Tuesday, December 16, 2008

Consequence assessment tool - how significant for risk assessment

There are a number of tools and techniques available for process hazards consequence assessment which includes models for manual use and computer codes. Many of the software programs use the Gaussian dispersion or similar algorithms to evaluate gas dispersion. These tools are often developed in order to assess a particular application (passive gas, dense gas, or specific chemical); some of them are further developed and modified to extend the range of usability.

Mostly, commercially marketed software models are validated using experimental field test, but often the results are far from the real scenarios experienced. The main reason being the limited range of application; in most process hazard cases, the materials involved are not a single, pure material and the effects of obstructions close to the release or incident site are not included in the model.

In general, for consequence assessment, using software tools some of the challenges are:
- Modelling the effects of multi-component material with varying physical & chemical properties
- Incorporating the effects of terrain, barriers, slops, structures and buildings
- Changes in weather condition during the release
- Near and far field effects

In order to overcome these challenges, the computational fluid dynamics technique which uses the physical formula was considered as an alternative to more conventional models. This paper looks into the modelling of dispersion characteristics using computational fluid dynamics around a built up area of a chemical plant and compares the results obtained using Gaussian algorithm. This is based on a consequence assessment study performed for a loss of containment event within a tank bund.

The CFD tool used is fluidyn-PANEPR and the tool used with gas dispersion algorithm is DNV PHAST.


The poster based on the above abstract was shown for ChemEng08 and is viewable from the following link:
http://myaker.net/_upl/icheme_poster_sreeraj.pdf

Acknowledgements: To co-author/contributor Mr.Ken Norrie

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About Me

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Professional practising process safety and loss prevention. Areas of expertise include: • Hazard identification, Consequence modelling and analysis • Risk evaluation (qualitative and quantitative) • Identify and evaluate cost-effective engineering solutions to reduce or mitigate risk • Emergency planning and preparedness • HSE training and audits

Publications by Author

  • Identifying Opportunities of Enhancing Safeguard Stewardship through IPL Rationalization, Global Congress on Process Safety, AIChE, March 2017
  • Identifying and managing process risks related to biofule project and plants, HAZARDS XXII, April 2011
  • Essence of the accuracy and acceptability of failure rate data in risk assessment, HAZARDS XXII, April 2011
  • Improving process safety performance using process hazard information, ChemInnovations, Oct 2010
  • Analysing the effectiveness of risk reduciton measures implemented, 13th Internationa Symposium on Loss prevention, June 2010
  • Determining process safety performance indicators for major accident hazards using site process hazard information, HAZARDS XXI, Nov 2009
  • Using predictive risk assessment to develop user-friendly tools for on-site and off-site emergency planning, HAZARDS XXi Nov 2009
  • Process Safety - staying ahead, The Chemical Engineer, IChemE, Oct 2009
  • SreeRaj R Nair, Determining the criteria for evaluation of toxic hazards, Journal of HSE and Fire Engineering, ASFE CUSAT, Issue 2 March 2009
  • S R Nair, Methods of avoiding tank bund overtopping using computational fluid dynamics tool, Paper 40, Page 479-495, HAZARDS XX, April 2008
  • Sreeraj R Nair, A review on Buncefield oil storage incident investigation, Petrosafe-07, April 2007
  • Sreeraj R Nair, Safety studies through project life cycle, Fire and Safety Journal, ASFE CUSAT, October 2006

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