Process-control applications, computers

As previously described, the use of computers and computerized systems in the pharmaceutical industry is growing at a rapid rate. Some of the systems used in the industry range in complexity from the use of personal computers for performing simple tasks (word processing, e-mail, Internet access) to the use of powerful computers in process-control applications. In addition, to help eliminate or reduce paper usage, the pharmaceutical industry has implemented a number of electronic batch record systems in drug substance and product manufacturing to keep track of process documentation. 

It is possible to develop second-, third-, or higher-order hold elements. They need three, four, or more initial discrete-time values before they can start the construction of a continuous signal. As the order of a hold element increases, the computational load increases and becomes more complex, with marginal improvements in the quality of the reconstructed signal. Therefore, for most process control applications the zero-order hold element provides satisfactory results with low computational load and is normally used. To improve the quality of a reconstructed signal, it is better to decrease the period between two successive discrete-time values rather than increase the order of the hold element. 

There are two classes of software programs needed for computer process control applications the computer system programs and the application programs. 

As seen in Section 3 excellent insight into surface quality, defects, and bulk purity can be obtained from scatter measurements. Also, astute analysis can result in simple, inexpensive in-process and final quality control procedures for production of a variety of surfaces, materials, and optics. As can be seen, much can be learned from visual examination of BRDF plots and raster scans. This is often sufficient for pass/fail tests of product quality. The data can also be analyzed in more detail using various formulas and computer programs. In addition, because the data are digital, they can be rapidly analyzed by computer in on-line process control applications. SORIC and leaders in the stray light community have developed a BRDF database (16, 17) for commonly used surfaces and materials employed by scientists and engineers (18,19, 20, 21, 22, 23). 

Doyle, F. J. Ill, E. P. Gatzke, and R. S. Parker, Practical Case Studies for Undergraduate Process Dynamics and Control Using Process Control Modules, Computer Applications in Engineering Educ. 6, 181-191 (1998). 

Single-loop controllers provide both the process control functions and the operator interface function. This makes them ideally suited to very small applications, where only two or three loops are required. However, it is possible to couple single-loop controllers to a personal computer (PC) to provide the operator interface function. Su(m installations are extremely cost effec tive, and with the keen competition in PC-based produc ts, the capabilities are comparable and sometimes even better than that provided by a DCS. However, this approach makes sense only up to about 25 loops. 

I /ci sonnel. They include applicable safety precautions and warnings regarding pressure limits, temperature ranges, flow rates, and the meanuig and response to alamis and instruments. Procedures for startup and shutdown are included with the appropriate ranges for the process parameters. They include instructions and commands for computer process control, if used. 

A detailed discussion of the application of digital computers and microprocessors in process control is beyond the scope of this volume. The use of computers and microprocessor based distributed control systems for the control of chemical process is covered by Kalani (1988). 

Process Control. The traditional process control will be expanded toward new applications such as nonlinear process control of biosystems. However, in the commodity chemicals industry there will be increased need for synthesizing plantwide control systems, as well as integrating dynamics, discrete events, and safety functions, which will be achieved through new mathematical and computer science developments in hybrid systems. 

When available, fundamental process models are preferred. For many complex processes such as composite manufacturing in general and autoclave curing in particular, however, these models are often not available. This lack of availability is due to an inadequate understanding of the complex events that take place during the process. A fundamental process model is occasionally available, but it is still unsuitable for on-line model predictive control application due to the extensive computing time required to solve the model s equations. This lack of... 

The computer systems that can directly impact the quality attributes of pharmaceutical drug products and associated production records include a wide range of applications. Typically candidate systems can include real-time process control/... 

The term computer system can define any of the following desktop systems client or of the following desktop systems client or server systems automated process control and laboratory systems host-based systems data acquisition and analysis systems and all associated software. The associated software comprises application software or firmware, system software, and computer system supporting documentation. ... 

The quality attributes applicable to all procedural controls are that they are appropriate, clear, and consistent with related procedures, adhere to regulatory, industry, and company standards, and are approved, available, accessible, followed, controlled, and periodically reviewed. The SLC process must be consistent with the applicable computer systems validation procedural controls. 

Operational checks are normally presenting process control computer systems. These systems may contain code that is part of the master production record. At the system level, the purpose of operational checks is to execute algorithms, sequencing of operations, and safety-related functions as required in the applicable customer specification. Inspections and testing are fundamental processes to be performed during the validation of critical system sequences. In addition, an ongoing program must be established to frequently verify that critical operations occur in the proper sequence. 

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