Report: APP CMHS Project 4

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2.1.6. Risk Assessment Techniques and Application

There are numerous techniques available for risk assessment (Table 3 and Table 4) – the choice of technique is dependent on a number of factors and must be determined as part of the scope of the process. Such factors include: the type and complexity of process; the types of hazards; level of risk; and stage of process lifecycle. National minerals industry safety and health risk assessment guideline is in

Table 3 Risk assessment techniques



Bow-tie analysis

Bow-tie analysis considers the hazards and consequences associated with an unwanted event. Potential hazards and controls are considered on the left hand side of the analysis. Consequences and mitigation of the consequences are treated on the right side of the analysis, thus forming a bow-tie shape. As for all other assessments, the important step is the translation of hazard and consequence controls into an action plan. Bow-tie analysis is particularly useful for major hazard mitigation.

Fault/Event Tree

Fault tree analysis is useful in identifying combinations of equipment failures and human failures that can lead to an accident. It uses a logic diagram to systematically work from an accident back to the range of initiating events that have the potential to lead to the accident. As well as being a useful Hazard Identification tool, a fault tree can be used to estimate the likelihood or probability of accidents event occurring.
Event tree analysis is primarily a tool used in consequence analysis, frequency analysis and risk summation, but it can also be valuable in the Hazard Identification process. The technique systematically works from an accident forward to the range of consequences that may result, with the end result a logic diagram showing the potential consequences of an accident, and the event sequences required to produce them.


Failure Modes, Effects and Criticality Analysis (FMECA) and Failure Modes and Effects Analysis (FMEA) are highly structured techniques. They are most often applied to a complex item of mechanical or electrical equipment, which contains a number of sub-systems and components. The overall system is broken down into a set of related of the equipment sub-systems, and each of these as a set of smaller sub-systems, and so on down to component level. Failures of individual systems, sub-systems and components are then systematically analysed to identify potential causes (which stem from failures at the next lower-level system), and to determine their possible effects (which are potential causes of failure in the next higher-level system). The technique is most often used to analyse the level of safety achievable by safety critical mechanical or electrical plant items such as firewater pumps, gas detection devices or trip systems.


Job Safety (or Hazard) Assessment a task oriented assessment applied by a work team prior to undertaking hazardous activities; useful for developing or modifying standard work procedures. Typical process is to identify the task steps, define any hardware needed, identify the hazards at each task step and describe the countermeasures to protect people from the hazards.


A Hazard and Operability Study was developed primarily for application to chemical process systems. It is a highly training structured technique that delivers a detailed understanding of the possible ‘deviations from design intent’, particularly those associated with process upsets and the operation of the process. HAZOP is less suitable for identification of hazardous scenarios associated with external events. Also, since HAZOP analyses a process using a ‘section by section’ approach, it may not identify hazards associated with the interactions between different nodes.


Human error analysis to identify and manage human error situations: describe the system, list and analyse the related human operations, analyse the human error potential, quantify the impact on the system, develop changes to the system.


Workplace Risk Assessment and Control a task oriented assessment applied by a multi-skilled team for the process of developing standard work procedures or management plans. Typical process is to identify task steps or activities, describe the hazards at each task step, list any existing controls for the individual hazard, consider the likelihood and consequence in determining the risk rank of each hazard and thereby indicate the criticality of administering the control and finally the establishment of an action plan for managing and implementing the controls.

Table 4 Websites of risk assessment techniques

Risk assessment technique


Bow-tie analysis

Fault tree

Event tree






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