Use of Guide Words

Use guide words such as no/less/excess/more/higher, etc., for various parameters such as flow of reactants, heating medium, cooling water, and levels in tanks for each section of the plant to examine further (more details are given below for such HAZOP study). 

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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. 

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

Part of Design intentions only partly achieved. It IS more precise to use the guide word less" wherever possible. However, fluctuations m a property word are covered by part of. 

While risk assessment in the context of protecting public health has been performed for many years, it is the 1983 U.S. National Academy of Sciences Report (Committee on the Institutional Means for Assessment of Risks to Public Health Commission on Life Sciences National Research Council 1983) that has served as the tenet for practicing risk assessors (see Chapter 1). Risk assessment was defined as the characterization of the potential adverse health effects of human exposures to environmental hazards. The predictive aspect of risk assessment was set by the use of the word potential. A fundamental expectation of the risk assessment process was that it should attempt to accm-ately predict adverse effects before there is evidence of disease in the population. Thus, risk assessment goes beyond the mere description of epidemiological and clinical case-control studies. In that report, the committee defined logical components of a risk assessment which still serve as guiding principles today. They were and are (a) hazard assessment or the qualitative determination that a stressor poses a hazard as evidence by causal evidence of an ill effect,... 

Tab. 10-1 Examples of guide words used in a HAZOP study (adapted from an ICI HAZOP seminar)...

Once the nodes have been defined, and the safe operating limits identified, the hazards are determined. A hazard is a deviation outside the safe operating limit that is identified through the use of deviation guide words. The most commonly used deviation guide words are ... 

The first set of postulations used a series of guide words, similar to that used in HAZOPs (HAZard and OPerability studies (Lees F. P. 2005)) in the chemical processing industry, to examine what if situations. 

Sometimes referred to as energy flow analysis, HazOps is used primarily in the petrochemical industry. It uses a multidisciplinary team similar to a system safety working group for the systematic review of the flow of materials through a process. It concentrates on key locations in the process known as study nodes and uses a series of guide words and parameters to examine possible deviations and the causes and consequences of deviations (Goidwaite 1985). 

HAZOPs usually require a series of meetings in which the team, using process drawings, systematically evaluates the impact of deviations from the desired practices. The team leader uses a set of guide words to develop discussions. As the team reviews each step in a process, they record any deviations, along with their causes, consequences, safeguards, and required actions, or the need for more information to evaluate the deviation. 

Hazard analysis aetivities have been performed for some time by the Trust. The added value of reeent improvements has been to provide a formal framework and associated methods into which they fit as a major component. The analyses were founded on traditional risk management techniques. These have been reviewed and developed, resulting in a similar format for the records produced. Improvements have been made by using a team rather than an individual for carrying out the analysis. The use of a set of guide words has helped to enable a consistent approach to the examination of design representations of the system under review. The technique was heavily based on the HAZOP method advocated in Def Stan 00-58 (MoD 1986) in this, it evolved into a similar form to that promoted as SHARD (Pumfrey 1999). 

Hazard and Operability study (HazOp) A technique for identifying hazards and operating problems by using a series of guide words to identify possible deviations from intended process parameters. 

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