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Heizer om10 ch17-maintenance and reliability

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  • 1. 10/16/2010 Maintenance and 17 Reliability Outline Global Company Profile: Orlando Utilities Commission The Strategic Importance of PowerPoint presentation to accompany Heizer and Render Maintenance and Reliability Operations Management, 10e Principles of Operations Management, 8e Reliability PowerPoint slides by Jeff Heyl Additional content from Gerry Cook Improving Individual Components Providing Redundancy© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 1 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 2 Outline – Continued Learning Objectives Maintenance When you complete this chapter you should be able to: Implementing Preventive Maintenance 1. Describe how to improve system Increasing Repair Capabilities reliability li bilit Autonomous Maintenance 2. Determine system reliability Total Productive Maintenance 3. Determine mean time between failure Techniques for Enhancing (MTBF) Maintenance© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 3 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 4 Learning Objectives Orlando Utilities When you complete this chapter you Commission should be able to: Maintenance of power generating plants Every year each plant is taken off-line 4. Distinguish between preventive and for 1-3 weeks maintenance breakdown maintenance Every three years each plant is taken E th h l ti t k 5. Describe how to improve maintenance off-line for 6-8 weeks for complete overhaul and turbine inspection 6. Compare preventive and breakdown maintenance costs Each overhaul has 1,800 tasks and requires 72,000 labor hours 7. Define autonomous maintenance OUC performs over 12,000 maintenance tasks each year© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 5 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 6 1
  • 2. 10/16/2010 Orlando Utilities Strategic Importance of Commission Maintenance and Reliability Every day a plant is down costs OUC $110,000 The objective of maintenance and Unexpected outages cost between reliability is to maintain the $350,000 d $600,000 $3 0 000 and $600 000 per d day capability of the system Preventive maintenance discovered a cracked rotor blade which could have destroyed a $27 million piece of equipment© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 7 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 8 Strategic Importance of Maintenance and Reliability Maintenance and Reliability Failure has far reaching effects on a firm’s Maintenance is all activities involved in keeping a system’s equipment in Operation working order Reputation Reliability is the p y probability that a y Profitability machine will function properly for a Dissatisfied customers specified time Idle employees Profits becoming losses Reduced value of investment in plant and equipment© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 9 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 10 Important Tactics Maintenance Management Employee Involvement Reliability Partnering with maintenance personnel Improving individual components Skill training Results Reward system Reduced inventory Providing redundancy Employee empowerment Improved quality Improved capacity Maintenance Reputation for quality Maintenance and Reliability Continuous improvement Implementing or improving Procedures Reduced variability preventive maintenance Clean and lubricate Monitor and adjust Increasing repair capability or speed Make minor repair Keep computerized records Figure 17.1© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 11 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 12 2
  • 3. 10/16/2010 Overall System Reliability Reliability 100 – Reliability of the system (percent) Improving individual components 80 – 60 – Rs = R1 x R2 x R3 x … x Rn e 40 – where R1 = reliability of component 1 20 – R2 = reliability of component 2 0 |– and so on 100 | | 99 | | 98 | | 97 | | 96 Average reliability of each component (percent) Figure 17.2© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 13 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 14 Reliability Example Product Failure Rate (FR) Basic unit of measure for reliability R1 R2 R3 Number of failures .90 .80 FR(%) = x 100% .99 Rs Number of units tested Number of failures FR(N) = Reliability of the process is Number of unit-hours of operating time Rs = R1 x R2 x R3 = .90 x .80 x .99 = .713 or 71.3% Mean time between failures 1 MTBF = FR(N)© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 15 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 16 Failure Rate Example Failure Rate Example 20 air conditioning units designed for use in 20 air conditioning units designed for use in NASA space shuttles operated for 1,000 hours NASA space shuttles operated for 1,000 hours One failed after 200 hours and one after 600 hours One failed after 200 hours and one after 600 hours 2 Failure rate per trip 2 FR(%) = (100%) = 10% FR(%) = (100%) = 10% 20 20 FR = FR(N)(24 hrs)(6 days/trip) 2 FR2= (.000106)(24)(6) failure/unit hr FR(N) = = .000106 failure/unit hr FR(N) = = .000106 20,000 - 1,200 20,000 - 1,200failures per trip FR = .153 1 1 MTBF = = 9,434 hrs MTBF = = 9,434 hrs .000106 .000106© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 17 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 18 3
