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Reliability Engineering

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Information about Reliability Engineering
Science-Technology
asq

Published on May 10, 2013

Author: baher

Source: authorstream.com

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PowerPoint Presentation: Main Concepts and Highlights Reliability Engineering Baher EL Shaikh baherfm@yahoo.com PowerPoint Presentation: The Certified Reliability Engineer Handbook (ASQ) 2. ISO 14224 Collection and exchange of reliability and maintenance data for equipment Baher El Shaikh Definitions Reliability 1 : The probability that an item will perform a required function without failure under stated conditions for a specified period of time. Failure 2 : termination of the ability of an item to perform a required function Maintainability 2 : the probability that a failed product will be repaired within a given amount of time once it has failed. Thus, maintainability is a function of time. Availability(A) 1 : the probability that a product is operable and in a committable state when needed. In other words it is the probability that an item has not failed or is not undergoing repair. Non Critical Failure 2 : failure of an equipment unit which does not cause an immediate cessation of the ability to perform its required function Hidden Failure 2 : failure that is not immediately evident to operations and maintenance personnel. Equipment that fails to perform "on demand" function falls into this category. PowerPoint Presentation: Baher El Shaikh PHA - Preliminary Hazards Analysis FMEA – Failure Modes and Effects Analysis CA - Criticality Analysis SFMEA - Simplified Failure Modes and Effects Analysis MI - Maintainability Information FTA - Fault Tree Analysis ETA – Event Tree Analysis TCO – Total Cost of Ownership LCC – Life Cycle Cost LCAM- Life Cycle Asset Management RCA / RCFA- Root Cause Analysis / Root Cause Failure Analysis CMMIS- Computerised Maintenance Management Information System MTBF- Mean Time Between Failure MTTF- Mean Time To Failure Abbreviated Terms Life Cycle Engineering “www.lce.com” 2. ISO 14224 Collection and exchange of reliability and maintenance data for equipment PowerPoint Presentation: The Certified Reliability Engineer Handbook Baher El Shaikh The study of reliability engineering is usually undertaken primarily to determine and improve the useful lifetime of products. Reliability techniques can also help other facets of an organization: Reliability analysis can be used to improve product design Marketing and advertising can be assisted as warranty and other documents that inform customer expectations are prepared Detect and prevent or mitigate product liability issues. The impact of process parameters on product failure rates can be studied Alternative processes can be compared for their effect on reliability Reliability data for process equipment can be used to determine preventive maintenance schedules and spare parts inventories. Safety can be enhanced through the understanding of equipment failure rates Vendors can be evaluated more effectively. Role Of Reliability Function in Organization 1 PowerPoint Presentation: Life Cycle Engineering “www.lce.com” Baher El Shaikh The primary role of the Reliability Engineer is to identify and manage asset reliability risks that could adversely affect plant or business operations. This broad primary role can be divided into three smaller, more manageable roles: Loss Elimination, Risk Management and Life Cycle Asset Management (LCAM). Reliability Engineer Responsibilities and Duties: Works with project engineering to ensure the reliability and maintainability of new and modified installations Participates in the development of design and installation specifications along with commissioning plans Participates in the final check out of new installations. This includes factory and site acceptance testing that will assure adherence to functional specifications. Guides efforts to ensure reliability and maintainability of equipment, processes, facilities, controls, and safety/security systems Professionally and systematically defines, designs, develops, monitors and refines an Asset Maint . Plan Provides input to a Risk Management Plan that will anticipate risks that could adversely impact plant ops. Develops engineering solutions to repetitive failures and all other problems adversely affect plant operations Provides technical support to production, maintenance management and technical personnel Applies value analysis to repair/replace, repair/redesign, and make/buy decisions Role Of Reliability Engineer 1 PowerPoint Presentation: The Certified Reliability Engineer Handbook Baher El Shaikh The study Reliability analysis provides estimates of the probability of failure . The reliability engineer must go beyond these calculations and examine the consequences of failure. These consequences typically represent costs to the customer. An important reliability function