Major Accident Event

Identify the possible major accident events on the asset/installation. 

Provide reasoned arguments and judgments about the risk acceptance criteria including the rationale for their acceptance, references used, and details of the risk acceptance studies conducted into potential major accident events that may occur during the life of the facility. 

Demonstrate that the operator has identified the nature, likelihood, and consequence of potential major accident events that may occur at the facility. 

Requirement for the SiS to survive a major accident event, e.g., whether fireproofing on shutoff vaives is required. 

Although a Safety Case can and should cover aU aspects of safety (occupational, process, and technical, as described in Chapter 1) the focus tends to be on identifying and avoiding what are known as Major Accident Events (MAE), i.e., catastrophic events such as fires, explosions, and the release of toxic chemicals. Associated with Major Accident Events are Safety Critical Elements and Performance Standards. 

A Major Accident Event (MAE) has the potential to cause multiple fatalities of persons at or near a facility. Natural events, such as a hurricane, can be counted as MAEs. The UK Health and Safety Executive (HSE) states that an offshore MAE generally involves one or more of the following ... 

Appropriate performance standards must be defined for the operation of the safety critical aspects. A performance standard is a standard established by the operator of the performance required of a system, item of equipment, person, or procedure which is used as a basis for managing the risk of a major accident event. 

The FSA should thoroughly analyze potential Major Accident Events that could lead to fatalities or major equipment and production loss. The analysis should show what safeguards have been put in place and how the facility would... 

Major accident event (this should be read in conjunction with Fig. 11/3.2.5-2) A major accident event is connected to the facility including external and natural events, which have the potential to cause fatality to persons at or near the facility including offsite (offsite is included here in light of the vastness of the major accident at Bhopal, India). 

Identification of hazards that can lead to a major accident event. 

In most cases a three tier approach is adopted, as shown in Fig. II/4.2.3-1. Initially, a qualitative or semiquantitative approach is taken to assess the risk and screen it. When risks are in a high risk zone or there is the possibility of a major accident event, then quantitative risk assessments are carried out to prescribe necessary control measures. It is quite common that in many cases a combined approach is necessary to justify consequence analysis. Mostly, when a quantitative approach is undertaken, prior preliminary analysis is done. From the diagram it is seen that whenever all replies to the queries shown in the diagram after qualitative analysis are NO, then the action stops. If any reply is YES, then the next level of analysis is carried out. A similar approach is applicable for semiquantitative and quantitative analyses (Fig. II/4.2.3-1). 

Some contents which are related to SIF, safe state, proof test interval, response time, manual shutdown, and etc. are commonly included as main requirements in all projects. However, safe process state, additional action, normal/abnormal mode and major accident event are sometimes dropped. There are some occasions that new requirements are often added to SRS such as design intent, consequence of failure and so on. 

Demonstrate that all reasonably practicable steps have been taken to ensure the safety of employees in the event of an emergency and during their transit to a place of safety. It should be demonstrated in particular that the integrity of the temporary refuge (TR), escape, and evacuation routes are maintained in the case of a major accident event, and that all reasonably practicable steps have been taken to ensure the safety of employees in the event of an emergency and during transit to a place of safety. 

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