FMEA: The concept (1) Maintenance Management Concepts and Practices. FMEA: The concept (2) Lecture Objectives. FMEA: The concept (3) Agenda

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1 Maintnanc Managmnt Concpts and Practics FMA: Th concpt (1) Systm undr considration Failur Mods ffcts and Criticality Analysis Dr. C. Kara-Zaitri Systm Sub-systm 1 Sub-systm 2 Sub-systm 3 5 Lctur Objctivs! To undrstand th basic thory and practics of FMCA FMA: Th concpt (2) Systm undr considration Systm Sub-systm 1 Sub-systm 2 Sub-systm 3 Modul 11 Modul 12 Modul 21 Modul 31 Modul32 Modul Agnda FMA: Th concpt (3)! MIL-STD-1629-A FMA Gnralisd FMA (45%)! Numbr FMA (45%)! Matrix FMA (4%)! SODA FMA (4%)! Conclusions (2%) Sub-systm 1 Modul 11 Modul 12 C111 C121 C112 C122 Systm undr considration Systm Sub-systm 2 Modul 21 Modul 31 C211 C311 C212 Sub-systm 3 Modul32 C321 Modul 33 C331 C333 C FMA: Th concpt (4) Gnralisd Failur Mod and ffct Analysis Systm undr considration Systm Sub-systm 1 Sub-systm 2 Sub-systm 3 Modul 11 Modul 12 Modul 21 Modul 31 Modul32 Modul 33 C111 C121 C211 C311 C321 C331 ffct Caus ffct Caus ffct Caus C112 C122 C212 C333 C113 8 FMA middl.doc 40

2 FMA: Th concpt (5) Approachs to FMA A bottom up approach dtailing th causs of failur of componnts and associatd ffcts, through all indntur lvls (subsystms, moduls, tc..), to th systm lvl.! Mil-Std-1629 : US! RPN Mthodology : UK FMA and othr rlatd tchniqus Mil-STD-1629 Criticality Analysis Two attributs: BFOR AFTR PHA HAZOP FMA FMCA FTA Unwantd vnt CCA TA 1. Th Svrity of th ffct occurring 2. Th Liklihood of ach vnt in trms of a probabilistic valu or class FMA Dfind Svrity catgoris FMA rprsnts a powrful, documntd mthod for analysts to prsnt in a structurd and formalisd mannr thir subjctiv thinking and xprinc in trms of! What might go wrong! What might caus it to go wrong! What ffcts would it hav. Catgory Dscription Charactristics 1 Ngligibl No injury or morbidity No damag to systm 2 Marginal Minor injury or morbidity Minor damag to systm 3 Critical Svr injury or morbidity Svr damag to systm 4 Catastrophic Dath Loss of systm Nd for FMA Liklihood catgoris Catgory Dscription Charactristics! Implmnting DIRTFTTON! Daling with rapidly changing xpctations! Complying with incrasd rgulation! Minimising liability claims! nsuring fficint us of rsourcs Impossibl Physically impossibl to occur. 2 xtrmly improbabl Probability of occurrnc can t b distinguishd from zro. 3 Rmot So unlikly, it can b assumd that it will not b xprincd. 4 Occasional Likly to occur during th lif of th itm. 5 Rasonably probabl Will occur scral tims during th lif of th itm. 6 Frqunt Likly to occur frquntly. 16 FMA middl.doc 41

3 Criticality Matrix 6 FMA Planning Liklihood ! Worksht formats! Ground ruls! Analysis assumptions! Idntification of lowst indntur lvl! Coding! Systm dscription! Failur dfinitions Svrity Criticality Matrix Svrity Liklihood Low High Low High Low - Low Low High - Low Modrat Low - High Modrat High - High High 18 Failur Mod and Caus! A failur mod is th mannr in which an itm can fail (.g.. brokn).! A failur caus is th caus for a givn failur mod (bcaus of corrosion). 22 FMA Managmnt Failur ffcts FMA is a snior managmnt rsponsibility Snior Managmnt! Ar th consquncs of ach failur mod on itm opration, function or status. DSIGN Organis Tam Dsign FMA QUALITY Intrfac btwn Dsign and Procss Co-ordinat and monitor PROCSS Organis Tam Procss FMA! Can b dscribd in trms of what th usrs xprinc or what would b drawn to thir attntion.! Could apply to a numbr of failur mods and indntur lvls Analysis rsolution Svrity of ffcts!th dpth of th analysis and th lvl at which it should b startd dpnd on th information and xprtis availabl.!this could dpnd on th stat or progrss of th dsign, th complxity of th systm, and th typ of systm.!can only b assssd in trms of potntial consquncs of th failur on th popl who us or manufactur th systm.! Should indicat th worst cas scnario and rmain th sam rgardlss of associatd causs of failur FMA middl.doc 42

