Maintenance Philosophies

 

Chapt pter er 5 Types of Ma int intena enance nce Prog rogra rams ms Cha 5.1 Introduction What is is maintenance aintenance and why is is it performed? Pas Pastt and current maint ntena enance practi ctices cesin both the the pri private vate and Governm Government sectors woul would im imply ply that maint ntena enance is is th the e acti ctions ons associate ociated d with with eq equi uipm pment repair after it is broken. T he dicti dictionary onary defines fi nes maintena aintenance asfol folllows: “the work of keepi ping ng something ething in proper conditi condition; on; upkeep.” T hi his s woul would impl imply that maintena aintenance should hould be be actions acti ons taken tto o prevent a device device or component ponent from fail failiing or to repair n norma ormal equi uipm pment degrada rada ti tion on expe experi rie enced nced wi with the ope operation ration of the the de device vice to keep it in proper working working order. U nfortunatel nfortunately, data obtained obtained in in many studies over over the the past decade cade indi indicate cates s that most private private and and Governm G overnment facil facil iti ties esdo not expend expend the necessary resources ources to main maintai tain n equi equipment in i n proper working working order. Rather, ather, they they wait for equi uipm pment fail failure ure to occur and then then take whateve whatever actions acti ons are necessary to repair or replace the the equipment. quipment. Nothing othi ng lasts lasts forever forever and al all eq equi uipm pment has associate ociated d with with iitt some prepredefi fined ned life li fe expectancy xpectancy or operational rational life. For example, ple, equipment may be designed to operate at fful ulll design lload oad for 5,000 5,000 hours and may be designed to go tthr hroug ough 15,000 15,000 start and sto top p cycles cycles.  The design lif life e of most equipm ipment require ires period iodic main inte tenance. Belt lts s need adju jus stment, align ment needsto be maintai aintained, ned, proper proper lubricati lubrication on on rotati rotating ng equipment quipment is is required, red, and so on. I n somecases, certai certain n components need replace replacement, e.g., e.g., a wheel bearing bearing on a motor otor vehi vehicl cle, e, to ensure the the main piece pieceof equipm equipment ent (i (in this thi s case a car) las l ast for its i ts design li life. A nytim nyti me wefai faill to perform rform main aintenance tenance activi cti viti ties esint ntende ended by the equi uipm pment’sdesigner, we shorten horten the operati operating ng li life of the the equipment. But what options opti ons do we have? Over the the last 30 years, diff different erent approaches approaches to how main tenance can be perform performed to ensure equipm quipment reachesor exceedsits design life have been developed developed in the Uni United ted States. I n add addiition ti on to waiting ti ng for a piece of equ equiipment to to fai fail (reacti ctive ve maintenance ntenance)), we can utilize preventive maintenance, predictive maintenance, or reliability centered maintenance.

5.2 Reactive Maintenance Reacti ctive ve maintenance aintenance is basically call y th the e “run it it ti till it i t breaks” maintenance aintenance mode. No acti ctions ons or ef forts are taken to maintain the equipment as the designer originally intended to ensure design life is reached. Studies Studies asrecent asth the e wint nter er of 2000 indi indicate cate thi this s is sti tilll th the e pred predom ominant mode mode of main tenance in in the the U ni nited ted States States. T he referenced study breaks down the average maintenance aintenance program program as follows: • >55% Reactive cti ve • 31 31% % Preventi Preventive ve • 12 12% % Predictive Predicti ve • 2% Other. ther. Note that more than than 55% of maint ntena enance res resources ources and acti ctivi viti ties esof an average faci cillity are sti tilll reactive. A dvantages to rea reacti ctive mai aint ntenance enance can be view vi ewed asa double-edg ouble-edged sword. I f we are dealing ali ng with wit h new equi uipm pment, we can expect xpect mini minimal inci i ncide dent nts s of fail failure. I f our maintena aintenance progra program is purely reactive, we will not expend manpower dollars or incur capitol cost until something breaks. O& M Best Practices

5.1

 

