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NATIONAL RESEARCH COUNCIL COMMISSION ON ENGINEERING AND TECHNICAL SYSTEMS NATIONAL MATERIALS ADVISORY BOARD CHAIRMAN Dr. Dona Id J. McPherson Vice President and Director of Technology Kaiser Aluminum & Chemical Corporation .KX) Lakeside Drive Oakland. C A 94643 PAST CHAIRMAN Mr. William D. Manly Senior Vice President Cahot Corporation I25 High Si reel Boston. MA 02II0 Members Dr. R.Byron Pipes Director. Center for Composite Materials Department of Mechanical At Aerospace Engineering University of Delaware Newark. DE I9'7|l Dr. Brian M. Rushton Vice President. Research AL Development Air Products A. Chemicals. Inc. P.O. Box 5.18 Allentown.PA IKI05 Dr. John J. Schan/, Jr. Senior Specialist Congressional Research Service ENR Library of Congress Washington. DC 20^40 Dr. Dorothy M. Simon Vice President A. Director ol Research AVC() Corporation I275 King Street Greenwich. C I' 068.10 Dr. Michael Tenenbaum I644 Cambridge Flossmoor. I1.60422 Dr. William A. Vogely Professor and Head Department ol Mineral Economics Pennsylvania Slate University University Park. PA I6802 Dr. Robert P. Wei Department of Mechanical Engineering and Mechanics Lehigh University Bethlehem. PA I80I5 Dr. Albert R. C. West wood Director. Martin Marietta Labs Martin Marietta Corporation I450 South Rolling Road Baltimore. Ml) 2I227 NMAB STAFF K. M. Zwilsky, Executive Director R. V. Hemm, Executive Secretary Dr. Arden L. Bement. Jr. Vice President. 'Technology Resources Science and Technical Department TRW. Inc. 2.1555 Euclid Ave. Cleveland. OH 44II7 Dr. H. Kent Bowen Professor, Ceramic and Electrical Engineering Massachusetts Institute of Technology 77 Massachusetts Avenue Cambridge. MA 02I.19 Dr. William J. Burlanl Director, Lexington Laboratory The Kendall Co". Lexington. MA 02I7.1 Dr. James C. Burrows Vice President Charles River Associates 2(K) Clarendon Street John Hancock lower. 4.1rd Floor Boston. MA 02II6 Dr. Raymond F. Decker Vice President. Corporate Technology & Diversification Ventures Inco Limited One New York Pla/a New York. NY KXXM Dr. Brian R. T. Frost Division Director. Materials Science Argonne National Laboratory 9700 South Cass Avenue A rgonne.lL 604.19 Dr. Serge Cratch Director of Chemistry Science Lab Engineering & Research Staff Ford Motor Co. P.O. Box 205.1 Dearborn. MI 48I2I Dr. NickHolonyak.Jr. Professor Electronic Engineering University of Illinois-Urbana Dept. of Electrical Engineering L'rhana.IL 6I80I Dr. Sheldon E. Isakoff Director, Engineering Research and Development Division E. I. du Pont de Nemours A. Company. Inc. Wilmington. DE I9N98 Dr. Frank F'. Jaumot. Jr. Director of Advanced Engineering Delco Electronics Division General Motors Corporation P.O. Box II04 Kokomo. IN 4690I Dr. Paul J. Jorgensen Stanford Research Institute .1.1.1 Ravcnswood Avenue Menlo Park. CA 94025 Dr. Alan Lawley Professor Metallurgical Engineering Drexel L'niversity Department of Materials Etngineerim; Philadelphia. PA I9I04 Dr. Raymond F. Mikesell W. E. Miner Professor of Economics University of Oregon Department of Economics Eugene. OR 9740.1 Dr. David Okrenl Professor of Engineering At Applied Science University of California, Los Angeles 55.12 Boelter Hall Los Angeles. CA 9(X)24 fa. I fa/82
PNEUMATIC DUST CONTROL IN GRAIN ELEVATORS; GUIDELINES FOR DESIGN OPERATION AND MAINTENANCE ^ Report of the C^ Panel on Causes and Prevention of Grain Elevator Explosions of the Committee on Evaluation of Industrial Hazards ^-SNATIONAL MATERIALS ADVISORY BOARD on Engineering and Technical Systems ^National Research Council National Academy of Sciences ,j NAS-NAE Publication NMAB 367-3 NATIONAL ACADEMY PRESS AUG 0 3 1982 Washington, D.C. 1982 ^ LIBRARY
C-, / 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 competences and with regard for appropriate balance. The 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. The National Research Council was established by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purposes of furthering knowledge and of advising the federal government. The Council operates in accordance with general policies determined by the Academy under the authority of its congressional charter of 1863, which established the Academy as a private, nonprofit, self-governing membership corporation. The Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in the conduct of their services to the government, the public, and the scientific and engineering communities. It is administered jointly by both Academies and the Institute of Medicine. The National Academy of Engineering and the Institute of Medicine were established in 1964 and 1970, respectively, under the charter of the National Academy of Sciences. This study by the National Materials Advisory Board was conducted under Contract No. J-9-F-8-0137 with the Occupational Safety and Health Administration (OSHA). Funding was provided by OSHA, National Institute for Occupational Safety and Health, and the Department of Agriculture. This report is for sale by the National Technical Information Service, Springfield, Virginia 22151. Printed in the United States of America. ii
