Carrying out a HAZOP

The methodology varies slightly according to whether the process is continuous or batch. In all cases it is the responsibility of the study leader to decide before the study how it will be conducted, the order in 

1 Continuous Processes. The main drawing is examined pipeline by pipe-line. For each line the designer s intention is made clear and written down. For example, the intention might be to convey a liquid from vessel A to vessel B, at a flow rate of x, pressure of y and a temperature of z. The composition is. .. and so forth. Since the process is continuous, each part of the intention will be independent of time. 

To each part of the intention a guide word is now applied. The guide words are typically  

More or too much (more than the intention takes place)  

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The fitter who installed the expansion joint incorrectly could have prevented the fire. So could the person who was responsible for her or his training and supervision so could the designers if they had not specified an expansion joint, had carried out a HAZOP, or had consulted experts so could the author of the company s design standards, and those responsible for the training of designers those responsible for inspection of workmanship, and anyone who kept his or her eyes open when walking round the plant. 

On one project, a team was asked to attend a 1-day meeting. In the morning, the team conducted a P ID review in the afternoon the same team, meeting in the same room, carried out a HAZOP on the same P IDs (with some marks from the morning s work). Yet the two meetings— the review and the HAZOP—were totally different in style and substance. 

The HAZOP technique also can be used for the evaluation of procedures. Procedures may be regarded as a system designed to program an operator to carry out a sequence of correct actions. Deviations from intent are developed, with the emphasis on operator action deviation rather than physical property deviation. It is the procedure, not the hardware, that is the object of study, but hardware modifications may be recommended to cover potential problems identified from procedure deviations. 

The team responsible to build the matrix should include, besides experienced DCU operators, automation specialists and process engineers involved in the DCU design and operation. Ideally, the experts responsible for the matrix development should integrate the H AZOF team, which is performed in a foUowing step inside the DCU basic design phase. During the hazard identification carried out with HAZOP methodology. 

The Gulf of Mexico has between 5000 and 6000 platforms—many of them small and in shallow water. It is simply not economically feasible to write a safety case for each platform. Arnold (2010) uses the example of the response to a proposed requirement from the MMS to carry out a Failure Modes and Effects Analysis (FMEA) on each facility. Instead of doing this, generic FMEAs and HAZOPs (Hazard and Operability Studies) were carried out on 13 facilities. This was done because the process equipment and instrumentation are very similar to one another for these platforms. 

In the forthcoming Hazop standard (IEC 61882, 1999) the Hazop studies are recommended to be carried out throughout the life cycle of a system. But for the concept and definition phase of a system s life cycle other basic methods are suggested (see Fig. 3). 

A HAZOP study is cumbersome and time-consuming. However, it is believed that the outcome of a perfectly carried out HAZOP study is that no HAZAN (or PRA) study is needed. 

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

A small team, similar to that used in HAZOP, carries out hazard analysis. The three steps in HAZAN are ... 

Hazard Study 3 (Hazard and Operability study, HAZOP) is carried out when the design of the process is finalised and detailed. The basic premise of a Hazard and Operability study is that hazards may occur on chemical plant when situations arise which the designer had not thought about. HAZOP sets out to identify these situations. There are many books and publications giving instruction, advice and background to these studies, and some organisations make these freely available (for example, the Royal Society of Chemistry Environmental Health and Safety Committee s Notes on Hazard and Operability Studies 13 March 2001). 

A basic assumption is that where a set of process considerations has been identified by the process engineer, the resulting design has been carried out accurately and competently. HAZOP looks for situations unrecognised by the designer ( deviations ) and examines whether there may be a hazardous implication. Thus, a HAZOP is NOT a place to carry out design work, a problem solving exercise, or a technique for... 

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 HAZOP technique can be used to identity human error potential. From a practical point of view, human error and its consequences can occur at all levels of a management structure as well as in the operation of a particular plant or process. Carried out correctly, Technica54 states that a HAZOP study will identify at least 70-75 percent of potential operational and safety problems associated with a particular design process, including human error. 

A brief outline of the technique is given in this section to illustrate its use in process design. It can be used to make a preliminary examination of the design at the flowsheet stage, and for a detailed study at a later stage, when a full process description, final flowsheets, P and I diagrams, and equipment details are available. An as-built HAZOP is often carried out after construction and immediately before commissioning a new plant. 

A method for carrying out process evaluation during project execution and/or immediately prior to entering start-up procedures was formalized and pioneered in the early 1960s by ICI (Imperial Chemical Industries, UK) [10.2]. The technique, called Hazard and Operability study (HAZOP), is designed to minimize sources and occurrences of failure. Basically, it is a deviation analysis. 

Before a process can be introduced into a factory, it is usual to carry out what is referred to as a hazard and operability study, or HAZOP. 

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