Hazard analysis examples

Equations (2-3.7) forQjand Eqs. (2-3.1), (2-3.2), and (2-3.8) forr are used extensively in static hazard analysis. Examples include selection and use of instrumentation (3-5.3) and residence time provisions for charged liquids (5-2.4). 

The effort and time that is required for a process hazard analysis for these examples should not be an issue. A thorough management of change system will call for the change coordinator to make a decision as to what type of review is appropriate for the change. 

Designs should be based on knowledge of what the human body (and human nature) will do. Include educated operators in design reviews. The HAZOP methodology for process hazard analysis offers an excellent opportunity to identify design and procedural opportunities for inherently safer systems. After all, the OP in HAZOP stands for operability (COPS, 1992). For example, a safe start-up procedure that requires the operator to walk up and down the stairs three times to manipulate valves in the correct sequence can be made inherently safer by locating the valves so that operator has to walk up the stairs only once during the start-up. 

In Chapter 4 we will diseuss the regulatory framework and analyti-eal tools to eonduet these assessments, sueh as JHA (job hazard analysis), job safety analysis (JSA), safety analysis reports, proeess hazard analysis (PHA), and job, task, and hazard analysis. The reader needs to understand that OSHAs view on physieal and ehemieal hazards is far reaehing, as stated in the HAZWOPER standard. Note the following examples. 

HAZWOPER applies only where exposure to hazardous substanees or to health and safety hazards resulting from a hazardous waste operation is likely (see Eigure 2-1). This ean be determined by analysis of exposure monitoring data, hazard eharaeterization, hazard analysis, or exposure assessment [1]. Some of the speeifle examples of work aetivi-ties and situations will be eovered later. 

DOE, 1993, Example Process Hazard Analysis of a Department of Energy Water Chl< Process, DOE/EH-0340, September. 

Analyses are types of calculations but may be comparative studies, predictions, and estimations. Examples are stress analysis, reliability analysis, hazard analysis. Analyses are often performed to detect whether the design has any inherent modes of failure and to predict the probability of occurrence. The analyses assist in design improvement and the prevention of failure, hazard, deterioration, and other adverse conditions. Analyses may need to be conducted as the end-use conditions may not be reproducible in the factory. Assumptions may need to be made about the interfaces, the environment, the actions of users, etc. and analysis of such conditions assists in determining characteristics as well as verifying the inherent characteristics. (See also in Part 2 Chapter 14 under Detecting design weaknesses.)... 

One illustrative example is presented in tliis final cliapter. It lias been adopted from tlie outstanding work of Kavianaian et al. and is concerned with an ethylene production plant. Tlie solution involves a prcliminaiy hazards analysis (PHA) and tlie development of a fault tree for tlie process. 

Suppliers should perform a hazard analysis on each product. For example, aerosols can... 

While quality was formerly achieved by inspection of final products, it is accomplished now by prevention through controlling critical steps in the production processes along the agri-food chain. Hazard analysis critical control points (HACCP) represent a typical example of such a preventive approach. Although this concept was developed primarily to assure food safety, the basic principle is also applicable to assuring non-safety quality attributes such as color, flavor, and nutritional value. " This section translates the HACCP principles into a critical quality control point (CQP) concept that can be part of a system to assure food quality. 

The term operability study should more properly be used for this type of study, though it is usually referred to as a hazard and operability study, or HAZOP study. This can cause confusion with the term hazard analysis , which is a technique for the quantitative assessment of a hazard, after it has been identified by an operability study, or similar technique. Numerous books have been written illustrating the use of HAZOP. Those by Hyatt (2003), AIChemE (2000), Taylor (2000) and Kletz (1999a) give comprehensive descriptions of the technique, with examples. 

The data on probabilities given in this example are for illustration only, and do not represent actual data for these components. Some quantitive data on the reliability of instruments and control systems is given by Lees (1976). Examples of the application of quantitive hazard analysis techniques in chemical plant design are given by Wells (1996) and Prugh (1980). Much of the work on the development of hazard analysis techniques, and the reliability of equipment, has been done in connection with the development of the nuclear energy programmes in the USA (USAEC, 1975) and the UK. 

