Useful Reliability and Maintenance Definitions

A Dictionary for Reliability and Maintenance

The definition of Maintenance is the act of maintaining, the state of being maintained, care or upkeep of machinery, the process of maintaining or preserving someone or something, the process of keeping something in good condition, the work of keeping something in proper condition.

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IDCON maintenance and reliability definitions

Browse our Maintenance Definitions in our Reliability and Maintenance dictionary for common maintenance terms used by professionals in the Reliability and Maintenance field. Do you have terms that you commonly use that aren’t included? Send us an email at [email protected] with the term and the definition and it may be added to the list.

Actuarial analysisStatistical calculation, especially of life expectancy
Add-on workWork added to a maintenance schedule after the agreed upon cut-off time for the schedule.
Action results IndicatorKey Performance Indicators used for measuring results of actions that indirectly or directly impacts the financial performance of the company. Examples
ApprenticeAn employee in a certified training program to become a craftsperson.
AssetAn accounting term for any physical thing owned by a plant, such as buildings, equipment, desks, software, computers etc.
Asset numberA number that follows a particular asset in a plant, should be used for accounting purposes. Note an asset number is different from an equipment location number. An equipment location number stays in the same location, where an asset number may move location.
Asset Replacement ValueThe current accounting value of all combined physical assets in a plant.
Assessment – reliabilityA study comparing the Current best Practices (CBP) with actual performance. The study assesses the effectiveness of processes in place.
Autonomous MaintenanceMaintenance processes driven by hourly workforce without management support or intervention.
Autonomous TrainingTraining that is incorporated into the day-to-day work processes. The training is based on experiences and findings from the daily work and is then communicated on a regular basis.
AvailabilityPercentage of total hours (8760/year) or scheduled operating time a system is available for production.
BacklogVolume of all requested maintenance work, yet not completed
Backlog – approvedThe approved backlog is all maintenance work that is not completed, but approved for execution.
BenchmarkingThe continuous, systematic search for, and implementation of, better practices that lead to improved performance
Bill of Materials (BOM)A document of all parts for an asset.
Break downWhen a piece of equipment ceases to function (according to predetermined parameters)
Break-In jobWork that changes a set schedule after an agreed upon cut-off time. Break in job are either:
  1. break-downs
  2. emotional add-on work
Capital workWork done for improvements or betterments which will increase the value of assets.
Capital SparesSpare parts that are depreciated (not expensed) in accounting books.
Charge rateThe amount per hour a resource cost for the company. Wages plus benefits. Benefits are usually around 35% of the salary in The USA, 50-60% in Europe. Benefits include insurances, vacations, and other time off.
ComponentA generic technical part. Many components make up equipment. Hierarchy is that parts make components, makes equipment, makes systems. illustration (30 KB)
Computerized Maintenance Management System (CMMS)A computer program or interfacing programs used to manage the maintenance function in a plant.
Condition Based Maintenance (CBM)Maintenance actions taken as a result of investigated condition of parts or components. The condition is measured or evaluated during programmed inspections of parts and components.
Condition MonitoringAll work performed in order to find failures early.
Consequence Of Break-Down (COB)The “cost”, not always measured in money, of a break down of equipment. COB is prioritized as follows:
  1. Environmental damage or safety hazard
  2. Production loss
  3. High Cost (equipment life)
Continuous ImprovementContinuous improvement of existing practices resulting in improved performance.
Corrective MaintenanceAll maintenance performed to correct a break down or failure.
Cost EffectiveWhen the monetary benefit exceeds the cost of implementing an improvement.
Crafts peoplePeople with professional skills in mechanical, electrical or instrumentation maintenance. Many plants require skills in several of the skills mentioned.
CriticalityThe criticality of a component, equipment, or system based on the consequence of Break-Down.
Current Best Practice (CBP)The best way known to do something in IDCON’s Results Oriented Maintenance (ROM) philosophy. The future might reveal a better way of doing something and thus change the CBP. A CBP is equal to an element, which is the lowest level of detail in a Key Process.
Cut-off timeTime when a schedule closes.
Defect 1Damage on final product which forces the plant to scrap product, or sell product for lower price.
Defect 2Can also mean a failure in a part or component.
DowntimeTime when a system is not producing product. Downtime includes scheduled and unscheduled downtime.
