Preliminary hazard analysis system risk evaluation

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... 

Preliminary Hazard Analysis (PHA) A system safety analysis method used to formally evaluate and document the hazard risks associated with a new or modified system. 

The goal of risk analysis is to identify events that may have one or several undesirable consequences on a system, and to assess the likelihood and severity of these consequences. A lot of methods can be used to conduct risk analysis (Flaus, 2013a) such as Preliminary Hazard Analysis (PHA) and Failure Mode Effects Analysis (FMEA) (Papadopoulos et al., 2004). In most of these methods, the obtained information may be used to build a risk model. The next step after risk analysis is to study the behavior of the system, when the undesirable events occur, in order to evaluate its performance in degraded conditions, and its robustness or resilience. An approach to allow integrated risk analysis and simulation has been proposed for business process management (Tjoa et al., 2011). 

In 1985, the American Institute of Chemical Engineers (AIChE) initiated a project to produce the Guidelines for Hazard Evaluation Procedures. This document, prepared by Battelle, includes many system safety analysis tools. Even though frequently identified as hazard and operability (HazOp) programs, the methods being developed by the petrochemical industry to use preliminary hazard analyses, fault trees, failure modes, effects, and criticality analyses, as well as similar techniques to identify, analyze, and control risks systematically, look very much like system safety efforts tailored for the petrochemical industry (Goldwaite 1985). 

Very little real analysis is completed during the concept phase because analysis detail and data are generally not available. A preliminary risk assessment code (RAC) is determined, however, as part of the preliminary hazard list. This initial RAC is used to aid in determining the initial scope of the system safety effort and in the early evaluation of alternative designs and approaches. 

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. 

PHL analysis is both a system safety analysis Type and Technique for identifying and listing potential hazards and mishaps that may exist in a system. The PHL is performed during conceptual or preliminary design, and is the starting point for all subsequent HAs. Once a hazard is identified in the PHL, the hazard will be used to launch in-depth HAs and evaluations, as more system design details become available. The PHL is a means for management to focus on hazardous areas that may require more resources to eliminate the hazard or control risk to an acceptable level. Every hazard identified on the PHL will be analyzed with more detailed analysis techniques. The primary output from the PHL is a list of hazards and the hazard sources that spawn them. It is also... 

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