I&EC REPORTS & COMMENTS Computers lift piping system design from engineers Nature of chemical engineering changes with the times
PIPING NETWORK DESIGN IS COMPUTERIZED Computer calculations plus visual display promise to relieve engineers of one more routine j o b Freeing engineers from routine design calculations by substituting computers continues to occur. Latest example is the development-simultaneously but independently by C. F. Braun Co. and The Badger Co.-of computer systems for design and drafting of process piping networks. Automatic drafting is achieved by tieing a computer to a n electronic display device. These computers, a Burroughs 5500 for C . F. Braun and an IBM 1620, reported to be Badger’s choice, are connected to a cathoderay tube thought to be an SC-4020 display device made by General Dynamics. The computer does the calculations; the display tube produces isometric drawings that can be photographed. Traditionally, where new piping systems had to be constructed, piping schedules were prepared and submitted for approval to a resident engineer. The schedule, detailing in tabular form the type and position of each pipe and fitting, described the exact length, end point, end elevation, slope angle, and tangent of each piece and section. I n addition, a separately prepared pipe summary listed pipes and special fittings according to type, number, and length. Manual preparation of these pipe schedules and of isometric drawings represents, according to Badger, from 40 to 50% of total engineering time in the engineering and construction of process plants. By 1961, computers fast enough to handle the millions of calculations required to place letters and lines on
drawings became commercially available. Electronic display devices, driven by magnetic tape, could produce on a cathode-ray tube faithful images which could be photographed and converted to working drawings. The system described by A. E. Kipps of C. F. Braun at the API meeting last month has four major segments: an input system to interpret the data put in by the engineer; a material control system to take off, summarize, and acquire the erection materials; a drafting system to place lines and letters on the output display device; and a stress analysis system to analyze specific pipelines subjected to thermal, dead load, and seismic action. The input system, designed to accept the engineer’s description of pipelines in coded form, also records material standards and project speci-
fications on magnetic tape. This tape, in turn, becomes the source of all data for materials control, isometric drawings, and stress analysis systems. Missing component data are provided by the computer from the project piping class files. Class files, drawing data from vendors’ catalogs, contain dimensions and weights of thousands of valves and fittings, allowable stress as a function of temperature in accordance with accepted standard specifications, and abbreviated and detailed descriptions for all materials. As input data are read in, the computer makes several logical checks to test their validity. Terminal coordinates from input are compared with those determined from point-bypoint details. If input data differ from programmed information, the computer adjusts the length of straight pipe to agree with the
Schematic representation of computer logic used to design pipinp networks PIPELINE DATA
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DATA PREPARATION
NATERIALS
DRAWINQS
CALCULATIONS
ESTINATES
lNSULATION SUNHARY
CONTROL REPORTS
ISOHETRIO DRAWINO
STRESS ANALYSIS
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VOL. 5 6
NO. 6
JUNE 1964
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IdEC REPORTS
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Hydroxylammonium Acid Sulfat rydroxylammonium Sulfate I ydroxylammonium Chloride
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12
NG OF IC FIBERS
terminal coordinates and informs the engineer of its actions. Out-of-class items can be identified and reported. A complete list of the materials needed in the job can be printed out and used for materials requisition and control. A record of piping materials is summarized on the materials record by type, size, and description, and is used to write purchase requisitions. Alternate inputs can be used to prepare piping estimates and to supply data for erection drawings. Drclwinpr
With all the necessary data available, the computer makes the necessary calculations for each segment of the piping network, and stores it, along with appropriate symbols, dimension lines, extension lines, leaders, and arrowheads, on magnetic tape in two tables, one for line work and another for lettering. It is from these tapes that drawings are made by the electronic display tube. Dimensions must be scaled down to fit within the grid of the display tube. The computer scales down the pipeline uniformly until the image size for any fitting reaches a specified minimum. Thereafter the size is fixed at a minimum and lengths of pipe are shortened until the entire pipeline fits within the grid. Vectors representing the pipeline and its components are put into a grid matrix from which the drawing will be made. During this operation, overlay interference is first encountered, since in an isometric drawing a pipeline may double back and cross over or under itself, showing an intersection where none existed. The computer corrects for overlay interference by breaking the line farthest from the viewer. Vectors are not placed into the grid matrix unless all overlay interferences are eliminated. Once placed, however, these vectors will not be altered by subsequent lines; the pipelines
