Preliminary hazard analysis discussion

All of the hazard analysis techniques discussed in this chapter follow this hazard analysis process. The remainder of this chapter describes the most coimnonly used hazard analysis techniques and gives some concrete examples of their applications. However, the first step in using hazard analysis is to create a preliminary hazard list (PHL). 

The job safety analysis (JSA) [also referred to as the job hazard analysis (JHA)], which is a more simplified form of task analysis, has been a longstanding tool for task and function analysis. JSA has been available and utilized in general industry for many years by the industrial safety community. However, many practitioners do not understand or are simply unfamiliar with the connection between the JSA and the system safety tasks of hazard identification and analysis. It has even been suggested by some in the profession that the JSA itself is a type of oversimplified system safety analysis and, if performed earlier in the job development phase, could be used as the basis of a preliminary hazard analysis for a specific task or set of tasks. However, because JSA is often (if improperly) used to analyze a function only after it has been implemented, much of the data is not factored into the system safety process. The primary purpose of the JSA is to uncover inherent or potential hazards that may be encountered in the work environment. This basic definition is not unlike that previously discussed regarding the various system safety analyses. The primary difference between the two is subtle but important and is found in the end-use purpose of the JSA. Once the job or task is completed, the JSA is usually used as an effective tool for training and orienting the new employee into the work environment. The JSA presents a verbal picture of a specific job. 

In an effort to demonstrate the utDity of the preliminary hazard list and the preliminary hazard analysis in the initial evaluation of system risk, an example of a simple vapor degreaser in a manufacturing facility will be examined. This illustration will utilize the PHL in the development of the PHA in the method discussed earlier in this chapter. However, it must be noted from the outset that this example is intended... 

The SSHA evaluates hazardous conditions, on the subsystem level, which may affect the safe operation of the entire system. In the performance of the SSHA, it is prudent to examine previous analyses that may have been performed such as the preliminary hazard analysis (PHA) and the failure mode and effect analysis (FMEA). Ideally, the SSHA is conducted during the design phase and/or the production phase, as shown in Chapter 3, Figure 3.4. However, as discussed in the example above, an SSHA can also be done during the operation phase, as required, to assist in the identification of hazardous conditions and the analysis of specific subsystems and/or components. In the event of an actual accident or incident investigation, the completed SSHA can be used to assist in the development of a fault tree analysis by providing data on possible contributing fault factors located at the subsystem or component level. 

This example will develop a hardware FMEA for a proposed system that is well into the design phase of the product life cycle. For informational purposes, it is assumed that a preliminary hazard analysis was previously performed during the early stages of the design phase of this system. The information from the PHA will be used to assist in the development of the hardware FMEA. It should also be noted that the nature of a FMEA requires evaluation of subsystems, subassemblies, and/or components. For this reason, more detailed and specific descriptive information is provided here than that supplied for previous examples discussed in this text. 

Definition of hazard, risk discussions on likelihood, consequence risk — register, matrix, ranking. Consequence ranking, preliminary hazard analysis tolerance point—ALARP refreshing on mathematics, fault tolerance, plant ageing, and basic functional safety fail safe operations in plants. 

It is common practice to identify the hazard control and follow up action as a part of hazard identification and preliminary hazard analysis (discussed in detail in the next chapter). In order to control hazard, one has to look for safety interfaces also. So, the following points need to form a part of initial hazard study especially for industrial or process plants, so that entire spectrum is well-covered ... 

In the previous chapter, it was established that in industry, plant hazards can cause harm to property (plant—machinery, asset), people, or the environment. So, it is important to develop some means of analyzing these and come up with a solution. Unfortunately, it is not as straightforward as it sounds. There are plenty of plant hazard analysis (PHA) techniques and each of them has certain strengths and weaknesses. Also each specific plant and associated hazard has specific requirements to be matched so that hazard analysis will be effective. In this chapter, various hazards (in generic terms) will be examined to judge their importance, conditions, quality, etc. so that out of so many techniques available for PHA it is possible to select which one is better (not the best because that needs to be done by experts specifically for the concerned plant) suited for the type of plant. So, discussion will be more toward evaluation of PHA techniques. Some PHA is more suited for process safety management (PSM) and is sometimes more applicable for internal fault effects [e.g., hazard and operability study (HAZOP)]. In contrast, hazard identification (HAZID) is applicable for other plants, especially for the identification of external effects and maj or incidents. HAZID is also covered in this chapter. As a continuation of the same discussion, it will be better to look at various aspects of risk analysis with preliminary ideas already developed in the previous chapter. In risk analysis risk assessment, control measures for safety management systems (SMSs) will be discussed to complete the topic. 

Preliminary hazard analysis As already discussed in Chapter I (also Chapter III), this can be utilized during conceptual design, front end engineering design (FEED), or R D stage. As stated earlier, one of the major purposes of preliminary hazard analysis is to identify the extent or boundary limits of complex hazards and analyze the risks and hazards associated with all the processes involved (see Clause 4.0 of Chapter I). 

However, initially, preliminary hazard analysis is often done for hazard screening processes to assess a major event. This will help in developing an SMS and FSA. Therefore the discussion may be concluded by saying that no potential danger situation is liable for rejection however low the likelihood of its occurrence is. Also if any assumption is considered it must be recorded for further review. 

Systems Hazard Analysis (SHA) is a qualitative method combining aspects of preliminary hazard analysis and failure-mode and effect analysis (Firenze 1973). Its emphasis is on work-tasks performed in various operational procedures. SHA adds two important pieces of information to those methods previously discussed the standards or regulations violated and the relevant subsystem. It chooses a task activity or a dynamic event as the focal point of the analysis rather than a more static component. As with the other methods, an analyst with detailed knowledge of the system is required. 

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