Prevent major accidents – limit the effects

Prevent major accidents – limit the effects

Within the fire & life safety sector we are all familiar with the terms hazard and risk. When we refer to hazards and risk in relation to occupational health and safety common definitions include ‘A hazard is a potential source of harm or adverse health effect on a person or persons’ and ‘risk is the likelihood that a person may be harmed or suffers adverse health effects if exposed to a hazard.’ Peter Stephenson, Business Development Director, Exova WarringtonFire explores this further.

High hazard and challenging sites are often categorised into industrial sites that manufacture, process or store dangerous chemicals and substances in quantities that could pose a risk to workers, people in the vicinity of the site and the environment. Examples of ‘major accidents’ include fires, explosions or incidents where hazardous substances are released into the environment. Fortunately, these major accidents are rare occurrences, however when they do occur their impact can be far reaching and often include sites such as large petrochemical plants to chemical storage warehouses.

Legislation around the world has evolved following major incidents and has focused on operators of these sites requiring them to take all necessary measures to:

  • prevent major accidents; and
  • in the event of such accidents, limit the effects on people and the environment.

From the San Juanico incident it can be seen that the implementation of an effective fire risk assessment (FRA) and hazard identification protocols is a critical factor in the overall risk management of a site and can confirm/influence the selection and application of appropriate fire protection systems, maintenance regimes having carefully considered guidance contained in codes and from the findings of the risk analysis.

Categorising risk

International fire Codes identify that high-hazard occupancies are often complex uses and can challenge design professionals if they are not experienced in designing buildings containing hazardous materials and/or processes. Nevertheless, the use of hazardous materials is very common. They are widely used in medical clinics and hospitals; manufacturing plants; research laboratories; aircraft and vehicle maintenance shops; and many other uses. If hazardous materials are expected to be used on a project, and the design professional does not have the experience designing for hazardous material uses, then hiring a specialist consultant may be well worth the additional fee.

The International Building Code (IBC) describes a high hazard occupancy as one “that involves the manufacturing, processing, generation or storage of materials that constitute a physical or health hazard in quantities in excess of those allowed”. The key to classifying a building as a Group H occupancy under the IBC lies within the last few words of that quote: `in excess of those allowed`. Without that provision, every building that has certain cleaning products, for example stored in a Cleaners Cupboard would be considered a Group H occupancy.

Common causes of a disaster?

Sadly, there are far too many examples of international disasters involving high risk and challenging buildings. Following investigation, the lessons learnt often highlight key areas that have influenced the outcome of an incident, namely;

  • Design
  • Material Standards – Defects
  • Maintenance
  • Human Error
  • External Influence – Economy
  • Environment – Climate/Weather etc.

In the UAE Fire & Life Safety Code, 2017 Edition, hazard content and hazard evaluation for occupancy type differ based on the materials involved and their burning characteristics. Civil Defence has approached the occupancy hazards based on the life safety, risk involved and fire protection system requirements and categorized the types of occupancies further into Group A, Group B and Group C occupancies. Correct and appropriate selection of fire fighting equipment, suppression systems, fire detection and evacuation planning are some of the key outputs from a robust risk assessment process.

Fire Risk Assessment (FRA)

The UAE Fire Code highlights that the purpose of conducting the FRA should be identified and documented. The purpose might be to identify the level of risk present in an existing building or facility, to identify methods of lowering the risk, or to identify methods of providing a level of risk deemed to be acceptable. The objectives of the FRA might be associated with the risk to life (occupants or fire fighters), the risk to property, the risk to operations (e.g., cost of business interruption), the risk to the environment, or the risk of loss of cultural resources.

In some instances, where there are particularly high quantities of dangerous substances, operators must detail their control measures to prevent major accidents and record this in a ‘safety report’.

Within the oil and gas sector a good starting place when looking at site safety is to conduct a Quantitative Risk Assessment (QRA) which will assist in identifying and prioritising the process risks present on the facility and should provide recommendations on cost effective ways of reducing the overall site risk. A QRA will typically include both the risks to life and the capital production losses associated with incidents that could escalate within the site.

The application of a robust risk assessment methodology will define the probability of an event with undesirable consequences and can also give more specific meaning to the frequency with which there may be a major incident resulting in loss of life, or significant financial loss. A site review can be undertaken which would include a brief hazard identification study for those areas significantly different from normal operational sites. The detailed analysis of the frequency of incidents, event hazard ranges, the probability of escalation of an initial event and the calculation of financial risk levels should also be considered.

Across all hazardous sites there is a wide variation in ignition probabilities. These are due to the nature of the equipment present, processes undertaken and the differing sizes of potential incidents. In combination with accessing the likelihood of ignition further analysis should be undertaken including:

Event Consequence Analysis – This defines the risk potential for the site, the consequences of ignited releases of gas and oil on plant and personnel must be considered. This analysis should also consider the effect of ignited and unignited releases from pipework and vessels.

Escalation Analysis – It is often important to determine and gain an understanding of which events are likely to lead to further damage to the plant across and potentially beyond the site. Here it is essential to identify the most important contributors to the overall site risk. Escalation analysis, by its nature, tends to produce a large amount of data. A common output of this type of analysis highlights the frequency of an incident in one area escalating to another area.

Individual and Societal Risk Analysis – This assessment identifies the risk of fatality at any position on site and the risk of an accident with a given number of fatalities.

Financial Risk Analysis – The financial risk from an incident is defined by the frequency of an incident and the potential costs of the incident. The costs are divided between the total cost of an incident, including capital losses and production losses, the cost to the organisation and its brand as well as the local community.

A risk assessment of this type produces a large amount of information on the nature of the risks at a facility. In making the assessment, a number of assumptions also have to be made. These include estimates of the levels of equipment, shutdown and intervention probabilities, escalation paths, ignition probabilities and cost implications of events. There are uncertainties associated with all of these, but the approach used provides a best estimate of all of these and is consistently applied across the whole site.

In interpreting the results, it is the order of the risk which should be considered most closely. Similarly, in estimating the financial risk of an event, it is possible to derive an appropriate level of capital investment for reducing the risk by a certain factor. This is not meant to provide a definitive estimate of the capital which should be allocated on a risk reduction option, but rather the order or investment which can be justified; in some cases it is impossible to make much impact on the risk without major (very expensive) modifications to the plant, whilst in others a very simple modification may effectively reduce the risk by an order of magnitude.

Operators are required to describe the consequences so that they can show that they have assessed the risks and that adequate control measures are in place to prevent major accidents. This does not mean that such accidents will happen; the chance could be negligible when compared with day-to-day risks.

The description of major accident scenarios allows Authorities Having Jurisdiction (AHJ) including Civil Defence to properly judge, for example:

  • how well the operator has assessed the risks on the site;
  • whether the measures the operator has in place are adequate to prevent major accidents; and
  • the priority the AHJ will give to inspection activities.

This information is also used to prepare on- and off-site emergency plans which set out the arrangements for emergency response if a major accident happens. By understanding the risks associated with high hazard sites and preparing safety plans accordingly the likelihood of a major incident is dramatically reduced.

 



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