INDUSTRIAL AND ENGINEERING CHEMISTRY
are placed first with other lines following in order. The most difficult programming task, dimension lines and their associated extension lines, can be handled by having the computer place the dimension line a set distance outside the view. On encountering overlay interference, the computer attempts to place the dimension inside the view. If unsuccessful, the computer gives up and displays its latest trial. At this point manual correction is required by the engineer on the final print. Flow arrows, area marks, and weld marks are added to the grid matrix. The north arrow is placed and attachments such as pressure gages are included. At this point the computer has assembled the grid matrix table with all of the vectors to describe the line work and the table containing all of the lettering. In the final step, the computer translates these tables for the electronic display and puts the information on magnetic tape from which off-line drawings can be made. Any necessary corrections are made by the engineer on the final 10-inchsquare print. The major logic problem encountered in the isometric program involves the recognition and correction of overlay interference. In the program a common procedure is used to recognize interference. Correction is done within each of the separate procedures before the program is allowed to go further. L. CRITIDES
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THE IDENTITY OF CHEMICAL ENPlNEERINQ
The implications of a reorganization of chemical engineering are being discussed with more than casual interest in many quarters of the profession, industrial and academic. Discussion usually centers upon the distinction between the (Contiiurd
011
page 74)
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I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
Ch.E.
unit operations and transport phenomena; it frequently seems as though the identity of modern chemical engineering resides in the transport phenomena. There is, however, a growing awareness that chemical engineering is composed of more than unit operations and transport phenomena. If one considers engineering to be the application of science, it follows that engineers should be concerned with the basic scientific principles and the methods of their application. Such has always been true. But the rather empirical organization of these methods of application in the past has produced a unique form of specialization based on personal experience. As the c o m p i t e of perS O Mexperience ~ has changed so has the form of chemical engineering. In a sense we are witnessing the growth of the "science of application'' which is natural to any profession. The fact of change is not new but the intensity of the present change is unusual. After the successful introduction of the unit operations established the identity of chemical engineering, there were immediate attemp$ to further consolidate the profession. Sherwood, for example [Shenvocd, T. K., IND. ENG. CHEM,,38, 4241, in 1941 discussed the classification of processing operations under conservation, equilibrium, and rate laws and s t r d the central role of diffusion in those operations. Until the early 1950's there was little change to be noted in the progress of the profession, but then came a rush of developments which, largely because of their number, disrupted the professional grasp of many people We are still attempting to re-establish our equilibrium amid the confusion, and it seems circumstantial and, perhaps, a bit unfortunate that transport phenom(Conhnucd on pagr 76)
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I&EC REPORTS
The Identity of Ch.E.,
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I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
ENOINEEIUNO CHEMISTRY,
Pierre Le Goffof the University of Nancy (France) makes such an assessment and illustrates the orderly transition from the remote past to the recent past. He does not feel that the fact t b t the transition has been more rapid than most people can comfortably digest is necessarily a cause for alarm. He shares the natural concern of professionals over the future of their profession and offers an optimistic view of the prospects. I n his assessment, Le Goff shows the order existing between the very basic ideas of thermodynamics, kinetics, structure, and optimal principles and the more familiar subjects of the unit operations, reactor design, and economics. Transport phenomena occupy a central position in this scheme but do so jointly with other, equally important subjects. W e Le Goffs characterization may not meet with total acceptance and may change with time, it does repreaent a much needed critique of matters so vital to the individual engineer.
THEEDITORS