4 and Dtction Criticality Analysis Th occurrnc rating rprsnts an stimat basd on availabl knowldg of th probability of th failur caus occurring. Th dtction rating is dfind as a factor that rflcts how difficult it is to dtct a failur mod bfor th itm lavs th factory.! Scond stag of FMA.! Th nw information rquird is th liklihood of ach vnt in trms of a probabilistic valu or class.! Th combinations of Svrity liklihood classs rprsnt th so calld Criticality Matrix Mil-Std-1629 A FMA MILITARY STANDARD PROCDURS FOR PRFORMING A FAILUR MOD, FFCT AND CRITICALITY ANALYSIS FMA advantags! Simpl tchniqu.! It can idntify systm failur mods which wr not obvious bfor th analysis.! Rsults can b prsntd in an asy to undrstand format.! It considrs all possibl componnt and systm failur mods individually.! It can b rvrsd and usd as a diagnostic tool for rpair procsss. 30 Mil-Std-1629 A FMA Contnts 1. Scop 2. Rfrncd documnts 3. Dfinitions 4. Gnral rquirmnts 5. Dtail rquirmnts FMA disadvantags! Cannot modl rdundant or stand quipmnt adquatly.! Cannot asily rprsnt th ffcts of multipl failurs on th systm.! Can gt vry complicatd and complx Mil-Std-1629 A: Tabl hadings Criticality Analysis (CA)! Idntification! Function! Failur Mod! Failur Caus! Failur Mod frquncy! Dtction! Corrctiv masur! Svrity! Can b usd to dtrmin prioritis for corrctiv action and to stablish a clar dmarcation btwn accptabl and unaccptabl risk FMA middl.doc 43

5 CA: Advantags (1) RA: xampls of Modls! Idntifis which itms should b givn mor attntion to liminat th hazard (Fail-saf dsign, rdundancy, damag containmnt)! Idntifis which itms rquir tightr quality control during manufacturing stags.! Mil-Std-1629-A! BS 5760! Mil-Std-882! Df-Std ! NR CA: Advantags (2) Mil-Std-882 Frquncy Hazard Catgory! Facilitats th idntification of spcial rquirmnts to b includd in spcifications for supplirs concrning dsign, prformanc, rliability, safty and quality assuranc.! Facilitats th stablishmnt of spcial procdurs, safguards, protctiv quipmnt, monitoring dvics and warning dvics. Qualitativ Quantitativ Catastrophic Critical Marginal Ngligibl Frqunt > 10-1 Probabl 10-1 to 10-2 Occasional 10-2 to 10-3 Rmot 10-3 to 10-6 Improbabl > Th succssful application of FMA dpnds on Mil-Std-882: Catgoris Frquncy Hazard Catgory Qualitativ Quantitativ Catastrophic Critical Marginal Ngligibl! Th lvl of xprtis of th popl carrying out th analysis.! Th data availabl.! Th commitmnt of Managmnt to implmnt th rcommndations. Frqunt > Probabl 10-1 to Occasional 10-2 to Rmot 10-3 to Improbabl > FMA should b a liv documnt! Spcification changs! Sals fdback! Dsign changs! Procss changs! Quality Control modifications! Industrial nginring changs.! Nw or rvisd Standards. Df-Stan Frquncy Hazard Catgory Qualitativ Quantitativ Catastrophic Critical Marginal Ngligibl Frqunt > 10-2 Probabl 10-2 to 10-4 Occasional 10-4 to 10-6 Rmot 10-6 to 10-8 Improbabl 10-8 to Incrdibl to FMA middl.doc 44

