Process Risk Analysis

The design of a process plant and the way it is operated are as important to safety as the intrinsic thermochemical hazards of the process chemistry. Systematic procedures should be used to identify operability hazards and, where appropriate, quantify them. (See also case histories Al 24-26, pages 168-172.) 

When designing a new plant the hazard identification procedure should be repeated at intervals, first on the pilot plant and then on the full-scale version, as the design becomes more closely defined. This may reveal new potential hazards whose significance can only be assessed with the help of new experimental data thus there will probably be some overlap with the assessment of chemical reaction hazards. 

References 77 and 78 review some of the procedures developed for identifying plant hazards systematically. Among the better known are the hazard and operability study (Hazop), a qualitative technique based on the piping and instrumentation diagram, and hazard analysis (Hazan), used to quantify 

Hazop solely identifies a potential hazard it says nothing about the likelihood of it occurring or its seriousness. Judgement is required. The designer may decide that the consequences of the hazard are trivial, or that it is so unlikely that it can be ignored. Sometimes the solution is obvious and the design can be modified on the spot. 

Sometimes the problem is more complicated. Where the consequences of the hazard are severe, or where its causes are many, a fault tree is useful. The fault tree shows how various events or combinations of events can give rise to a hazard. It can be used to identify the most likely causes of the hazard and hence to show where additional safety precautions will have the best effect. 

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Process research, in fine chemical research and development, 11 426 Process reviews, 10 163 Process risk analysis, in large-scale pharmaceutical synthesis, 16 726 Process safety, 20 731-732 Process safety management, 21 826 standards for, 21 592 Process Safety Management (PSM) of Highly Hazardous Chemicals standard, 21 829... 

Gather the requirements for the systems including functional (e.g. operational checks) requirements, nonfunctional (e.g., coding standards) requirements, users, company-wide regulatory compliance (e.g., Part 11 technical control), safety, process, and other applicable requirements Characterize information, assess its value to the organization, and incorporate information quality as part of the project plan Conduct a system (hardware, software, and process) risk analysis. New requirements may be found as the result of the risk analysis. Any new requirements must be documented in the requirements specification deliverable... 

To scale up a chemical process to pilot or commercial-scale operations, a significant laboratory effort is required to define the operating ranges of the critical process parameters. A critical process parameter is any process variable that may potentially affect the product quality or yield. This information is required to prepare a Process Risk Analysis, which is an FDA prerequisite for process validation. Process parameters that are often evaluated as part of the risk analysis include reaction temperature, solvent systems, reaction time, raw material and reagent ratios, rate and orders of addition, agitation, and reaction concentration. If catalysts are employed as part of the process, additional laboratory evaluation may also be required to further define the process limits. Experimental design is often used for the evaluation of critical process parameters to minimize the total laboratory effort (4). 

Savkovic-Stevanovic, J., T. Mosorinac, S. Krstic (2006) Process risk analysis operation modelling, Comput. Ecol. Eng. 2, No. 1, 31-37. 

This type of hazards analysis can be either deductive or inductive. A deductive (top-down) analysis is one that first defines an undesirable event, and then considers what events and chains of circumstances are needed to occur before the overall undesirable event occurs. A deductive approach is used by detectives to solve crimes. A widely used type of deductive analysis in process risk analysis is the fault tree method, described in the next chapter. 

Fischhoff, B. (1995) Risk perception and communication unplugged Twenty years of process, Risk Analysis, 15 (2) 137-145. 

Example 34-3 Six departments in a plant seek money to improve process safety. The company elects to use logical process risk analysis as a guide for aUocafing funds. The goal is to reduce potential losses. The company completes analysis for each department to determine hazard scores, control scores and exposure dollars. Table 34-10 presents the data. The company ranks departments based on the data. Table 34-11 presents the results. 

Use the logical process risk analysis method to determine the ranking for applying funds to each of five plants in a company. Several plants were part of the analysis. The following table lists data for the five plants under current consideration. 

To what is logical process risk analysis applied ... 

K. H. Frank and H. W. Morgan, A Logical Process Risk Analysis, Professional Safety, June 23-30 (1979). 

Fusible Link a mechanical release device actiwited by the heat effects of a fire. It usually consist of two pieces of metal joined by a low melting solder. Fusible links are manufactured as various incremental temperature ratings and are subjected to varying normal maximum tension. When installed and the fixed temperature is reached, the solder melts and the two metal parts separate, initiating the desired actions Hazard Analysis the systematic identification of chemical or physical characteristics and/ or processing conditions and/or operating conditions that could lead to undesired events Hazardous Area, Electrical a US classification for an area in which explosive gas/air mixtures are, or may be expected to be, present in quantities such as to require special precautions for the construction and use of electrical apparatus HAZOP an acronym for Hazard and Operability study, which is a qualitative process risk analysis tool used to identify hazards and evaluate if suitable protective arrangements are in place if the process were not to perform as intended and unexpected consequences were to result... 

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