(81b) QRA and Its Role In Managing the Risks to Personnel within Occupied Buildings From Flammable Hazards

Authors: 
Cavanagh, N., DNV Software


Accidents like Buncefield and Texas City have put the risk to people in occupied buildings from flammable hazards high on the agenda of both regulators and operators. Regulatory regimes for assessing the safety of those in occupied buildings are becoming more demanding and the need for accuracy and transparency has increased. For example, regulatory guidelines like API RP752 and RP 753 provide guidance on the design and location of permanent and portable buildings to minimise risks to occupants. This paper focuses on advances in software models for assessing risks to people in buildings from releases of flammable materials. When deciding on the location and construction of occupied buildings in the vicinity of hazardous installations, a number of factors must be considered during the design and operational phases. Key to the process of deciding where to locate buildings and what level of protection they should offer their occupants are the level of risk to which it is acceptable to expose those occupants. Traditional QRA tends to use ?generic? vulnerability for people indoors where their probability of death when particular levels of different types of hazardous effects are exceeded, such as explosion overpressure, radiation from fires, flame impingement or toxicity, is treated as being independent of the type of building within which they reside, This is obviously a significant limitation to using the results of traditional QRA in selecting appropriate building types in different situations or to locate buildings in the safest place from the standpoint of risk to occupants. Risk to building occupants is a function of both building location and construction. In order to minimise risks to personnel in the most cost effective way, plant designers and safety managers need to be able to compare and assess different options with ease. This paper describes recent advances in the capabilities of the Phast Risk QRA tool (Cavanagh et al 2009, Cavanagh 2010) which allow analysts to assess the relative benefits of using different building types to reduce risks to their occupants. These new features enable individual definition of building types and associated occupant vulnerability. In addition, GIS facilities allowing analysts to locate buildings of a particular type in various locations help ensure overall risks can be minimised, or location specific risks for particular buildings can be assesed. A case study is to illustrate the application of the new vulnerability modelling to selecting suitable building types, and locating them in the most appropriate position to minimise risks to occupants. In addition, techniques are described for using these methods to help locate and design buildings to withstand the possible explosion, radiation and flammable effects to which they may be subjected. Cavanagh, N.J., Xu, Y. and Worthington, D.R.E., A Software Model for Assessing Fatality Risk from Explosion Hazards using the Multi Energy Method and Baker Strehlow Tang Approach, Hazards XXI Symposium, November 10th-12th 2009, Manchester, UK. Cavanagh, N.J., Recent advances in software for modelling the risks associated with gas explosions in congested spaces using the Multi Energy Method, 13th International Symposium on Loss Prevention and Safety Promotion in the Process Industry, June 6th- 9th, Bruges, Belgium, 2010.