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Quantitative Risk Analysis: What You Need To Know

A QRA is a valuable tool for determining the risks associated with (petro) chemical processes, transportation, and or storage of dangerous substances. In Singapore, QRA is a requirement by the Major Hazard Department (MHD) which consists of several agencies like the Ministry of Manpower (MOM), the National Environment Agency (NEA), and the Singapore Civil Defence Force (SCDF). The results of the QRA provide Singapore’s MHD with the information they need to assess the acceptability of new projects against predefined risk thresholds. The assessments can also be used to inform emergency response plans and to recommend measures to ensure any observed hazards are kept as low as reasonably practicable (ALARP).

Section 26 of the Environmental Protection and Management Act, the Fire Safety Act and Fire Safety (Petroleum and Flammable Materials) Regulations empower the Singapore Authorities to require the Responsible Party (the owner/occupier) for a hazardous installation to conduct hazard/ risk impact studies. The scope of work of the QRA comprises the following:

  • Hazard identification – a qualitative review of possible accidents that may occur (based on industrial accident records or, as necessary, professional judgment) involving the hazardous substances stored and/or utilised by the project;

  • Scenario identification – definition of the specific scenarios to be studied in this QRA, with each scenario assigned a unique identification code or isolatable section number;

  • Event tree and frequency analysis – determination of the frequency or likelihood of occurrence of all identified scenarios;

  • Consequence modelling – determination of the consequence distances (harm zones) that would result from the realisation of each scenario identified by the outcome, e.g. pool fire, jet fire, BLEVE (a boiling liquid expanding vapour explosion), fireball, flash fire, vapour cloud explosion (VCE), pressure vessel burst (for example due to runaway reaction or internal explosion), and toxic release;

  • QRA Results – summation of consequences and frequencies of all isolatable sections to determine the Individual Risk (IR) of fatality (on and offsite), injury, cumulative escalation (offsite), and to individuals in onsite occupied buildings, together with the identification of specified harm zones;

  • Comparison with PCD Risk Acceptance Criteria – provide the authorities with the appropriate information to facilitate land use planning in the vicinity of the hazardous installation;

  • Prioritisation & ALARP assessment – recommendation of mitigation measures, as and where required, to reduce risks or manage the hazards; and

  • Emergency Response Planning - facilitate the development of an emergency response plan (ERP) to deal with all possible accident scenarios.

ESC is a registered QRA Consultant with the National Environment Agency (NEA) and has conducted numerous QRAs for our clients in Singapore.

For more information or assistance in performing a comprehensive QRA for your facilities, please get in touch with our team of experts or visit our contact page.


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