Types of Maintenance M aintenancePrograms ograms

Si Since nce we do not seeany associated oci ated mai ain n tenance cost, wecould could view viewth thiis period eriod as saving aving money. T he downs downside is reality. • Low cost. cost. I n real reality, duri during ng th the e tim time we believe we • Less staf staff. f. are saving aving maintenance aintenance and capitol capitol cost, cost, we are really reall y spending pending more doll dollars th than an Disadvantages we would have under a di diff fferent erent maint nte e • Increased Increased cost due to unplanned downtime of nance approach. We are spending pending more equipment. dollars associated with capitol cost • Increase Increased d labor labor cost cost,, especial pecially ly if if overt overtim ime e is because, whil while wa waiti ting ng for the the equi uipm pment needed. to break, we are shortening the life of the • Cost involve involved d with repair or replace replacement ent of equipment resulting in more frequent equipment. replace repl acement nt.. We may incur cost upon • Possib Possible le secondary secondary equipment or proces process s damage fai faillure of the the prim primary devi device ce associate ociated d from equipment failure. with its failure causing the failure of a • Inefficient Inefficient us use e of staff resources. secondary device. vice. T hi his s is an increa increased costt we woul cos would not have experi xperience enced iiff our maint maintenance enance program programwasmore proactive. acti ve. Our lab labor or cost cost associate ociated d wi with rep repair air wil will probably bly b be e hi hig gher than normal becaus cause th the e fai faillure will most likely require more extensive repairs than would have been required if the piece of equip Advantages

ment had not been run to fail failure. Chances hances are th the e piece pieceof equi equipm pment will wil l fai faill during during off hours or clos close to the the end of the the normal workday. I f iitt is i s a cri criti tical cal piece pieceof equi equipm pment that that needsto be back on-lline qui onquickl ckly y, we will wil l have to pay maintenance aintenance overtim overtime cost. cost. Since Since we expect expect to run equipm equipment ent to fail failure, we will wil l requi require re alarge materi aterial al inventor inventory y of repair repair parts. parts. T hi his s is a cost we could could mini nim mize under a di diff fferent erent maint ntenance enance str trateg ategy.

5.3 Preventive Maintenance Preventive maintenance can be defi fined ned asfol folllows: A ctions cti ons perform rformed on a ti tim me- or machineachine-runrun-bas based schedule chedule that detect, preclude, or mitigate degra dation dati on of a component or system with with th the e aim of sustaining or extending its useful life through controlling degradation to an acceptable level.  The U.S. U.S. Nav Navy pion ioneered preventive tive maintenance ntenance asa means to inc i ncreas rease the the relia reli abil biliity of thei their ves vessels. By simply expending nding the the nece necessary resources resources to conduct maintenance activities intended by th the e equipme equipment designer, equipment life is is extended and its reliability is increased. I n additi addition on to an an incre i ncrease in relia reli abil biliity, dolllars are saved over that dol that of a program  jus  ju st usin ing g reacti tiv ve main inte tenance. Studie ies s indicate that this savings can amount to asmuch as 12% to to 18% on the average. 5.2

Advantages • Co Cost st effective in many capi capital tal intensive intensive pro process cesses. • Flexibili Flexibility ty allows allows for tthe he adj adjus ustm tment of maint aintenance enance periodicity. • Increased Increased component life life cycle. • Energy Energy sav savings. ings. • Reduce duced d equipment or pro proces cess fai failure. lure. • Estimated 12% to 18% cost savings avings ove overr reacti reactive ve maintenance program. Disadvantages • Catastrophic failures failures still ill likely to occur. • Labor intensive intensive.. • Includes Includes perfor perform mance of unneeded mainten aintenance. ance. • Potent Potentia iall for incident i ncidental al da dam mage to to components in conducting unneeded maintenance.

