Symbols, process piping

Each plant will have a file of its standardized piping symbols. Process technicians should carefully review these piping symbols for major and minor flows, and for electric, pneumatic, capillary, hydraulic, and future equipment. The major flow path through a unit illustrates the critical areas a new technician should concentrate on. Some of the devices used in piping are strainers, filters, flanges, spool pieces, and steam traps. A variety of piping symbols can be found in Figure 7-7. 

This part of BS 1553 specifies graphical symbols for use in flow and piping diagrams for process plant. 

Many chemical and petroleum companies are now using Process Industry Practices (PIP) criteria for the development of P IDs. These criteria include symbols and nomenclature for typical equipment, instrumentation, and piping. They are compatible with industry codes of the American National Standards Institute (ANSI), American Society of Mechanical Engineers (ASME), Instrument Society of America (ISA), and Tubular Exchanger Manufacturers Association (TEMA). The PIP criteria can be applied irrespective of whatever Computer Assisted Design (CAD) system is used to develop P IDs. Process Industries Practice (1998) may be obtained from the Construction Industry Institute mentioned in the References. 

The temperature points, with their index numbers, will be found on the process control diagrsim. These require thermowell installations in the piping. The temperature index numbers assign to each point are designated by conventional symbols such as TI, (Temperature Indicator), TH, TIC, TC, TRC, TR, TIA, TRCA, TT and TW followed by the number assigned to each of the points. 

Separation processes typically consist of hrmdreds of elements (pipes, vessels, heat exchangers, columns, pumps, compressors, engines, measuring and control devices, etc.) that are too complex for exact graphical depiction. Therefore, the process structures are depicted in a very abstract and geometrically nonsimilar manner in the form of flow sheets. Flow sheets show the process structure with symbols for the essential process elements according to international standards (e.g., DIN, ISO). 

To understand the design and function of a chemical plant it is a useful preliminary to study the flow diagram (sometimes called a flow sheet). Its purpose is to illustrate diagrammatically, on one sheet of paper, all the items of equipment required for a chemical process or series of processes to be operated. Items are represented by simple symbols which are usually those recommended by the British Standard 974 1953 and subsequent editions (your supervisor may have a copy). The route of materials through the equipment is indicated by arrows and interconnecting lines and, in some instances, the materials of construction, size or capacity, flow rates, power requirements, and pipe dimensions are also shown. 

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. 

Process symbols—images that graphically depict process equipment, piping, and instrumentation. 

There are a number of symbols that are universally employed to represent equipment, equipment parts, valves, piping, etc. These are available in the literature. Although a significant number of these symbols are used to describe some of the chemical and petrochemical processes, only a few are needed for even the most... 

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