Symbols and Diagrams

Orifice piates are flat plates with holes that are typically smaller than the inside diameter of the pipe. The intent is to place the device between two flanges and restrict flow so that an artificial high- and low-pressure zone is created on each side of the orifice. A transmitter is used to calculate the differential and calculate a flow rate. The venturi flow nozzle uses the same principle as 

Rotameters have a glass tube with a flow element trapped between the measurement grid. This type of device provides direct contact between the measurement element and the fluid. Flow typically enters at the bottom of the rotameter and lifts the flow element. Oval gear meters and turbine flow meters displace a specific amount of liquid on each rotation. This is used to calculate total flow rate through the system. Pitot tubes are positioned perpendicular to flow. As the liquid enters the tube, precision-machined sensing vents determine flow rate. 

One of the more difficult tasks a new process technician is faced with is memorizing the hundreds of symbols and diagrams associated with the process industry. These process symbols form the 

Symbols and diagrams can be broken down into four primary parts  

GATE VALVES, . HXl- i Operated Pneumatic Motor Hydraulic Bleeder Bleeder  

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If we look at a piece of chemical text, we see that it is made up of characters, generally numeric digits, alphabetic characters, punctuation marks, and perhaps a few special symbols and diagrams. Information is conveyed by arranging these characters and symbols into particular sequences, words, numbers, etc., which convey particular meanings. Even a superficial study is sufficient to diow that there are basically three different types of information — numerical, structural, and conceptual. 

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

Symbols and diagrams have been developed for most pieces of industrial equipment, process flows, and instrumentation. The symbols covered in this chapter include those typically used with valves, piping, tanks, pumps, compressors, steam turbines, motors, heat exchangers, cooling towers, furnaces, boilers, distillation columns, and reactors. Figure 7-6 shows many of the basic symbols for valves. 

Some symbols are common between plants, whereas others change depending on the company. In other words, two different symbols may be used to identify a centrifugal pump or a valve, for example. Some standardization of process symbols and diagrams is taking place, but the process technician must learn what symbols his or her employer uses. The symbols shown in this chapter reflect a wide variety of petrochemical and refinery operations. 

Electrical drawings include symbols and diagrams that depict an electrical process system. Electrical drawings show unit electricians where power transmission lines run and places where it is stepped down or up for operational purposes. A complex P ID is designed to be used by a variety of crafts. The primary users of the document after plant start-up are process technicians, instrument and electrical, mechanical, safety, and engineering. 

The information provided must take into account the level of training, knowledge and experience of the employees. It must take account of language difficulties and be provided in a form that can be understood by everyone. The use of translations, symbols and diagrams should be considered. Where children under school leaving age are at work, information on the risk assessments and control measures must be provided to the child s parent or guardians of children at work before the child starts work. It can be provided verbally or directly to the parent, guardians or school. 

Graphical symbols for diagrams - Symbol elements, qualifying symbols and other symbols having general application 12032 BSEN 60617-2/1996 ... 

Figure 4.8 shows a specific example of this type of diagram which includes some symbols. The diagram shows the tasks that the operator and the computer must perform in a computer controlled reactor. The central column is used to show any functional requirements of the human-computer interface. 

We report the structure of a cell in a symbolic cell diagram, by using the conventions specified by IUPAC and used by chemists throughout the world. The diagram for the Daniell cell, for instance, is... 

Davidowitz, B., Chittleborough, G. (2008). Linking the sub-micro and symbolic levels Diagrams. In J. K. Gilbert D. F. Treagust (Eds.), Mutliple representations in chemical education. Dordreeht Springer. 

Figure 19. p Pa/ °Th) versus diagram after Thomas et al. (2002). Symbols and data... 

Roald Hoffmann and Pierre Laszlo recently have clarified the kind of argument that we find in Urbain s statement, noting that structural formulas in chemistry are "in-between symbols and models," existing in uneasy hybrid states. "A chemical formula is at one and the same time a metaphor, a model in the sense of a technical diagram, and a theoretical construct." 106... 

Figure 7.5 The acetonitrile-[C4CiIm][PF ]-water ternary mass phase diagram at room temperature. Closed symbols compositions belonging to the 50 50 w/w [C4CjIm][PF6]-water initial mixtures (dotted line) that separate in two phases whose compositions are listed in Table 7.2 and located by the corresponding open symbols and tie-lines. (Adapted from Berthod, A. and Carda-Broch, S., /. Liq. Chromatogr. Rel. TechnoL, 26,1493-1508, 2003.)...

We cannot present here the complete derivation, as it is very lengthy. However, we shall discuss some representative cases in detail and these should serve to convey the essential ideas. For each illustrative case, we shall give the space group symbol and the conventional diagrams and tables used by X-ray crystallographers. On the basis of these specific examples the general rules for notation and diagrams will be relatively easy to appreciate. 

Fig. 6.12 Phase diagram for blends of various PS homopolymers with nearly symmetric PS PI and PS PB diblocks, with approximately constant copolymer composition (/PS -0.44-0.55) (Winey et al. 19926). Symbols and annealing conditions as for Fig. 6.10.

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