Process performance indices

Finally, in multipurpose plants compounds, which can be deposited in various places (e.g. corners, zones near sealings) in equipment, can contaminate products of the subsequent batch. Therefore, all equipment must be thoroughly cleaned before the next production campaign starts. Contaminants can be formed in the process, sometimes at ppm level, and be recycled with streams of solvents and/or reactants. Hence, the influence of recycling on process performance indices must be included in the program of laboratory studies, at least in their final stage. 

Sometimes an analysis of process capability is desired when the process is not in a state of strict statistical control. When this occurs, process performance indices should be used. Process performance indices can be defined as Pp = (USL — LSL)/6crp, and PpK = MIN[(USL — ii)/3(7p,(ii — LSL)/3(Tp], where up is now the overall standard deviation of the process output characteristic. 

Process performance indices strictly apply only to the data set being examined because the process is not predictable into the future when it is not in statistical control. However, in practice, the indices are often interpreted to provide an assessment of the process as it currently exists. 

Customer satisfaction with the organization shall be monitored through continual evaluation of performance of the realization processes. Performance indicators shall be based on objective data and include, but not be limited to ... 

The aim of this study was to calibrate a model of an old newspaper and magazine deinking plant by applying data reconciliation, and to design a sensor system capable of identifying key process performance indicators with satisfactory precision and at minimal cost... 

For example, the squealing of vehicle belt during its operation process performance indicates the need for its preventive replacement. However, the occurred noise during operation processes performance of construction machines (e.g. wheel loader) will only indicate a problem in the drive system, which may regard to e.g. differential problems or transmission problems (e.g. propeller shaft). 

The numerical values of the Cp and Cp capability indices in (21-25) and (21-26) are only meaningful when the process is in a state of control However, other process performance indices are available to characterize process performance when the process is not in a state of control They can be used to evaluate the incentives for improved process control (Shunta, 1995). 

If a reliable process model is available and can provide solutions in real time, the model can be used to provide the corrected setpoint trajectories for u without decouphng or empirical tuning of controller gains. If a process performance index is defined, then the controller action can be computed directly by inverting the process model. For instance, if it is assumed that the current process states [x(f),y(f)] are known and that it is desired to reach the optimum reference trajectory after tf time units, then Equations 8.18b and 8.35 can be written as... 

Except as an index of respiration, carbon dioxide is seldom considered in fermentations but plays important roles. Its participation in carbonate equilibria affects pH removal of carbon dioxide by photosynthesis can force the pH above 10 in dense, well-illuminated algal cultures. Several biochemical reactions involve carbon dioxide, so their kinetics and equilibrium concentrations are dependent on gas concentrations, and metabolic rates of associated reactions may also change. Attempts to increase oxygen transfer rates by elevating pressure to get more driving force sometimes encounter poor process performance that might oe attributed to excessive dissolved carbon dioxide. 

A useful index of process performance is the oxygen uptake rate, OUR, that is calculated from the difference in oxygen concentration of the inlet air and the exiting gas. Also important is the respiration ratio defined as the carbon dioxide evolved divided by the oxygen consumed. 

The performance index which accounts for process centering and defined as the minimum of the upper or lower specification limit minus the average value divided by 3o. 

In this chapter, state sequence network (SSN) representation has been presented. Based on this representation, a continuous-time formulation for scheduling of multipurpose batch processes is developed. This representation involves states only, which are characteristic of the units and tasks present in the process. Due to the elimination of tasks and units which are encountered in formulations based on the state task network (STN), the SSN based formulation leads to a much smaller number of binary variables and fewer constraints. This eventually leads to much shorter CPU times as substantiated by both the examples presented in this chapter. This advantage becomes more apparent as the problem size increases. In the second literature example, which involved a multipurpose plant producing two products, this formulation required 40 binary variables and gave a performance index of 1513.35, whilst other continuous-time formulations required between 48 (Ierapetritou and Floudas, 1998) and 147 binary variables (Zhang, 1995). 

Safety culture, for nuclear power facilities, 17 538 Safety data, developing, 21 844 Safety factors, See also Process safety Safety inspections, OSHA, 21 829 Safety issues/considerations for heated and cryogenic tanks, 24 303 teaching related to, 24 184 Safety issues, emulsion-related, 10 128 Safety measures, improved, 24 184 Safety performance indexes, nuclear power facility, 17 539 Safety regulation(s)... 