is the anticipation of possible failures and the establishment of reliability acceptance goals that will limit their occurrence and consequent costs Failure Consequence and Liability Management 1 PowerPoint Presentation: The Certified Reliability Engineer Handbook Baher El Shaikh The study Reliability engineers are involved in project teams in various ways. They may be called on to support design projects, provide assistance to supplier selection or FMEA, or be involved in other projects where their expertise is needed. In each case an understanding of project management tools is essential. Project Management 1 The tools most frequently employed are : Gantt Chart Activity Network Diagram (AND) Critical Path Method (CPM) Program Evaluation and Review Technique (PERT) PowerPoint Presentation: The general goal of reliability efforts is to delight customers by increasing the reliability of products. The reliability program accomplishes this goal by establishing reliability goals and meeting them. 1. Established reliability goals and requirements. The reliability program must have a mechanism for translating the minimum reliability requirements into design requirements. 2. Product and Process design. The reliability program must facilitate tests that are conducted to validate that the reliability requirements do indeed produce the desired product reliability. 3. Validation and verification. 1 2 3 Elements of A Reliability Program 1 The Certified Reliability Engineer Handbook Baher El Shaikh 1 4 The reliability program must make provisions for collecting and analyzing data from products during their useful life 4. Post-production evaluation. PowerPoint Presentation: No reliability program can succeed without a basic understanding of its elementary concepts by people at all levels. Support from key managers is essential because their cooperation is needed for the testing and analysis process. Top-level management must see the importance of the program to the success of the enterprise. So this element of the reliability program must sometimes be given first priority if the rest of the program is to succeed. 5. Training and education 1 Elements of A Reliability Program 1 The Certified Reliability Engineer Handbook Baher El Shaikh 5 Elements of A Reliability Program 1 -Cont. PowerPoint Presentation: Elements of A Reliability Program 1 The Certified Reliability Engineer Handbook Baher El Shaikh Product Life cycle and Costs 1 This the constant failure rate stage, the random causes stage, or the useful life stage. During the useful life stage the failure rate is approximately constant. Note that the failure rate is not necessarily zero. During this stage the failures have random causes and can’t usually be assigned to production problems. Reducing the failure rate during this stage usually requires changes in product design. Second Stage First Stage the wear-out stage, fatigue stage, or the increasing failure rate stage. The wear-out stage is characterized by an increasing failure rate over time. These failures are caused by product or component fatigue. Third Stage The early failure stage, the infant mortality stage, or the decreasing failure rate stage. The failures that occur during the early failure stage are usually associated with manufacturing rather than design. Examples of causes of failure include inadequate test or burn-in time, poor quality control, poor handling, weak materials or components, and human error in fabrication or assembly. Ideally, all these failures should occur in-house and be corrected before the customer takes possession. Reliability engineers identify three stages in the lifecycle of a product PowerPoint Presentation: Elements of A Reliability Program 1 The Certified Reliability Engineer Handbook Baher El Shaikh Product Life cycle and Costs-Cont. 1 First Stage Third Stage These stages are depicted in the bathtub curve During the useful life (constant failure rate stage) of the product the formula for product reliability is PowerPoint Presentation: Elements of A Reliability Program 1 The Certified Reliability Engineer Handbook Baher El Shaikh Probability and Statistics of Reliability First Stage Third Stage The tools most frequently employed are: measure of central tendency (Mean, Median and Mode) measures of dispersion (Standard Deviations, Sample Variance) The general Limit Theorem Basic Probability Concepts (Conditional Probability, Complementary rule, Addition roles,… etc.) Discrete and Conditional Probability Distribution) Statistical Process Control (SPC) Attribute Charts and Variable Charts Statistical Inference Point and interval estimates o parameters Hypothesis testing Goodness of fit test PowerPoint Presentation: Elements of A Reliability Program 1 The Certified Reliability Engineer Handbook Baher El Shaikh Reliability Design Techniques First Stage Third Stage Stress Strength Analysis Failure of a part will occur when a stress exceeds the strength of the part for that stress. Accepted design practice is