Hazards and operability analysis

At various stages of the design process, a HAZOP (Fig. 7) must be conducted on the project. The purpose of this analysis 

The HAZOP reviews will look at each detail of the process, examine what is happening in that stage of the process, and then question a series of what if potential failures. Questions such as a failure of a control, loss of power, will generate a list of possible reactions to that failure mode. The failure list is then generated from experience with similar process arrangements 

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Hazard and Operability Analysis. The hazard and operabihty analysis (HAZOP) procedure is quite popular because of its ease of use, the abihty to organize and stmcture the information, minimal dependence on the experience of the analysts, and the high level of results. Furthermore, the approach is capable of finding hazards associated with the operation of a faciUty, hence the incorporation of the word operabihty in the name. 

Another widely used safety analysis method in process industry is the Hazard and Operability Analysis, better known as Hazop (Kletz, 1992). The conventional Hazop is developed to identify probable process disturbances when complete process and instrumentation diagrams are available. Therefore it is not very applicable to conceptual process design. Kletz has also mentioned a Hazop of a flowsheet, which can be used in preliminary process design, but it is not widely used. More usable method in preliminary process design is PIIS (Edwards and Lawrence, 1993), which has been developed to select safe process routes. 

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. 

Hazard and Operability Analysis (HAZOP) Identification of process disturbances with the quide words No, not more, less as well as part of reverse other than sooner, later other place... 

Hazard and operability analysis (HAZOP) A qualitative hazard analysis technique to identify and... 

If there is no hypothesis for the event, use an inductive method to find potential scenarios. Inductive methods speculate a given fault or failure, then look forward in time to determine the probable outcome, that is, What would happen if... Inductive methods include using a Checklist or a Hazard and Operability Analysis (HAZOP). 

Methods for performing hazard analysis and risk assessment include safety review, checklists, Dow Fire and Explosion Index, what-if analysis, hazard and operability analysis (HAZOP), failure modes and effects analysis (FMEA), fault tree analysis, and event tree analysis. Other methods are also available, but those given are used most often. 

Basically, it remains up to the design engineer and/or end user to determine whether and which type of SRV is to be used when doing a hazard and operability analysis (HAZOP). 

Identifying the potential hazards (PHA, process hazard analysis, or HAZOP, hazard and operability analysis) during operation must be done from a wide-angle approach dangerous situations can occur due to many root-cause situations other than those specified by, for instance, ASME or PED. Based on the results of the risk assessment, the pressure equipment can be correctly designed and the most effective safety system selected. 

Chapter 3 presents introductory aspects of safety and human factors. Chapter 4 is devoted to methods considered useful to perform patient safety analysis. These methods include failure modes and effect analysis (FMEA), fault tree analysis (FTA), root cause analysis (RCA), hazard and operability analysis (HAZOP), six sigma methodology, preliminary hazard analysis (PFfA), interface safety analysis (ISA), and job safety analysis (JSA). Patient safety basics are presented in Chapter 5. This chapter covers such topics as patient safety goals, causes of patient injuries, patient safety culture, factors contributing to pahent safety culture, safe practices for better health care, and patient safety indicators and their selection. 

The hazard and operability analysis (HAZOP) technique was developed to identify both hazards and operability problems in chemical process plants. An interdisciplinary team and an experienced team leader are required. In a HAZOP application, a process or operation is systematically reviewed to identify deviations from desired practices that could lead to adverse consequences. HAZOPs can be used at any stage in the life of a process. 

Where multiple, diverse hazards exist, the practical approach is to treat each hazard independently, with the intent of achieving acceptable risk levels for all. In the noise and toluene example, the hazards are indeed independent. In complex situations, or when competing solutions to complex systems must be evaluated, the assistance of specialists with knowledge of more sophisticated risk assessment methodologies such as Hazard and Operability Analysis (HAZOP) or Fault Tree Analysis (FTA) may be required. However, for most applications, this author does not recommend that diverse risks be summed through what could be a questionable methodology. 

In ANSI/ASSE Z590.3—2011, the Prevention through Design standard, Addendum G comments on only eight hazard analysis and risk assessment techniques, intentionally. They are Preliminary Hazard Analysis, What-If Analysis, Checklist Analysis, What-If Checklist Analysis, Hazard and Operability Analysis, Failure Mode and Effects Analysis, Fault Tree Analysis, and Management Oversight and Risk Tree (MORT). It was also said in Z590.3 that ... 

There are many hazard analysis formulations which may be used effectively to assess process hazards. These include fault-free analysis, failure mode and effect analysis (FMEA), what-if analysis, hazard and operability analysis (HAZOP), check list analysis, and safety review, among others. The specifics associated with these analyses can be reviewed by consulting the appropriate American Institute of Chemical Engineers Center for Chemical Process Safety reference. " ... 

Other methods such as Failure Mode and Effects Analyses (FMEA) and Hazard and Operability Analysis (HAZOP) were developed not just to analyse possible causes of hazards (and, later on, causes of accidents), but also systematically to identify hazards and risks before a system was taken into operation or when a major change was considered. 

The second and much more detailed step was a HAZard and OPerability analysis (HAZOP). (A detailed description of this method can be found in [5], too.) Each node... 

The methods used to identify PIEs should be described. This may include, among other things, the use of analytical methods such as master logic diagrams, hazard and operability analysis, and failure mode and effects analysis (FMEA). Initiating events that can occur owing to human error should also be considered in the identification of PIEs. Whichever method is used, it should be demonstrated that the identification of PIEs has been performed in a systematic way and has led to the development of a comprehensive list of events. 

However, failure analyses have been carried out long before that. The first failure analyses were based on methods brought to the US from German scientists after the Second World War but also in other industries some methods developed and became standards. This chapter will also cover reliability block diagrams (which can be certainly directly derived from Lusser s law) as weU as HAZOP (hazard and operability) analysis, which has its roots in the chemical industiy as well as the oil and gas industry. 

Compare hazards and operability analysis with interface safety analysis. 

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