Chemicals HAZOP study

The primary limitation of a HAZOP study is the length of time required to perform it. Because the study is designed to provide a complete analysis, study sessions can be intensive and lii ing. HAZOP studies typically do not look at occupational hazards (e.g., electrical equipment, rotating equipment, hot surfaces) or chronic hazards (e.g., chronic chemical exposure, noise, heat stress). For experience with HAZOP see Swann (1995). 

HAZOP studies typically do not look at occupational hazards (e.g., electrical equipment, rotating equipment, hot surfaces) or chronic hazards (e.g., chronic chemical exposure, noise, heat stress). 

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. 

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. 

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. 

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.). 

Several qualitative approaches can be used to identify hazardous reaction scenarios, including process hazard analysis, checklists, chemical interaction matrices, and an experience-based review. CCPS (1995a p. 176) describes nine hazard evaluation procedures that can be used to identify hazardous reaction scenarios-checklists, Dow fire and explosion indices, preliminary hazard analysis, what-if analysis, failure modes and effects analysis (FMEA), HAZOP study, fault tree analysis, human error analysis, and quantitative risk analysis. 

The CSB survey identified examples of modified or hybrid techniques to identify reactive hazard scenarios and ensure the implementation of adequate safeguards. For example, companies conducting reactions in batch chemical reactors often conduct HAZOP studies by evaluating deviations from... 

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... 

Action Prepare a HAZOP study for a particular item (or section) of the chemical plant. 

The HAZOP Study is a very popular predictive method which was developed in the Mond Division of Imperial Chemical Industries during the 1960s. A HAZOP (Hazard and Operability) study is an analysis method for identifying hazards and problems which prevent efficient operation. Trevor Kletz was an early promoter of the HAZOP Method and in one of his recent books [18], he states ... 

HAZOP stands for Hazard and Operability Studies, a set of formal hazard identification and elimination procedures designed to identify hazards to people, processes, plants, and the environment. The techniques aim to stimulate the imagination of designers and operations people in a systematic way so they can identify potential hazards. In effect, HAZOP studies assume that there will be mistakes, and provide a systematic search for these mistakes. In some European countries, HAZOP studies are mandatory and attended by observers from regulatory authorities to ensure that the studies are carried out correctly. The examination of accidents52 during 1988 at a large U.S. chemical company revealed that the accidents could be classified as follows ... 

The term operability study should more properly be used for this type of study, though it is usually referred to as a hazard and operability study, or HAZOP study. This can cause confusion with the term hazard analysis , which is a technique for the quantitative assessment of a hazard, after it has been identified by an operability study, or similar technique. The Chemical Industries Association has published a Guide to Hazard and Operability Studies, CIA (1979b), which gives a comprehensive description of the technique and examples of its application. The method is also explained fully by Kletz (1999). Further examples are given by Lawley (1974), Wells (1980) and Austin and Jeffreys (1979). 

Identify hazardous chemicals from databases as discussed in Section 16.4.4 and from local legal regulations. Identify the potential for hazards from the checklist for reactivity (in Section 16.4.4) and from HAZOP-type studies or fault-tree analysis (Crowl and Louvar, 1990). In HAZOP studies, use checklist key words as triggers to systematically analyze the impact of changes to flow rate, temperature, pressure, composition, level, viscosity, heat transfer, reaction, and conditions and the potential for barrier failure and startup and shutdown to cause hazards. 

NUCLEAR HAZARD CATEGORY 1 FACILITIES. Fault tree/eveut tree analyses are required if the facility is a large reactor. If the facility is not a reactor and a PSM Rule PrHA is required, the analyses can be conducted as described for Nuclear Hazard Category 2 Facilities. Different systems or processes within the facility may be analyzed using different methods. For example, HAZOP studies may be used as the PrHA method for processes that contain chemical hazards. Fault tree/event tree analyses may be used to analyze systems that do not need to comply with the PSM Rule. 

The discussions to do with hazards analyses that have been provided up to this point in this chapter have been predicated on an assumption that the unit being analyzed is a processing operation— typically a section of a refinery, chemical plant, or oil/gas production facility. However, the techniques that have been discussed can be used, when adapted appropriately, to other types of industrial operation. For example, the deviation guidewords of a HAZOP study (the technique is discussed in the next chapter) can be modified to address transportation issues, as illustrated in Table 5.7. Reverse Flow, e.g., becomes Vehicle, Train, or Ship Reverses. ... 

As mentioned above an EIA may be prepared in the case of accidents. This requires preparation of an operational hazards (HAZOP) study, which indicates the emissions during the accident. Obviously the concentrations of the chemical substances in this case would greatly exceed allowable levels inside the factory site and outside the fences. The duration of this exposure would have an impact on the environment and health of the local population. This case requires preparation of special plans, e.g., contingency plans. Because modem... 

In HAZOP studies and what-if analyses, the review team must first identify the areas or components of the system that will each be analyzed during the review process. In the chemical industry, these individual components are typically referred to as nodes. There are three basic criteria for identifying the nodes to be reviewed (Nolan 1994) ... 

Once all what-if analysis questions have been asked and answered along with all completed HAZOP studies of system components, a final report should be written to document all findings and recommendations. In the chemical industry (in the United States), this report is normally referred to as a process hazard analysis. This report is required under both OSHA and EPA regulations for facilities that handle or contain certain chemical commodities at certain defined quantity thresholds. However, when HAZOP studies and what-if analyses are used in general industry application, documentation of the results can be included in a written report along with any other system safety analyses that may have been performed (as described in previous chapters). If the HAZOP and what-if exercises were conducted as standalone analyses, then a final written report should be... 

The analytical techniques known as the hazard and operability (HAZOP) study and the what-if analysis have their roots in the chemical industry. Their specific utility, when used either together or separately, has been demonstrated time and again in the analysis of hypothetical failure events and scenarios in large- and small-scale chemical production and processing facilities. However, there is no... 

Further information on Hazop studies may be found in the Chemical Industries Association s publication on the subject. ... 

A HAZOP study requires a multi-disciplinary approach by a team made up of technical specialists, i.e. chemical engineer, chemist, production manager, instrumentation engineer, safety adviser, etc. It is co-ordinated by a leader who guides the systematic investigation into the effects of the various faults that could occur and their effects. The success of this study depends heavily on the quality of the leader and the positive and constructive attitude of the team members. It is essential that the team have all the basic data plus line diagrams, flow charts etc. 

Dr. H.G. Lawley is very much associated with HAZOP for his contribution. HAZOP study was developed by ICl in the 1960s. Later the Chemical Industries Association supported HAZOP and produced a number of guidelines in 1977. 

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