Downtime scheduledWhen a system is down, and the downtime was documented as scheduled before cut-off time.
Downtime unscheduledWhen a system is down, and the downtime was NOT documented as scheduled before cut-off time.
ElementIn the IDCON assessment. A CBP is equal to an element, which is the lowest level of detail in a Key Process. The best way known to do something. The future might reveal a better way of doing something and thus change the CBP. illustration
Emergency WorkEmergency work is a synonym to break-in work.
EquipmentAn asset that performs a function e.g. a motor coupling pump, pumps water from pint A to point B.
Equipment HistoryDocumentation for all events such as repairs, modification, and preventive maintenance performed for a specific equipment.
Equipment locationA physical location in the plant for a piece of equipment.
Equipment Location numberA unique number assigned to an equipment location.
Equipment reliabilityTime, speed, and quality performance as it relates to equipment. In IDCON’s ROM philosophy, equipment reliability is the result of maintenance work.
Essential CareA compilation of processes that will prevent failures from occurring. For example lubrication, alignment, balancing, cleaning, and operating procedures, adjustments and installation procedures. Essential Care prevents failures (prolong life of equipment).
Estimated Replacement ValueEstimated present value of assets. Shortened to ERV
FailureWhen equipment condition reaches an unacceptable level. Example: A motor may run, but the temperature is 250 °F (unacceptable)
Failure CodeA classification of a failure.
Failure Developing PeriodThe time lapsed between a failure and the break down. illustration
Failure ModeAny event that may cause a failure.
Failure Mode and Effects Analysis (FMEA)Analysis tool to Identify Failure modes, assign priorities to each failure mode based on cost and occurrences.
Failure RateAn average of how often a component, equipment or system fails in a given time period.
FeedbackIn maintenance. Most commonly used when referring to written description of the work completed on a work order.
Fixed Time Maintenance (FTM)This tactic provides for scheduled overhauls or replacements of components often based on recommendation from the equipment vendor, general plant experience with similar components or analysis of the maintenance history of an individual piece of equipment and its components. Note: Only 10-15% of all component types have a predictable failure rate. Cost effective use of FTM is therefore limited.
Frequency of InspectionThe time period between a repetitive inspection. The inspection frequency should be based on the failure developing period. Note: A rule of thumb is that the inspection frequency should be: Failure Developing Period/ 2.
Gantt ChartA bar chart (histogram) of scheduled tasks. Microsoft Project, and timeline are examples of software using Gantt charts.
Gap AnalysisA rated comparison of Current Best Practices and actual performance.
GoalMeasurable results you wish to accomplish at a projected point in time.
IatrogenicIn maintenance. Failures induced by own employees. Note: Iatros means physician in Greek, and -genic, meaning induced by, is derived from the International Scientific Vocabulary. Combined, of course, they become iatrogenic, meaning physician-induced. Iatrogenic disease is obviously, then, disease which is caused by a physician.
Infant mortalityComponent failures occurring during early life of component (1-12 months).
InspectionAny activity performed to find a failure or break-down.
Inspection ListThe printed list of an inspection route.
Inspection RouteDocumented instructions for condition monitoring tasks, sorted in an effective walking path through an area. example paper, example handheld
InspectorThe person doing the inspection routes. Note: This could be an operator, crafts person, supervisor, engineer or a manager.
Key performance Indicator (KPI)A measurement of process performance.
Key ProcessThe key processes for IDCON’s Current Best Practice (CBP) assessment format are:
1.Leadership and organization
2.Preventive Maintenance
3.Planning and Scheduling
4. Shutdown Turnaround Management
5.Root Cause Problem Elimination
6.Technical Database
7.Materials Management
8.Skills Development maintenance
9.Safety – Maintenance
10.Engineering Interface
Life Cycle Cost (LCC)Total cost for acquiring, owning and disposing physical assets. Includes direct operational and maintenance costs and indirect costs for lost production when system fails.
Life Cycle Profit (LCP)The present value of all revenue the equipment has generated less the LCC.
Log BookUsually refers to operations log for problems found during shift.
Logic TreeA charting method for why-why analysis.
Management of Change (MOC)A process used to track and manage any physical or specification changes made to process related equipment in a plant.
MaintainabilityThe ease to maintain equipment.
Maintenance meaningMaintenance consists of corrective maintenance, preventive maintenance, and continuous improvement. illustration
Maintenance EngineeringMaintenance Engineers work on design specifications of minor modifications, preventive maintenance documentation, problem identification and elimination, maintenance training, and maintenance technical database.
