Industrial Instrumentation

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Industrial Instrumentation

• (Instruments, Importance, Characteristics and
  case studies)

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• Presenter
• Muhammad Khurram
• 07-Chem-45

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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

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Temperature sensors

• RTDs
• Thermocouple
• Infrared thermometry
• Pyrometers
• Thin film heat flux gauge
  

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Pressure sensors

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

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Level sensors

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

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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

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Importance of industrial instrumentation

• Greater safety of operation
• Better Quality of products
• Greater operation economy

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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.

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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.

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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

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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.

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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

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Other characteristics are

• Range
• Span
• Resolution
• Hysteresis
• Linearity
• Backlash

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Linearity

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

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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

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Dynamic characteristics

• Speed of response
• Lag
• Fidelity
• Dynamic error

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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?

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Solution

• 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.

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Storage tank case

• 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?

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Solution

• 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.

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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.

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Solution

• Sensor which dont have direct contact with
  soup in the kettle will be used. Radar sensor is
  best suited for this situation.

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Heat Exchanger Case study
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Solution
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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.

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

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Websites

• 6) Halley Crast, Andrew Laskowski, Maurice
  Telesford, Emily Yatch, (December 14, 2009). PID
  standard notation online. Availablehttp//contr
  ols.engin.umich.edu/wiki/index.php/PIDStandardNota
  tion. 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_inst
  ru_charac_new.pdf. Accessed 28 Oct, 2010

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• 8) Overview of Temperature Measurement
  online.
• Available eng.sjsu.edu//Overview20ofTemp
  erature20Measurement.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 users guide
  online.
• Available http//www.wetlabs.com/products/p
  ub/flowsensor/flowsensorf.pdf. Accessed 25 Oct,
  2010