6 Df-Stan-00-56: Catgoris Frquncy Hazard Catgory Qualitativ Quantitativ Catastrophic Critical Marginal Ngligibl Frqunt > 10-2 A A A B Probabl 10-2 to 10-4 A A B C Occasional 10-4 to 10-6 A B C C Rmot 10-6 to 10-8 B C C D Improbabl 10-8 to C C D D Incrdibl to C D D D 41 SMMT guidlins on Dtction Rating Liklihood of dtction 1 A rmot probability of th failur raching th customr. 2, 3 or 4 A low probability that this failur will rach th customr. 5, 6 or 7 Thr is a modrat probability of this failur raching th customr. 8 or 9 Thr is a high probability of this failur raching th customr. 10 It is crtain that this failur will rach th customr. 45 Th RPN mthodology! Svrity rating (S) ! rating (O) ! Dtction rating (D) ITB guidlins on Svrity Rating Svrity Dscription 1 Minor: Would hav no noticabl ffct on th vhicl or systm prformanc. 2 or 3 Low: Would caus slight customr annoyanc but no noticabl dtrioration of subsystm or vhicl. 4, 5 or 6 Modrat: Would caus som customr dissatisfaction or noticabl dtrioration in subsystm or vhicl. 7 or 8 High: Would ngndr a high dgr of customr dissatisfaction but dos not affct vhicl safty. 9 Vry high: Would affct safty Catastrophic: May caus damag to proprty, srious injury or dath. 46 SMMT guidlins on Svrity Rating 1 Will hav no ffct. Svrity Dscription 2 or 3 Would caus slight annoyanc but would only hav a minor ffct. 4 or 5 Modrat svrity causing problms on subsqunt oprations. 6 or 7 High svrity causing a hign dgr of customr annoyanc. 8 or 9 A vry high svrity failur which could affct safty in th long trm. 10 A most svr failur which could rsult in a suddn safty - rlatd failur. 43 ITB guidlins on Rating Liklihood of occurrnc 1 Rmot: Would b unrasonabl to xpct th failur to occur. 2 or 3 Low: Gnrally associatd with dsigns similar to prvious ons with a rlativly low numbr of failrs. 4, 5 or 6 Modrat: Gnrally associatd with dsigns similar to prvious ons without thrown up occasional failurs, but not in major proportions. 7 or 8 High: Gnrally associatd with dsigns similar to prvious ons which hav traditionally causd problms. 9 or 10 Vry high: Nar crtainty that major failurs will occur. 47 SMMT guidlins on ITB guidlins on Dtction Rating Liklihood of occurrnc Rating Liklihood of dtction 1 It is unlikly that this failur will occur. 2, 3 or 4 Thr is a low probability that this failur will occur. 5 or 6 Som failurs ar likly but in major proportions. 7, 8 or 9 Thr is high probability that this failur will occur. 10 This failur is crtain to occur in high proportions. 1 Rmot: Would b unrasonabl to xpct such a dfct to undtctd during inspction, tst or assmbly. 2 or 3 A low probability that th dfct will rach th customr. 4, 5 or 6 Thr is a modrat probability that th dfct will rach th customr. 7 or 8 Thr is a high probability that th dfct will rach th customr. 9 or 10 Thr is a vry high probability that th dfct will rach th customr FMA middl.doc 45

7 Th Numbr RPN = S x O x D Minimum = 1 Maximum = NR Factors (Numbr stimating th ) Four factors including: 1. Th possibility of xposur to th risk (0: Impossibl to 15: Crtain) 2. Th frquncy of xposur to th risk (0.1: Rar to 5: Continuous) 3. Th numbr of popl at risk (1: on or two popl to 12: Fifty or mor popl) 4. Th maximum loss (0.1: slight injury to 15: Dath). 53 Th RPN mthodology in practic Gnral ruls AND / OR Spcial ruls. 50 NR Catgoris 0 to 1 : Accptabl risk 1 to 5 : Vry Low risk (action in 1 yar) 5 to 10 : Low risk (action in 3 months) 10 to 50 : Significant risk (action in 1 month) 50 to 100 : High risk ( in 1 wk) 100 to 500 : Vry High risk (action in 1 day) 500 to 1000 : xtrmly High risk (Immdiat action) Ovr 1000 : Unaccptabl risk (mrgncy). 54 RPN: Gnral ruls: xampls! Th rang of RPN valus is dividd into classs: From 1 to 180 : No action ncssary From 181 to 342 : Corrctiv action is advisabl From 343 to 1000 : Immdiat corrctiv action! Th classification varis from on organisation to anothr. Th Numbr mthodology 51 RPN: Spcial ruls xampls Th RPN mthodology! Any on high rating : Immdiat corrctiv action Numbr! Any two mdium ratings : Immdiat corrctiv action. Dsign FMA Procss FMA FMA middl.doc 46

