Understanding Major Accident Hazards

Training from ESR Technology

ESR Technology has built a long track-record, over many years, in delivering its Major Hazard Risk Assessment training programme throughout the Energy Industry and to its Regulators e.g. UK Health and Safety Executive Inspectors.  From this we have developed a series of free web based introductory modules to deliver an understanding of:

  • Hazard Identification – what are the hazards, can they be eliminated?
  • Scenario Definition – how might a hazardous event develop; how do we prevent it?
  • Consequence Analysis – if the event happens, how bad will it be, who or what will it harm?
  • Frequency Determination – how often is an event likely to happen, can we tolerate it?

The modules provide a high-level overview of the content within ESR Technology’s comprehensive Major Hazard Risk Assessment training programme, accessible to delegates on a module-by-module or whole course basis via on-demand/webinar sessions, and can be tailored to accommodate any specific requirements of Companies and the delegates.  They are aimed at engineers and scientists with a practical interest in the application of risk management and major hazards assessment. 


Hazard Identification – What can go wrong?

The identification of what can go wrong is an important stage of the risk assessment process.  Accidents can only be prevented by anticipating how they can occur.  Every industry operation using power, machinery, chemicals etc is hazardous, with work-place accidents like tripping, falling, electrical shocks, etc being commonplace events.  The types of hazards that we are principally concerned with here, however, are MAJOR HAZARDS, i.e. accident events that could affect a significant proportion of the workforce and also affect members of the general public outside the plant site.

Hazard identification involves the rigorous consideration of all situations in which the potential for harm may exist, followed by a disciplined analysis of the combination or sequences of events, which could transform this potential into an accident.  Normally consideration must be given to the following aspects for hazard identification relating to major hazards:

  • Determining whether a given operation or activity has the potential to give rise to a major hazard situation.
  • Determining the range of major hazard events which the operation or activity could present. This is typically performed using either:
    • Comparative Methods: these draw mainly on knowledge gained from experience. Checklists and hazard indices are comparative methods.
    • Analytical Methods: these are structured ways for stimulating a group of people to apply foresight in conjunction with their knowledge to the tasks of identifying hazardous scenarios by raising “What If?” type questions.



Scenario Definition – How could it develop?

A conceptual framework for scenario definition can be characterised as a Hazard-Vector-Target or Source-Pathway-Receptor approach as it is more commonly characterised when discussing environmental hazards. Without all three of the elements being present, no harm occurs.

Effective scenario definition depends on knowledge and experience of the hazard and relies on systematic methods to ensure that this knowledge and experience is applied to identifying the routes by which each of these major hazard events could be realised, i.e. identify potential accident scenarios.  Such accident scenarios include combinations or sequences of events, with possible escalation from an initiating minor accident event into a major hazard event.

Typically, analytical methods are used to define scenarios. These are structured ways for stimulating a group of people to apply foresight in conjunction with their knowledge to the tasks of identifying hazardous scenarios by raising “What If?” type questions.  Examples of this type of methodology are:

  • Hazard and Operability Studies (HAZOP).
  • Failure Modes and Effects Analysis (FMEA).
  • Fault tree, event tree and Bow-Ties.


Consequence Analysis – How bad will it be?

Once a scenario has been defined, consequence analysis may be undertaken to understand the impact the hazard has upon the target / receptor. This consists of:

  • Defining ‘inventories’ of hazardous materials. The ‘inventory’ may be a material with a hazardous property such as flammability or toxicity, or it may have stored energy such as a pressurised gas.
  • Defining the release conditions. The release conditions may be normal operating conditions, or abnormal conditions. The release path will depend on the failure mechanism, and may be low velocity, high velocity or explosive.
  • Evaluating the effects to personnel and the environment of all end consequences. These may be immediate, delayed or knock-on from the initial event.


Frequency Determination – How likely is it to happen?

The purpose of frequency analysis is to determine the likelihood of each of the undesired events or accident scenarios identified at the hazard identification stage.  There are two basic approaches which are commonly employed in trying to estimate event frequencies.  These are:

  • To use relevant historical data
  • To synthesise event frequencies using techniques such as Fault Tree Analysis and Event Tree Analysis

The two approaches are in fact complementary, each having strengths where the other has weaknesses and hence, wherever possible, it is useful to pursue both approaches.  In this way, the two approaches can be used as independent checks on one another and hence, hopefully, serve to increase confidence in the results. 


Further Modules

The above introductory videos are a taster of the training we can offer on the ESR Technology Major Hazards course. We offer several of the course modules in the form of on-demand/webinar sessions. If you would like further information, please indicate which modules are of interest and complete the contact form below

Hazard Identification
Scenario Representation
HSE - Management Systems
Reliability Definition
Event Tree Analysis
Fault Trees
Bow-Tie Analysis
Data Sources
Human Factors
Milestone Disasters
Safety Integrity Level
Consequence Analysis
Source Terms and Gas Dispersion
Thermal Radiation
Toxic Hazards
Blast Overpressure
Risk Calculation
Risk Criteria and ALARP Demonstration

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Major Hazards Risk Assessment Training Programme

This course is well established and has been delivered by ESR Technology for over 20 years and is used widely as formal major hazards and practical risk assessment training by industrial and regulatory personnel both in the UK and internationally. The course involves formal lectures and interactive syndicate exercises and provides an ideal vehicle for managers and engineers to gain an appreciation of the application of risk assessment techniques and the benefits that may be gained. This course can be presented in its standard form or can be tailored to accommodate any specific requirements of Companies and the delegates.

It is aimed at Engineers and Scientists with a practical interest in the application of risk management and major hazards assessment.

Full Course Duration: 3-5 days (also available as shorter individual modules)

Objectives: The objective of the course are to provide an:

  • Understanding of the risk assessment process
  • Knowledge of tools and techniques for hazard identification
  • Knowledge of tools and techniques for frequency analysis and synthesis
  • An introduction to the modelling of major hazard consequences
  • An understanding of how risks are calculated and issues surrounding their use.

ESR Technology is one of the world’s leading practitioners in the development and application of Safety and Engineering Support Services, having largely pioneered the use of safety engineering and risk assessment techniques across many industries (including the chemical process, oil and gas, power generation, utilities, transport, petrochemical, military and food) and governing bodies both in the UK and internationally.

For more information please contact Terry Atkinson (This email address is being protected from spambots. You need JavaScript enabled to view it.).

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