MAINTAINABILITY DESIGN TECHNIQUES METRIC - AcqNotes.com

More documents

Recommendations

Info

Downloaded from http://www.everyspec.com on 2011-10-29T14:56:01.DOD-HDBK-791(AM)Figure 8-1.Relation of Equipment Status on Availabilitysary, can be deferred until the equipment is idle (betweenmissions) or until scheduled maintenance; this results inincreased equipment availability.Preventive maintenance and servicing are more applicableto mechanical systems and basic structural elementsthan to electronic or electrical equipment. The routinecheckout of electronic or electrical equipment indicatesthat the equipment is performing satisfactorily or unsatisfactorily.Physical inspection remains the primary meansfor detecting degradation of structures and of manymechanical and electromechanical devices.8-2 RELIABILITY CENTEREDMAINTENANCE8-2.1 GENERALThe Reliability and Maintainability Subcommittee ofthe Air Transport Association published a MaintenanceSteering Group document, Airline Manufacturer's MaintenanceProgram and Planning Document (MSG-2)(Ref.1), which described the reliability centered maintenance(RCM) concept for new aircraft. This concept was sosuccessful in its initial application that the airlines appliedit to revise maintenance programs for older aircraft. TheUS Navy tailored the concept and applied it to the P-3aircraft. Through the issuance of Program ObjectiveMemorandum (POM) 78-82 (Ref. 2), the Army establishedthe requirement that the MSG-2 concept, under thetitle “Reliability Centered Maintenance (RCM)”, beincorporated on all Army weapon systems and equipmentby the end of fiscal year 1979. DA Pam 750-40 (Ref. 3)implements Ref. 2. The US Army Materiel Command(AMC) integrated the provisions of Ref. 3 into AMC-P750-2, Guide to Reliability Centered Maintenance (Ref.4). AMC-P 750-2 provides assistance in the preparationand implementation of the RCM program as directed inthe policies of DOD Directive 4151.16 (Ref. 5). AR 750-1(Ref. 6), AR 700-127 (Ref. 7), and MIL-STDS-1388 (Refs.8 and 9). Through the proper use of RCM procedures, aviable, realistic scheduled maintenance program can bedeveloped. Ref. 4 describes in detail how to use the RCMlogic and the failure mode, effects, and criticality analysis(FMECA) to develop a scheduled maintenance plan thatincludes the maintenance task and the maintenance intervalfor preventive maintenance checks and services(PMCS) and provides information for overhaul, ageexploration, economic analysis, and redesign.8-2.2 OBJECTIVEMaintenance planning one of nine principal elementsof integrated logistics support (ILS)—includes developmentof the maintenance concept, reliability and maintainabilityparameters, repair level determinations, maintenancerequirements. and supply support essential toadequate and economical support of the system orequipment (Ref. 4). As such, maintenance planning isnormally integrated into equipment design during theconcept exploration phase of the acquisition process aspart of the logistical support analyses. RCM is an essentialinput to this planning.RCM is based on the premise that maintenance cannotimprove upon reliability inherent in the design of hardware;good maintenance can only preserve this character-8-2
Downloaded from http://www.everyspec.com on 2011-10-29T14:56:01.DOD-HDBK-791(AM)istic. The object of RCM is to preserve the inherent designlevels of reliability and accomplish it at minimum cost.The RCM concept uses decision logic to evaluate andconstruct maintenance tasks which are based on theequipment functions and failure modes. Evaluation ofequipment designs in accordance with RCM techniqueswill also determine when it is cost-effective to employpreventive maintenance and when it is not cost-effective.It is essential that the RCM analysis be integrated with themaintainability concepts for testability and diagnostictechniques.8-2.3 RELIABILITY CENTEREDMAINTENANCE LOGICRCM logic is intended for application when the failuremode, effect, and criticality of component failure hasbeen identified. Fig. 8-2 (Ref. 4) illustrates the RCManalysis process—a process that is applied to each repairableitem in the