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TEST EQUIPMEN r FOR USE IN DETERMINING CLASS IFICATIONS OF COMBUSTIBLE DUSTS :~ i.. Report of the Pane ~ on Dust Tes t Equipment of the Committee on Evaluation of Industrial Hazards NATIONAL MATERIALS ADVISORY BOARD Corrunission on Sociotechnical Systems National Research Counc i 1 Pub] ication STAB 353-2 Nat iona ~ Ac ademy 0 f Sc fences Washington, DC 1979

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NOTICE The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the Councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competence and with regard for appropriate balance. This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. This study by the National Materials Advisory Board was initiated under Contract No. J-9-F-5-0070 with the Occupational Safety and Health Administration and continued under Contract No, 210-78-0120 with the National Institute of Occupational Safety and Health. This report is for sale by the National Technical Information Service, Springfield, VA 22151. Printed in the United States of America. 11

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Hi: if: :: : :~: ~ .7 ~ ' . .~"i' ~~:~ I: Pre face The Occupational Safety and Health Administration (OSHA) requested that the National Research Council 's Committee on Evaluation of Industrial Hazards classify several hundred gases, vapors, and dusts in accordance with the classification groups in Article 500 of the National Electrical Code . Work previous ly conducted for the U. S . Coast Guard by the National Research Council 's Cornrnittee on Hazardous Materials, Electrical Hazards Pane I, had already established a method of .ciassification of flammable gases and vapors, but no such method had been established for the many combustible e dusts. Accordingly, the Committee on Evaluation of Industrial Hazards established the Panel on Dust Test Equipment to recommend proper test methods. These recommended test methods are described in this document, which is the second of a series of reports on the committee 's activities. The first report of the series, Matrix of Combustion-Relevant Properties and Classifications of Gases, Vapors, and Selected Solids (MOB 353-1), lists, in accordance with Artic le 500 of the National Electrical Code, the classifications of certain chemicals of interest to OSHA . The report conta ins phys ic a 1 and f lammabi lity data for the chemical s reviewed along with a grouping by chemical families to make it easier to classify new materials not in the present matrix. Homer W. Carhart, Chairman Committee on Evaluation of Industrial Haz arcs Peter J. Schram, Chairman Pane 1 on Dust Test Equipment

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I: : :l COMMITTEE ON EVALUATION OF INDUSTRIAL HAZARDS HOMER W. CARHART, Naval Research Laboratory Washington, DC, Chairman FREDERICK R. EIRICH, Polytechnic Institute of New York LE LAND J. HALL, The Mill Mutuals, Chicago, IL ERNEST C. MAGISON, Honeywell, Inc., Fort Washington, PA J. ARTHUR NICHOLLS, University of Michigan PETER Je SCHRAM, Underwriters Laboratories Inc., North- brook, IL ROGER A. STREHLOW, University of Illinois at Urbana-Champaign Liaison Representatives: THOMAS H. SEYMOUR, Occupational Safety and Health Administra- tion, Department of Labor, Washington, DC CHIA CHEN, occupational Safety and Health Administration, Department of Labor, Washington, DC JOSEPH E. PIPKIN, Occupational Safety and Health Administra- tion, Department of Labor, Washington, DC GLEN E. GARDNER, Occupational Safety and Health Administra- tion, Department of Labor, Washington, DC ; . D.Y. CORNOG, U.S. Postal Service, Rockville, MD DAVID R. FORSHEY, Division of Mining Research, Health and Safety, Department of the Interior, Washington, DC JOHN A. GERARD, National Institute for Occupational Safety and Health' Morgantown, WV EARL P. SHOUB, National Institute for Occupational Safety and Health, Morgantown, WV ANDREW M. COWAN, Department of Agriculture, Beltsvi1le, MD ERSKINE HARTON, Department of Transportation, Washington, DC ELTON LITCHFIELD (deceased), Bureau of Mines, Department of the Interior, Pittsburgh, PA JOSEPH CLARK, U.S. Fire Administration, Department of Commerce, Washington, DC JOHN B. FERGUSON, U. S . Fire Administration' Department of Commerce, Washington, DC 1V 5 t J - J 5,: ,.: , i:; at i/, .':, At: By: V. :. it: 51 I: I: it; Hi: : : ~ :

