Mean Time Between Failure Users Guide

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Most companies do not measure Mean Time Between Failure (MTBF). Yet, it is one of the first and most basic measurements you can use to measure reliability. MTBF is the average time an asset will function before it fails. This document is a guide which will take you from just starting to expert.

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Mean Time Between Failure Users Guide

  1. 1. We optimize your people, processes, and technology so that youcan achieve sustainable, reliable resultsMTBF User’s GuideMeasuring Mean Time Between FailureDo you want stop failure? MTBF is the most used metric for failure elimination worldwide. This guidewill walk you through what you need to know to effectively measure MTBF within your organization.A DIVISION OF ALLIED RELIABILITY GROUP
  2. 2. MTBF User’s GuideMeasuring Mean Time Between Failurewww.gpallied.comCopyright 2013A division of Allied Reliability GroupPage 1GPAllied4200 Faber Place DriveCharleston, SC 29405Office (888) 335-8276Most companies do not measure Mean Time Between Failure (MTBF). Yet, it is one of the first and most basicmeasurements you can use to measure reliability. MTBF is the average amount of time that an asset,component, part, etc. will function before it fails.Understand DefinitionsIt is important to have definitions because in reality, the true meaning of terms is not always what typicalindustry believes. What is important is that everyone within your organization has a common understanding of adefinition. Bad Actors = Equipment or assets that have typically long-standing reliability issues. Some companiesidentify “bad actors” by the amount of maintenance dollars spent on the assets in terms of labor andmaterial. MTBF is a simple measurement to pinpoint these poor performing assets. Note that the mostsystematic, technically-based method of determining if an asset is critical is to conduct an assessmentbased on consequence of failure and risk of failure to the business. Total Equipment Failure = Total Equipment Failure occurs when an asset completely fails or breaksdown; it is not operating at all. Partial Failure = The inability of an asset to fulfill one or more of its functions (for example, it no longerproduces product that meets quality standards, but the production line continues to meet productionrate or capacity). MTBF = The average amount of time that an asset will function before it fails. Emergency Work Order = A formal document that is written anytime an asset has a problem and amaintenance person is called to investigate or make a repair. Reliability = The ability of an item to perform a required function under stated conditions for a statedperiod of time.
  3. 3. MTBF User’s GuideMeasuring Mean Time Between Failurewww.gpallied.comCopyright 2013A division of Allied Reliability GroupPage 2GPAllied4200 Faber Place DriveCharleston, SC 29405Office (888) 335-8276The ProcessStep 1: Ensure that all work is covered by a work order, no matter how minor, and that the asset information iscaptured in your Computerized Maintenance Management System (CMMS) or Enterprise Asset Management(EAM) system by asset number.Step 2: Begin tracking MTBF, focusing on one production area or asset group.o Calculate on a daily basis the MTBF.− For plants just starting to measure MTBF:MTBF =TimeNumber of emergency work orders(for all failures: total, functional, and partial)− For more mature maintenance organizations:MTBF =TimeNumber of maintenance events(all events: planned, unplanned, or otherwise)o Trend the data you find in this production area or asset group daily on a line graph and post it foreveryone to see.**Many people may not like to see this data or even believe it, but it provides knowledge of how theequipment has been performing to date and increases the awareness of the need to find a solution toimprove reliability.o Once you feel comfortable tracking and trending MTBF for this one production area or asset group,begin stepping down to the next level in your asset group. This group is typically called the “child” inyour equipment hierarchy. What you have been measuring thus far is what I call the ‘father’ or ‘parent’in the equipment hierarchy. You may define the hierarchy differently, but in general the message isunderstood.o More mature maintenance organizations will want to switch to tracking all maintenance events,planned or unplanned. Tracking to this level makes it much easier to see the total impact of allmaintenance decisions, not just the ones that result in lost production. At some point, the organizationhas to come to terms with the fact that down is down, whether you planned it or not. Even if you didplan it, it was an impending failure that has to be counted for the calculation of reliability for a systemor machine.Step 3: Continue the process throughout your organization’s production areas and component/maintainableitems.
  4. 4. MTBF User’s GuideMeasuring Mean Time Between Failurewww.gpallied.comCopyright 2013A division of Allied Reliability GroupPage 3GPAllied4200 Faber Place DriveCharleston, SC 29405Office (888) 335-8276Example of Calculation Number of emergency work orders in the past 24 hours = 8:o Total equipment failure = 3o Functional equipment failure = 1o Partial equipment failure = 4NOTE: Do not worry about the exact definition of each type of failure. An emergency work orderneeds to be written any time an asset has a problem and a maintenance person is called to theasset to investigate or make a repair. Time: 24 hours Calculation:MTBF =24 hours= 3 hours8 emergency work ordersTrend this data on a line or bar graph and measure it by day or by week depending on the amount of failuresyou see. It may take 3 months to begin to send a trend, or you may find high variation in your maintenanceprocess.Actual MTBF for 900 Electric Motors
  5. 5. MTBF User’s GuideMeasuring Mean Time Between Failurewww.gpallied.comCopyright 2013A division of Allied Reliability GroupPage 4GPAllied4200 Faber Place DriveCharleston, SC 29405Office (888) 335-8276NOTE: If you find that measuring MTBF by day is too difficult to interpret, move to measuringMTBF by week. In this case, you would measure the number of failures that occurred during aweek and divide this number into the number of operating hours that the equipment wasscheduled to operate.SummaryThe process of measuring MTBF is important for a company to know the current status of reliability in all of itsassets. From here, it can be determined which assets are in need of improved reliability.We hope you find this document both useful and helpful. If you have any questions, please email Ricky Smith,rsmith@gpallied.com, or Andy Page, apage@gpallied.com.
  6. 6. www.gpallied.com | info@gpallied.comWorld Headquarters4200 Faber Place DriveCharleston, SC 29405O. 888.335.8276F. 843.414.5779gpAllied europeGuldensporenpark 21-Blok CB-9820 Merelbeke, BelgiumO. +32(0)9.210.17.20F. +32(0)9.210.17.28GPAllied CANADA2572 Daniel Johnson, 2nd FloorLaval, QC | Canada H7T 2R3O. 450.902.2569F. 450.902.2568

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