Design control needs analysis

The specific designed controls need not all be identified before the rest of the analysis starts. Additional controls will be identified as the analysts go through the next steps of the process, but a good start can usually be made early in the analysis process. 

The risk assessment process can be conducted by examining record types to see if they are GxP or non-GxP, and then applying severity checks, likelihood, and probability of detection criteria, as illustrated in Figure 15.2. The most severe scenarios shonld be linked to direct patient/consnmer impact. GxP noncompliance and broken license conditions are severe in their own right bnt not as critical as patient/consumer health in this analysis." Its likelihood will be influenced by the degree of human error in how the record is input and used. The probability of detection needs to take into account the probability of the impacted record being used. Once failure modes are understood, then the appropriate design controls can be introduced. These should be documented and validated as part of the computer system life cycle discussed earher in this book. 

Outline an overall process flow sheet and material balance including solvent recovery and recycle. This should be done with the aid of process simulation software. [See Seider, Seader, and Lewin, Product and Process Design Principles Synthesis, Analysis, and Evaluation, 2d ed. (Wiley, 2004) and Turton et ah. Analysis, Synthesis, and Design of Chemical Processes, 2d ed. (Prentice-Hall, 2002)]. In the flow sheet include methods needed for controlling emissions and managing wastes. Carefully consider the possibility that impurities may accumulate in the recycled solvent, and devise methods for purging these impurities, if needed. 

Effective process control needs reliable, robust, often rapid inputs from measurement techniques. Spectroscopy can provide such inputs if the right technique is selected, the sample interface is weU designed and the data analysis is carried out effectively. 

To provide cost-effective safety engineering, the system and safety analysis and design process needs to consider the humans in systems—including those that are not directly controlling the physical processes—not separately or after the fact but starting at concept development and continuing throughout the life cycle of the system. 

To accomplish these goals, a feedback control loop is needed to regularly track and assess the effectiveness of the development safety control structure and its controls. Were hazards overlooked or incorrectly assessed as unlikely or not serious Were some potential failures or design errors not included in the hazard analysis Were identified hazards inappropriately accepted rather than being fixed Were the designed controls ineffective If so, why ... 

Rothbart, H. A., and T. H. Brown Jr., eds. 2006. Mechanical Design Handbook Measurement, Analysis, and Control of Dynamic Systems, 2nd ed. New York McGraw-Hill. This work focuses on the fundamentals and design considerations that need to be taken into account by anyone interested in designing and constructing machines of various types. 

Minimizing Electrolysis Time The current-time curve for controlled-potential coulometry in Figure 11.20 shows that the current decreases continuously throughout electrolysis. An exhaustive electrolysis, therefore, may require a long time. Since time is an important consideration in choosing and designing analytical methods, the factors that determine the analysis time need to be considered. 

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