HAZOP parameters

Appendix E HAZOP Parameters, Deviations, and Possible Causes... 

Parameters for HAZOP Parameters for Organizational Change Review... 

ABSTRACT The risks of manufactoring explosives are related to the energy accumulation which is the main property of explosives, and the subsequent risk of its unwanted liberation. Therefore, the risks managements programs and risks assessment tools are very important for explosives manufacturing. So, the main goal of this work is to discuss the suitability of HazOP and Fault Tree Analysis to the explosives industry, as well as propose a variation of HazOp parameters to best suit explosives manufactory... 

FIAZOP is a formally struetured method of systematieally investigating eaeh element of a system for all ways where important parameters ean deviate from the intended design eonditions to ereate hazards and operability problems. The HAZOP problems are typieally determined by a study of the piping and instrument diagrams (or plant model) by a team of personnel who eritieally analyze eflfeets of potential problems arising in eaeh pipeline and eaeh vessel of the operation. 

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. 

The HAZOP study proceeds in a systematic mamier that reduces the possibility of omi ssion. Within a study node, all deviations associated with a given process parameter should be analyzed before the ne.xt proces.s parameter is considered. All deviations for a study node should be analy zed before the team proceeds to the next node. 

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 4.15. Example HAZOP Study Process Parameters and Deviations...

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... 

Perform a HAZOP study on this unit to improve the safety of the process. Use as study nodes the cooling coil (process parameters flow and temperature) and the stirrer (process parameter agitation). 

These reviews can be either in addition to or combined with periodic process hazard analyses (PHAs) by using methods such as what-if analysis and HAZOP studies. The latter should consciously focus on identifying scenarios in which intended reactions could get out of control and unintended reactions could be initiated. One means of accomplishing this as part of a HAZOP study has been to include chemical reaction as one of the parameters to be investigated for each study node. Johnson and Unwin (2003) describe other PHA-related approaches for studying chemical reactivity hazards. 

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

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... 

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. 

Table 5.5. Common HAZOP analysis process parameters... 

A fundamental objective of a computer system applied to automate a pharmaceutical GMP operation is to ensure the quality attributes of the drug product are upheld throughout the manufacturing process. It is therefore important that quality-critical parameters are determined and approved early in the validation life cycle. The exercise should be undertaken to a written procedure with base information from the master product/production record file examined and quality-critical parameter values and limits documented and approved for the process and its operation. In addition, the process and instrument diagrams (P IDs) should be reviewed to confirm the measurement and control components that have a direct impact on the quality-critical parameters and data. This exercise should be carried out by an assessment team made up of user representatives with detailed knowledge of both the computer system application and process, and with responsibility for product quality, system operational use, maintenance, and project implementation. This exercise may be conducted as part of an initial hazard and operability study (HAZOP) and needs to confirm the quality-related critical parameters for use in (or referenced by) the computer control system URS. 

The HAZOP study was instrumental in determining the need for an adequate alarm system on each of the specified controllers. If liquid levels within the column are not well controlled, then either flooding (too much liquid) or plate by-passing bythegas (too little liquid) will occur. Both situations lead to a substantial reduction in absorption efficiency with large increases in emission levels. The other important control parameter was shown to be the temperature. If the temperature in the cooling-coil section rises, then there is an appreciable reduction in absorption. Control of temperature is important in the upper sections of the column because it is here that the greatest effect on emission levels occurs. 

HAZOP reviews have been stated as arising from the chemical industry in Britain during the 1960 s. Imperial Chemical Industries, Ltd. (ICI) developed a standardized method of analyzing processing hazards based on the basic operation conditions and then changed individual parameters one at a time to see the subsequent consequences. This evolved into a standard practice within their company and soon found its way into the general chemical industry (although it was not universally or consistently applied). 

A HAZOP study is undertaken by the application of formal, systematic, and critical examination of the process and engineering intentions of the process design. The potential for hazards or operability problems are thus assessed, and malfunction of individual items of equipment and associated consequences for the whole system are identified. This examination of the design is structured around a specific set of parameters and guidewords, which ensures complete coverage of all major possible problems. 

The following are typical guideword parameter, deviations, and possible causes that are used in HAZOP reviews. This listing is by no means exhaustive and each review should be supplemented or tailored to meet the needs of a particular facility. 

Figure 2. Simplified reflneiy SC flow diagram Table 1. Sample guidewords and parameters for HAZOP...

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