Plant representation

In multipurpose batch plants, a wide variety of products can be produced via different processing recipes by sharing all available resources, such as equipment, raw material, intermediates and utilities. In order to ensure that any resource in the design can be used as efficiently as possible, an adequate methodology is necessary in order to address such type of problems without creating ambiguities in the process/plant representation. 

Fig.6 Example of trend vs time parameter representation the view is Epical of a paper recorder, with time in Y coordinate decreasing from the top to the bottom. The eight top buttons represent the different choice of plant parameters...

Fig. 1. A schematic representation of the xylan backbone of arborescent plants, where Xylp = xylopyranosyl unit ...

Flow-sheet models are used at all stages in the life cycle of a process plant during process development, for process design and retrofits, and for plant operations. Input to the model consists of information normally contained in the process flow sheet. Output from the model is a complete representation of the performance of the plant, including the composition, flow, and properties of all intermediate and product streams and the performance of the process units. 

Extended Plant-Performance Triangle The historical representation of plant-performance analysis in Fig. 30-1 misses one of the principal a ects identification. Identification establishes troubleshooting hypotheses and measurements that will support the level of confidence required in the resultant model (i.e., which measurements will be most beneficial). Unfortunately, the relative impact of the measurements on the desired end use of the analysis is frequently overlooked. The most important technical step in the analysis procedures is to identify which measurements should be made. This is one of the roles of the plant-performance engineer. Figure 30-3 includes identification in the plant-performance triangle. 

Focus For the purposes of this discussion, a model is a mathematical representation of the unit. The purpose of the model is to tie operating specifications and unit input to the products. A model can be used for troubleshooting, fault detection, control, and design. Development and refinement of the unit model is one of the principal results of analysis of plant performance. There are two broad model classifications. 

It is important to note, however, that all this is not free. The designer must invest the time to set up the cases and evaluate the results. Only the designer can make the final decision as to whether the cases and the comparisons are valid (a true representation of the plant). The computer printout is simply the results of matrix manipulation and should be considered suspect until given the designer s stamp of approval. 

Figure 4.45 shows the bloek diagram representation of a proeess plant being eon-trolled by a PID eontroller. 

If Pmfv) and the plant uncertainty A(.v) are combined to give P(.v), then Figure 9.29 can be simplified as shown in Figure 9.30, also referred to as the two-port state-space representation. 

Cutsets are the least compact representation of a complex plant, they may be so numerous that they are unmanageable which obscures significant risk contributors. To address this hydra-like expansion, cutsets may be truncated according to order, probability, or risk. Truncation by order is an approximation to truncation by probability as if each component has about the same probability of failure (a very gross assumption). Truncation by order and by probability are featured in most codes that calculate cutsets. A better truncation method is by risk, as provided in ALLCUTS in as much as a low probability cutoff may delete a high consequence, significant risk contributor. Truncation by risk is difficult because the consequence of a sequence may not be known when the... 

Representational layout of control panels. Where the physical location of items is important, for example, area displays in fire control systems, the layout of the displays on a control panel should reflect the geographical layout of the plant. In other cases a functional arrangement of the elements of the process plant will be appropriate, for example, when monitoring the status of the system via an alarm panel. 

Embrey, D. E., Humphreys, P. (1985). Support for Decision-Making and Problem-Solving in Abnormal Conditions in Nuclear Power Plants. In L. B. Methlie R. H. Sprague (Eds.), Knowledge Representation for Decision Support Systems. Amsterdam North Holland. 

Years ago plastic scale models were fabricated for each plant under construction, providing excellent three-dimensional representations of the actual facilities. Today, in the age of the microcomputer, it is quicker, easier, and much cheaper to generate models by means of computer graphics. 

Many s)mbols are pictorial which is helpful in representing process as well as control and mechanical operations. In general, experience indicates that the better the representation including relative locating of connections, key controls and even utility connections, and service systems, the more useful will be the flowsheets for detailed project engineering and plant design. 

Unlike the two trending techniques, signature analysis provides visual representation of each frequency component generated by a machine-train. With training, plant staff can use vibration signatures to determine the specific maintenance required by plant machinery. 

The pitfalls of a computer model are obvious in that it is only a conceptual representation of the reactor and includes only as many aspects of the real reactor as present knowledge permits. In addition, even the most perfectly conceived description will still depend upon the accuracy of the physically measured constants used in the model for the quality of the process representation. The goal of this report is, however, only to show conceptual trends and the technological base is developed to the extent that the conceptual trends will be correct. In some respects the computer model is a better process development tool than the pilot plant used for the LDPE process since the pilot reactor does not yield directly scaleable information. The reader should take care to direct his attention to the trend information and conceptual differences developed in this work very little attention should be paid to the absolute values of the parameters given. 

Fig. 1. (a) Schematic representation of the three types of anoxygenic ([1] and [2]) and oxygenic ([3]) photosynthesis found in plants and bacteria, (b) Phylogenetic tree based on 16S-rRNA sequence comparisons featuring only photo synthetic phyla. 

Fig. 2. Schematic representation of the Ti-plasmid of Agrobacterium, showing the genes involved in transformation of host plants. Note that the genetic map is not to scale in reality, the T-region makes up about 10% of the total plasmid genome (from Bryant, 1988).

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