Hazard analysis and risk assessment techniques

If safety professionals are to anticipate hazards, they must participate in the design process. To be involved in the design process effectively, they must be skilled in hazard analysis and risk assessment techniques. Being a participant in the design process and using hazard analysis and risk assessment techniques are the basics of system safety. 

To be effective, safety professionals must understand hazards, risks, the relationship between hazards and risks, and hazards analysis and risk assessment techniques. In the use of hazard analysis and risk assessment matrices, judgments of incident probability and consequence will often be made on a subjective basis. And such systems can be made to work. They should be considered more art than science. 

Many hazard analysis and risk assessment techniques have been developed. These are just a few of the methodologies mentioned in the literature preliminary hazard analysis gross hazard analysis hazard criticality ranking catastrophe analysis change analysis energy flow/barrier analysis energy transfer analysis event tree analysis human factors review the hazard totem pole and double failure analysis. There are many other hazard analysis systems. 

This revision of an important ANSI standard is another indication of a trend, which emphasizes the need for safety practitioners to have knowledge of hazard analysis and risk assessment techniques. Almost all businesses and industries have lockout/tagout needs. 

Applying specifically developed hazard analysis and risk assessment techniques is a necessity in system safety applications. 

A bit of history on the evolution of system safety will give an insight into its origins, the need for the hazard analysis and risk assessment techniques which were developed, and the place that system safety has attained. Authors don t agree on when or where it all started. But, all the historical references on system safety do relate to the military or to aeronautics. 

DESCRIPTIONS OF HAZARDS ANALYSIS AND RISK ASSESSMENT TECHNIQUES... 

Over the past 40 years, a large and unwieldy number of hazard analysis and risk assessment techniques have been developed. For example, Pat Clemens gives brief... 

All the hazard analysis and risk assessment techniques previously discussed relate principally to the design process or achieving risk reduction in the operational mode before hazards-related incidents occur. MORT was developed principally for incident investigations. In the Abstract for the Guide To Use Of The Management Oversight And Risk Tree, this is how MORT is described ... 

Looking to the future, safety professionals can expect that being knowledgable about hazard analysis and risk assessment techniques will be required for job retention and career enhancement. Fortunately, it is not difficult to acquire the knowledge and skill required to fulfill almost all their needs. 

Hazard Analysis and Risk Assessment Techniques Top management shall adopt and apply the hazard analysis and risk assessment techniques suitable to the organization s needs and provide the training necessary to employees who will be involved in the process. Descriptions of eight selected techniques are presented in Addendum G. Addendum H is a Failure Mode and Effects Analysis form. 

In ANSI/ASSE Z590.3—2011, the Prevention through Design standard, Addendum G comments on only eight hazard analysis and risk assessment techniques, intentionally. They are Preliminary Hazard Analysis, What-If Analysis, Checklist Analysis, What-If Checklist Analysis, Hazard and Operability Analysis, Failure Mode and Effects Analysis, Fault Tree Analysis, and Management Oversight and Risk Tree (MORT). It was also said in Z590.3 that ... 

There is a reality in Browning s observations System safety literature at the time he wrote his book was loaded with governmental jargon, and it easily repelled the uninitiated. It made more of the highly complex hazard analysis and risk assessment techniques requiring extensive knowledge of mathematics and probability theory than it did of concepts and purposes. 

Safety professionals cannot properly give advice on hazards and risks unless the hazards are analyzed and the risks deriving from them are assessed as to their significance. This chapter works through the process of hazard analysis and subsequent risk assessment. It explores hazard analysis and risk assessment methods, discusses the jeopardy in using some published techniques, and concludes with a practical methodology outline. Since there has been a proliferation of risk assessment matrices in recent years, some of them are examined, for their pros and cons. 

For example, the hazard analysis and risk assessment requirements of the European Standard ISO 14121, Safety of Machinery—Principles for risk assessment (formerly EN 1050), have been adequately met in some companies in the design or redesign stages by applying an adaptation of the preliminary hazard analysis technique. 

Some who oppose the use of qualitative risk assessment techniques do so because the outcomes are not stated in absolutely assured, precise numbers. Such accuracy is not attainable because incident probability data are lacking and the severity of event outcomes is a best estimate. Expecting such results is unrealistic. Fortunately, recognition continues to grow that hazard analysis and risk assessment methods, although qualitative, add value to safety decision making. 

All employed dryers must be equipped with clear and comprehensive operating manuals prepared jointly by the equipment supplier and the plant operating management. The manual should be learned by the operators, who are to be trained in recognition of hazardous situations and risk assessment with the material being dried. Very useful techniques, known as Hazop (hazard and operability studies) and Kazan (hazard analysis), may be applied successfully in both new and existing processing plants [39,40]. 

Based on any unacceptable and unmitigated risk identified during hazard analysis, further risk assessment and risk mitigation techniques need to be applied. LORA and conceptual SIS designs based on Risk Matrix can be employed if a qualitative to semi-quantitative method is preferred. Fault tree and event tree analyses with a robust LOPA can be applied if a quantitative method is essential... 

Hazard analysis (HAZAN) is a quantitative way of assessing the likelihood of failure. Other names associated with this technique are risk analysis, quantitative risk assessment (QRA), and probability risk assessment (PRA). Keltz [44] expressed the view that HAZAN is a selective technique while HAZOP can be readily applied to new design and major modification. Some limitations of HAZOP are its inability to detect every weakness in design such as in plant layout, or miss hazards due to leaks on lines that pass through or close to a unit but cany material that is not used on that unit. In any case, hazards should... 

This chapter provides general information for performing qualitative or quantitative risk assessments on buildings in process plants. For detailed guidance on risk assessment techniques, the user is referred to other CCPS books on this subject, including Reference 3, Guidelines for Hazard Evaluation Procedures, Second Edition, and Reference 4, Guidelines for Chemical Process Quantitative Risk Analysis. 

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