MAINTAINABILITY DESIGN TECHNIQUES METRIC - AcqNotes.com

Downloaded from http://www.everyspec.com on 2011-10-29T14:56:01.DOD-HDBK-791(AM)CHAPTER 8PREVENTIVE MAINTENANCEThis chapter describes the types of maintenance that are classified as “preventive’; the means for determiningthe cost-effectiveness of preventive maintenance, and the trade-of between the inherent downtime forpreventive maintenance and the desired level of equipment performance and reliability. Reliability CenteredMaintenance (R CM) is discussed, and an example of its application is given. The Army Oil Analysis Program(AOAP) is presented as a major contributor to more efficient maintenance. Design considerations for ease oflubrication, servicing, and cleaning and preservation of equipment for use and for longtime storage areoutlined. A servicing checklist is provided.8-0 LIST OF SYMBOLS8-1 INTRODUCTIONMaintenance—actions necessary for retaining materielin, or restoring it to, a serviceable condition is precipitatedby various causes and can occur in different locations.Maintenance actions can be categorized as fallinginto three types—preventive, corrective, and servicing—defined as follows:1. Preventive Maintenance. Performed to retain anitem in satisfactory operational condition by providingsystematic inspection, detection, and prevention of incipientfailures. Detection and prevention may take placeeither before failures occur or before they develop intomajor defects.2. Corrective Maintenance. Performed to restore anitem to a satisfactory condition by correcting a malfunctionthat has caused degradation of the item below thespecified performance level.3. Servicing Maintenance. Performance of any act—other than prevention or correction-–required to retainan item of equipment in operating condition. Suchactions include lubricating, fueling, oiling, cleaning, etc.Servicing does not include periodic part replacements orany corrective maintenance tasks.The basic maintenance actions—preventive and corrective—canoccur while the equipment is in or out of service.Thus in maintenance planning evaluations it isnecessary to recognize not only the type and criticality ofaction required but also the operational status and role ofthe equipment. This relationship is illustrated by Fig. 8-1,which shows that noncritical repairs, even though neces-8-1