equipment or system. The logic isdesigned to accomplish the following (Ref. 4):1. By using data from the system safety and reliabilityprograms, identify components in the system orequipment that are critical in terms of mission or operatingsafety.2. Provide a logical analysis process to determinethe feasibility and desirability of scheduled maintenancetask alternatives.3. Highlight maintenance problem areas for designreview consideration.4. Provide the supporting justification for scheduledmaintenance task requirements.Par. 4-9, Ref. 4, presents a detailed discussion on theapplication of the logic steps identified in Fig. 8-2.The functional failure identified by the application ofRCM logic can be assessed for consequence of failure andis processed according to its severity category—i.e., catastrophic,critical, marginal, or minor. The logic process isbased on the following (Ref. 4):1. Minor or Marginal Severity Categories. Scheduledmaintenance tasks should be performed only whenperformance of the scheduled task will reduce the lifecycle cost of the equipment or system.2. Critical and Catastrophic Severity Categories.Scheduled maintenance tasks should be performed whensuch tasks will prevent a decrease in reliability or deteriorationof safety to unacceptable levels or when the taskwill reduce the life cycle cost of ownership of the equipmentor system.Reliability (R) and Maintainability (M) Characteristicsform, Fig. 8-3, is used to record the disposition. Instructionsfor locating the data on the form are contained inpar. 4-8 (Ref. 4).8-3 PREVENTIVE MAINTENANCEEVALUATION PARAMETERSAND TRADE-OFFSThe relative values of preventive maintenance actionsmay be determined as a function of several performanceand cost parameters. The value should be quantifiedwhenever possible to remove the decision from subjectivejudgment. However, performance and cost must never betraded off with safety.Preventive maintenance actions incur cost in terms ofmaterials, man-hours, and equipment downtime; hencethe detailed analysis discussed in par. 8-2. The cost ofman-hours and repair parts and materials can be determinedrather easily. The cost of equipment downtime,however, is a function of the operational value of theparticular equipment in the situation that exists when it isdown. Accordingly, maintenance is scheduled into theoperations when there is the minimum risk that theequipment will be required for an operational assignment.The two chief parameters—availability and cost ofownership—relative to an optimum preventive maintenanceprogram are discussed in the paragraphs thatfollow.8-3.1 AVAILABILITYAchieved availability is the probability that a system orequipment, when used under stated conditions in an idealsupport environment—i.e., available tools, parts, manpower,manuals, etc.—shall operate satisfactorily at agiven time. Note that supply downtime and waiting oradministrative downtime are excluded. Two equationsfor achieved availability are given8-2.4 DISPOSITION OF RELIABILITYCENTERED MAINTENANCEANALYSISEach failure analyzed by the application of the RCMlogic leads the analysts to make a decision on the dispositionof each failure mode. The Data Record B: Item8-3
Page 3 and 4:
Downloaded from http://www.everyspe
Page 6:
Page 9 and 10:
Page 11 and 12:
Page 13 and 14:
Page 15 and 16:
Page 17 and 18:
Page 19 and 20:
Page 21 and 22:
Page 23 and 24:
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
Page 69 and 70:
Page 71 and 72:
Page 73 and 74:
Page 75 and 76:
Page 77 and 78:
Page 79 and 80:
Page 81 and 82:
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96: Downloaded from http://www.everyspe
Page 145: Downloaded from http://www.everyspe
Page 197 and 198:
Page 199 and 200:
Page 201 and 202:
Page 203 and 204:
Page 205 and 206:
Page 207 and 208:
Page 209 and 210:
Page 211 and 212:
Page 213 and 214:
Page 215 and 216:
Page 217 and 218:
Page 219 and 220:
Page 221 and 222:
Page 223 and 224:
Page 225 and 226:
Page 227 and 228:
Page 229 and 230:
Page 231 and 232:
show all

MAINTAINABILITY DESIGN TECHNIQUES METRIC - AcqNotes.com

Create successful ePaper yourself

Delete template?

Save as template?