O& M Best Practices

 

Types o off M aintenancePrograms ograms

Depending on the facilities current maintenance practices, present equipment reliability, and facility downtime, there is little doubt that many facilities purely reliant on reactive maintenance could save much more than 18% by iinsti nstitut tutiing a prope properr preventi preventive ve maintenance aintenance prog program ram. Whi hille preventive venti ve maintena aintenance is is not the the optim optimummaintenance aintenance prog program ram, it does have several advant ntag agesover that that of a purely reactive reactive program program. By performi rforming ng th the e preventive preventi ve maintenance aintenance as th the e eq equi uipm pment designer envis nvi sioned, oned, we will wil l extend th the e life of the equipment quipment clos closer to design. T hi his s trans trans latesinto dolla doll ar s sa aving vings s. Preventi Preventive ve maintenance ntenance (lub ubri rica cati tion, on, fil fi lter chang nge e, etc.) will wil l generally run run the equ equiipment more effi ffici cie ently ntl y result ultiing in doll dollar sa saving vings s. Whi hille we will not prevent equi equipment cat astr trophi ophic c fai failures ures, wewill wil l decrease th the e number of fai failures. Mini nim mizing fai faillurestr trans anslate int nto o mainte ainte nance and capitol capitol cost saving avings.

5.4 Predictive Maintenance Predict redictiive mai aint ntenance enance can bedefined defined as fol folllows: Measurements that detect the the onset onset of a degra dation mechanism, thereby allowing casual stressors to be eliminated or controlled prior to any signif ica cant nt deterioration terioration in i n tthe he component phys physica call state. tate. Result ults s indicate current current and future future functional capability. Basically, predictive maintenance dif

Advantages

fers from preventive preventineed ve maintenance ain by bas • Increase Increased d component ponent operat operational ional life/ life/ availabi availability lity.. ing maintenance ontenance the actual • Allo llows ws for preemptive corrective actions. condition of the machine rather than on some preset sched chedul ule. e. You wi will recall th that at • Decrease in equipm equipment or pro process cess downti downtim me. preventi ntive maintena ntenance is i s tim ti me-based. • Decrease Decrease in cost costs s for par parts ts and labor labor. A cti ctivi viti tie es such as as c chang hanging lubrica lubricant nt are • Be Bett tter er pro product duct quality. quality. based on ttiime, li like cal calendar endar tim ti me or • Improved wor worker ker and environmental safety. equipment run tim ti me. For example, ple, most ost • Im Improved proved worker moral. oral. people change the oil in their vehicles every 3,000 to 5,000 milestrave traveled ed.. T hi his s • Energy Energy savings. savings. is effectively ffecti vely basing the oil oil change need needs s • Estimated 8% to 12% cost savings over predictive predictive on equipm quipment ent run tim ti me. No concern concern is maintenance program. given to the actual condition and perfor Disadvantages mance ca capa pabil biliity of the oi oil. I t is is chang change ed because it is is tim ti me. T hi his s methodolog ethodology y • Increased Increased inve nvest stm ment in diagno diagnost stiic equip equipm ment ent.. would woul d beanalog analogous to a preventive preventi ve mai ain n • Increased Increased investment in st staff aff trai training. ning. tenance task. I f, on the other other hand, the • Savings Savings potential not readi readily ly s seen een by managem anagement. ent. operator of the car discounted the vehicle run ti time and had the the oil oil analyzed at some some periodicity to determine its actual condition and lubrication properties, he/she may be able to extend the oil change until the vehicle had trave traveled 10,000 miles. T hi his s is th the e fundamental difference di fference between predi predicti ctive ve maintenance aintenance and pre pre ventiive mai vent aint ntenance, enance, whereby whereby predict predictiive mai aint ntenance enance is used to define defi ne needed mai aint ntenance enance task based on quantified material/equipment condition.  The advantages of predictiv ictive e main inte tenance are many. A we well-or ll-orchestra trated predic icti tiv ve main inte te nance programwill wil l all but eliminate catastr trophi ophic c equipment quipment failures fail ures. We wi will be able to schedule main aintenance tenance activi activiti ties esto mini nim mize or delete overtim overti me cost. We will be ab ablle to mini nim mize inventory nventory and order parts rts, as required, required, well ahead of ti time to support support the the downstream downstreammaintenance aintenance needs. We can opti optim mize the the operation ration of the the equipment nt,, saving ving energy cost and increa increasing pl plant ant reli reliability. Past Past O& M Best Practices

