Hazards and Operability HAZOP

Hazards and Operability (HAZOP) analysis is an accident detection and prevention technique used primarily by the chemical process industry (CPI) (Lees, 1980). Even though the CPI operates in a different regulatory environment from the commercial nuclear power industry, the goals of risk reduction while maintaining productivity are similar. 

A HAZOP team evaluates the plant through a process that involves sele tem, 

A key member of the HAZOP is the HAZOP leader whose duties are to  

The expertise of the HAZOP team depends on the system being analyzed. A typical HAZOP team should have expertise for the study in the following areas  

Electrical power Reactor physics Reactor systems Accident phenomenology 

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The cost of performing the hazard identification step depends on the size of the problem and the specific techniques used. Techniques such as brainstorming, what-if analyses, or checklists tend to be less expensive than other more structured methods. Hazard and operability (HAZOP) analyses and failure modes and effects analyses (FMEAs) involve many people and tend to be more expensive. But, you can have greater confidence in the exhaustiveness of HAZOP and FMEA techniques—their rigorous approach helps ensure completeness. However, no technique can guarantee that all hazards or potential accidents have been identified. Figure 8 is an example of the hazards identified in a HAZOP study. Hazard identification can require from 10% to 25% of the total effort in a QRA study. 

Hazards and Operability (HAZOP) Facility Risk Review Quantitative Risk Analysis... 

The what-if analysis is a creative, brainstorming examination of a process or operation conducted by a group of experienced individuals able to ask questions or voice concerns about undesired events. It is not as inherently structured as some other methods, such as the hazard and operability (HAZOP) study or a failure mode and effects analysis (FMEA). 

V Process hazard analysis (PHA) must be performed by a team of experts, including engineers, chemists, operators, industrial hygienists, and other appropriate and experienced specialists. The PHA needs to include a method that fits the complexity of the process, a hazards and operability (HAZOP) study for a complex process, and for less complex processes a less rigorous process, such as what-if scenarios, checklists, failure mode and effects analysis, or fault trees. 

Hazards and operability (HAZOP) studies This approach allows the mind to go free in a controlled environment. Various events are suggested for a specific piece of equipment with the participants determining whether and how the event could occur and whether the event creates any form of risk. 

The hazards identification procedures presented in chapter 10 include some aspects of risk assessment. The Dow F EI includes a calculation of the maximum probable property damage (MPPD) and the maximum probable days outage (MPDO). This is a form of consequences analysis. However, these numbers are obtained by some rather simple calculations involving published correlations. Hazard and operability (HAZOP) studies provide information on how a particular accident occurs. This is a form of incident identification. No probabilities or numbers are used with the typical HAZOP study, although the experience of the review committee is used to decide on an appropriate course of action. 

Failure mode and effect analysis (FMEA) A hazard identification technique in which all known failure modes of components or features of a system are considered in turn and undesired outcomes are noted. It is often used in combination with hazard and operability (HAZOP) studies or fault tree analysis. 

See also Hazard acceptance Hazard assessment Hazard identification entries limitations of, 13 153-154 probability, 13 166-170 purpose of, 13 152 scenario identification, 13 165 source modeling and consequence modeling, 13 165-166 sustainable development and, 24 183-188 techniques for, 13 152-154 Hazard and operability (HAZOP) analysis, 13 154, 157-159 guide words for, 13 158t sample, 13 159... 

Many different loss event scenarios are possible with intentional chemistry. All of them relate to losing containment or control of the intended reaction, starting another reaction, side reaction or series of reactions that are not intended or expected. A process hazard analysis, using a hazard and operability (HAZOP) study or other appropriate method, should be used to systematically identify and evaluate a full set of loss event scenarios. General causes of uncontrolled reactions include, but are not confined to, the following list ... 

For larger or more complex facilities, a systematic approach to identifying incompatibility scenarios and analyzing their severities and likelihoods may be warranted. A process hazard analysis (PHA) approach such as a hazard and operability (HAZOP) study can be an effective tool to facilitate such an effort, and may be required by regulation if the process falls within the scope of regulations. These methods are discussed in Section 4.5. 

Hazard and Operability (HAZOP) Study Scenario- based Inductive/ deductive By deviation from intended operation Processing systems with parameters such as flow, pressure, and temperature Good for both procedure-based and continuous operations Can analyze complex processes with multiple safeguards Only looks at causes that could lead to identified deviations Higher... 

Mosley et al. (2000) describe a "chemistry hazard analysis" approach, similar to a hazard and operability (HAZOP) study method applied at the early development stages of a new process. Deviations from an intended chemical reaction are identified using typical HAZOP guidewords. Examples of deviations and consequences developed using this approach are shown in Table 4.10. Analyzing the basic chemistry of a process, where chemical reactions are intended to occur, can help ensure the consequences of deviating from the intended reaction are understood. 

Hazard and operability (HAZOP) study, screening methods, 38-39, 63... 

Five of the seven respondents who use a matrix also use chemical testing results as a data source. A similar number review the matrix during qualitative hazard evaluation studies (i.e., hazard and operability [HAZOP] studies, what-if, checklist, etc.). 

PHA techniques involve a combination of what if for unit operations and hazard and operability (HAZOP) for both equipment- and procedural-based deviations. 

Checklists may also be used to supplement other tools for example, checklists on human factors may be used in conjunction with logic trees. Similarly, checklists may be used in combination with structured brainstorming tools such as What If/Checklist and Hazard and Operability (HAZOP) Analysis.(P It is also a good practice to apply a tool like the 5-Whys to the root causes identified from the checklist to verify whether they are truly root causes. 

Hazard and risk analysis is a vast subject by itself and is extensively covered in the literature [22]. In order to plan to avoid accidental hazards, the hazard potential must be evaluated. Many new methods and techniques have been developed to assess and evaluate potential hazards, employing chemical technology and reliability engineering. These can be deduced from Fault Tree Analysis or Failure Mode Analysis [23], In these techniques, the plant and process hazard potentials are foreseen and rectified as far as possible. Some techniques such as Hazards and operability (HAZOP) studies and Hazard Analysis (HAZAN) have recently been developed to deal with the assessment of hazard potentials [24]. It must be borne in mind that HAZOP and HAZAN studies should be properly viewed not as ends in themselves but as valuable contributors to the overall task of risk management... 

Process Hazards Analysis. Analysis of processes for unrecognized or inadequately controlled hazards (see Hazard analysis and risk ASSESSMENT) is required by OSHA (36). The principal methods of analysis, in an approximate ascending order of intensity, are what-if checklist failure modes and effects hazard and operability (HAZOP) and fault-tree analysis. Other complementary methods include human error prediction and cost/benefit analysis. The HAZOP method is the most popular as of 1995 because it can be used to identify hazards, pinpoint their causes and consequences, and disclose the need for protective systems. Fault-tree analysis is the method to be used if a quantitative evaluation of operational safety is needed to justify the implementation of process improvements. 

Before any mitigation measures can be designed, an effective hazard identification study must be conducted. The results of such a study (a set of release scenarios) can be used to develop a coherent set of mitigation strategies. In the process industries, these studies are most commonly conducted using hazard and operability (HAZOP) studies, what-if checklists, failure modes and effects analyses (FMEA), and several other comparable techniques (CCPS, 1992). 

Allowing time in the early stages of design for critical reviews and evaluation of alternatives would involve studies such as an early hazard and operability (HAZOP) study, using flowsheets, before final design begins,4 Fault tree analysis, quantitative risk assessment (QRA), checklists, audits, and other review and checking techniques can also be very helpful. These techniques are extensively discussed in the technical literature and will not be discussed in detail here. 

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