The use of QRA in risk-based decision making

Quantified Risk Assessment (QRA) of major accident hazard sites is well established in the oil and gas industry.  It is a process of assessing, evaluating and understanding risk, and depending on the size of the site under assessment a QRA involves anywhere between a few days’ to several months’ effort.  In addition to providing operators with an understanding of risk and compliance with risk tolerability criteria, a significant benefit of QRA is the basis it provides for risk-based decision making and in making use of the underlying data which when aggregated describes the risk picture of a site.  Some examples of the use of QRA in risk-based decision making include both design and operational decisions such as:

• Assessing the reduction in risk by moving administration activities from one building to another (Onshore).
• Optimising blowdown strategy (Offshore).
• Defining, from a risk perspective, locations that require Passive Fire Protection (Offshore).
• Determining liferaft and lifeboat locations (Offshore).
• Assessing and evaluating risk during Combined Operations (COMOPs) and optimising the gangway location (Offshore).
• Determining the need for additional risk mitigation measures when a Safety and Environmental Critical Element (SECE) is degraded (Offshore).
• Providing thermal radiation and overpressure exceedance data at a proposed location of a new structure (Onshore and Offshore).
• Assessing societal risk during periods of construction activity and setting manning limits where areas are too densely populated (Onshore and Offshore).
• Evaluating the likelihood of muster locations being impaired during an emergency scenario (Onshore and Offshore).
• Using consequence data in emergency response plans (Onshore and Offshore).

This exemplifies the types of decision that can make use of QRA and can aid in demonstrating that risks are As Low As Reasonably Practicable (ALARP), particularly where there is more than one course of action available. 

Most safety related decisions, particularly those which may seem difficult at first glance, require an understanding of the interactions between hazards and hardware and can be evaluated this way. However, it requires the QRA to be constructed on a sound basis, with understanding of the sensitivity to assumptions and validity of the consequence models.  DNV GL has a strong experimental background in major hazard understanding, model development and risk-based decision making.  Details of our capabilities can be found on our website.