PC_exam_2_solution

PC_exam_2_solution - Spring 2003 10.450 Process Dynamics,...

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10.450 Process Dynamics, Operations, and Control Spring 2003 Exam 2 from the 10.450 Policies: "The grade for either test may be raised by reworking the test out of class and turning it in the next class meeting. Final test grade will then be 2/3 in-class and 1/3 at-home. Up to 5 bonus points will be added for creativity in the presentation of the at-home portion." (1) (20%) Process optimization is a wonderful thing, but many companies refuse to spend resources to improve an old plant, reasoning that it’s better simply to milk it for what it’s worth. You’ve been assigned as keeper of a plant in its dotage; you’re given a scant budget, and you are to keep it running as best you can. When your venerable temperature controller dies, you have to scrounge in the scrapyard to find a spare. The good news is that both controllers use 4-20 mA input and output terminals, so no other equipment in the loop has to be changed. (Even the boxes are the same size, so the spare fits right into the panel!) However, your operator Fran reports that the old controller used settings of gain (gpm ºC -1 ) = 27, integral time (min) = 1.3, and derivative time (min) = 0.4, but the new controller is calling for a proportional band, a reset rate in s -1 , and a derivative time in s. Fran is too smart to re-use the old numbers, and curious to see if the new engineer can figure out what the new ones should be. Set the problem up, and then list the additional pieces of information you need to get from Fran. (Be realistic; the operator will know the equipment and settings, but not math models and transfer functions). The key is to realize that the old controller communicates by 4-20 mA signals, just as the
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This note was uploaded on 12/01/2011 for the course EE 223 taught by Professor Thw during the Spring '09 term at MIT.

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PC_exam_2_solution - Spring 2003 10.450 Process Dynamics,...

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