Maintenance ManagementMaintenance management is the collective term for describing the management process of leadership and organization, planning and scheduling, preventive maintenance, condition monitoring, execution of maintenance repairs, recording, root cause failure analysis, spare parts management, and management of technical data supporting the processes above.
Maintenance OpportunitySee maintenance window
Maintenance PlanningSee definition for “Planning”
Maintenance preventionAll actions performed to prevent failures. Lubrication, alignment, balancing, installation and equipment design, operating procedures, detailed cleaning, adjustments, fixed time replacements, and filtration. Note: Maintenance prevention and condition monitoring are the two components of preventive maintenance
Maintenance WindowDefined time slots when maintenance can be performed on equipment without disturbing production.
Mean Down Time (MDT)Average time equipment is down (for any reason).
Mean Time Between Failures (MTBF)Total calendar operating time divided by number of failures.
Mean Time To Repair (MTTR)Average Repair time for component.
Mean Wait Time (MWT)All time during downtime that isn’t repair time. MDT=MWT + MTTR
Mission StatementSummarizes how to achieve a vision.
Model Work OrderSee Standard Job Plan
Non Destructive testing (NDT)Any material testing that doesn’t destroy material. During the testing process. Note: Usually we think of Ultrasonic Thickness Testing. Also included in NDT is usually dye-penetrant testing, x-ray testing, and electrical resistance testing. Vibration, thermography, look, listen, feel, smell, winding test etc are not included since they are testing components, and equipment, not material.
Non-Scheduled workSee unscheduled work
Objective Condition MonitoringPreferred over subjective condition. Objective methods are for example vibration analysis, ultrasonics, and temperature-, pressure-, voltage- and ampere readings. Subjectiveinspections are look, listen, feel and smell
Off-lineDowntime for a component or system without affecting production. Note: If production is down it’s considered an outage, or shutdown/ Turnaround.
Oil AnalysisTesting of oil in order to find failures early
Operate To Break-Down (OTB)A maintenance strategy which operates equipment until break-down. A maintenance strategy which sometimes can be the most cost effective. Note: OTB is used when the consequence of failure is small enough that the benefit of preventing or finding failure early is more costly. OTB will be the fact for failures that occurs randomly and have no failure developing period.
OutageA shutdown/ turnaround that affects the whole plant for more than 16 hours.
Overall Production Efficiency (OPE)The product of Quality [%] * Speed [%] * Uptime [%] for a production line.
Overall ReliabilitySee Production Reliability
PartsSee spare parts
Planned JobA planned job includes:
  • The person planning the job verifies the scope of the job.
  • Lifting Equipment, tools, parts, material and personal. Equipment needed to do the jobs are identified and allocated.
  • Skills needed are identified?
  • A description of job steps is documented.
  • Lock out tag out and other safety requirements are identified.
  • Necessary technical documentation is available.
  • Crafts people are part of the planning process.
  • Estimated job duration by skills and the number of people needed for the job.
  • Required permits available.
  • The cost of each job is estimated.
  • Define physical and environmental constraints.
PlanningThe process of determining the resources, methods, and processes needed to perform maintenance work efficiently and effectively. Note: Planning is different from scheduling. Planning short definition is to decide what, how and time duration.
Predictive MaintenanceA synonym to condition monitoring. Note: IDCON don’t use this term because it is often referred to as ONLY vibration analysis. There are many other condition monitoring tools besides vibration analysis.
Preventive MaintenanceEssential care and fixed time maintenance together. Both essential care and fixed time maintenance PREVENTS (both prevent) FAILURES, while Conditions Monitoring only DETECTS FAILURES EARLY.
PriorityThe assigned importance of a maintenance job.
Priority CodeThe importance of a maintenance job is defined by a priority code. A priority code represents a deadline for when the maintenance job has to be completed.
Priority GuidelineAgreed upon guidelines for assigning a priority to maintenance work.
ProactiveActions that are planned, scheduled and executed before a break-down occurs. Includes maintenance prevention activities.
ProblemAny issue that can be improved cost effectively.
ProcessA work system that is documented, executed, and measured.
Process reliabilityTime, speed, and quality performance as it relates to manufacturing process.
Production reliabilityThe product of process and equipment reliability.
Purchase Order (PO)The document sent to a supplier to order parts, services, material, or machines.
Reliability Centered Maintenance (RCM)A maintenance philosophy which is heavily designed by engineers supported by sound theoretical practices. Note: No known plant have been able to implement a full RCM strategy. It is often a very complicated theory for simple common sense actions. RCM has a given place in the specification phase when designing new equipment. (IDCON’s opinion).