PLEASE NOTE CAREFULLY This handbook has been compiled as a guide for designers, installers, and owners of pneumatic dust collection systems. Most of the information contained herein is equally applicable to new and existing facilities. It must be emphasized, however, that the traditional grain elevator has certain inherent structural features, which render the total control of layered dust virtually impossible by pneumatic means. The difficult areas are typically the interiors of working bins in the headhouse, concrete legwells, tanks and interstice bins. In any part of the stock handling systems or storage facilities where layered dust can accumulate in significant quantities, there is always the possibility of "cling" dust being dislodged by pressure from a primary explosion or by the dropping of a leg belt. The growth of these layered dust formations will be retarded by a properly functioning dust control system, but their presence should always be anticipated, and appropriate means should be employed to remove them as necessary. iii
PREFACE The National Materials Advisory Board is a unit of the Commission on Engineering and Technical Systems of the National Research Council. Its general purpose is the advancement of materials science and engineering in the national interest. It fulfills that purpose by providing advice and assistance to government agencies and private organizations on matters of materials science and technology affecting the national interest, by focusing attention on the materials aspects of problems and opportunities, and by making appropriate recommendations for the solution of such problems and the exploitation of the opportunities. The Occupational Safety and Health Aministration (OSHA) requested that the National Research Council (NRC) of the National Academy of Sciences undertake a study of the causes and prevention of grain elevator explosions. The NRC through the National Materials Advisory Board (NMAB) appointed the Panel on the Causes and Prevention of Grain Elevator Explosions. This panel serves under the Committee on Evaluation of Industrial Hazards. The panel is composed of experts in many fields related to explosions, the grain industry, and systems analysis. Grain-handling facilities have suffered from devastating fires and explosions for well over 100 years in this country. A common ingredient in all of these occurrences has been the accumulations of grain dust in sufficient quantities to support such fires and explosions. A variety of approaches has been used in the past to control dust accumulations. One of the most common systems used nowadays is pneumatic dust control, which is the subject matter of this manual. There is a wide variety of designs and sizes of such pneumatic systems with accompanying variations in the degree of effectiveness. The manual addresses pneumatic dust control system design, installation, operation, and maintenance. Recommendations are made on the necessary qualifications for designers and installers of such pneumatic dust control systems and on guidelines on design, including fundamental principles and suggested specifications. Housekeeping criteria are addressed to minimize both explosive airborne concentrations and dangerous static dust accumulations of grain dust in grain elevators and grain-handling facilities. Guidelines for operation of the system and criteria for determining permissible alterations to the system are presented as well as recommendations for maintenance of the system, including training of personnel. Suggested acceptance test procedures for guidance to grain elevator operators are also given. An appendix is included in which technical terms used in the text are defined.
References to proprietary products are for illustrative purposes only and do not constitute endorsements or recommendations. It is recognized that certain specific facets of pneumatic dust control are susceptible to further improvement. Therefore, we urge that efforts be made toward removal of explosive dust suspensions from bucket elevator legs, and for dust removal and dust emission control from truck and car dumps. Designers are requested to keep abreast of developments in this and other areas. I would like to thank the participants in the Subpanel on Pneumatic Dust Control for their untiring efforts in preparing this manual. Roger A. Strehlow, Chairman vi
SUBPANEL ON PNEUMATIC DUST CONTROL Chairman ALBERT S. TOWNSEND, National Agra Underwriters, Inc., Camp Hill, Pennsylvania Members JOHN E. ALBERTSON, American Federation of Government Employees, Washington, D.C. ROBERT M. FRYE, MAC Pneumatic Systems, Inc., Kansas City, Missouri ROBERT F. HUBBARD, Cargill, Inc., Minneapolis, Minnesota ALLEN I. ORMSBEE,* University of Illinois, Urbana-Champaign Technical Consultants WAYNE DAVIS, Ohio Farmers, Inc., Fostoria, Ohio ROBERT E. FREY, Donaldson Company, Inc., St. Paul, Minnesota GARY L. McDANIEL, MAC Equipment, Inc., Sabetha, Kansas ROBERT PACQUER, Marshall, Barr and Pacquer, Inc., Seattle, Washington CHARLES ROCKWELL, CEA Carter-Day Company, Minneapolis, Minnesota Liaison Representatives! MARTIN A. ESHLEMAN, Department of Agriculture, Washington, D.C. THOMAS H. SEYMOUR, Occupational Safety and Health Administration, Washington, D.C. NMAB Staff STANLEY M. BARKIN, Staff Scientist NELSON T. GRISAMORE, Staff Scientist *Appointed during the course of the study. vii
