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Test Equipment for Use in Determining Classifications of Combustible Dusts (1979) / Chapter Skim
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Chapter 3: Electrical Resistivity
Pages 19-24

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From page 19...
... The result ts wit ~ be used to determine whether dusts have resistivities similar to metallic dusts or to agricultural dusts; therefore minor differences in measurement technique and experimental conditions are not likely to lead to differences in classification.
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From page 20...
... Direct current measurement is recommended to avoid possible complications of capacitance effects. The measurement of resistance can be carried out with any convenient instrumentation suitable for resistance measurement in the range of 10 4 to loons, depending upon specific cell dimensions.
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From page 21...
... . method for determining electrical 'resistivity of-dust, two panel members constructed three different test ce'l~Is and tested four dusts (corn starch,' powdered sugar, activated' charc'oal, and powdered graphite)
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From page 22...
... Test Cells 1 and 2, testing corn starch and powdered sugar, used General Radio No. 1644A Megohm Bridge at 500 volts dc; Test Cells 1 and 2, testing activated charcoal and graphite, used Fluke digital ohmmeter.
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From page 23...
... D groups: Recommended Resistivity Criteria for NEC Article 500 The 1978 National Electrical Code recognizes three dust Group E -- metallic dusts, Group Fe-carbonaceous dusts and Group G -- agricultural dusts.
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From page 24...
... Requiring that equipment containing uninsulated live metal parts operating at greater than 600 V be required to comply with the requirements for equipment for use in Division 1 locations; and 2. Requiring that plugs and receptacles connected to circuits rated over 600 V be considered unacceptable where semi-conductive dusts are present.
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Key Terms

  • powdered sugar
  • test cell
  • activated charcoal
  • corn starch
  • dust resistivity

  • current measurement
  • power supply
  • compute dust
  • test cells
  • electrical code

  • national electrical
  • nec article
  • voltage varied
  • surface resistivity
  • resistivity criteria

  • measurement technique
  • convenient instrumentation
  • filled sample
  • electrodes similar
  • code recognizes

  • cell construction
  • cell dimensions
  • determining electrical
  • rectangular electrodes
  • megohm bridge

  • solid maternal
  • recommends tilat
  • classifying dusts
  • electrically conductive
  • dust layers


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