8 RPN FMA: Stp 1 RPN FMA Issus: Stp 2 (c) Dfinition of systm including functional and prformanc rquirmnts. Systm Brackt (for pump box support) Nois Pump loos Failur ffcts Sub-systm 1 Sub-systm 2 Sub-systm 3 Failur Mod Corrosion Componnt 1 Componnt 2 Componnt 1 Componnt 2 Componnt 1 Componnt 2 Failur Caus Wrong paint 57 Failur mod with multipl causs 61 RPN FMA: Stp 2 (a) RPN FMA Issus: Stp 2 (d) Idntification of potntial failur mods and associatd causs and ffcts Basic Triplt Modl Failur ffct Failur Mod Failur Caus 58 Lvl warning indicator Failur ffct Failur Mods 1 2 No warning 1. Failur to dtct chang in fluid lvl. 2. Failur to mak contact. Failur Causs Impropr or no movmnt of float 2. No lctrical continuity Diffrnt failur mods and causs with th sam ffct. (SMMT) 62 RPN mthodology! FC--> FM --> F > RPN1! FC--> FM --> F > RPN2! FC--> FM --> F > RPN3! ! RPS = (RPN1 + RPN2 + RPN3)! Compar RPSs and RPNs RPN FMA Issus: Stp 2 () Gnralisd modl Failur ffcts Failur Mods Failur Causs Diffrnt failur mods and causs with th sam ffct RPN FMA Issus: Stp 2 (b) RPN FMA Issus: Stp 2 (f) Brackt (for garbox support) ffct at a lowr lvl bcoms a caus at th nxt hirarchical lvl (SMMT) Cannot d-activat hatr Failur to oprat Command Unit Failur ffct Gar box falls on ngin Rlay stuck at ON position Failur Mod Brokn 1. Matrial too thin Failur Causs 2. Wrong matrial Failur mod with multipl causs 60 Rlay stuck at ON position Cannot wld failur Wlding matrial out of spcification Rlay modul 64 FMA middl.doc 47

9 RPN FMA Issus: Stp 2 (g) Dsign FMA (3) ffct at a lowr lvl bcoms a failur mod at th nxt hirarchical lvl (SMMT) Fluid lakag Damagd sal Poor finishd surfac Piston Itm Issu No. Dscription B100 Issu R Brackt Damagd sal Poor finishd surfac Sal Faulty machining procss Dsign FMA Dsign FMA (4) Itm Issu No. Dscription Function B100 Issu R Brackt Support ngin 70 Dsign FMA (1) Dsign FMA (5) Itm Itm Issu No. Dscription Function Failur Mod B100 B100 Issu R Brackt Support ngin Curling of vrtical walls Dsign FMA (2) Dsign FMA (6) Itm Issu No. Failur Mod Failur ffct Failur Caus Control B100 Issu R Curling of vrtical walls ngin drop Incorrctly spcifid matrial thicknss Strss tstd to FMA middl.doc 48

10 Dsign FMA (7) Dsign FMA (11) Failur ffct Failur Caus ngin drop Incorrctly spcifid matrial thicknss Control Strss tstd to Svrity Svrity Dtction Numbr Corrctiv 8 3 3x8x3 = 72 Strss tst to 150 and rport. By Tst Dpartmnt Dsign FMA (8) Dsign FMA (12) Failur Caus Incorrctly spcifid matrial thicknss Control Strss tstd to 100 Svrity Dtction Dtction Numbr Corrctiv 3 3x8x3 = 72 Strss tst to 150 and rport. to carrid out b compltd Tst 25/01/96 Dpartmnt Dsign FMA (9) Dsign FMA (13) Control Strss tstd to 100 Svrity Dtction Numbr x8x3 = 72 Numbr 3x8x3 = 72 Corrctiv Strss tst to 150 and rport. carrid out to b compltd takn Tst Dpartmnt 25/01/96 Strss Tst to 150 compltd. Satisfactory Dsign FMA (10) Dsign FMA (14) Svrity Dtction Numbr Corrctiv x8x3 = 72 Strss tst to 150 and rport. Corrctiv Strss tst to 150 and rport. carrid out Tst Dpartmnt to b compltd takn 25/01/96 Strss Tst to 150 compltd. Satisfactory FMA middl.doc 49

11 Dsign FMA (15) Procss FMA (1) to carrid out b compltd takn Tst Dpartmnt 25/01/96 Strss Tst to 150 compltd. Satisfactory 2 8 Svrity Itm B Dsign FMA (16) Procss FMA (2) to b compltd takn Svrity 25/01/96 Strss Tst to 150 compltd. Satisfactory Dtction Itm B100 Issu No. Issu R Dsign FMA (17) Procss FMA (3) takn Svrity Dtction Numbr Strss Tst to 150 compltd. Satisfactory x8x2 = 32 Itm Issu No. Dscription B100 Issu R Brackt Procss FMA (4) Procss FMA Itm Issu No. Dscription Procss B100 Issu R Brackt Drill two hols FMA middl.doc 50