to design so that the strength is always greater than the expected stress FMEA “Failure Modes and Effects Analysis” in Design Apply the techniques and concepts and evaluate the results of FMEA during the design phase. FMECA “Failure Mode Effects and Criticality Analysis” in Design Apply the techniques and concepts and evaluate the results of FMCEA at each step of the design process FTA “Fault Tree Analysis” in Design FTA is very useful in the early stages of design, especially in situations where the product being designed is complex and/or has interdependencies with other components Tolerance and Worst Case analysis Robust design approaches Human Factors Reliability PowerPoint Presentation: Elements of A Reliability Program 1 The Certified Reliability Engineer Handbook Baher El Shaikh Reliability Modeling First Stage Third Stage Source of Reliability data Reliability data are generally available to a manufacturer from several sources both external and internal to the company . Reliability block diagram and models There are several advantages to modeling the system, including predicting system reliability using reliability predictions for the various subsystems. The model can be used to identify weak links in the system and to indicate where reliability improvement activities should be introduced. PowerPoint Presentation: Elements of A Reliability Program 1 The Certified Reliability Engineer Handbook Baher El Shaikh Reliability Modeling – Static Systems First Stage Third Stage Static System Reliability Models 1. Series Model : system block diagram reduces the system to its subsystems and provides a tool for understanding the effect on the system of a subsystem failure. System modeling will assist in identifying reliability problems and the implementation of a reliability improvement effort 2. Parallel Model : Redundancy can be designed into a system to increase system reliability. A parallel system provides more than one path for system success 3. Series-Parallel Model : A system may be modeled as a combination of series and parallel subsystems. PowerPoint Presentation: Elements of A Reliability Program 1 The Certified Reliability Engineer Handbook Baher El Shaikh Reliability Modeling-Static System, Cont’d First Stage Third Stage 4. System Model Using Bayes’s Theorem Another special case is a coherent system, a connection of subsystems that can not be reduced to a series or parallel model. One method to solve for system reliability of such a system is known as Bayesian analysis. 5. Truth Table Method . System reliability can be found from any block diagram, when the subsystem reliabilities are known, using a systematic method to identify all the events that will result in system success. 6. Special Cases Reliability Modeling PowerPoint Presentation: Elements of A Reliability Program 1 The Certified Reliability Engineer Handbook Baher El Shaikh Reliability Modeling- Dynamic System First Stage Dynamic System Reliability Models Dynamic math models are time dependent. To analyze a dynamic model, it is necessary to assume a failure distribution for the subsystems. 1. Load Sharing Model: The subsystems of an active parallel system are connected such that each shares equally in the total load. The subsystems are derated so that each is operating at less than its maximum load capacity. The failure rate of each subsystem is lowered and reliability is improved because the units are operating at a lower stress level. 2. Standby Redundant System: A system that has parallel units that are utilized only in the event of a failure is a standby redundant system. PowerPoint Presentation: Elements of A Reliability Program 1 The Certified Reliability Engineer Handbook Baher El Shaikh Reliability Modeling- Simulation Technique First Stage Identify, select, and apply various simulation methods (e.g., Monte Carlo, Markov) and describe their advantages and limitations. 1.Monte Carlo simulation: a repeated calculations of system performance are made using randomly selected values based on the probability distributions that describe each element of the model. The large number of values of system performance generated can be used to develop a probability distribution of system performance. Monte Carlo simulation does not involve complex mathematics; however, it requires an extensive use of computer time as each possible event for each unit of the model must be repeatedly sampled over the desired mission time. 2. Markove Simulation Process: A complex system can be analyzed as a Markov process. The Markov process can be used to find the probability of being in a given state at some time in the future if the probability of moving from one state to another state is known and the probability remains constant. The system can exist in only one state at a time, and xcept for the immediately preceding state, all future states are independent of past states. PowerPoint Presentation: Elements of A Reliability Program 1 The Certified Reliability Engineer Handbook Baher El