Guided word HAZOP

One of the above methods—the guide word HAZOP —is recommended for detailed qualitative analysis if a detailed hazard identification is warranted at the end of an SLRA. Qualitative analysis generally ... 

Develop scope for more detailed hazard identification (e.g., guide word HAZOP ), and quantitative analysis, such as consequence modeling for establishing hazard zones for emergency response planning purposes. 

Since the original guide word HAZOP technique was developed, some companies have developed the knowledge-based HAZOP technique. It relies on the knowledge of team members to identify hazards with the design or operation of the facility, and as such can be considered as more of a safety review/checklist technique. We shall focus on the guide word technique in the remainder of this section. 

Table 1. List of Guide Words for HAZOP Procedure ...

This gives a process plant a specific HAZOP guide-word list with a process variable, plant condition, or an issue. 

Hazard and Operability Study (HAZOP) A systematic qualitative technique to identify process hazards and potential operating problems using a series of guide words to study process deviations. 

A HAZOP (Hazard and Operability Study) involves a fonual review of proeess and instrumentation diagrams by a speeialist team using a stmetured teehnique, based upon key words. These eomprise property words and guide words , e.g. as in Table 12.4. 

The procedure for a HAZOP study is to apply a numher of guide words to various sections of the process design intention. The design intention informs what the process is expected to caiTy out. Table 12-6 shows these guide words, and Figure 12-42 summarizes the entire procedure. Common property words are ... 

List of guide words used for the HAZOP procedure... 

I iach study node is examined for potentially hazardous process deviations. First, i he design inte-iit of the equipment and the process parameters is determined and recorded. Process de iatiuns from the design are determined by associating guide words with important process parameters. (iiiidt words for a HAZOP analysis are shown in Table 3.3.4--1 process parameters and dt. i itions are shown in 1 able, T3.4-2. 

When studying a batch plant, the guide words should be applied to the instructions as well as the pipelines. For example, if an instruction says that I ton of A should be charged to a reactor, the hazop team should consider the effects of the following deviations ... 

Another danger of an inadequate appreciation of human causes of hazards is that the HAZOP analyst may consider a particular high risk event (identified by a guide word and deviation) to be noncredible, because he or she only takes into accoimt the hardware failures (with an extremely low probability) that could give rise to the event. When human causes are taken into accoimt, the likelihood of the event may actually be quite high. 

TABLE 15.7.1 Guide Words Used in HAZOP Studies... 

Another qualitative approach to recognizing imd identifying possible hazards that may cause problems is a hazard and operability study (HAZOP). By identifying the goals of the study and by using guide words, a comprehensive report on the safety of a system can be created. 

List and discuss the seven key guide words that are employed in a HAZOP study. 

The basic concept behind HAZOP studies is that processes work well when operating under design conditions. When deviations from the process design conditions occur, operability problems and accidents can occur. The HAZOP study method uses guide words to assist the analysis team in considering the causes and consequences of deviations. These guide words are applied at specific points or sections in a process and are combined with specific process parameters to identify potential deviations from intended operation. 

The HAZOP team examines each study node for potentially hazardous process deviations. First, the design intent is defined to delineate the purpose of the equipment and the process parameters. Process deviations are determined by combining guide words with the important process parameters. The established set of guide words is shown in Table 4.14. 

The process parameters and example deviations typically used in a HAZOP study are shown in Table 4.15. Additional process parameters can be added if warranted. One purpose of the guide words is to assure that all relevant deviations of process parameters are evaluated. 

Table 10-3 Guide Words Used for the HAZOP Procedure...

Table 10-6 presents one type of basic HAZOP form. The first column, denoted Item, is used to provide a unique identifier for each case considered. The numbering system used is a number-letter combination. Thus the designation 1 A would designate the first study node and the first guide word. The second column lists the study node considered. The third column lists the process parameter, and the fourth column lists the deviations or guide words. The next three columns are the most important results of the analysis. The first column lists the possible... 

Identify as many failure modes as possible. Use the HAZOP guide words to identify additional possibilities. 

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. 

HAZOP (HAZard and OPerabdity study) A formal hazard identification and evaluation procedure based on the application of guide words to identify possible deviations from the intended operation of the process. 

TABLE 23-21 Some HAZOP Guide Words Used in Conjunction with Process Parameters ... 

The guide words are used in conjunction with the process intentions to generate possible deviations from the intended operation (see Table 23-21). Some examples of deviations that might be generated in the course of a HAZOP study include... 

TABU 23-22 HAZOP Guide Words Associated with Time... 

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... 

Based on personal experience, the what-if analysis and HAZOP seem to be the most user-friendly methodologies to use. In the following example we describe the what-if analysis procedure and sample checklists typically used for chemicals used in wastewater treatment. Moreover, guide words, meanings, process parameters, and procedures for conducting HAZOP are also presented. 

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