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Technica l Advisors 4~ . ~~ . MURRAY JACOBSON, Mine Safety and Health Administration, Department of Labor, Arlington, VA RICHARD F. SCHWAB, A' lied Chemical Corporation, Morristown, NJ JOHN MAGY (retired), Mine Department o f Labor, Pittsburgh, PA Staff Member: Safety and Health Administration, STANLEY M. BARKIN, National Materials Advisory Board, National Academy of Sciences, Washington, DC v

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PANEL ON DUST TEST EQUIPME:NT PETER J. SCHRAM, Underwriters Laboratories, Inc., Northbrook, IL, Chairman LE LAND J. HALL, The Mill Mutual s, Chicago, IL MURRAY JACOBSON, Mine Safety and Health Administration, Department 0 f Labor, Ar ~ ington, VA ELTON LITCHFIELD ~ deceased), Bureau of Mines, U. S . Department of the Interior, P ittsburgh, PA ERNEST C. MAGISON, Honeywell, Inc:., Fort Washington, PA ROGER A. STREHLOW, Univers ity of I llinois at Urbana-Champaign ~1

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Page Pref ace . . . CONTENTS Chapter 1 SUMMARY AND RECOl!L`lENDATIONS A. Background ...... B . Ob j ectives . . . . . C. Recommendations . ~ . . Chapter 2 LAYER IGNITION TEMPERATURE A. Background ...... B. Recommended Test Method For Igni- tion Temperature of Dust Layers 1. 2. 3. 4 . 5. 6. 7. 8. Scope . . . . . . . . . . . Definitions . . . . . . . . Preparation of Dust Sample Apparatus . . . . . . . . . Procedure . . . . . . . . . Validity of Test Results . Reporting of Results . . . Application of Results . . C. Recommendation for Installation Codes . . . . . . . . . . . . . Chapter 3 ELECTRICAL RESISTIVImY A. Background . . . . . . . . . . B. Recommended Method of Measurement of Dust Resistivity ~ ~ ~ ~ 6 6 7 7 11 16 16 17 19 19 Scope . . . . . . . . . . . . 19 2. Sample Chamber . . . . . . . 19 3. Preparation of Dust Sample . .20 4. Procedure . . . . . . . . . . 21 At. .. . ~ V11

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Page C. Validation of Test Method D . Recornmendec3 yes istivity Criteria f or {JEC Artic le 5 0 0 . . . . . REFERENCE S . 21 . 23 APPENDIX A Cons truction of Bleater Surf ace APPENDIX B [;leasure~nent of Temperature Distribution on Ilot P late . . ~ . . ~ . . . ~ . APPENDIX C Dusts With Cloud Ignition Temperatures Lower Than Their Layer Ignition Temperatures . . . . . . . . . . FIGURES & TABLES: 28 31 8 Figure 1 General Arrangement of Hot P late . . . . . . . . . , Figure 2 Scoops Reco~ru~nencled f or Form- ing Dus t Layers . . . . . . 10 Figure 3 Ring for Forming Bus t Layers 12 Figure 4 Typical Temperature-Time Curves for Ignition of Dust Layer on lIot Surf ace . . . 14 Figure 5 Sample Chamber 2 0 Figure 13-1 Smoldering Temperature According to SIDE 0 16 5, Measurement of Surface Temperature . Figure B-2 Fluctuations of Surface Temperature Over Entire Plate . . . . . . . . . Table ~ Typical Table of Test Results .. .. Table 2 P~esistiv-ity of Test Dusts Under Various Conditions . ~ 30 17 22