This document provides an overview of maintenance and reliability engineering. It discusses the evolution of maintenance from an emphasis on fixing equipment after failure (first generation) to preventing failures through planned maintenance (second generation) to today's focus on predictive and condition-based maintenance using data and analytics (third generation). Key concepts covered include definitions of reliability as the probability of an item performing as intended for a given period, methods for measuring reliability through metrics like MTBF and MTTF, and the objectives of reliability engineering in preventing, identifying, and mitigating failures. The next lecture is outlined to cover more reliability theory concepts and probabilistic reliability analysis.
This document provides an overview of maintenance and reliability engineering. It discusses the evolution of maintenance from an emphasis on fixing equipment after failure (first generation) to preventing failures through planned maintenance (second generation) to today's focus on predictive and condition-based maintenance using data and analytics (third generation). Key concepts covered include definitions of reliability as the probability of an item performing as intended for a given period, methods for measuring reliability through metrics like MTBF and MTTF, and the objectives of reliability engineering in preventing, identifying, and mitigating failures. The next lecture is outlined to cover more reliability theory concepts and probabilistic reliability analysis.
This document provides an overview of maintenance and reliability engineering. It discusses the evolution of maintenance from an emphasis on fixing equipment after failure (first generation) to preventing failures through planned maintenance (second generation) to today's focus on predictive and condition-based maintenance using data and analytics (third generation). Key concepts covered include definitions of reliability as the probability of an item performing as intended for a given period, methods for measuring reliability through metrics like MTBF and MTTF, and the objectives of reliability engineering in preventing, identifying, and mitigating failures. The next lecture is outlined to cover more reliability theory concepts and probabilistic reliability analysis.
This document provides an overview of maintenance and reliability engineering. It discusses the evolution of maintenance from an emphasis on fixing equipment after failure (first generation) to preventing failures through planned maintenance (second generation) to today's focus on predictive and condition-based maintenance using data and analytics (third generation). Key concepts covered include definitions of reliability as the probability of an item performing as intended for a given period, methods for measuring reliability through metrics like MTBF and MTTF, and the objectives of reliability engineering in preventing, identifying, and mitigating failures. The next lecture is outlined to cover more reliability theory concepts and probabilistic reliability analysis.
ENGINEERING CGE676 Lecture 1: Introduction of Maintenance & Reliability Engineering
Faculty of Chemical Engineering
What is reliability? ability of an item to perform a required function under given conditions for a given time interval IEC 60050 the probability that an item will perform a required function without failure under stated conditions for a stated period of time Smith, D.J. (2005)
Faculty of Chemical Engineering
Development of maintenance & reliability engineering First generation maintenance (pre-WW2) Industry not highly mechanized so downtime not particularly important. Most equipment simple and over-designed Reliable and easy to repair. Eventually just wore out. Only systematic maintenance required - simple cleaning, servicing and lubrication. Philosophy: Fix it when it breaks!
Reproduced with permission from Andrew
K. S. Jardine
Faculty of Chemical Engineering
Second generation maintenance (WW2 to mid-70s) More mechanisation and concern over downtime. Idea that failures could and should be prevented. Awareness of burn-in failure mode Bath-tub curve ) Increase in maintenance costs as a proportion of total operating costs. Development of first planning and scheduling tools. Philosophy: Preventative overhauls Reproduced with permission from Andrew K. S. Jardine Faculty of Chemical Engineering 3rd generation maintenance (mid-70s +) Aircraft data identifies 6 different failure mode patterns. Growth of mechanisation and automation increases focus on plant availability and reliability. Effect of failures on HS&E becomes important as regulations tighten. Cost of maintenance increases: Often 1st or 2nd highest of all operating costs. New techniques become available to collect data that would enable maintainers to: To predict failures - Predictive Maintenance Optimise maintenance decisions - Asset Management Reproduced with permission from Andrew K. S. Jardine Faculty of Chemical Engineering SoReliability Can be defined as - The probability that an item/system will perform a required function without failure under stated conditions for a stated period of time Can also be expressed as the number of failures over a period A time dependent characteristic. It can only be determined after an elapsed time but can be predicted at any time. It is the probability that a product or service will operate properly for a specified period of time (design life) under the design operating conditions without failure. Faculty of Chemical Engineering Key variables for reliability Since reliability is defined as a probability, its definition will be based on a few key (random) variables, e.g. Time to failure Time between failures Number of failures in a given period of time
Faculty of Chemical Engineering
How reliability is measured? The probability of an item that does not fail in a time interval (0,t], survival probability Beside being measured as a probability, reliability can be quantified via e.g. the following parameters or metrics: Mean number of failures in a given time (failure rate) Mean time between failures (MTBF) the average time between successive failures. Mean time to failure (MTTF) - the average time that elapses until a failure occurs.
Faculty of Chemical Engineering
Probabilistic nature of reliability To quantify reliability, probability and statistical methods must be used Usually concerned with probability values that are very high or very low Quantifying these numbers requires further information We are concerned with the extreme tails of distributions Reliability data from past cannot be used to make credible forecasts of the future behaviours, without taking non-statistical factors into account Faculty of Chemical Engineering Objectives of Reliability Engineering To apply engineering knowledge and specialist techniques to prevent or reduce the likelihood or frequency of failure To identify and correct the causes of failures that do occur, despite of the efforts to prevent them To determine ways of coping with failures that do occur, if their causes have not been corrected To apply methods for estimating the likely reliability of new designs, and for analysing reliability data
Faculty of Chemical Engineering
Theory and basic concepts Qualitative reliability FTA, FMEA, FMECA Quantitative reliability Statistical reliability Physics-based reliability Maintenance Time-based maintenance Condition-based maintenance