16M:MaintainabilityMaintenance:The combination of all technical and administrative actions,including supervision actions,intended to retainan itemin,orrestoreitto,astateinwhichitcanperformareguiredfunction.Maintainability:Theprobabilitythatagivenactivemaintenanceaction,foran item undergivenconditionsof usecan be carriedoutwithinastatedtimeinterval,whenthemaintenanceisperformed understated conditions andusing statedproceduresandresources.Themeasureoftheabilityofanitemtoberetained inorrestoredtospecifiedconditionwhenmaintenanceisperformedbypersonnel having specified skill levels,usingprescribedproceduresandresources,ateachprescribedNTNU-Trondheimlevelofmaintenanceandrepair.Norwegian University ofScienceandTechnologywww.ntnu.edu
16 M: Maintainability Maintenance: The combination of all technical and administrative actions, including supervision actions, intended to retain an item in, or restore it to, a state in which it can perform a required function. Maintainability: – The probability that a given active maintenance action, for an item under given conditions of use can be carried out within a stated time interval, when the maintenance is performed under stated conditions and using stated procedures and resources. – The measure of the ability of an item to be retained in or restored to specified condition when maintenance is performed by personnel having specified skill levels, using prescribed procedures and resources, at each prescribed level of maintenance and repair
17A:AvailabilityAvailability:Theabilityof an item to perform its requiredfunctionata stated instant of time or overastatedperiodoftime.Appliestorepairablesystemsand/orsystemsthatoperateindifferentstates.Acombinationof reliabilityperformance,operating strategies,and externalinfluencesNTNU-TrondheimNorwegian University of梦ScienceandTechnologywww.ntnu.edu
17 A: Availability Availability: The ability of an item to perform its required function at a stated instant of time or over a stated period of time. • Applies to repairable systems and/or systems that operate in different states. • A combination of reliability performance, operating strategies, and external influences
18A: AvailabilityTheavailabilityof an itemattimetA(t)=Pr(itemisfunctioningattimet)The average availability (under certain conditions)MTTFAavgMTTF+MTTRReliabilityMaintainabilityAvailabilitywhereConstantDecreasesDecreasesMTTF=MeantimetofailureConstantIncreasesIncreasesIncreasesConstantIncreasesMTTR=MeantimetorepairDecreasesConstantDecreasesNTNU - Trondheim?Norwegian UniversityofScienceand Technologywww.ntnu.edu
18 A: Availability The availability of an item at time ݐ ܣ ݐ ൌ Pr ሺitem is functioning at time ݐሻ The average availability (under certain conditions) ܣୟ୴ ൌ MTTF MTTF MTTR where – MTTF = Mean time to failure – MTTR = Mean time to repair