NFPA 68 2023 Standard on Explosion Protection by Deflagration Venting.pdf

NFPA 68 Standard on Explosion Protection by Deflagration Venting 2023 NFPA
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68-1 Copsright O 2022 National Fire Protection Association°. All Rights Reserved. NFPA°68 Standard on ExplosionProtection byDeflagrationVenting 2023 Edition This citinoNFPA ndExplsiPrtiobDtiingwaspreparedby te Technical Comittee onExploionProttionSstemIwsisd by theStandarlsCocil on Noxember 29 2022 with an effective date of December 19 2022 and supersedes all previous editions. This ecdition of NFPA 68 was approwed as an American National Stanard on December 19 2022. Origin and Development of NFPA 68 in1945iPA8TES954maranwsla NFPA 6S ExPt bDefVig statdtastna staa with NFPA 68Gide fo Exple ting hich brought together all thebest available information on the fnlamentals and paramters of cxplosioms the lata developed by smallscal tts the inteprtati thrultsf those testsand theusefvents anentcuresthatwerecurentat the timc.Th infomaionwasthnrelated orleofthmbveraiorecolatonshich were u frmanyasSmef tvens thatwere degneduing thos lof thm functioned well while others were never put to the test. Beginning in 1954 extensive cxperimentation was carried out in Great Britain and Germany and adled to the existing information.The US. Brcan of Mines also did some work in thisarea. However the work was not pleted bccause the group invoed was reassigned to diferent programs. In 1974 NFPA 68 was revised and the work done in Great Britain and Gemany was incladed with thehopethatthfmaind idamansfrcalatingentrtiswithagreat degr ofaccrac than that prwided btherleofthmh.h1978reisnncldd sutantal data that were more valuable in dlesigning explosion relief vents. In 1979 the miee began a major efforto rewrite te guide in rder to incorporate the results of the test work donc in Gcrmany. In addition the 1988 cdition titled Guide for liting Defgtiontineri txtthatmorelearxplained thearis paramt that aft the venting of deflagrations. The 1994 edition of NFPA 68 was pletely rewriten to more clearly explain the principles of document without changing the venting methodology.The thnast of this revision was to improwe the venting deflagrations. Revisions to cach chapter improwed the organization of information within the The1998cdiionincedupattilgytoheconsstenwithurret ital practi.wfmtinasanthfsftdtsallatnmhfr those ffcts and the effects of vent discharge. The reision alo incorporated the weak roof-o- she joint design as a mcans of venting silos and bins and prwidled new information on cxplosions in clongated vesels. It also clarified the prwisions for securing restraint panels. Thc 2002 cdiion represented a lete reison of the guide and incldedupat and enhanced treamentfrdeflagratinventing deigfrsts andhridmtureThrevisinalo incldnwvent igqutinhaseuponthemethoolgy deelopedbyFactory ul ResearchCorratinnadiionotgneralizecorrlatin for dstsrnemethod All desiggilieframixerembindiingehptand tedt was cahatetheffets fvent dutspartallmesvent panlneriand initiall leated re. revised in accordance with the NFPA Menl f Syle for NFPA Tchniral Committe Decmms. NFPA and Ntial Fie Ptecti Aciati are rgistd ademr ofte National Fie Pectio Aciatin Qcy Maache 0210. Copyrighi NFPAFor excluse use n NFPA Free Access platlormNot for distribution，downicading.or prining For inquiries contact custservnpaorg.To repor unauthorized use conacl legal@nlp.rg.
68-2 EXPLOSION PROTECTION BYDEFLAGRATION VENTING Tc 2007ditin rrentd alete isoncling a change fromgud stanad.T wtand id StdExlPtbeftnpiandryqirmnthigcatall maintenanc and use of devices and sstems to vent bustion gases an presures from deflagrations. The Comitee incorporated aew chapter on erformancbased desig thatenabed uss to presentaltmatie lsign methoairqifoasandistrsranfrixTCtteai Comittppisttcqnngithchgtqisflla the gencralized correlation for dusts on the hasis of a resview of additional experimental data. That resiew cnabled the inetia patiam nill atd prs an vent duts T Comie al add aw chapt nptin ad maintenance. Thc 201dition intocdreisd calculatnmthodfrventing of deflagratsfgasmtresTechaptn venting of deflagrations in dust mixtures was revised to adres differences between translating vent panels and hinged vent panels to permit sub atmospheric initial presures and to incorporate new rescarch on the entrainment of accumulated dust in a bilding ew scctions adresed bucket leators and grain silos and new annex material prowided guidance on designing vent ducts and estimating the funcamental burning velocity of a fuel. In te2018iineqirmntwasadathalsfrcrtinmtldsthKalwasinna eemller than1mAnatwasad o ti thraic diamteforrectanglarcloeThchap on venting gas mixture and mist deflagrations was reorganized to clarify the order and applicahility af the various afjustments andcorrectionstoreqiredventarcaAnewanex was added toimplementthequations and calulation procedures inclding partia ffcsThereqiremen for detrmining wererelaced with reqirment for detmining P and the cquations to determine the turbulent flame enhancement factor were revised. Thc chapern vening dst and hyrid mixe lgratios was also reorganizd in ordr ofintnde executin.The cqtionrtiningthventareafrlatdrashc rasreedndanmleallatias tmodinglfllinrf filter was ardedl. Requirements for the use of plastic buckets in bucket elevators were mowed from the annex to the body of the standard. For the2023 ition tefirhallan azard istancereqirmens forgaseand duss haebnbinedandmd intoChaptfconisteinaplicaionTh paal lecalasfrbthassandshabenrevis accot frsolid jctsrecingthopnair ailablfrmixingnd tccoutfr psbldstconcetatins belo theorstcase concentratinshfunametalbminglcityastheanex haebeenupaedhaedn current anailable cata and an annex on vent sizing for hydrogen mistures has been added. 2023 Edition CoyrihNFPAFoxlusenFPAFrecs plaotrdstbiningr priing For inquiries contact custservnipa.org.To reporr unauthorized use contacl legal@nlpa.org.