Reliability – EquipmentThe product of Quality [%] * Speed [%] * Uptime [%] as it relates to equipment.
Reliability – ProcessThe product of Quality [%] * Speed [%] * Uptime [%] as it relates to the process (operation of equipment).
Reliability – productionThe product of process reliability and equipment reliability. Measured by Quality [%] * Speed [%] * Uptime [%]
RepairAny activity intended to bring a component, equipment, or system back to a specific condition.
Repetitive workType of work that are done often in the plant. Repetitive work should have standard job plans.
ResultsFinancial outcome of an action, or several actions.
Results IndicatorsGlobal Key Performance Indicators measuring results directly impacting the financial performance of a plant.
ReworkAll repairs that have to be done again due to a poor repair the first time. Note: A combination of poor planning and scheduling. Usually due to lack of skills, material problem, missing spare parts, or not enough time assigned to do a precision job before starting equipment again.
Results Oriented Maintenance (ROM)Maintenance Philosophy developed by IDCON, INC.
Root Cause Failure Analysis (RCFA)A systematic way to collect select, analyze, and solve failures
Root Cause Problem Elimination (RCPE)A systematic way to collect select, analyze, solve and eliminate a problem. (An IDCON CBP Key Process)
SafetyThe result of all actions executed to prevent personal injuries.
Service FactorA key performance indicator for the storeroom measuring the % of times the correct quantity of the correct part is received when requested. Note: If the service factor falls below 95% maintenance people begin to lose confidence in the store room’s ability to supply the correct material & parts when needed. Usually result in growth of “unofficial personal stores” at frontline level.
Scheduled jobA job put on the schedule before the cut-off time. Specific people, start time and end time is documented.
SchedulingThe process of determining what jobs gets worked on, when, and by whom based on the priority and resource/equipment availability. Note: that this process should take place before the job is executed. See definition for ”break-in job”. Scheduling short definition is when and who.
Scheduling complianceA KPI measuring: The sum of Add-on jobs and jobs, on the schedule, not completed OVER the jobs on the schedule before cut-off time.
Shock Pulse measurement (SPM)A condition Monitoring Tool measuring the shock pulse in rotating equipment. Note: Shock pulse is the pressure wave generated through materials when two materials hit each other. A vibration will wave will be generated by the Shock pulse
ShutdownScheduled or unscheduled downtime for a system or plant area.
SourceAn event that triggers a failure. illustration
Spare PartsAll machine parts, materials and supplies that may be required to repair an asset
Standard Job PlansA documented plan for a type of job that can be used repetitively. See planning for definition of “plan”
Sub processA process with lower hierarchy than a key process in IDCON’s CBP material. illustration
Subjective maintenanceLook, listen, feel and smell
System (1)A combination of equipment that are dependent of each other to complete a production task.
System (2)Can refer to a computer software, a work system or production system.
TerotechnologyMaintenance management and technology. A term often used by universities in the UK.
Total Productive Maintenance (TPM)A maintenance philosophy. TPM is usually profiled for the strong operator involvement in equipment care.
Trades personSee craftsperson
TribologyThe science and technology of interacting surfaces in relative motion, including the study of lubrication, friction and wear.
Tribological wearWear that occurs as a result of relative motion at the surface.
TurnaroundSee shutdown. Term usually used in steel, alumina, and mining industry.
Unplanned Maintenance workA maintenance job where necessary planned activities are incomplete before job is scheduled. Planning should always be done before scheduling.
Unscheduled Maintenance WorkWork added to the schedule after the cut-off time.
UptimeOpposite to Downtime. Time when a component, equipment or system is producing product. Note: The component, equipment or system may produce defect product or at a slower speed than usual.
Vibration AnalysisA condition Monitoring tool measuring the vibration in equipment.
Vision StatementSummarizes what an organization (or individual) want to achieve in the future. A vision must be supported by a mission statement and a goal.
Why-why analysisA problem solving method which forces the problem solver to break down and analyze different possible causes as to why a problem occurred.
Work LoadAll work in the approved backlog. Can be measured as follows: The sum of estimated hours in the approved backlog divided by the craftspeople available for a particular area, or supervisor. Best is to trend this number over time. A well managed maintenance area has about 2-4 weeks of workload.
Work OrderAn approved work request.
Work RequestA request to do maintenance work.

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Torbjörn Idhammar

Torbjörn Idhammar

President & CEO, IDCON Inc. Reliability and Maintenance Consultant

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