ASTM_E_1248_-_90_2009.pdf

Designation:E124890(Reapproved 2009)Standard Practice forShredder Explosion Protection1This standard is issued under the fixed designation E1248;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice covers general recommended design fea-tures and operating practices for shredder explosion protectionin resource recovery plants and other refuse processing facili-ties.1.2 Hammermills and other types of size reduction equip-ment(collectively termed shredders)are employed at manyfacilities that mechanically process solid wastes for resourcerecovery.Flammable or explosive materials(for example,gases,vapors,powders,and commercial and military explo-sives)may be present in the as-received waste stream.There ispotential for these materials to be released,dispersed,andignited within or near a shredder.Therefore,explosion preven-tion and damage amelioration provisions are required.2.Referenced Documents2.1 National Fire Protection Association Standards:National Electrical CodeNFPA 13 Sprinkler SystemsNFPA 68 Guide for Explosion VentingNFPA 69 Explosion Prevention SystemsNFPA 497A Classification of Class I Hazardous(Classified)Locations for Electrical Installations in Chemical ProcessAreas3.Terminology3.1 Definitions:3.1.1 deflagrationan explosion in which the flame orreaction front propagates at a speed well below the speed ofsound in the unburned medium,such that the pressure isvirtually uniform throughout the enclosure(shredder)at anytime during the explosion.3.1.2 detonationan explosion in which the flame or reac-tion front propagates at a supersonic speed into the unburnedmedium,such that pressure increases occur in the form ofshock waves.3.1.3 explosiona rapid release of energy(usually bymeans of combustion)with a corresponding pressure buildupcapable of damaging equipment and building structures.3.1.4 explosion ventingthe provision of an opening(s)inthe shredder enclosure and contiguous enclosed areas to allowgases to escape during a deflagration and thus prevent pres-sures from reaching the damage threshold.3.1.5 explosion suppressionthe technique of detecting andextinguishing incipient explosions in the shredder enclosureand contiguous enclosed areas before pressures exceed thedamage threshold.3.1.6 inertingthe technique by which a combustible mix-ture is rendered nonflammable by addition of a gas incapable ofsupporting combustion.3.1.7 shreddera size-reduction machine that tears orgrinds materials to a smaller and more uniform particle size.4.Significance and Use4.1 Shredder explosions have occurred in most refuse pro-cessing plants with shredding facilities.Lessons learned inthese incidents have been incorporated into this practice alongwith results of relevant test programs and general industrialexplosion protection recommended practices.Recommenda-tions in this practice cover explosion protection aspects of thedesign and operation of shredding facilities and equipmentused therein.4.2 This practice is not intended to be a substitute for anoperating manual or a detailed set of design specifications.Rather,it represents general principles and guidelines to beaddressed in detail in generating the operating manual anddesign specifications.5.Design Practices5.1 Design Rationale:5.1.1 Each of the following design features is better suitedfor some types of combustible/explosive materials and shred-ders than for others.The selection of a particular combinationof explosion prevention features or damage control features,orboth,should be made with an understanding of the types ofrefuse entering the shredder,shredder operating conditions,theinherent strength of the shredder and surrounding structures,and the operating controls for screening input materials andrestricting personnel access during shredding operations.1This practice is under the jurisdiction of ASTM Committee D34 on WasteManagement and is the direct responsibility of Subcommittee D34.03 on Treatment,Recovery and Reuse.Current edition approved Sept.1,2009.Published November 2009.Originallyapproved in 1990.Last previous edition approved in 2004 as E124890(2004).DOI:10.1520/E1248-90R09.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.1.2 Several of the following explosion protection designpractices are effective for deflagrations but not for detonations.Deflagrations usually result from accumulations of flammablegas-air,vapor-air,or powder(dust)air mixtures in or around theshredder.However,commercial explosives and military ord-nance usually generate detonations.A few flammable gases(for example,acetylene and hydrogen)are also prone todetonate when dispersed in highly turbulent,strong ignitionsource environments such as exist inside a sh