Performing the task

The approach described reflects an industrial view of the preparative isolation of impurities based on a meta-model developed with the aim of implementing a functional process while maximizing success under a given set of constraints and mitigating risk. This chapter is a snapshot of its current state of evolution. 

Aranyi, Progress in Pharmaceutical and Biomedical Analysis, 4 (Identification and Determination of Impurities in Drugs), 2000,240-251. 

Ludemann-Hombourger, G. Pigorini,R. M.Nicoud,D. S.Ross and G. Terfioth, Journal of Chromatography A, 2002,947(1), 59-68. 

Coyne and K. Oldenburg, Society for Biomolecular Screening, 10th Conference and Exhibition, 2004, Orlando, FL., USA. 

Shen and C. Zhu, Combinatorial Chemistry High Throughput Screening, 2002, 5(7), 575-581. 

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In conjunction with the production operations input into the FDP describing how the process will be operated, maintenance engineering will outline how the equipment will be maintained. Maintenance is required to ensure that equipment is capable of safely performing the tasks for which it was designed. This is often stated as maintaining the technical integrity of the equipment. 

Review the list with your Subject Matter Experts (SMEs). Subject matter experts are generally persons who can competently perform the task. This review will enable you to remove tasks that are no longer performed, add any tasks that were omitted, and correct any errors. 

What tools, equipment, and references are used m performing the task ... 

What safety precautions does the person performing the task need ... 

The preceding chapters offered some general guidance on the sizing of the various types of compressors. Before the start of the specification, the equipment should be sized, at least in a preliminary manner. Actually, part of this may be integrated into the process calculation. However, after the process calculations are complete, a review of the equipment best suited to perform the task at hand should be made. 

In any given situation, there may be different levels of dependence between an operator s performance on one task and on another because of the characteristics of the tasks theraseb e.s. or because of the manner in which the operator was cued to perform the tasks. Dependence levels between the performances of two (or more) operators also may differ. The analyses should account for dependency in human-error probabilities. In addition, each sequence may have a set of human recovery actions that if successfully performed will terminate or reduce the consequences of the sequence. This information, coupled with a knowledge of the system success criteria leads to the development of human success and failure probabilities which are input to the quantification of the fault iices or event trees. With this last step, the HRA is integrated into the PSA, and Pl. ise 4 is complete. 

All processes and equipment should be proven capable of performing the task for which they were designed and so should either be subject to qualification tests or process capability tests. There may be documentation available from the supplier of the equipment which adequately demonstrates its capability, otherwise you may need to carry out qualification and capability tests to your own satisfaction. In the process industries the plant is specially designed and so needs to be commissioned and qualified by the user. Your procedures need to provide for such activities and for records of the tests to be maintained. 

This section is concerned with errors that are often classified as "violations," that is, situations where established operating procedures appear to have been deliberately disregarded. Such violations sometimes arise because the prescribed way of performing the task is extremely difficult or is incompatible with the demands of production. Another cause is lack of knowledge of the... 

As process plants become more complex, it becomes apparent that it is not possible to rely exclusively on the process worker s skills and memory required to perform the task. Job aids and procedures are devices which aim to reduce the need for human retention of procedures and references as well as the amount of decision making required. Job aids assume a variety of formats including flowcharts, checklists, decision tables, etc., while procedures refer to other systems of documentation such as standard operating instmctions and emergency procedures. 

Detailed procedures will only be required in unusual situations where the usual rules of thumb do not apply and the worker is likely to be in the knowledge-based mode. In Chapter 4, and case study 3 in Chapter 7, a systematic framework for developing procedures, in which their format and content is based on a detailed analysis of the tasks to be performed and the normal skill level of the person who will perform the tasks, will be described. 

Although checklists are a useful way of transferring information about human-machine interaction to designers and engineers, they are not a standalone tool and they cannot provide a substitute for a systematic design process. The main concern with checklists is that they do not offer any guidance about the relative importance of various items that do not comply with the recommendations, and the likely consequences of a failure due to a noncompliance. To overcome such problems, checklists should be used in combination with other methods of task analysis or error analysis that can identify the complexities of a task, the relationships among various job components, and the required skills to perform the task. 

Modify the basic data according to guidelines provided in the handbook, to reflect differences in the assumed "nominal" conditions and the specific conditions for the task being evaluated. The major factor that is taken in to account is the level of stress perceived by the operator when performing the task. 

Modify the value obtained from the previous stage to reflect possible dependencies among error probabilities assigned to individual steps in the task being evaluated. A dependence model is provided which allows for levels of dependence from complete dependence to independence to be modeled. Dependence could occur if one error affected the probability of subsequent errors, for example if the total time available to perform the task was reduced. 

Ambiguous or difficult-to-detect information which is necessary to perform the task (possible failure to acquire critical information, see the flow diagram in Chapter 2, Appendix 2B)... 

Human error tmalysis (HEA) is a systematic evaluation of the factors tliat influence tlie performance of human operators, maintenance staff, teclmicians, and otlier persomiel in tlie plant. HEA involves the evaluation of one of several types of task analysis, which is a metliod for describing tlie physical and enviromiiental characteristics of a task along witli tlie skills, knowledge, and capabilities required of tliose who perform the task. Tliis type of analysis can identify error-likely situations tliat can cause or lead to an accident. 

To use CPM or PERT, the job must first be divided into a number of tasks, and the average time to perform each of the tasks must be estimated. These tasks are called activities. The average time is the usual time it would take to perform the task when doing it the most economical way. To illustrate this, consider a job we have all performed, changing the front tire on an automobile. A list of the activities involved and a time estimate for them is given in Table 13-1. Before looking at that table, the reader should develop his own list and estimate how long each task will take. 

Hemoproteins which engage in electron transport — the cytochromes — are much more widely dispersed among living species and occur in microorganisms, plants and animals (13). Again there are two types of iron proteins which can perform the task of electron transport, the heme and the non-heme. The latter term has become practically synonymous... 

The undecidability results do not say that a task is always impossible - just that no program can be written to perform the task properly in all cases. But programs could be written to handle special cases. Thus we cannot completely mechanize the verification procedure so it will succeed eventually whenever it should succeed. We can of course verify particular programs and we can improve the verification procedure and increase the set of cases where it will work. As a practical matter, complexity questions will probably swamp one first - classes of programs for which verification is possible but it simply takes too long. 

Rather than writing a short program in Matlab for this result, we demonstrate how to perform the task of a straight line fit in Excel. Excel actually provides several ways of performing the job of fitting the best line through a set of data pairs. The most convenient is probably the Add Trendline. .. tool which delivers the result in a few clicks. 

Instead of developing a program that performs the task as just explained, we move to the 2-parameter case. Subsequently, we generalise to the np-parameter case and then we analyse the relationship with the Newton-Gauss algorithm for least-squares fitting. 

The output of this short program is 9500 characters, too much to be included here. We leave it to the readers to perform the task on their computer. 

The approach taken is loosely based on the input-process-output meta-model utilized to transform a problem statement into a functional process. The section Scope definition discusses the intended purpose and potential constraints of the isolation effort, followed by an overview of the Toolbox available to the practitioner (input). The section Method development scouting and scale-up reviews platform-based, highly automated approaches to selectivity scouting, development of the isolation as well as options for scaling up the chromatographic separation depending on purpose and constraints (process). The final section. Performing the task, explores a work breakdown structure approach to the preparative isolation of impurities as a unit operation in the development process (output). 

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