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LOPA/SIL
Home | Services | Process Safety | LOPA/SIL

LOPA/SIL

Risk-Based Analysis for Safety Instrumented Systems (SIS)

View All Process Safety Services
process safety consultancy - SIL & LOPA

Functional Safety & Risk Reduction for High-Hazard Industries

Arthian provides Layer of Protection Analysis (LOPA) and Safety Integrity Level (SIL) Determination to help clients assess and reduce risk from high hazard events. These studies support the design and justification of Safety Instrumented Functions (SIFs)—ensuring systems are reliable enough to prevent major incidents.
 
We support:

     

  • Distilleries and drinks manufacturing
  • Chemical and pharmaceutical facilities
  • Energy from waste and renewables
  • Industrial gases, fuels and storage
  • High-risk manufacturing and processing sites

 
Our approach aligns with IEC 61511 and IEC 61508 standards, and integrates with HAZOP, COMAH and broader process safety frameworks.

What Is LOPA?

LOPA is a semi-quantitative method used to evaluate the risk of hazardous scenarios and determine whether existing safeguards are sufficient. It helps:

 

     

  • Identify risk gaps after HAZOP
  • Quantify the effectiveness of protection layers
  • Justify the need for SIFs or other mitigation
  • Support SIL assignment and functional safety planning

 
LOPA is often used when risks are too complex for qualitative methods but don’t require full quantitative modelling.

SIL Determination and our LOPA & SIL Services

We define Safety Integrity Levels (SIL) based on required risk reduction, ensuring Safety Instrumented Functions (SIFs) meet performance targets, prevent high-consequence events, and comply with IEC 61511. Using calibrated risk graphs, LOPA, and fault tree analysis, we assign SIL ratings and guide design decisions with confidence.

LOPA Facilitation and Documentation
SIL Determination Studies Using Risk Graphs and LOPA
Hazard Scenario Definition and Risk Gap Analysis
Integration with HAZOP, COMAH and Safety Lifecycle
Support for SIF Design and Verification (via Trusted Partners)
Planning-Ready Reporting and Regulator Engagement
LOPA consultants

LOPA Facilitation and Documentation

We support effective risk management by guiding Layer of Protection Analysis (LOPA) sessions and delivering structured outputs that inform safety decisions.
 
Our services include:
 

  • Facilitation of LOPA workshops with cross-disciplinary teams to evaluate risk scenarios
  • Documentation of initiating events, independent protection layers (IPLs), and risk reduction targets
  • Support in determining tolerable risk levels and identifying gaps in safeguards
  • Integration of LOPA findings into broader safety studies, including SIL determination and HAZOP reviews

 
Our approach ensures LOPA outputs are clear, traceable, and aligned with regulatory expectations—helping clients prioritise controls and strengthen process safety.

risk-matrix-process-safety

SIL Determination Studies Using Risk Graphs and LOPA

We conduct Safety Integrity Level (SIL) assessments to define the reliability requirements of Safety Instrumented Functions (SIFs) based on risk reduction needs.

 
Our approach includes:

 

  • Use of calibrated risk graphs to evaluate consequence severity and likelihood
  • Application of Layer of Protection Analysis (LOPA) to assess independent safeguards
  • Determination of appropriate SIL ratings to guide system design and performance targets
  • Alignment with IEC 61511 to ensure functional safety compliance


 
Our structured methodology supports robust decision-making and helps clients design systems that prevent high-consequence events.

process safety consultancy SIL

Hazard Scenario Definition and Risk Gap Analysis

We support effective risk management by identifying credible hazard scenarios and evaluating the adequacy of existing safeguards.
 
Our services include:
 

  • Definition of realistic and regulatory-relevant hazard scenarios
  • Assessment of current safeguards against required risk reduction targets
  • Identification of risk gaps and prioritisation of mitigation measures
  • Integration of findings into broader safety studies and compliance frameworks

 
This approach ensures your risk evaluations are defensible, targeted, and aligned with industry standards.

process safety COMAH consultants

Integration with HAZOP, COMAH and Safety Lifecycle

We ensure safety studies are fully aligned with key regulatory and operational frameworks to support consistent, compliant decision-making.
 
Our services include:
 

  • Integration of HAZOP outputs into downstream safety assessments and documentation
  • Alignment with COMAH (Control of Major Accident Hazards) reporting requirements
  • Support across the full functional safety lifecycle, from concept to decommissioning
  • Consistent traceability of risk decisions and safety functions across all stages

 
This holistic approach strengthens regulatory compliance and ensures safety is embedded throughout project delivery.