Crowley et al. performed some interesting work with Pichia pastoris in a fed-batch process.19 The complex mixture was measured using a multibounce attenuated total reflectance (HATR) cell. The authors developed models for glycerol, methanol, and the product, a heterologous protein. The results are reported somewhat differently from normal chemometric results. The authors used root-mean square error (RMSE) for the product as a performance index and measured a percent difference for the methanol and glycerol. 

There is one method that is based on a time-domain model. It was developed at Shell Oil Company (C, R. Cutler and B. L. Kamaker, Dynamic Matrix Control A Computer Control Algorithm, paper presented at the 86th National AlChE Meeting, 1979) and is called dynamic matrix control (DMC). Several other methods have also been proposed ihat are quite similar. The basic idea is to use a time-domain step-response model of the process to calculate the future changes in the manipulated variable that will minimize some performance index. Much of the explanation of DMC given in this section follows the development presented by C. C. Yu in his Ph.D. thesis (Lehigh University, 1987). 

The Exxon Donor Solvent (EDS) Process, developed by the Exxon Research and Engineering Co., differed from the typical process in that, before being recycled, the solvent was hydrogenated in a fixed-bed reactor using a hydrotreating catalyst, such as cobalt or nickel molybdate. Exxon found that use of this hydrogen donor solvent with carefully controlled properties improved process performance. Exxon developed a solvent index, based on solvent properties, which correlated with solvent effectiveness. 

Volumetric productivity is a good performance index in what concerns the optimization of bioreactor operation. It can be used in process improvement at a defined scale and also for process scale-up, since it is a dimensionless variable. Therefore bioreactor operation and scale-up for CLP and VLP production will be addressed as the identification of the operational conditions that result in the best volumetric productivity. 

A second capability index Cpl is based on average process performance x as well as process variability a. It is defined as... 

A common parameter used by quality professionals to gauge whether or not the manufacturing process and analytical methodology is within the desired state of statistical process control (SPC) is a process capability index [11], such as the Cpk value. The Cpk value is the value of the tolerance specified for the given performance characteristic divided by the actual process capability. 

It is important to remember that the capability and performance indices calculated from the data are only estimates and thus have uncertainty associated with them. Confidence intervals can be calculated for these indices to reflect this imprecision. For example, a 100(1 — a)% two-sided confidence interval about the estimated process capability index Cp is ... 

The process of estimating the distribution corresponds to determining the coefficients that minimize the performance index ... 

It is desired to produce a list of N batches of different products so as to minimize a composite performance index that consists of a weighted sum of three terms namely due date penalties, change over costs and completion times of last batches or jobs on the two production lines. The scheduling algorithm is to determine the processing orders of various jobs on each batch unit and the start times of all operations. 

This chapter considers the practical problem of feed optimization of the FCC process in a local refinery. A thorough study of the FCC process and the formulation of the feed optimization problem will be presented. Accounting for the coirflicting nature between the various objectives, the FCC feed optimization is solved by a multi-objective evolutionary toolbox developed by the authors (Tan et al, 2001a). Finally, for the actual implementation of the FCC process, three major key performance indexes are adopted to rate the various solutions evolved, so as to facilitate the decision-making process. 

To better illustrate the effect of the optimization process, Table 9.10 summarizes the various key performance indexes considered in terms of dollars. The best solution is point C optimized by MOEA, where the total consumption of fuel and steam is the lowest while the energy gain is the highest. However it has the highest steam consumption. 

Another pitfall is to design a process where the operating limits for one or more critical parameters are too narrow and cannot be consistently achieved. It is not acceptable if the process can be performed only by experts in R D. Many pharmaceutical companies apply some measurement of process and equipment capability to demonstrate the reproducibility and consistency of the process in meeting specification limits. The Process Capability Index (CpK) is often used to measure the reproducibility as a function of the specification limits. It is normally, calculated from either of the two equations below, whichever gives the lowest number ... 

Materials of Constrnction Process Machinery Drives Analysis of Plant Performance Index... 

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