  • 4. 10/16/2010 Providing Redundancy Redundancy Example Provide backup components to A redundant process is installed to support increase reliability the earlier example where Rs = .713 R1 R2 R3 Probability Probability Probability Reliability has of first of second of needing 0.90 0 90 0.80 0 80 increased from component + component x second working component .713 to .94 working 0.90 0.80 0.99 (.8) + (.8) x (1 - .8) = [.9 + .9(1 - .9)] x [.8 + .8(1 - .8)] x .99 = .8 + .16 = .96 = [.9 + (.9)(.1)] x [.8 + (.8)(.2)] x .99 = .99 x .96 x .99 = .94© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 19 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 20 Maintenance Implementing Preventive Maintenance Two types of maintenance Need to know when a system requires service or is likely to fail Preventive maintenance – routine inspection and servicing p g High initial failure rates are known as to keep facilities in good repair infant mortality Breakdown maintenance – Once a product settles in, MTBF emergency or priority repairs on generally follows a normal distribution failed equipment Good reporting and record keeping can aid the decision on when preventive maintenance should be performed© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 21 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 22 Computerized Maintenance System Data Files Maintenance Costs Output Reports Equipment file with parts list Inventory and purchasing reports The traditional view attempted to balance preventive and breakdown Maintenance and work order schedule Equipment parts list maintenance costs Repair Equipment history reports hi t t Typically this approach failed to yp y pp history file Cost analysis consider the true total cost of Inventory of (Actual vs. standard) breakdowns spare parts Work orders – Preventive Inventory maintenance Personnel data with skills, – Scheduled downtime – Emergency Employee morale wages, etc. maintenance Schedule unreliability Figure 17.3© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 23 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 24 4
  • 5. 10/16/2010 Maintenance Costs Maintenance Costs Total costs Total costs Preventive Full cost of maintenance breakdowns osts sts costs Cos Co Breakdown maintenance Preventive costs maintenance costs Maintenance commitment Maintenance commitment Optimal point (lowest Optimal point (lowest cost maintenance policy) cost maintenance policy) Traditional View Full Cost View Figure 17.4 (a) Figure 17.4 (b)© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 25 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 26 Maintenance Cost Example Maintenance Cost Example Should the firm contract for maintenance 1. Compute the expected number of on their printers? breakdowns Number of Number of Months That Number of Frequency Number of Frequency Breakdowns Breakdowns Occurred Breakdowns Breakdowns 0 2 0 2/20 = .1 2 6/20 = .3 1 8 1 8/20 = .4 3 4/20 = .2 2 6 3 4 Expected number of breakdowns = ∑ Number of breakdowns x Corresponding frequency Total : 20 = (0)(.1) + (1)(.4) + (2)(.3) + (3)(.2) Average cost of breakdown = $300 = 1.6 breakdowns per month© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 27 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 28 Maintenance Cost Example Maintenance Cost Example 2. Compute the expected breakdown cost per 3. Compute the cost of preventive month with no preventive maintenance maintenance Expected Expected number Cost per Cost of expected breakdown cost = of breakdowns x breakdown Preventive e e t e Cost of o breakdowns if service + = maintenance cost service contract contract signed = (1.6)($300) = (1 breakdown/month)($300) + $150/month = $480 per month = $450 per month Hire the service firm; it is less expensive© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 29 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 30 5
  • 6. 10/16/2010 Increasing Repair How Maintenance is Capabilities Performed 1. Well-trained personnel Operator (autonomous Maintenance Manufacturer’s Depot service 2. Adequate resources maintenance) department field service (return equipment) 3. Ability to establish repair plan and Competence is higher as we priorities move t the right to th i ht Preventive 4. Ability and authority to do material maintenance costs less and is faster the more we move to the left planning Increasing Operator Ownership Increasing Complexity 5. Ability to identify the cause of breakdowns 6. Ability to design ways to extend MTBF Figure 17.5© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 31 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 32 Autonomous Maintenance Total Productive Maintenance (TPM) Employees accept responsibility for Observe Designing machines that are reliable, easy to operate, and easy Check to maintain Adjust Emphasizing total cost of Clean ownership when purchasing Notify machines, so that service and Predict failures, prevent maintenance are included in the breakdowns, prolong equipment life cost© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 33 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 34 Total Productive Techniques for Enhancing Maintenance (TPM) Maintenance Developing preventive Simulation maintenance plans that utilize the Computer analysis of complex best practices of operators, situations maintenance departments and departments, Model maintenance programs depot service before they are implemented Training for autonomous Physical models can also be used maintenance so operators maintain their own machines and partner with maintenance personnel© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 35 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 36 6
  • 7. 10/16/2010 Techniques for Enhancing More on Maintenance – Maintenance Supplemental Material Expert systems A simple redundancy formula Computers help users identify problems and select course of action Problems with breakdown and preventive maintenance Automated sensors Predictive maintenance Warn when production machinery is Predictive maintenance tools about to fail or is becoming damaged Maintenance strategy implementation The goals are to avoid failures and Effective reliability perform preventive maintenance before machines are damaged© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 37 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 38 Providing Redundancy – Problems With Breakdown An Alternate Formula Maintenance The reliability of one pump = The probability of one pump not failing = 0.8 “Run it till it breaks” P(failing) = 1- P(not failing) = 1 - 0.8 = .2 Might be ok for low criticality If there are two pumps with the equipment or redundant systems same probability of not failing Could be disastrous for mission- P(failure of both pumps) = critical plant machinery or P(failure) pump #1 x P(failure) pump #2 equipment P(failure of both pumps) = 0.2 x 0.2 = .04 Not permissible for systems that P(at least one