Shaikh Reliability Predeiction First Stage A reliability prediction, is a design tool to be used early in the design and development stage. To be effective, the prediction is started before the design is completed and completed before production tooling is set and hardware is procured for production. Many times the prediction is done without any actual reliability data on the particular system, although there may be data on some of the components. Advantages of Reliability Prediction: The reliability of a product needs to be continually evaluated using the available information during all stages of design, development, and production. Early reliability predictions using the system model can be very useful to the reliability engineer. Predictions can be used to determine weak spots in the design and initiate a redesign effort.` Predictions can be used to choose between alternate designs Predictions can be used to evaluate the effect on reliability of a design change. Limitations of Reliability Prediction: Predictions have the limitation that they are based on the simplifying assumption that each component has an inherent constant failure rate. Predictions can not take into account the human factors that most likely cause failure prediction has no statistical confidence PowerPoint Presentation: Elements of A Reliability Program 1 The Certified Reliability Engineer Handbook Baher El Shaikh Reliability Testing First Stage Elements of Reliability Testing 1. Reliability Test Planning 2. Development Testing 3. Product Testing PowerPoint Presentation: Elements of A Reliability Program 1 The Certified Reliability Engineer Handbook Baher El Shaikh Reliability Test Planning First Stage Elements of Reliability Test Plan 1. Determine the test requirements and objectives. 2. Review existing data to determine if any requirements can be met without testing. 3. Review the list of tests to determine whether combining any tests would be economically feasible. 4. Determine the necessary tests. 5. Allocate the resources necessary to perform the tests. 6. Develop test specifications, data handling and storage procedures. Review acceptance and qualification criteria. Establish procedures for making future changes in the test specifications. 7. Assign the responsibility for conducting the tests, analyzing the results, and providing the overall integration of the testing program. 8. Develop forms and procedures for reporting the test results. 9. Develop procedures for maintaining the test status information throughout the entire testing program. PowerPoint Presentation: Elements of A Reliability Program 1 The Certified Reliability Engineer Handbook Baher El Shaikh Types and Application of Reliability Testing First Stage Product development tests These tests are performed with the intent of taking action to improve the design in the event of failures, and to evaluate the system design, including the compatibility of subsystems. Reliability performance tests performed after the design is completed. They will demonstrate that the system can meet the specified requirements under the specified conditions of operation Reliability acceptance tests Conducted during the production phase, these tests will demonstrate that reliability parameters of the design have not been compromised by the production process. These tests might be part of the overall quality program, but with an emphasis on the reliability parameters. 4. Reliability verification tests These tests are performed to show compliance to stated reliability parameters such as MTBF or failure rate. It may be required to demonstrate compliance at a given confidence level . PowerPoint Presentation: Elements of A Reliability Program 1 The Certified Reliability Engineer Handbook Baher El Shaikh Maintainability and Availability First Stage Availability , is a measure of the likelihood that a system will be ready to operate (system is up) when it is called on to operate. Maintenance strategies: Maintenance strategies should be chosen to ensure a high level of availability while controlling costs. Preventive maintenance does not improve the inherent reliability of the system. Preventive maintenance will maintain the reliability level of useful life, keeping the failure rate low. Predictive and Reliability Centered Maintenance (RCM) Predictive maintenance assumes that the operator can detect the imminent failure of a unit. This detection can be by observation, analysis, or using test equipment. The analysis of an oil sample or the measurement of increased vibration might indicate wear and increasing failure probability. RCM, This strategy uses the predicted failure distributions to determine the optimum replacement time for units about to enter the wear-out phase. It is possible that any maintenance action can negatively impact reliability by inducing failure modes due to the maintenance action PowerPoint Presentation: THANK YOU! Baher EL Shaikh baherfm@yahoo.com

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