5.3

 

Types of Maintenance M aintenancePrograms ograms

studies tudi eshave esti tim mated th that at a properly properly functi functioning oni ng predict predictiive mai aint ntenance enance programcan provide provide a sav ingsof 8% to 12% 12% over over a progra program util utilizing preventi preventive ve maintenance aintenance alone. Depending nding on a faci cillity’s reliance on reactive maintenance and material condition, it could easily recognize savings opportuni ti ties esexceedi eding 30% to 40%. I n fact, inde i ndepe pendent ndent surveys indicate ndicate th the e fol folllowing owing industr triial averag average savings resultant from initiation of a functional predictive maintenance program: • Return on investment nt:: 10 tim ti mes • Reduction uction in maintenance aintenance costs: costs: 25% to 30% • Eli Elimination of brea breakdowns kdowns:: 70 70% % to 75% • Reducti Reduction on in downti downtim me: 35 35% % to 45% 45% • I ncrease in produ producti ction: on: 20 20% % to 25% 25%.. On the down side, to initially start into the predictive maintenance world is not inexpensive. Much of the equipment quipment requi requires rescost in i n excess of $50,000. Traini Training ng of inin-pl plant ant personnel rsonnel to effec ti tively vely uti utillize predictive cti ve maintenance aintenance technolog technol ogiieswill wil l require considera considerable ble funding. funding. Prog Programdevel opment will require an understanding of predictive maintenance and a firm commitment to make the programwork by all facil facility organi niz zati ations ons and management.

5.5 Reliability Centered Maintenance Reliabil Reli biliity ce centered ntered maintenance ntenance (RCM RC M) magazine providesthe foll followi owing defi fini niti tion on of of RCM RC M: “a process used to determine the the maintenance aintenance requirements of any physical asset in in iits ts operating rating context.” context.” Basically call y, R RC CM methodolog ethodology deals with with some key issues not dealt with with by other other maintenance aintenance proprograms. I t recogni recogniz zesthat that all eq equi uipm pment in in a facil cility is is not of eq equa ual importance to eith either er the proces process or facillity safe faci safety. I t reco recog gni niz zesthat that equipme equipment design and opera operati tion on differs differs and that that differe different nt equi uipm pment will have a higher probability to undergo fai faillures ures from di different degradati radation on mech Advantages anis ani sms th than an ot others. hers. I t also approaches th the e str tructur ucturiing of a maintenance aintenance program program • Ca Can n be the most efficient efficient mai ainte ntenance nance progra program m. recognizing that a facility does not have • Lower costs by eli elim minating inating unneces unnecessary mainte mainte≠ ≠ unliimited financial unl financial and personnel rsonnel resources nance or overhauls. and that the the use of both both need to be prior prior • Mini inim miz ize e frequency frequency of overhauls. overhauls. iti tiz zed and optimiz optimize ed. I n a nutshel hell, RCM RC M • Reduce duced d probabi probabilility ty of sudden sudden equipment quipment fai failures. lures. is asystemati tic c approach to to evalua evaluate a facillity’s eq faci equi uipm pment and resources to best • Able to focus maintenanc aintenance e activities activities on critical components. mate the ttwo wo and resul resultt in a hig hi gh degree of facili facility relia reliabili bility and costt-e effecti ffective vene nes ss. • Increased Increased component reli reliabi abilility ty. RCM is highly reliant on predictive main • Incorporates Incorporates root cause analysis. tenance but als also recogniz recognizesth that at maint nte e nance activities on equipment that is Disadvantages inexpensive and unimportant to facility • Can have significant ignifi cant startu artup p cost, training, equip≠ reliability may best be left to a reactive ment, etc. main aintenance tenance ap approa proach. ch. T he fol folllowing owing • Savi Savings ngs potential not readil readily y seen by managem anagement. mai aint ntenance enance programbreakdowns of

5.4

O& M Best Practices

 

Types o off M aintenancePrograms ograms

continually top-performing facilities would echo the RCM approach to utilize all available mainte nance approacheswith with the the predom predominant methodolog ethodology being predicti dictive. ve. •