PANEL ON CAUSES AND PREVENTION OF GRAIN ELEVATOR EXPLOSIONS Chairman ROGER A. STREHLOW, University of Illinois, Urbana-Champaign Members JOHN E. ALBERTSON, American Federation of Government Employees, Washington, D.C. WILLIAM C. BRASIE, Dow Chemical Company, Midland, Michigan ROBERT M. FRYE, MAC Pneumatic Systems, Inc., Kansas City, Missouri VERNON L. GROSE, Tustin Institute of Technology, Santa Barbara, California ROBERT F. HUBBARD, Cargill, Inc., Minneapolis, Minnesota CHARLES W. KAUFFMAN, University of Michigan, Ann Arbor ERNEST C. MAGISON, Honeywell Inc., Fort Washington, Pennsylvania ALLEN I. ORMSBEE*, University of Illinois, Urbana-Champaign ALBERT S. TOWNSEND, National Agra Underwriters, Inc., Camp Hill, Pennsylvania Liaison Representatives EDWARD J. BALLITCH, Food and Drug Administration, Washington, D.C. PETER BOCHNAK, National Institute for Occupation Safety and Health, Morgantown, West Virginia MARTIN A. ESHLEMAN, Department of Agriculture, Washington, D.C. DON GOODWIN, Environmental Protection Agency, Research Triangle Park, North Carolina ix
DONALD D. HERRING, Department of Agriculture, Washington, D.C. JOHN F. McANULTY, U.S. Coast Guard, Washington, D.C. THEODORE A. PETTIT, National Institute for Occupational Safety and Health, Morgantown, West Virginia JOSEPH E. PIPKIN, Occupational Safety and Health Administration, Washington, D.C. YESHAJAHU POMERANZ, Department of Agriculture, Manhattan, Kansas THOMAS H. SEYMOUR, Occupational Safety and Health Administration, Washington, D.C. BERNARD T. WOLFSON, U.S. Air Force, Washington, D.C. NMAB Staff STANLEY M. BARKIN, Staff Scientist NELSON T. GRISAMORE, Staff Scientist *Appointed during the course of the study.
COMMITTEE ON EVALUATION OF INDUSTRIAL HAZARDS Chairman HOMER W. CARHART, Naval Research Laboratory, Washington, D.C. Members FREDERICK R. EIRICH, Polytechnic Institute of New York, New York LELAND J. HALL, The Mill Mutuals, Chicago, Illinois ERNEST C. MAGISON, Honeywell Inc., Fort Washington, Pennsylvania J. ARTHUR NICHOLLS, University of Michigan, Ann Arbor PETER J. SCHRAM, Underwriters Laboratories, Inc., Northbrook, Illinois ROGER A. STREHLOW, University of Illinois, Urbana-Champaign Liaison Representatives PETER BOCHNAK, National Institute for Occupational Safety and Health, Morgantown, West Virginia CHIA CHEN, Occupational Safety and Health Administration, Washington, D.C. ANDREW M. COWAN, Department of Agriculture, Beltsville, Maryland JOHN A. GERARD, National Institute for Occupational Safety and Health, Morgantown, West Virginia RICHARD W. McQUAID, David W. Taylor Naval Ship Research and Development Center, Annapolis, Maryland JOSEPH E. PIPKIN, Occupational Safety and Health Administration, Washington, D.C. THOMAS H. SEYMOUR, Occupational Safety and Health Administration Washington, D.C. xi
Technical Advisors ERSKINE HARTON, Consultant, Falls Church, Virginia MURRAY JACOBSON, Mine Safety and Health Administration, Arlington, Virginia NMAB Staff STANLEY M. BARKIN, Staff Scientist xii
CONTENTS Section 1 Introduction Causes of Explosions Methods of Dust Control Page 1 2 2 Section 2 Dust-Control Techniques and Equipment Minimizing Generation of Dust Manual Housekeeping Mechanical Housekeeping Use of Pneumatic Systems 5 5 7 9 Section 3 Hoods, Transitions, and Ductwork Capture Velocity Hood and Transition Design Ductwork Design Materials of Construction 11 12 14 23 Section 4 Dust Filters Fabric-Filtration Practice Disposal of Collected Dust Cyclone-Filter Facilities 29 29 34 36 Section 5 Exhaust Fans Selecting a Fan Fan Size and Speed Fan Installation Modifying a System 37 37 40 44 47 Section 6 Dust Control in Problem Areas Enclosed Problem Areas Unenclosed Problem Areas Truck and Rail Unloading Truck and Rail Loading Marine Loading 49 49 60 64 66 67 xiii
Paqe Section 7 Requirements for Design, Installation, and Acceptance of Pneumatic Dust-Control Systems Qualifications for Designers and Installers Summary of Intent Specification and Acceptance Testing Guidelines for Specification and Acceptance Testing 73 74 75 75 76 Section 8 Instrumentation, Operation, and Maintenance Instrumentation Basic Monitoring Equipment Electrical Interlock Using the Instruments Sample Maintenance Schedule 79 79 80 81 81 86 Appendixes A Definitions B Sample of a Contractor's Qualification Statement C Results of an Experiment to Determine Whether Dust Suspensions in Bucket Elevator Legs Can Be Kept Below the Lower Explosive Limit by Pneumatic Means D Steady State Velocities Curricula Vitae for Panel Members 89 95 103 109 117 xiv