hazards, safeguards, and required risk reduction.
- Reporting and Close-Out
Finally, the results are consolidated and translated into clear deliverables:
- Compiling LOPA worksheets, a scenario list, and a recommendations register.
- Providing an executive summary for leadership and auditors.
- Delivering marked-up references to drawings or procedures where this adds clarity.
- Agreeing on ownership, priorities, and due dates for actions.
- Proposing revalidation timing aligned with your PSM or management system cycle.
The outcome is an auditable record that supports both ongoing operations and future revalidations.
Deliverables and Value
Deliverables
- LOPA report with scope, basis, and method.
- Scenario list with initiating frequencies and consequence categories.
- LOPA worksheets showing IPLs, credits, and resulting frequency.
- SIL target summary for SIS design and verification.
- Action register with owners, priorities, and target dates.
- Executive briefing pack and assumptions log.
Value for our Client
- A defensible link from hazards to safeguards and risk decisions.
- Quantified insight that focuses budgets where they matter most.
- A clear handover to functional safety and SIS engineering.
- Smoother regulator and third-party audits under PSM/COMAH/Seveso expectations.
- Less uncertainty during design, commissioning, and operations.
- Confidence that the team is applying recognized good practice.
Our process safety specialists will provide an initial consultation and support your team through the LOPA process — from defining scope and criteria to delivering a practical, compliant result.
