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1、NFPA 61 Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Products Facilities 1999 Edition National Fire Protection Association, 1 Batterymarch Park, PO Box 9101, Quincy, MA 02269-9101 An International Codes and Standards Organization The Standard is downloaded from
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25、rth above do not extend to the index of this document. (For further explanation, see the Policy Concerning the Adoption, Printing, and Publication of NFPA Documents, which is available upon request from the NFPA.) The Standard is downloaded from Standard Sharing 611 Copyright 1999 NFPA, All Rights
26、Reserved NFPA 61 Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Products Facilities 1999 Edition This edition of NFPA 61, Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Products Facilities, was prepared by the Technical Committee
27、on Agricultural Dusts and acted on by the National Fire Protection Association, Inc., at its May Meeting held May 1720, 1999, in Baltimore, MD. It was issued by the Standards Council on July 22, 1999, with an effective date of August 13, 1999, and supersedes all previous editions. Changes other than
28、 editorial are indicated by a vertical rule in the margin of the pages on which they appear. These lines are included as an aid to the user in identifying changes from the previous edition. This edition of NFPA 61 was approved as an American National Standard on August 13, 1999. Origin and Developme
29、nt of NFPA 61 The NFPA 61 standard had its origin back in 1923 when standards development for dust explosions in grain terminals and flour mills was begun. There were four standards associated with agricultural dusts. In 1995, the following four agricultural dust standards were combined into a singl
30、e standard: NFPA 61A, Standard for the Prevention of Fire and Dust Explosions in Facil- ities Manufacturing and Handling Starch; NFPA 61B, Standard for the Prevention of Fires and Explo- sions in Grain Elevators and Facilities Handling Bulk Raw Agricultural Commodities; NFPA 61C, Standard for the Pr
31、evention of Fire and Dust Explosions in Feed Mills; and NFPA 61D, Standard for the Prevention of Fire and Dust Explosions in the Milling of Agricultural Commodities for Human Con- sumption. The Technical Committee on Agricultural Dusts determined that the four standards were largely duplicative, and
32、 it therefore created one comprehensive standard covering the full range of requirements for good design, operating practice, and protective features. Previously, in 1969, NFPA 61B was adopted by the Association as a tentative standard to replace three former standards: NFPA 61B, Code for the Preven
33、tion of Dust Explosions in Terminal Grain Elevators; NFPA 64, Code for the Prevention of Dust Ignitions in Country Grain Elevators; and NFPA 661, Suction and Venting in Grain Elevators. In addition, NFPA 93, Standard for Dehydrators and Dryers for Agricultural Products, was withdrawn in 1968 and its
34、 text was incorporated as a chapter in NFPA 61B. The 1969 tentative edition of NFPA 61B was officially adopted at the 1970 NFPA Annual Meeting. In this latest edition, the first revised edition after the combination of the four documents, requirements were clarified, and additional advisory material
35、 was added. The Standard is downloaded from Standard Sharing 612FIRES AND DUST EXPLOSIONS IN AGRICULTURAL AND FOOD PRODUCTS FACILITIES 1999 Edition Technical Committee on Agricultural Dusts Lee M. Sargent, Chair Todd or (2) where mechanical failure or abnormal operation of machin- ery or equipment
36、could cause such explosive or ignitible mix- tures to be produced, and could also provide a source of ignition through simultaneous failure of electrical equipment, operation of protection devices, or from other causes. The design of such explosion relief venting shall consider the lim- itations imp
37、osed by the structural design of the area and shall offer the least possible resistance to explosion pressures. Exception No. 1: Tunnels and pits where explosion venting is not practical due to confinement by soil, building constraints, or both. Exception No. 2: Bins and silos where explosion ventin
38、g is not prac- tical due to bin or silo geometry, building constraints, or both. 4-2.2* Explosion relief panels, windows, or other venting devices shall be designed to prevent reclosing after relieving the explosion pressure and shall be attached to retention cables or restrained by equivalent means
39、 such that they will not become a hazardous projectile upon relief. 4-3 Requirements for Equipment. 4-3.1 Equipment requiring explosion prevention shall be pro- tected by containment, suppression, inerting, or explosion venting. 4-3.2 Suppression, containment, or inerting systems shall be designed a
40、ccording to NFPA 69, Standard on Explosion Preven- tion Systems. 4-3.3* Venting shall be directed to a safe, outside location away from platforms, means of egress, or other potentially occupied areas or directed through a listed Flame Arresting and Particulate Retention Device. Chapter 5Equipment 5-
41、1 Bearings. 5-1.1 Antifriction bearings shall be used on all machinery, conveyors, legs, and processing equipment. Exception: Sleeve and friction-type bearings, plastic bearings, or oil- impregnated wood bearings shall be permitted for equipment operating at 150 rpm or less. 5-1.2 All bearings shall
42、 be properly maintained per manufac- turers recommendations and shall be kept free of dust, prod- uct, and excessive lubricant. 5-1.3* All bearings on legs and conveyors shall be located out- side of machinery enclosures and isolated from the product The Standard is downloaded from Standard Sharing
43、 EQUIPMENT617 1999 Edition stream to minimize exposure to dust and to be more accessi- ble for inspection and service. Exception: Antifriction support bearings on screw conveyors and sim- ilar equipment requiring bearings to be within the product stream shall be of the sealed type. Sleeve and fricti
44、on-type bearings shall be permitted for equipment operating at 150 rpm or less. 5-2 Drive Belts. 5-2.1 Where drive assemblies involve the use of belts, such as V-belts, timing belts, flat belts, and so forth, they shall be elec- trically conductive at 1 megohm or less and shall be fire resis- tant a
45、nd oil resistant. 5-2.2 Where a drive belt is used, the drive train shall be designed with a minimum service factor of 1.5, or higher if the manufacturer of the drive components recommends a higher service factor for continuous service for the type of equipment to be driven. Exception: Line shaft dr
46、ives as used in the milling industry. 5-3* Conveyors, Spouts, and Throws of Material. 5-3.1* Screw, drag, or en-masse conveyors shall be fully enclosed in metal housings and shall be designed to either relieve or stop if the discharge end becomes plugged. 5-3.2 Bulk material conveyor belts and laggi
47、ng shall have a surface resistivity not greater than 100 megohms per square and shall be fire resistant and oil resistant. 5-3.3 Fixed spouts shall be dusttight. 5-3.4 Portable, automatic distributing, and movable spouts shall be permitted in work areas, bin areas, and distribution areas. Such spout
48、s shall be as dusttight as practicable when in use. 5-3.5* Spouts that direct material into bins, tanks, or silos shall be designed and installed so that any foreign objects (such as metal or stones) in the material stream do not strike the walls of the container, as far as is practicable. 5-4 Bucke
49、t Elevators (Legs). 5-4.1 Legs Handling Bulk Raw Grain. 5-4.1.1 Only outside legs, as defined by this standard, shall be used for handling bulk raw grain. Exception: As permitted in 5-4.1.3. 5-4.1.2* All newly installed outside legs handling bulk raw grain shall be provided with explosion relief panels, located at intervals no greater than 20 ft (6 m) along the casings as shown in Figures 5-4.1.2(a) and (b). To minimize personnel exposure, explosion venting for outside legs shall start between 8 and 12 ft