西门子安全PLC 的调试 Commisioning with safety PLC

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1、Commissioningwith“safetyPLC”and“F-I/O”-SpreaderincidentonBargeCrane-InternalDate:28-03-08Version:1.0DocumentAuthor:ing.R.PeetersM.Sc.Pages:8CopyrightSiemensAG.AllRightsReserved.CommissioningwithsafetyPLCandF-I/OScopeDuetoacommissioningerror(onaBargecrane)asafetyrelatedincidenthappened,

2、andaspreadercrashedtotheground.Thescopeofthisdocumentistodiscusswhatwentwrong,howthisispossibleandhowwecanpreventthisfromhappeningagain.WhatHappenedDuringcommissioningaVATtablewasusedtomonitorandmodifyI/O’sandmemorybits.TheVATtableisshownbelow.WiththeVATtableabove,themotorbrakesandthesafe

3、tybrakeswerereleasedunconditionally,bydirectlymodifyingtheoutputstotherelays.Afterthemodificationwasapplied,allbrakeswerereleasedandthespreadercamedown.Itseemsthereforepossibletomodifyoutputsdirectly,eveniftheyaresafeoutputsofthesafetyPLC!!Attemptstostopthemotionbypushingtheemergencystops

4、didn’thaveanyaffect,becausethemodificationsbytheVATtablewhereappliedattheendofeverycycle.Thismeansthateverysafetysystemwasbypassed.HowisthispossibleInprevioussystemswithoutsafetyPLC’s,theemergencystops,overspeeddetectionandtheemergencylimitswitcheswereconnectedtothe-K00relaybyhardware.Thi

5、smeansthatthesesafetyfunctionswerestillactive,evenifthecommissionermodifiesthebrakerelayinthesoftwareusingaVATtable.WiththeintroductionofthesafetyPLCthere’snolongera-K00relaypresent,andthereforethesafetyhastobeguaranteedbythesafetyPLCincombinationwithasafeprogramandsafeI/O’s.Thesafetyprog

6、ramonthesafetyPLChastwomodes:SafetymodeactivatedSafetymodedeactivatedIfthesafetymodeisactivateditisnotpossibletomodifysafebitsand/orsafetyrelatedI/O’swithaVATtableorinanyotherwaywhilethesystemisrunning.ThisisprohibitedbythesafetyPLC.Ifyoutrytomodifyanoutput(aswasdoneintheBargeproject),the

7、PLCgivesyouthefollowingwarnings:Onlyifyouacceptallthewarningsaboveandyouenterthecorrectpassword,theoperationmodegoesto“safetymodedeactivated”.Onlyinthisstateitispossibletomodifyinputsandoutputsinthesafepart,withoutanyfurtherwarnings!!DuringthecommissioningoftheBarge