Ten good reasons not to use EN 954-1 - Control in Motion

It is widely accepted that EN 954-1 is inadequate for use with complex or very hazardous machinery, so applying this standard instead of EN ISO 13849-1 or EN ( ... 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Search --CALLUSON--  Tel.+44(0)1612177100 --FOLLOWUS-- -ISO9001/2015- Publishednews ReviewMotorTechnologynewsonanumberofrespectedengineeringsites...  AlltipsforNewsArchive E-mailAFriend Print Home > News > NewsArchive > TengoodreasonsnottouseEN954-1 TengoodreasonsnottouseEN 954-1 InthisissueofMotorTechnologyNewsJonSevern,editorofMachineBuilding.net,suggeststenreasonsnottouseEN954-1fordesigningsafety-relatedcontrolsystemsformachinery,butrathertouseENISO13849-1orEN(IEC)62061. visitthemachinebuilding.netsiteformoreusefulinformation... TheEuropeanCommitteeforStandardisation,CEN,hasannouncedthatthetransitionperiodduringwhichmachinebuilderscanchoosebetweenEN954-1andENISO13849-1hasbeenextendedbytwoyears.Nodoubtsomemachinebuilderswillwelcomethis,asEN954-1iseasier,simplerandcheapertoworkwiththaneitherofthealternatives,ENISO13849-1orEN(IEC)62061.However,thereareplentyofreasonsfornotusingEN954-1. 1MachinesdesignedtoEN954-1maynotbeassafe ItiswidelyacceptedthatEN954-1isinadequateforusewithcomplexorveryhazardousmachinery,soapplyingthisstandardinsteadofENISO13849-1orEN(IEC)62061couldresultinmachinerythatispotentially'lesssafe.'BearinmindalsothatEN954-1wasfirstpublishedin1997sobynowitdoesnotreflectthestateoftheart.Asidefromtheuseofsoftwarewithinsafety-relatedcontrolsystems,forexample,EN954-1doesnotaddressthehandlingofcommon-causefailuresortheadequatefrequencyofdiagnostictestsoncategory2systems. 2Pressurefromcustomers BecauseoftheinadequaciesassociatedwithEN954-1,togetherwiththerecentuncertaintyoverthefutureofEN954-1andthedesireto'future-proof'theirmachines(seebelow)machinespecifiersmaystarttoinsistthatEN954-1isnotused.Inparticular,customersarelikelytoprefermachineswithsafety-relatedpartsofcontrolsystemsdesignedusingENISO13849-1orEN(IEC)62061,ratherthanthosedesignedtoastandardthatdoesnotreflectthestateoftheart. 3CompliancewiththenewMachineryDirective2006/42/EC ENISO13849-1andEN(IEC)62061arebothfoundedontheconceptoffunctionalsafety-whichEN954-1isnot-andarebetteralignedtothenewMachineryDirective2006/42/EC.Assuch,thetwonewerstandardsareinherentlybettersuitedtothedesignofmachinesdestinedfortheEuropeanmarket. 4EN954-1isnotaninternationalstandard WhereasbothENISO13849-1andEN(IEC)62061areinternationalstandardsandwidelyrecognisedinglobalmarkets,EN954-1isaEuropeanstandard(EuroNorm).IfmachineryisdestinedformarketsoutsideEurope,thenEN954-1isunlikelytobeapplicable. 5EN954-1isnolongercitedinTypeCstandards WhileitistruethatsomeTypeCstandardshavenotyetbeenrevisedinlinewithENISO13849-1,manyofthemhaveandtheremainderwillbeintime.Onceamended,thestandardswillnolongerciteEN954-1,whichcouldputmachinebuildersinadifficultpositionwhenCEmarkingtheirmachines.AlthoughEN954-1islistedintheOfficialJournaloftheEuropeanUnion(see'EN954-1harmonisedtoMachineryDirective2006/42/EC'),ifaDeclarationofConformitycitesaTypeCstandardthatreferstoENISO13849-1,thenEN954-1cannotbeusedforthedesignofthesafety-relatedpartsofthecontrolsystem. 