Quantitative Risk Assessment

Quantitative of Risk in terms of IRPA, PLL and graphical demonstrations such as FN Plots.

Quantitative Risk Assessment


Quantitative Risk Assessment (QRA) is a method which allows for quantitative estimation of risk, given the parameters defining them. The risk is calculated for the potential for safety, environmental or financial impact. the method can be defined as a formal and systematic approach in identifying hazardous events, estimating the likelihood of the hazardous event and the associated consequences.

Typical QRA Life Cycle



 – Process Hazard Assessment;

 – Quantitative estimation of Hazardous Event Frequencies;

 – Hazard Severity Assessment and Consequence Analysis;

 – Location Specific Risk;

 – Individual Risk Per Annum (IRPA) Calculation;

 – Potential Loss of Life (PLL) Calculations;

 – Frequency and Fatality plot (FN Plots), Cumulative FN Plots;

 – Risk Reduction Measure Verification;

 – Demonstration of Tolerable Levels of Risk and principle of As Low As Reasonably Practicable (ALARP);

 – Sensitivity Analysis;

 – System Narrative / Safety Requirement Specification.




The following are typical graphical representations of the risk contours.

Location Specific Individual Risk (LSIR) Contours represented on Map

Quantitative Risk Assessment - LSIR Risk Contours for an Offshore Facility

FN Plots demonstrating Risk to Personnel On-site




What software does FSES utilise in order to conduct QRA’s?

FSES are able to utilise their own in-house tool for the calculation of risk. Our consultants are also trained to use commercially available risk analysis tools (i.e. DNV PHAST Risk / SAFETI) when needed.

What inputs are required by FSES in order to conduct the QRA?

As a minimum the following information would be required in order to conduct the workshop:

 – P&ID’s

 – Cause and Effects Diagrams

 – Facilities Design

 – Operating Data and Procedures

 – Heat and Material balances

 – Equipment Rating and Data Sheets

Based on the project requirements, additional information may be required, which will be highlighted within the Terms of Reference (ToR).

What is the expected output of the QRA?

On award of the study FSES will issue a project ToR, which will highlight the assumptions that shall be made in the study, along with the study methodology and data sources that will be utilised as well as any further information required from the client.

Upon acceptance of the ToR, FSES will conduct the QRA and will prepare a report describing the facility, the scope of work, a detailed methodology, the results of the analysis (i.e. IRPA and PLL compared against the risk criteria) and any recommendations for further risk reduction.

What is the expected Delivery Schedule?

On award of the study, FSES shall develop a project schedule similar to below in order to provide an overview of project deliverables and schedule.




FSES are a globally renowned providers of QRA studies having conducted a number of high profile onshore and offshore QRA’s in the Middle East and elsewhere including the Safaniya, Marjan, Zuluf and Hasbah facilities amongst others.

For more information, or to discuss your needs for conducting a QRA, please contact us using the form below or email info@fses.global.


Further Information


FSES Quantitative Risk Assessment Life Cycle Methodology – Download here.

FSES Quantitative Risk Assessment Publication in HAZARDEX – Download here.

Our Services at FSES

Compliance to the international Standards such as IEC 61508 and IEC 61511 are imperative to meeting the Functional Safety requirements for many processes and have formed part of the quality management systems of many companies. Provision of Functional Safety Services in line with the Phases and Activities detailed in the Safety Life-cycle is an area in which our consultants are able to demonstrate experience and expertise.

Learn more about our services

PHA, HAZID and HAZOP Studies

FSES can provide Process Hazard Analysis (PHA) and HAZard and OPerability (HAZOP) study chairpersons. Our expert PHA facilitators hold certification in conducing HAZOP, HAZAN and CHAZOP.

Functional Safety Training

FSES provide various Functional Training services for all of specific parts of IEC 61508 and its sector derivatives.

Consequence Modelling

Discharge and Dispersion is often required to evaluate the consequence of identified hazardous events.

Design Engineering

Functional safety activities are most effective by integration into a well-established and proven quality management system.

Building Risk Assessment

Building Risk Assessment (BRA) is a tool used to assess the risks to people in occupied buildings in the facility.

Dropped Objects Analysis

Dropped Objects Analysis

Escape, Evacuation and Rescue Analysis

Escape, Evacuation and Rescue Analysis ensures that the design of a facility is such that the risk to personnel is kept to within the ALARP region.

Functional Safety Assessment

Independent Management of Functional Safety Assessments, Audits & Support.

Functional Safety Lifecycle and Management

Functional Safety Lifecycle and Management is a key requirement demonstrating how Functional Safety is to be implemented and achieved.

Human Factors

Human factor assessment is a key area in identifying potential hazards which may be instigated by human errors.

Legacy Systems

Legacy Systems Review and Compliance.

Prior Use

Prior Use Assessment.

Proof Testing Procedures

Proof Testing is one of the main requirements to ensure that Functional Safety is maintained throughout the operational phase.

Operation and Maintenance

FSES can carry out review studies and provide consultancy to ensure Functional Safety requirements are maintained during Operation and Maintenance.

Quantitative Risk Assessment

Quantitative of Risk in terms of IRPA, PLL and graphical demonstrations such as FN Plots.

Reliability, Availability and Maintainability Study (RAMS)

Reliability, Availability and Maintainability Study (RAMS) is used as a decision making tool to increase the availability of the system, and thus increase the overall profit as well as reducing the life cycle costs.

Process Hazard Assessment (PHA)

FSES can provide Process Hazard Analysis (PHA) and HAZard and OPerability (HAZOP) study chairpersons. Our expert PHA facilitators hold certification in conducing HAZOP, HAZAN and CHAZOP.

Safety Requirements Specification

The Safety Requirements Specification (SRS) is a core document, which is used as the main reference to be followed by designers, installers, and operators of a Safety Instrumented Function (SIF).

SIL Determination

FSES are able to us various methods in identifying SIL targets; qualitatively by Risk Graphs, semi-quantitatively by Layers of Protection Analysis (LOPA) or fully quantitatively by Fault Tree Analysis (FTA).

SIL Verification

Calculation of Random Hardware Reliability and Architectural Assessments for Safety Instrumented Functions (SIFs).

SIS Conceptual Design

Safety Instrumented System (SIS) Conceptual Design.