Quantitative Risk Assessment: Tips for an Effective QRA

Posted on 27/10/2016

When things go wrong, engineering processes such as those associated with oil & gas and chemical plants can clearly cause significant impact and damage to people, environment and assets.  For  assessment of particularly high-consequence and more complex hazardous events, a semi-quantitative method (e.g. LOPA) won’t always ‘cut the mustard’.  Similarly, if the results of a semi–quantitative study simply don’t reflect reality, a full QRA may be the right approach.

QRA Process

What is a Quantitative Risk Assessment (QRA)?

A QRA study is a formal and systematic approach to quantify the risks associated with the operation of an engineering process, and is now seen as an essential tool to support the understanding of risk, to make cost-effective decisions and to provide evidence of meeting risk targets.

The objectives of a QRA is to provide answers to fundamental questions such as:

• What hazards are associated with the engineering facilities and their associated risks?
• Are the current safety risks tolerable or acceptable?
• Are the safety functions in place sufficient to reduce the risk to an acceptable level?
• What are the additional safety barriers and where should be they implemented?
• What is the most cost-effective option in terms of risk management?

Quantified safety risk results are typically presented as risk contours based on Location Specific Individual Risks (LSIR), Individual Risk Per Annum (IRPA), Potential Loss of Life (PLL) and F-N Curves.

Tips for a successful QRA

A QRA can only be considered a success if it produces correct and meaningful results to the process owners and operators to effectively reduce and control their risks. Here are a few tips for conducting a successful QRA:

1. Technically competent and experienced person(s) to conduct the analysis

This may seem obvious, but due to the variety of different studies which make up a full QRA, having suitably experienced and competent person(s) conducting the correctly identified task is key. For example, if using software for consequence modelling it essential that the different models within the software are understood in order to select the most appropriate model, as well as someone understanding the full results and outputs from the modelling. The key is to select the most appropriate person for the specific task based on meeting the specific required competencies for that particular task.

2. Clear and correct definition of project boundaries

What is the scope of the study? This is a fundamental factor which needs to be clearly defined and understood by all parties. Incorrectly defined boundaries could potentially invalidate all QRA analysis and results. This is particularly important as it is not uncommon that the boundary of a QRA study will go beyond the scope of the process facilities or even beyond the physical plant boundary.

3. Good plan of the project delivery

A quantified risk assessment is based on a number of tasks and activities including hazards identification, safety integrity level determination, frequency estimation, consequence modelling, impact analysis and risk calculation. A project delivery plan should be produced to ensure that all activities are planned and scheduled in the most efficient manner. Furthermore,  contingency should be added to account for unexpected changes, delays or variations caused by any of the sub task, for example, a change and update to one document may have a knock on effect on all other documentation and analysis.

4. A good hazard identification study and team

The basis of any QRA is dependent on the Hazard Identification process which forms the foundation of any study.

A good HAZOP / LOPA workshop is critical for a meaningful QRA. Why not check out our Top Ten Tips for an Effective HAZOP?

5. Communications with stakeholders

Companies invest a lot of time and money into conducting QRAs therefore communicating with the appropriate stakeholders at the appropriate times should be a given.  Regular communications are required at different levels and with different groups of people (e.g. project management, operations, maintenance, control and instrumentation, loss and prevention and other subcontractors).

What ESC can do for you?

ESC is a global Functional Safety Management Consultancy Company whose primary function is to support their customers in the technical safety aspects of the process, systems and equipment.  ESC has delivered numerous QRAs for clients in various industries and locations around the world and have developed a robust methodology of planning a QRA study and this method has been proved to be very effective in different industries.

• Contact ESC

• Phone: +44 (0) 20 3206 5200 (Environmental Resources Management [ERM] switchboard)
• Email: info@esc.uk.net

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