6Customerswant'future-proof'machines Machinesoftenundergomodificationsduringtheirlifetime,whichcouldbebythecustomer,OEMorathird-party.Dependingonthenatureofthemodifications(forexample,ifthemachine'sperformanceischangedortherearealterationstothesafety-relatedcontrolsystem)itmaybenecessarytoCEmarkthemachineagain.IfthemachinewasoriginallydesignedtoEN954-1buthastobefreshlyCEmarkedafterEN954-1hasbeenwithdrawn,partsofthecontrolsystemmighthavetoberedesignedtocomplywiththenewstandard.Customers-andOEMs-maythereforewanttoavoidtheriskofthispotentiallycostlysituationarisingbyspecifyingthateitherENISO13849-1orEN(IEC)62061isusedfortheoriginaldesign. 7EN954-1restrictstheuseofnewtechnology OneofthemajordrawbacksofEN954-1isthatsafety-relatedcontrolsystemsareeffectivelyrestrictedtotheuseofrelaylogic.Modernconfigurableandprogrammablesafetycontrollersoffermachinebuildersandusersconsiderableopportunitiesforcostsavings.Forexample,complexlogiccanbemoreeasilyimplementedusingaconfigurable/programmablecontrollerthanbyusingrelays,andthepotentialforwiringerrorsisgreatlyreduced.Furthermore,improveddiagnosticscancutdowntimeandenablenon-expertstotroubleshootmachinestoppages. 8EN954-1canwastemoneythroughover-engineering The'riskgraph'inEN954-1tendstobeused(incorrectly)asariskassessmenttool,leadinguserstodesignatea'safetycategory'foraparticularmachine.Foramachineonwhichthereisonehigh-riskarea,alltoooftenthedesignertreatstheentiremachineas'category4'andthereforeover-specifiesmuchofthesafety-relatedcontrolsystem,includingalloftheguardswitches.Thisresultsinexcessiveexpenditure.Incontrast,ENISO13849-1canenabledesignerstocreatesafety-relatedcontrolsystemsthatrequirefewercomponentsandlesswiring,withmanyofthecomponentsbeingtoalowerspecificationand,therefore,lesscostly. 9Freesoftwareforthenewstandards AcomplaintoftenlevelledagainstENISO13849-1andEN(IEC)62061isthattheyrequiremorecomplexcalculationstobeperformedthanwhenusingEN954-1.However,theSISTEMAsoftwarepackagecanbedownloadedfreeofchargefromtheGermanBGIAwebsiteandgreatlyassiststhecalculationsrequiredinENISO13849-1.Alternatively,somemachinebuildershavefoundthatcontrolsystemsforrelativelysimplemachinescanbedesignedwiththeaidofspreadsheets;creatingthefirstspreadsheetistime-consuming,butsubsequentdesignsforsimilarmachinescanbecompletedcomparativelyeasily. 10StopusingEN954-1forpeaceofmind Ifanyoneoftheninereasonsabovehassownaseedofdoubtinyourmind,switchingfromEN954-1toeitherENISO13849-1orEN(IEC)62061willgiveyoupeaceofmind.Andifyouareinanydoubtabouthowtoproceedwiththenewstandards,thereareplentyofcompaniesthatcanprovideassistancethroughtrainingcourses,seminars,guidancedocuments,software,FAQsontheirwebsitesandfacilitiesforaskingquestionsoftechnicalexperts. Anycommentsontheabovecanbeemailedtotheauthorateditor@machinebuilding.net. ReadthearticlehereonmachineBuilding.netwithlinkstomoreinformationonthesubject.   MotorTechnologyLtd. MotecHouse,ChadkirkBusinessPark,Stockport,CheshireSK63NE Tel:+44(0)1612177100   Fax.+44(0)1612177101 WebsitedesignbyKrannLtd,Poynton,Cheshire