Process Instrumentation One

After studying this chapter, the student will be able to  

Electrical drawings—graphical representations that use symbols and diagrams to depict an electrical process system. 

Elevation drawings—graphical representations showing the location of process equipment in relation to existing structures and ground level. 

Equipment location drawings—show the exact floor plan location of equipment in 

Flow diagram—a simplified diagram that uses process symbols to describe the primary flow 

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Process Instrumentation and Control Systems. Investment for instmmentation and control systems and their installation typically range between 3 to 10% of the total installed cost for a grassroots continuous process faciUty. Instmmentation and control systems also represent a substantial percentage of the overall faciUty maintenance (qv) costs. Investment costs may be placed in one of two categories, ie, nondiscretionary and discretionary. 

The flow capacity of the transducer can be increased bv adding a booster relav like the one shown in Fig, 8-7.3/ , The flow capacity of the booster relav is nominally fiftv to one hundred times that of the nozzle amplifier shown in Fig, 8-7.3 3 and makes the combined trans-diicer/booster suitably responsive to operate pneumatic actuators. This type of transducer is stable into all sizes of load volumes and produces measured accuracy (see Instrument Society of America [ISA]-S5l, 1-1979, Process Instrumentation Terminology for the definition of measured accuracy) of 0,5 percent to 1,0 percent of span. 

Instrument Productivity. The number of samples that can be processed by one instrument in a given period of time is determined by the length of time each sample has to be read by the photodetector or other read-out device, or by the number of cuvets per unit time which pass the detector. For example. 

Other analyzers such as the Gilford Automated Enzyme Analyzer and the LKB-8600 Reaction Rate Analyzer analyze discrete samples one at a time. These instruments provide kinetic analyses, digital data reduction at the time each sample is analyzed, and excellent electronic and optical characteristics. Recently, Atwood has developed kinetic enzyme analyzers which require only 9 seconds for measuring an enzyme activity, using highly stable and sensitive electronic circuits (12). This short read out time allows a large number of samples to be processed by one instrument in an automated mode. 

The development of a calibration model is a time consuming process. Not only have the samples to be prepared and measured, but the modelling itself, including data pre-processing, outlier detection, estimation and validation, is not an automated procedure. Once the model is there, changes may occur in the instrumentation or other conditions (temperature, humidity) that require recalibration. Another situation is where a model has been set up for one instrument in a central location and one would like to distribute this model to other instruments within the organization without having to repeat the entire calibration process for all these individual instruments. One wonders whether it is possible to translate the model from one instrument (old or parent or master. A) to the others (new or children or slaves, B). 

In the process industries, flow measurement devices are the largest market in the process instrumentation field. Two web sites for process equipment and instrumentation, www.globalspec.com, and www.thomasnet.com, both list more than 800 companies that offer flow measurement products. There are more than one hundred types of flowmeters commercially available. The aforementioned web sites not only facilitate selection and specification of commercial flowmeters, but also provide electronic access to manufacturers technical literature. 

A pilot-scale demonstration remediating harbor sediment was conducted 1 year before the SITE demonstration. Based on the pilot-scale demonstration, the processing costs for a fuU-scale, 110-ton/day unit were projected to be 230/ton (September 1992 U.S. dollars). It is assumed that the unit will be down approximately 30% of the time for maintenance and design improvements in the first year of operation. Based on this system availability, 28,105 tons can be processed in one year. This cost included estimates for variable costs, fixed costs, and deprecia-tion/insurance. Variable costs include diesel fuel for a mobile generator, hydrogen, and caustic. Fixed costs include labor diesel fuel for pumps, heaters, process equipment, and instrumentation propane, water and sewer and parts and supplies. Depreciation/insurance costs include capital cost depreciated over a 3-year period, general insurance costs, and pollution liabihty insurance. This analysis does not include costs for setup and demobilization (D128007, pp. 5.12-5.14). 

There are several uses of tablet press instrumentation in the scale-up process itself. One of these involves obtaining a sample of the scale-up batch and compacting that sample on the pilot-plant or research instrumented tablet press on which the formulation has been previously evaluated. Similarity of the fingerprint or the various research plots (Heckel, force-displacement, radial vs. axial plots) is evidence that the scale-up batch is similar to the previously evaluated research batch [2]. 

Just how these modes of action are achieved in relatively inexpensive pneumatic or electrical devices is explained in books on control instruments, for example, that of Considine (Process Instruments and Controls Handbook, Sec. 17,1974). The low prices and considerable flexibility of PID controllers make them the dominant types in use, and have discouraged the development of possibly superior types, particularly as one-shot deals which would be the usual case in process plants. Any desired mode of action can be simulated by a computer, but at a price. 

An intermediate level of sophistication was achieved by semiautomated sorting of radiofrequency tagged containers (e.g., MicroKans,8 Lanterns11). A simple instrument that integrates the process of one-dimensional necklace encoding by creating a linear sequences of solid-phase particles is the Encore synthesizer. 

Amoco selected Perkin Elmer to be the company that would produce the analyzer that Dr Vickers team had developed. The first item was to go over the specifications for the analyzer. I had the pleasure of presenting those based on laboratory work done with other NIR analyzers which showed that the natural line-width in liquid gasoline was about 3 nm, dramatically less than the 10 nm optical resolution of the NIR analyzers on the market at that time. When the specifications were presented in relationship to resolution and stability, one of the gentlemen from Perkin Elmer stated, it can t be done, at which time Dr Vickers said, come on down to the lab and I ll show you how we did it. This instrument, with a 3 nm resolution over the spectral range of 800—1100 nm, became known as the PIONIR 1024, where PIONIR stands for Process Instrument On-line NIR and 1024 denotes the number of silicon diodes in the diode-array readout. 

If a surface-sensitive solid is processed in one site and needs to be transported to the analysis site without exposure to the atmosphere, a vacuum briefcase or special transportation module needs to be used. This would consist of a small portable vacuum chamber that is capable of attaching and transferring samples between processing and analysis stations. Understandably, designs of such instruments are system specific and often complicated. Most manufacturers of vacuum and surface analysis systems can offer customized options for specific systems. 

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