pump working) = could imperil life or limb (like aircraft) 1.0 - .04 = .96© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 39 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 40 Problems With Preventive Another Maintenance Strategy Maintenance Predictive maintenance – Using “Fix it whether or not it is broken” advanced technology to monitor equipment and predict failures Scheduled replacement or adjustment of parts/equipment with Using technology to detect and predict imminent equipment failure q p a well established service life well-established Visual inspection and/or scheduled Typical example – plant relamping measurements of vibration, temperature, oil and water quality Sometimes misapplied Measurements are compared to a Replacing old but still good bearings “healthy” baseline Over-tightening electrical lugs in Equipment that is trending towards failure switchgear can be scheduled for repair© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 41 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 42 7
  • 8. 10/16/2010 Predictive Maintenance Predictive Maintenance Tools Vibration Analysis Vibration analysis Using sensitive transducers and instruments to detect and analyze Infrared Thermography vibration Oil and Water Analysis Typically used on expensive mission- expensive, critical equipment–large turbines, Other Tools: motors, engines or gearboxes Ultrasonic testing Sophisticated frequency (FFT) analysis Liquid Penetrant Dye testing can pinpoint the exact moving part that is worn or defective Shock Pulse Measurement (SPM) Can utilize a monitoring service© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 43 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 44 Predictive Maintenance Predictive Maintenance Infrared (IR) Thermography Oil and Water Analysis Taking oil samples from large Using IR cameras to look for gearboxes, compressors or turbines for temperature “hot spots” on equipment chemical and particle analysis Typically used to check electrical Particle size can indicate abnormal equipment for wiring problems or wear poor/loose connections Taking cooling water samples for Can also be used to look for “cold (wet) analysis – can detect excessive rust, spots” when inspecting roofs for leaks acidity, or microbiological fouling High quality IR cameras are expensive – Services usually provided by oil most pay for IR thermography services vendors and water treatment companies© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 45 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 46 Maintenance Strategy Predictive Maintenance Comparison Other Tools and Techniques Resources/ Ultrasonic and dye testing – used to Maintenance Strategy Advantages Disadvantages Technology Required Application Example find stress cracks in tubes, turbine Breakdown No prior Disruption of May need Office copier blades and load bearing structures work production, labor/parts required injury or death at odd Ultrasonic waves sent through metal hours Preventive Work can Labor cost, Need to Plant Surface coated with red dye, then be may replace obtain relamping, scheduled healthy labor/parts Machine cleaned off, dye shows cracks components for repairs lubrication Shock-pulse testing – a specialized Predictive Impending failures can Labor costs, costs for Vibration, IR analysis Vibration and oil form of vibration analysis used to detect be detected detection equipment analysis of a & work equipment and or large flaws in ball or roller bearings at high scheduled services purchased gearbox frequency (32kHz) services© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 47 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 48 8
  • 9. 10/16/2010 Maintenance Strategy Is Predictive Maintenance Implementation Cost Effective? Percentage of Maintenance Time by Strategy In most industries the average rate of 100% return is 7:1 to 35:1 for each predictive 80% maintenance dollar spent Predictive Vibration analysis IR thermography and analysis, 60% Preventive oil/water analysis are all economically 40% proven technologies Breakdown The real savings is the avoidance of 20% manufacturing downtime – especially 0% crucial in JIT 1 2 3 4 5 6 7 8 9 10 Year© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 49 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 50 Predictive Maintenance and How Predictive Maintenance Effective Reliability Improves Effective Reliability Effective Reliability (Reff) is an extension Example: a large gearbox with a reliability of Reliability that includes the probability of .90 has vibration transducers installed of failure times the probability of not for vibration monitoring. The probability of detecting imminent failure g early detection of a failure is .70. What is y Having the ability to detect imminent the effective reliability of the gearbox? failures allows us to plan maintenance Reff = 1 – (P(failure) x P(not detecting failure)) for the component in failure mode, thus Reff = 1 – (.10 x .30) = 1 - .03 = .97 avoiding the cost of an unplanned breakdown Vibration monitoring has increased the effective reliability from .90 to .97! Reff = 1 – (P(failure) x P(not detecting failure))© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 51 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 52 Effective Reliability Caveats Increasing Repair Predictive maintenance only Capabilities increases effective reliability if: 1. Well-trained personnel You select the method that can detect the most likely failure mode 2. Adequate resources You monitor frequently enough to have 3. Proper application of the three high likelihood of detecting a change in maintenance strategies component behavior before failure 4. Continual improvement to improve Timely action is taken to fix the issue and forestall the failure (in other words equipment/system reliability you don’t ignore the warning!)© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 53 © 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 54 9
  • 10. 10/16/2010 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Printed in the United States of America.© 2011 Pearson Education, Inc. publishing as Prentice Hall 17 - 55 10