Hazards evaluations

The hazards to be identified are those associated with machinery, equipment, tools, procedures, tasks, processes and the physical aspects of the plant and the site or premises where the work will be done - everything. Evaluation of the hazards is achieved by assembling information from those familiar with the hazards, such as insurance companies, professional societies, government departments and agencies, manufacturers, consultants and trade unions. Learning from records, including old inspection reports (both internally and externally produced), accident reports and standards is also important. 

Even so, some hazards may not be readily identifiable, and there are techniques which can be applied to assist in this respect. These include inductive analysis, which predicts failures - failure modes and effects analysis (FMEA) is one of these job safety analysis (JSA) is another. Inductive analysis assumes failure has occurred and then examines ways in which this could have happened by using logic diagrams. This is time-consuming, and therefore expen- 

As with many new processes, the goal of plasma etching was to find a more cost effective, environmentally sound, safer alternative to a chemically intensive procedure, in this case wet resist stripping. However, as with many new processes, new or subtle hazards may be introduced. Plasma-assisted etching was welcomed by the safety community since early plasma systems used nonhazardous gases such as oxygen and freons to perform operations that were traditionally performed in open tanks of corrosives and solvents. 

Since the list of plasma processing chemicals is limited only by the imagination, it is imperative that the researcher or process engineer assess the hazards of each process and process chemical change to eliminate fires, explosions or business interruption, adverse environmental effects, and most importantly, assure the safety of persormel. 

There are many hazard analysis formulations which may be used effectively to assess process hazards. These include fault-free analysis, failure mode and effect analysis (FMEA), what-if analysis, hazard and operability analysis (HAZOP), check list analysis, and safety review, among others. The specifics associated with these analyses can be reviewed by consulting the appropriate American Institute of Chemical Engineers Center for Chemical Process Safety reference.  

The important point in implementing any of these procedures effectively is to assemble a multidisciplinary team (review committee) represented by a technical representative or the principal investigator, safety, operations and/or other specialists or personnel as appropriate. Each representative brings knowledge and expertise of the process technology under review and provides differing perspectives of the hazards or problems to be assessed. 

Many different factors need to be evaluated when determining which process hazard review methodology should be utilized. These include the complexity of the equipment or process, previous e q)erience of accidents or incidents and the potential consequences of an adverse event such as serious injury or community contamination. Other parameters include time available, cost, etc., since the time and complexity of the various analyses varies widely. In general, the what-if analysis is the simplest and least expensive. 

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Center for Chemical Process Safety, Guidelinesfor Hazard Evaluation Procedures, American Institute of Chemical Engineers, New York, 1992. 

U.S. Dept, of Health, Education and Welfare, Health Hazard Evaluation Report 71 —72, NIOSH, Washington, D.C., July 1973. 

It is important to remember that some materials of low acute toxicity may have a significant potential for producing harmful effects by repeated exposure, and vice versa. This stresses the need for a complete overview of the toxicity of a chemical by acute and repeated exposure in the process of hazard evaluation. 

Table 15. Fire and Explosion Hazard Evaluation Data...

As the project progresses, more information is available therefore, the review technique used can be different at each stage of the project. The use of various hazard evaluation techniques, such as checklist analyses, relative rankings, what-if analyses, ana hazard and operabil-... 

FIG. 26-11 Hazard evaluation at various project stages. (CCPS, 1993, hy petmission of AIChE. )... 

Hendershot, D. 1992. Hazard Evaluation through the Life of a Process. AIChE Process Plant Safety Symposium, pp. 887-900. Houston, Texas, February 18-19, 1992. American Institute of Chemical Engineers, South Texas Section. 

Typical results from the various types of hazard evaluation techniques. 

How to select and use a hazard evaluation technique for your process. 

Two members selected from the team act in supportive roles during the PHA. These roles are the leader and the scribe. A team leader is always needed for a PHA and should double as the scribe only for extremely simple hazard evaluations. For more complex analyses or the HAZOP study method, a separate person should always be assigned to scribe. 

Is a decommissioning phase hazard evaluation needed The AIChE/CCPS text. Guidelines for Hazard Evaluation Procedures, Second Edition, offers direction for addressing this type of evaluation. 

The hazard evaluation step is where the issue of completeness primarily arises. It is impossible for the QRA analyst to identify and model all of the things that can possibly go wrong, and it is impractical to evaluate the frequency and consequences of every identified event. But you can reasonably expect trained and experienced practitioners using systematic... 

In the past, qualitative approaches for hazard evaluation and risk analysis have been able to satisfy the majority of decision makers needs. In the future, there will be an increasing motivation to use QRA. For the special situations that appear to demand quantitative support for safety-related decisions, QRA can be effective in increasing the manager s understanding of the level of risk associated with a company activity. Whenever possible, decision makers should design QRA studies to produce relative results that support their information requirements. QRA studies used in this way are not subject to nearly as many of the numbers problems and limitations to which absolute risk studies are subject, and the results are less likely to be misused. 

The PHI-TEC II adiabatic calorimeter as shown in Figure 12-17 was developed by Hazard Evaluation Laboratory Ltd. (UK). The PHI-TEC can be used both as a high sensitivity adiabatic calorimeter and as multi-purpose vent sizing device [17,18]. The PHI-TEC employs the principles established by DIERS and includes advanced features compared to the VSP. It also provides important information for storage and handling and provides useful insight into the options suitable for downstream disposal of vented material. 

Figure 12-17. PHI-TEC adiabatic calorimeter. (Source Hazard Evaluation Laboratory Ltd.)...

Figure 12-23. In(k seconds) versus -1,000/Absolute temperature plot of 20 w/w% di-tertiary butyl peroxide <(i = 1.09, (() = 1.75, and (() = 2.00). (Source Hazard Evaluation Laboratory Ltd.)...

The SIMULAR, developed by Hazard Evaluation Laboratory Ltd., is a chemical reactor control and data acquisition system. It can also perform calorimetry measurements and be employed to investigate chemical reaction and unit operations such as mixing, blending, crystallization, and distillation. Ligure 12-24 shows a schematic detail of the SIMULAR, and Ligure 12-25 illustrates the SIMULAR reaction calorimeter with computer controlled solids addition. 

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