Support for SIF Design and Verification (via Trusted Partners)

We collaborate with trusted engineering partners to ensure Safety Instrumented Functions (SIFs) are designed and verified in line with SIL targets and industry standards.
 
Our support includes:

     

  • Coordination with qualified partners for SIF design and technical validation
  • Alignment of SIFs with defined SIL ratings and functional safety requirements
  • Verification of system architecture, reliability data, and performance criteria

 
This partnership-driven approach ensures robust, compliant safety systems tailored to your project’s risk profile.

process safety reports UK

Planning-Ready Reporting and Regulator Engagement

We produce clear, planning-ready reports and support engagement with regulators to demonstrate risk reduction, compliance and safety assurance.

LOPA consultants

LOPA Facilitation and Documentation

We support effective risk management by guiding Layer of Protection Analysis (LOPA) sessions and delivering structured outputs that inform safety decisions.
 
Our services include:
 

  • Facilitation of LOPA workshops with cross-disciplinary teams to evaluate risk scenarios
  • Documentation of initiating events, independent protection layers (IPLs), and risk reduction targets
  • Support in determining tolerable risk levels and identifying gaps in safeguards
  • Integration of LOPA findings into broader safety studies, including SIL determination and HAZOP reviews

 
Our approach ensures LOPA outputs are clear, traceable, and aligned with regulatory expectations—helping clients prioritise controls and strengthen process safety.

risk-matrix-process-safety

SIL Determination Studies Using Risk Graphs and LOPA

We conduct Safety Integrity Level (SIL) assessments to define the reliability requirements of Safety Instrumented Functions (SIFs) based on risk reduction needs.

 
Our approach includes:

 

  • Use of calibrated risk graphs to evaluate consequence severity and likelihood
  • Application of Layer of Protection Analysis (LOPA) to assess independent safeguards
  • Determination of appropriate SIL ratings to guide system design and performance targets
  • Alignment with IEC 61511 to ensure functional safety compliance


 
Our structured methodology supports robust decision-making and helps clients design systems that prevent high-consequence events.

process safety consultancy SIL

Hazard Scenario Definition and Risk Gap Analysis

We support effective risk management by identifying credible hazard scenarios and evaluating the adequacy of existing safeguards.
 
Our services include:
 

  • Definition of realistic and regulatory-relevant hazard scenarios
  • Assessment of current safeguards against required risk reduction targets
  • Identification of risk gaps and prioritisation of mitigation measures
  • Integration of findings into broader safety studies and compliance frameworks

 
This approach ensures your risk evaluations are defensible, targeted, and aligned with industry standards.

process safety COMAH consultants

Integration with HAZOP, COMAH and Safety Lifecycle

We ensure safety studies are fully aligned with key regulatory and operational frameworks to support consistent, compliant decision-making.
 
Our services include:
 

  • Integration of HAZOP outputs into downstream safety assessments and documentation
  • Alignment with COMAH (Control of Major Accident Hazards) reporting requirements
  • Support across the full functional safety lifecycle, from concept to decommissioning
  • Consistent traceability of risk decisions and safety functions across all stages

 
This holistic approach strengthens regulatory compliance and ensures safety is embedded throughout project delivery.

Support for SIF Design and Verification (via Trusted Partners)

We collaborate with trusted engineering partners to ensure Safety Instrumented Functions (SIFs) are designed and verified in line with SIL targets and industry standards.
 
Our support includes:

     

  • Coordination with qualified partners for SIF design and technical validation
  • Alignment of SIFs with defined SIL ratings and functional safety requirements
  • Verification of system architecture, reliability data, and performance criteria

 
This partnership-driven approach ensures robust, compliant safety systems tailored to your project’s risk profile.

process safety reports UK

Planning-Ready Reporting and Regulator Engagement

We produce clear, planning-ready reports and support engagement with regulators to demonstrate risk reduction, compliance and safety assurance.

Frequently Asked Questions

What is LOPA and when is it used?

LOPA is a structured method for evaluating risk and protection layers. It’s typically used after HAZOP to assess whether additional safeguards are needed.

What does SIL mean in safety systems?

SIL (Safety Integrity Level) defines how reliable a safety function must be to reduce risk to an acceptable level. It’s determined based on the severity and likelihood of hazardous events.

Do you design or verify safety systems?

We support SIL Determination and risk analysis. For detailed design and verification, we work with trusted functional safety partners to ensure compliance.

Can LOPA and SIL support COMAH compliance?

Yes—LOPA and SIL studies are often required to justify risk reduction measures in COMAH safety reports and major hazard assessments.

Get in Touch

We’d love to hear from you – whether you have a question, a project in mind, want to explore job opportunities, or just want to say hello.

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