PROCESS HAZARD ANALYSIS METHODS WITH EXAMPLES... 

Partial what-if analyses for the two example processes described in Section 4.0 are shown in Tables 4.9 and 4.10. Although for actual, more complex analyses, the what-if tables for each line or vessel would be separate, for these examples, a single table was developed. A preliminary hazard analysis (PHA) would identify that the intrinsic hazards associated with HF are its reactivity (including reactivity with water, by solution), corrosivity (including carbon steel, if wet), toxicity via inhalation and skin contact, and environmental toxicity. The N2 supply system pressure is not considered in this example. The specific effects of loss of containment could be explicitly stated in the "loss of HF containment" scenarios identified. Similarly, the effects of loss of chlorine containment, including the reactivity and toxicity of chlorine, could be specified for the second example. 

Ref. 39 suggests an initial qualitative hazards analysis early in systems design, with only general levels of hazard probabilities identified, in addition to severity categories. An example of such a qualitative ranking from Ref. 39 appears in Table V. 

Although risk analysis of new facilities is required by Ref. 39, the method of conducting the analysis is left quite open. The reference suggests fault hazard analysis, fault tree analysis, or sneak circuit analysis. Ref. 41 is an example of a thorough hazards evaluation and risk analysis for a new facility at Radford Army... 

Process hazard analysis (PHA) Any of a number of techniques for understanding and managing the risk of a chemical process or plant. Examples of PHA techniques include HAZOP, checklists, what-if methods, fault tree analysis, event tree analysis, and others. 

Mosley et al. (2000) describe a "chemistry hazard analysis" approach, similar to a hazard and operability (HAZOP) study method applied at the early development stages of a new process. Deviations from an intended chemical reaction are identified using typical HAZOP guidewords. Examples of deviations and consequences developed using this approach are shown in Table 4.10. Analyzing the basic chemistry of a process, where chemical reactions are intended to occur, can help ensure the consequences of deviating from the intended reaction are understood. 

Example Chemistry Hazard Analysis Scenarios (Mosley et al. 2000)... 

The process hazard analysis required by OSHA PSM is an example of a performance-based approach it allows for a variety of hazard analysis methodologies. A performance-based system requires experts to identify and evaluate all relevant reactive hazards of a process and to determine the complexity of the hazards analysis. If the hazard evaluation demonstrates the possibility of a catastrophic consequence, the process has regulatory coverage. This approach to hazard evaluation allows for both a comprehensive analysis and flexibility in implementation however, if applied to reactive hazards, it requires expertise for implementation and regulatory evaluation. 

For example, the hazard review requirements have the following differences from OSHA s process hazard analysis provision ... 

What is a Fire Hazard Analysis (FHA) and how are they used How do you determine the potenbal impact of fires tVhat are examples of some typical fire hazard problems and how do you solve them ... 

On the other hand, there are a number of elements of fire prevention that overlap with elements of other programs. For example. Incident Investigation, Management of Change (MOC), Process Safety Information (PSI), and Process Hazard Analysis (PHA) input required for fire prevention can be derived from these same elements of the Process Safety Management (PSM) program. 

Fire hazard analysis (FHA) is the process to determine the size, severity, and duration of a scenario and its impact on personnel, equipment, operations, and the environment. Chapter 5 provided details of performing an FHA. The following paragraphs provide an overview of the FHA process. For example, one scenario could be a seal failure where the material being released is ignited and afire results. In assessing consequences, several questions must be considered ... 

Process Hazard Analysis (PHA) can be defined as the application of a systematic method to a process design in order to identify potential hazards and operating problems. It determines the causes and consequences of abnormal process conditions that arise from equipment failure, human error or other events. The goal is to determine whether opportunities exist to reduce the risks of the toll s hazards and then to implement warranted action items. The AJChE CCPS guideline Guidelines for Hazard Evaluation Procedures, Second Edition with Worked Examples is a good resource for fully detailed approaches to process hazard analysis. It provides an introduction to hazard evaluation as well as guidance on ... 

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