Process metrics

It should be understood from consideration of the items in Table 2.5 that choices of materials (chemicals, solvents, reagents, etc.) will directly affect choices about which 

Physical form and properties (i.e., gas, liquid, solid) Unit operation type Throughput/cycle time Occupational exposure Purity/impurity profile 

Mass (i.e., total, solvent, reactant, process, etc.) No. of unit operations Robustness Environmental - air, water, land  

Inherent hazard (e.g., toxicity, stability, reactivity) Cost Renewability Recyclability Size (volume) Scalability Controllability Energy (i.e., total, heating, cooling, recovery, treatment, etc.) Ease of cleaning and maintenance Safety/process safety  

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Another general principle for good process metrics is that these should promote strategic analysis and continuous improvement. If the metrics are being collected but not evaluated on a regular basis, and decisions based upon the metrics results are not made, there is no point in collecting them. This may seem to be an obvious point, but metrics are not always routinely questioned, assessed, evaluated and evolved to help make strategic decisions or make them more useful to a business. 

For the sake of simplicity. Table 6.1 contains a small collection of general categories of interest or concern that should be considered for metrics application in any route or pro cess development. As will be immediately obvious from the table, the list mostly contains categories that would generally be found in many texts on process metrics. It should be... 

Table 6.1 General areas of interest for process metrics.

Figure 6.1 Interrelationships between process metrics categories. 

Figure 6.1 is presented as an attempt to show the interrelationships between the process metrics categories shown in Table 6.1. Materials (chemicals, solvents, reagents, etc.) choices will directly affect the choice of unit operations and the combination of materials and equipment will directly impact the operability of the process. Materials, equipment and operability all have EHS impacts and opportunities associated with them and ultimately impact product and product quality. 

At the beginning of this chapter, several points were made about general metrics principles that are particularly applicable within the context of equipment and operability. It is worth to revisit them for just a moment to say that good process metrics for these categories are especially dependent on an understanding of the overall process, and optimization of a process should be done from a multivariate perspective. Metrics in these categories should be seen as having considerable dependencies on each other and on the materials and chemicals used in the process. 

A QMS should be comprised of all the processes supporting that business and include an effective management review of those process metrics. Management needs to be aware of and understand process performance through structured metrics review programs in order to take appropriate action, providing resources and capital to improve the QMS. This hierarchy is illustrated in Figure 2. 

An important barometer of process performance is the number of nonconformances, corrective and preventive actions taken, and planned deviations initiated against a process. These types of process artifacts must be known and owned by the process owner and stakeholders. The process owner must consider these process metrics for evaluation of and changes to process design, training, documentation, and performance. 

Once the metrics program is in place, the system and process metrics require visibility to process owners, upper management, and stakeholders. Process owners require understanding of the metrics trends, issues, and associated risks. Stakeholders must work with the process owner to identify and propose process improvement opportunities. Leadership is accountable to understand the issues and associated risks and responsibly apply resources for remediation efforts. 

Ignorance of system and process performance leads to inefficiency, poor compliance, and low employee morale. It is good business practice to have regular review of process metrics to gauge the health and output of the system and processes that drive the organization. 

In addition to extractive analysis techniques, other analytical and process metrics are routinely used to characterize and profile the hazard level of chemical agent in secondary waste at chemical agent disposal facilities. These include the short-term exposure limit (STEL), the vapor screening level (VSL), the shortterm limit (STL), and the Army s 0, IX, 3X, and 5X designations for various levels of agent contamination. These metrics are explained briefly below and summarized in Table 3-3. 

TABLE 31.7. Process Metrics for the Glucose Isomerase Process... 

It is important to analyze the current process. What are the process metrics For example ... 

Process and ownership are defined, personnel are trained, process metrics are in place but process is not always followed and results need improvement to meet minimum standards. 

For each key process there should be a set of metrics. These process metrics could consist of process cost, effectiveness, right-first-time, and customer satisfaction. Examples of metrics for the change control process are ... 

Table 5.1 Comparing alternative production processes - metrics for hexamethylenediamine production (more favorable metrics are shown in bold). Source Schwarz et al. [21],...

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