Design risk assessment

The assessment team shouid have aooess to any information they deem necessary for them to conduct the assessment. This should include information from the hazard and risk assessment, design phase through instailation, commissioning and validation. 

An important part of hazard analysis and risk assessment is the identification of the scenario, or design basis by which hazards result in accidents. Hazards are constandy present in any chemical faciUty. It is the scenario, or sequence of initiating and propagating events, which makes the hazard result in an accident. Many accidents have been the result of an improper identification of the scenario. 

DATTA-BARUA Natural Gas Measurement and Control DEAN Lange s Handbook of Chemistry, Fourteenth Edition DESHOTELS, ZIMMERMAN Cost-Effective Risk Assessment for Process Design... 

Hazard and Risk Assessment Tools The hazard and risk assessment tools used vary with the stage of the project from the early design stage to plant operations. Many techniques are available, both quahtative and quantitative, some of which are hsted in the following section. Reviews done early in projects often result in easier, more effective changes. 

The proposed method can be applied to the speciation analysis of environmental solids for risk assessment of their contaminants as well as to design of effective leaching schemes. 

Next, we review the eosts of quality that typieally exist in a manufaeturing business, and how these are related to the way produets fail in serviee. The remainder of the ehapter diseusses the important elements of risk assessment as a basis for design. This puts in eontext the work on designing for quality and reliability, whieh are the main topies of the book. 

Many designers consider risk assessment to be an intuitive element of their work. ITowever, a formal process model that makes risks explicit, and stresses accountability, can only be an advantage. 

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... 

Transportation should be considered when assessing risks associated with planned or existing plants. The design of new chemical processing units should include at the earliest opportunity a qualitative or quantitative risk assessment of the whole system including production, use, and transportation in order to minimize overall risk. A brief discussion of the inherent safety aspects of transportation is included in Chapter 5. 

Plant designs should be based on a risk assessment that considers the process and the site in detail as well as all of the principles of inherently safer operation. Earlier decisions may limit the options in... 

Core damage and containment performance was assessed for accident sequences, component failure, human error, and containment failure modes relative to the design and operational characteristics of the various reactor and containment types. The IPEs were compared to standards for quality probabilistic risk assessment. Methods, data, boundary conditions, and assumptions are considered to understand the differences and similarities observed. 

The Pickering A Risk Assessment (PARA) (Ontario Hydro, 1995) is also a level 3 PSA for 1 of the 4 units at Pickering. A difference between PARA and DPSE is that sequences beyond the design basis were modeled using the MAAP-CANDU codes with best estimate assumptions. Other parts of the analysis used licensing-type conservative assumptions. 

Risk assessment The sequence of events necessary to ensure that a system is designed to provide the safest possible working arrangement. 

Capital Project Review and Design Procedures (for new or existing plants, expansions, and acquisitions) Appropriation request procedures Risk assessment for investment purposes Hazards review (including worst credible cases)... 

The third category of methods addressed in this chapter are error analysis and reduction methodologies. Error analysis techniques can either be applied in a proactive or retrospective mode. In the proactive mode they are used to predict possible errors when tasks are being analyzed during chemical process quantitative risk assessment and design evaluations. When applied retrospectively, they are used to identify the underlying causes of errors giving rise to accidents. Very often the distinction between task analysis and error analysis is blurred, since the process of error analysis always has to proceed from a comprehensive description of a task, usually derived from a task analysis. 

The other main application area for predictive error analysis is in chemical process quantitative risk assessment (CPQRA) as a means of identifying human errors with significant risk consequences. In most cases, the generation of error modes in CPQRA is a somewhat unsystematic process, since it only considers errors that involve the failure to perform some pre-specified function, usually in an emergency (e.g., responding to an alarm within a time interval). The fact that errors of commission can arise as a result of diagnostic failures, or that poor interface design or procedures can also induce errors is rarely considered as part of CPQRA. However, this may be due to the fact that HEA techniques are not widely known in the chemical industry. The application of error analysis in CPQRA will be discussed further in Chapter 5. 

Apostolakis, G. Data Analysis in Risk Assessments. Nuclear Engineering and Design, Vol. 71, July 1982. 

It is wortli noting tluit design calculations for tlie sizing of relief systems (relief valves, headers, scmbbers and knock-out drums, etc.) are conservative in order to protect tlie integrity of vessels and relief systems. Tlie calculations used for risk assessments are tliose which most accurately describe the discliarge rate from tlie luizardous incident being modeled. 

Once tlie system components and their failure modes have been identified, tlie acceptability of risks taken as a result of such failures must be determined. Tlie risk assessment process yields more comprehensive and better results when reliable statistical and probability data are available. In tlie absence of such data, tlie results are a strong function of tlie engineering judgment of tlie design team. The important issue is tliat both tlie severity and probability (frequency) of the accident must be taken into account. 

In addition to the product, the designer, equipment installer, user, and all others involved in production should all consider performing a risk assessment and target in the direction of perfection. The production is reviewed for hazards created by each part of the line when operating as well as when equipment fails to perform or complete its task. This action includes startups and shutdowns, preventative maintenance, QC/inspection, repair, etc. 

An exercise comprising individual statements, some describing everyday events and others more unusual, designed to increase participants awareness and understanding of the risk assessment procedure, both for themselves and others. 

Quantitative risk assessment is now used extensively for determination of chemical and microbial risks in food. This concept helps to systematically and scientifically judge whether certain hazardous compounds may reach unacceptable risk levels when ingested. Quantitative risk assessment can support both quality design and quality assurance but, we discuss it from the assurance perspective. In the past decade, much attention has been paid to assessment of microbial risks due to then-typical differences as compared to chemical risks ... 

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