12 Procss FMA (5) Procss FMA (9) Itm Issu No. Dscription Procss Failur Mod B100 Issu R Brackt Drill two hols Hols out of position Control Inspction Vrnir on frquncy basis Svrity Dtction Numbr x7x6 = Procss FMA (6) Procss FMA (10) Failur Mod Hols out of position. Failur ffct Failur Caus Difficult Incorrct assmbly of location in ngin drill fixtur. mounting. Control Inspction Vrnir on frquncy basis. 5 Svrity Dtction Numbr Corrctiv x7x6 = 210 Positiv location using spcial gaug Procss FMA (7) Procss FMA (11) Failur ffct Failur Caus Difficult Incorrct assmbly of location in ngin drill fixtur. mounting. Control Inspction Vrnir on frquncy basis. 5 7 Svrity Svrity Dtction Numbr Corrctiv 7 6 5x7x6 = 210 Positiv location using spcial gaug By Production Dpartmnt Procss FMA (8) Procss FMA (12) Failur Caus Incorrct location in drill fixtur Control Inspction Vrnir on frquncy basis Svrity Dtction Dtction Numbr Corrctiv 6 5x7x6 = 210 Positiv location using spcial gaug. to carrid out b compltd Production 25/01/96 Dpartmnt FMA middl.doc 51

13 Procss FMA (13) Procss FMA (17) Numbr Corrctiv 5x7x6 = 210 Positiv location using spcial gaug. to carrid out b compltd takn Production Dpartmnt 25/01/96 Spcial gaug usd for positiv location. takn Svrity Dtction Numbr Spcial gaug usd for positiv location x7x2 = Procss FMA (14) Matrix FMA Corrctiv Positiv location using spcial gaug. to carrid out b compltd takn Production Dpartmnt 25/01/96 Spcial gaug usd for positiv location. 2 Th NASA approach 98 Procss FMA (15) Hirarchical structur lctrical xampl to carrid out b compltd takn Production Dpartmnt 25/01/96 Spcial gaug usd for positiv location 2 7 Svrity Rsistor Circuit Unit Systm Sub-systm Procss FMA (16) Hirarchical structur Mchanical xampl to b compltd takn Svrity 25/01/96 Spcial gaug usd for positiv location Dtction Nut Part Pump Airplan Ful systm FMA middl.doc 52

14 Failur Mods Symbols Indntur Lvls (2) Opn mod Short mod Opn / short mod Lowr lvl ffct mod Unit 1 Circuit Hirarchical structur Indntur Lvls (3) Sub-systm Matrix FMA Sub-systmUnit Unit 1 Unit 1 Unit 2 Unit 3 Circuit 1 Circuit 11 Circuit 21 Circuit 31 Circuit 12 Circuit 22 Circuit Matrix FMA Matrix FMA Inputs Outuputs Parts 5 V DC RTN Driv Out A Out B R1 R2 R3 O1 U1 R No ffct Marginal out-of spcification conditions No output from outputs A and B No output from A No output from B Inputs Outuputs Parts 5 V DC RTN Driv Out A Out B R1 R2 R3 O1 U1 R No ffct Marginal out-of spcification conditions No output from outputs A and B No output from A No output from B Indntur Lvls (1) Matrix FMA: Main advantag Matrix FMA can b usd as a diagnostic tool Circuit FMA middl.doc 53

15 Diagnostics (1) Sub-systm FMA: Survy rsults (2) Circuit 1 Unit 1! Thr is insufficint tim to carry out th analysis proprly.! A larg numbr of practitionrs hav a poor undrstanding of th importanc of FMA.! Practitionrs ar inadquatly or poorly traind.! Thr is a lack of snior managmnt commitmnt to FMA Diagnostics (2) Summary Circuit 1 Unit 1! Tam work and carful planning! Parts count! Criticality matrix! Matrix FMA! SOD-A Matrix FMA advantags! FMA rsults at ach indntur lvl constituts a discrt modul of data which can b usd in othr FMAs.! Matrix FMA rsults provid a tracabl and graphical systm.! Th mthodology can b rvrsd and usd for diagnostics.! Matrix FMA can also b usd for contingncy planning, fault isolation and safty and quality analyss. 115 FMA: Survy rsults (1)! Th majority of supplirs ar using FMA only bcaus it is a contractual rquirmnt placd on thm th customr.! FMA is prcivd as difficult, laborious and boring.! Thr is a nd for improvd computrisd aids to rduc th ffort in prparing and analysing FMAs. 116 FMA middl.doc 54

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