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Industrial Instrumentation

Industrial Instrumentation. ( Instruments, Importance, Characteristics and case studies ) . Presenter Muhammad Khurram 07-Chem-45. Instruments . Instruments are devices that measure and regulate the process variables, such as flow, temperature, pressure, level.

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Industrial Instrumentation

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  1. Industrial Instrumentation (Instruments, Importance, Characteristics and case studies)

  2. Presenter Muhammad Khurram 07-Chem-45

  3. Instruments • Instruments are devices that measure and regulate the process variables, such as flow, temperature, pressure, level. Basic measurements in process industries • Temperature • Pressure • Level • Flow

  4. Temperature sensors • RTDs • Thermocouple • Infrared thermometry • Pyrometers • Thin film heat flux gauge

  5. Pressure sensors • Hydrostatic pressure gauges • McLeod gauge • Aneroid • Bourdon tube gauge • Thermal conductivity gauges • Pirani gauges • Molecular method • Hot cathode and cold cathode

  6. Level sensors • Sight glass • Magnetic float method • Cable and float • Conductivity method • Resistance wire • Float and hydraulic pressure • Strain gauge

  7. Flow meters • Direct volume measurement • Displacement method • The voltage created by a moving liquid • The amount of heat required to raise the temperature by known value • Venturi tube • Flow nozzle • Orifice plate

  8. Importance of industrial instrumentation • Greater safety of operation • Better Quality of products • Greater operation economy

  9. Performance characteristics of Instruments Static Characteristics Characteristics which are related to instruments when there is no change in conditions with time. Dynamic Characteristics Characteristics which are related to instruments when there is change with respect to time.

  10. Static Characteristics • Accuracy Degree of conformity of an indicated value to a recognized accepted standard value, or ideal value. • Static error The difference between measured and actual value.

  11. Reproducibility • Closeness of agreement among a number of consecutive measurements of same variable under same operating conditions over a period of time approaching from both directions Drift • Measure of difference in Repeatability Two ways to find drift • Point Drift • Calibration Drift

  12. Sensitivity • The ratio of the change in output magnitude to the change of the input which causes it after the steady state has been reached. Dead Zone • Dead zone is the largest range of values of a measured variable to which the instrument does not respond. Sometimes also called dead spot or Hysteresis.

  13. Repeatability • Closeness of agreement among a number of consecutive measurements of the output for the same value of the input under same operating conditions, approaching from same direction. Precision • The degree of exactness for which an instrument is designed or intended to perform is known as precision

  14. Other characteristics are • Range • Span • Resolution • Hysteresis • Linearity • Backlash

  15. Linearity • Linearity describes the closeness of a curve to a straight line

  16. Backlash • Backlash, also called lash or play, is basically clearance between mating components, may also be described as the quantity of lost motion clearance or slackness when movement is reversed and contact is re-established. For example, in pair of gears, backlash is the clearance between mated gear teeth Lack of backlash causes • Noise • Overheating of gears and bearings • Seizing and failure

  17. Dynamic characteristics • Speed of response • Lag • Fidelity • Dynamic error

  18. Case studies Exothermic reaction in CSTR Following diagram is of continuous stirred tank reactor where gas phase exothermic reaction is taking place. The reaction temperature is to be maintained at 250 degree centigrade. Reactor is supplied with cooling water in the jacket outside the reactor. Pressure inside reactor becomes danger when reactor becomes full of reactants. So continuous monitoring of pressure is also required. How these two factors can be controlled effectively and which type of sensors will be used?

  19. The temperature will be controlled by controlling cooling water outlet temperature. This can be simply done by using thermocouple because it is easily installed and low cost. Reactor pressure will be controlled by using Pirani gauge to control reactants pressure. Solution:

  20. Condensed product from reactor is fed into a storage tank. When the storage tank became full then it can clog the reactants in reactor. It is decided that condensed product is allowed to fill the tank upto 90% of total volume to efficiently control the process. If level increases 90% alarming situation can occur. What type of level sensor will be used? Storage tank case

  21. Float will be used for level control because it is hi level control system. And level controller will be connected with the inlet and outlet valves. On alarming situation controller will open the drain valve and close the inlet valve. Solution

  22. Reliable level measurementincreases quality andconsistency in commercialsoup production Challenge: Selection of level sensor for soup production kettle. Level controlles the agitators speed in the kettle for mixing ingredients.

  23. Solution: Sensor which don’t have direct contact with soup in the kettle will be used. Radar sensor is best suited for this situation.

  24. Heat Exchanger Case study

  25. Solution:

  26. References Books • Fribance, Austin. E. Industrial Instrumentation Fundamentals. New York: McGraw- Hill, 1962; (a) p.3-10; (b) p.298-305. • Eckman, Donald. P. Industrial Instrumentation. New York: John Wiley& Sons, Inc, 1957; page.1-12. • Krishnaswamy, K., and S. Vijayachitra. Industrial Instrumentation, 1st ed. New Delhi: New Age International (P) Limited, 2005; p. 5-11. • Padmanabhan, Tattamangalam. R. Industrial instrumentation Principles and Design. London: Springer-Verlag London limited, 2000; page.9-18.

  27. 5) Padmanabhan, Tattamangalam. R. Industrial instrumentation Principles and Design. London: Springer-Verlag London limited, 2000; page.9-18.

  28. Websites 6) Halley Crast, Andrew Laskowski, Maurice Telesford, Emily Yatch, (December 14, 2009). PID standard notation [online]. Available:http://controls.engin.umich.edu/wiki/index.php/PIDStandardNotation. [Accessed 28 October, 2010] 7) Assist. Prof. Pakorn Kaewtrakulpong, Ph.D. INC KMUTT. Generalized Performance Characteristics of Instruments [online]. Available: http://www.inc.eng.kmutt.ac.th/inc100/100_instru_charac_new.pdf. [Accessed 28 Oct, 2010]

  29. 8) Overview of Temperature Measurement [online]. Available: eng.sjsu.edu/…/Overview%20of%Temperature%20Measurement.ppt [Accessed 25 Oct, 2010] • SMD Fluid Control, (2002). Float switch and Liquid level sensor [online]. Available: http://www.fluidswitch.com. (Accessed 25 Oct, 2010) 10) Wet Labs, (2006). Float Sensors user’s guide [online]. Available:http://www.wetlabs.com/products/pub/flowsensor/flowsensorf.pdf. [Accessed 25 Oct, 2010]

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