Approach to Hazards

Hazard and Operability Analysis (Hazop) (Kletz, 1992) is one of the most used safety analysis methods in the process industry. It is one of the simplest approaches to hazard identification. Hazop involves a vessel to vessel and a pipe to pipe review of a plant. For each vessel and pipe the possible disturbances and their potential consequences are identified. Hazop is based on guide words such as no, more, less, reverse, other than, which should be asked for every pipe and vessel (Table 1). The intention of the quide words is to stimulate the imagination, and the method relies very much on the expertise of the persons performing the analysis. The idea behind the questions is that any disturbance in a chemical plant can be described in terms of physical state variables. Hazop can be used in different stages of process design but in restricted mode. A complete Hazop study requires final process plannings with flow sheets and PID s. 

The process hazard analysis required by OSHA PSM is an example of a performance-based approach it allows for a variety of hazard analysis methodologies. A performance-based system requires experts to identify and evaluate all relevant reactive hazards of a process and to determine the complexity of the hazards analysis. If the hazard evaluation demonstrates the possibility of a catastrophic consequence, the process has regulatory coverage. This approach to hazard evaluation allows for both a comprehensive analysis and flexibility in implementation however, if applied to reactive hazards, it requires expertise for implementation and regulatory evaluation. 

Fire, F. A., The common Sense Approach to Hazardous Materials, PennWell Publishers, New York, 1986. 

Fire, F.L. (1986) The Common Sense Approach to Hazardous Materials, PennWell Publications, Tulsa,... 

This type of incident is difficult to predict. Nevertheless, by using a systematic approach to hazard identification it should become clear that any water entering the reactor could lead to an explosion. Therefore when changing some parts of the equipment, even if they are not directly involved in a given process, especially in multi-purpose plants, one should at least consider possible consequences on the safety parameters of the process. 

NCRP undertook a study of waste classification because of the importance and visibility of hazardous waste management in the United States coupled with the observation that the existing classification systems for hazardous wastes are increasingly complex and inefficient. This determination led to the independently conceived alternative approach to hazardous waste classification described in this Report. 

The approach to hazard identification in the proposed revision of the cancer risk assessment guidelines (EPA, 1996a) differs from the... 

To develop a tiered approach to hazard classification, it is first necessary to use existing data to develop the CMs that will serve as the individual steps of the tiered strategy. The example presented in this chapter used existing data on skin corrosion, and represents a development of earlier work (Worth et al., 1998). 

Figure 18.2 A tiered testing strategy for skin corrosion based on the OECD approach to hazard classification.

III. EVALUATION OF THE TIERED APPROACH TO HAZARD CLASSIFICATION A. Evaluation Method... 

The tiered approach to hazard classification was evaluated by simulating possible outcomes obtained when a stepwise strategy comprising three alternative tests and one animal test (Figure 18.2) is applied to a heterogeneous set of 51 chemicals (Table 18.7). The decision rules in steps 1 to 3 are based on the CMs for skin corrosion developed above. 

The results of this study and of a previous study (Worth et al., 1998) show that stepwise approaches to hazard classification, in which alternative methods are applied before animal tests, provide a promising means of reducing and refining the use of animals. In these approaches, fewer animal experiments need to be conducted, and of those chemicals tested in vivo, the majority are found to be non-toxic. 

Finally, it is important to note that the approaches to hazard classification described in this chapter represent just two possible ways of integrating the use of different CMs other designs are conceivable. For example, if each prediction of toxic and non-toxic potential were associated with a probability (e.g., a 70% probability of being corrosive), thresholds other than 50% could be chosen for the identification of toxic and non-toxic chemicals. In fact, models derived by logistic... 

In certain cases, such as changes created by a significant expansion, it is better to have a small group of specialists first identify the potential hazards and seek our inherently safer designs prior to any type of committee review. Brief descriptions of various approaches to hazard identification are presented in Appendix B to this chapter. 

HACCP provides a very basic approach to hazard analysis and control. Computer systems supporting licensed products with medicinal properties should consider more rigorous techniques, such as CHAZOP and FMEA, described below. 

When prioritizing validation, it is important to consider critical dependencies on particular computer systems. Hazards must be controlled. A stepwise approach to Hazard Control is given below ... 

As a result of the considerations presented here, it is not believed that MCS represents a viable scientific basis for developing AEGL values, including further adjustments for susceptible subpopulations, at the present time. However, the NAC/AEGL Committee recognizes the need for scientific research on this proposed syndrome that may help explain and describe its features, enable scientifically vahd approaches to hazard or risk assessment, and define appropriate clinical interventions. Also, the committee considers all new data or information that is scientifically credible and relevant to the development of AEGL values. 

We present a new approach to hazard analysis and assessment, one that begins with the inductive determination of hazardous chemical or physical... 

McKim, J.M., S.P. Bradbury, and G.L Niemi. 1987. Fish acute toxicity syndromes and their use in the QSAR approach to hazard assessment. Environ. Health Perspect. 71 171-186. 

Lunn G, Sansone EB, Keefer LK. 1983. Reductive destruction of hydrazines as an approach to hazard control. Environ Sci Technol 17 240-243. 

Use of an integrated approach to hazard analysis will result in effectively identifying site and facility hazards, including chemical hazards and the hazards associated with the disposal of the hazardous chemicals. Analysis can begin at these levels by assessing chemicals present in quantities greater than the threshold quantities (TQ) found in 29 CFR 1910.119 and 40 CFR 355. These materials are generally analyzed from the process safety perspective, i.e., potential for a catastrophic accident with immediate consequences. 

DOE-STD-1120-98 Table 1, Hazard Analyses Required by Directives (taken from DOE-STD-1120-98, Integration of Environment, Safety, and Health into Facility Disposition Activities ), presents a model integrated approach to hazard analysis, which was piloted at Hanford. This table illustrates one example of the types of hazard analyses required by various directives. 

The most widely used existing hazard analysis techniques were developed fifty years ago and have serious limitations in their applicability to today s more complex, software-intensive, sociotechnical systems. This chapter describes a new approach to hazard analysis, based on the STAMP causality model, called STPA (System-Theoretic Process Analysis). 

For example, the FTA approach is logical and rational. The persons building the tree assume that the base events, and the manner in which they interact with one another, have been defined before the analysis starts. However, fault tree analysts will often identify new incident scenarios and find new types of hazard. In other words, this logical/rational approach to hazards analysis can also be creative and imaginative. ... 

An FMEA is a bottom-up approach to hazards analysis. When linked with a top-down method (such as FTA) a powerful synergy can ensue. The top-down method will highlight those areas which pose the greatest risk the FMEA can then be used to investigate those areas in greater detail. Like other types of hazards analysis, an FMEA should be carried out by a team. In most cases, however, only two or three team members—who are specialists in the required fields— are involved. 

Those professionals involved in establishing effective loss control programs must understand the interrelationships in the worker-equipment-environment system. A system approach to hazard control recognizes the interaction between the worker, equipment, materials, and the environment in the performance of work [p. 104]. 

For small Category A reactors, all Category B reactors, and critical facilities, implementation of the graded approach to hazard analysis should be used to evaluate the application of containment related design criteria. 

Attention focuses on individual error Systems approach to hazards and prevention... 

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