Operations Management: Sustainability and Supply Chain Management

Third Canadian Edition

Chapter 17

Maintenance and Reliability

17 – #

If this PowerPoint presentation contains mathematical equations, you may need to check that your computer has the following installed:

1) Math Type Plugin

2) Math Player (free versions available)

3) NVDA Reader (free versions available)

Outline

Global Company Profile: Ontario Power Generation

The Strategic Importance of Maintenance and Reliability

Reliability

Maintenance

Total Productive Maintenance

Techniques for Enhancing Maintenance

17 – #

Learning Objectives (1 of 2)

When you complete this chapter you should be able to:

Describe how to improve system reliability

Determine system reliability

Determine mean time between failure (MTBF)

17 – #

Learning Objectives (2 of 2)

When you complete this chapter you should be able to:

Distinguish between preventive and breakdown maintenance

Describe how to improve maintenance

Compare preventive and breakdown maintenance costs

Define autonomous maintenance

17 – #

Ontario Power Generation (OPG) (1 of 2)

OPG operates the Pickering Nuclear Generating Station in Ontario

Supplies 13% of the provinces electricity supply

The Canadian Nuclear Safety Commission requires inspection at least every 10 years

Support from an additional 1900 extra staff is brought in to work with existing 2730 employees

17 – #

The Global Company Profile of the Ontario Power Generation provides a perfect lead-in to the power and importance of preventive maintenance. The risk for safety and electricity cut-offs is enormous without preventive maintenance. The costs would be staggering if there was a breakdown. Therefore careful planning to carry out preventive maintenance is crucial.

Ontario Power Generation (OPG) (2 of 2)

40,000 tasks related to the facilitys inspection and maintenance have to be carried out

Shutdowns between six to eight weeks are rotated between the various units

This ensures that electricity is not shut down completely

The maintenance contributes to an excellent record of reliability in electricity generation

17 – #

Strategic Importance of Maintenance and Reliability (1 of 2)

The objective of maintenance and reliability is to maintain the capability of the system

17 – #

Strategic Importance of Maintenance and Reliability (2 of 2)

Failure has far reaching effects on a firms

Operation

Reputation

Profitability

Dissatisfied customers

Idle employees

Profits becoming losses

Reduced value of investment in plant and equipment

17 – #

This list is not in the text. It provides a nice summary of the potential far-reaching implications of a system failure. Another potential disastrous consequence would be a safety hazard, possibly damaging the environment or even causing injury or death to employees, customers, or surrounding residents.

Maintenance and Reliability

Maintenance is all activities involved in keeping a systems equipment in working order

Reliability is the probability that a machine will function properly for a specified time

17 – #

The respective definitions of maintenance and reliability are provided in this slide. Slide 10 identifies two primary tactics for both. Slide 11 (Figure 17.1) illustrates that good maintenance and reliability management requires employee involvement and good procedures, resulting in enhanced company performance. The interdependence of operator, machine, and mechanic is a hallmark of successful maintenance and reliability.

Important Tactics

Reliability

Improving individual components

Providing redundancy

Maintenance

Implementing or improving preventive maintenance

Increasing repair capability or speed

17 – #

Maintenance Management

17 – #

Reliability

Improving individual components

Rs = R1 x R2 x R3 x x Rn

where R1 = reliability of component 1

R2 = reliability of component 2

and so on

17 – #

LO 1: Describe how to improve system reliability.

Any component or system must have some probability of failure. If someone thinks it is 0%, then that person probably rounded too much. And while 99% reliability may sound like a high figure, it depends upon the context. If a 99% daily reliable dishwasher is run every day for a year, chances are that it will fail at least three times during the yearnot very acceptable to most consumers. Furthermore, the cost of a failure should play a role in reliability. A manned rocket ship certainly needs to be more than 99% reliable, because the cost of a failure is catastrophic. Slide 12 presents the formula for the reliability of a system with n individual independent components that all must work in order for the system to work (referred to as components in series). (The independence assumption means that the probability of failure of one component has no correlation with the probability of failure of any of the other componentscertainly true for some systems but not others.) The calculation is a simple multiplication of terms, but the implications may surprise students. As Slide 13 (Figure 17.2) graphically illustrates, the degradation can compound quickly. Here are three more examples: 10 parts at 90% reliability each would produce a 35% reliable system (0.9010); 100 parts at 99% reliability each would produce a 37% reliable system (.99100); and 1000 parts at 99% reliability each would produce a 0.004% reliable system (.991000) that essentially would never work at all (think about how many parts go into an airplane). This simple reliability formula has a clear implication for new product development. That is, try to limit the number of components in series in the product design (for example, consider a single molded interlocking part instead of using a hinge with four separate screws).

Overall System Reliability

17 – #

Reliability Example

Reliability of the process is

Rs = R1 x R2 x R3 = .90 x .80 x .99 = .713 or 71.3%

17 – #

LO 2: Determine system reliability

Product Failure Rate (FR)

Basic unit of measure for reliability

Mean time between failures

17 – #

LO3: Determine mean time between failures (MTBF).

The basic unit of measure for reliability is the product failure rate (FR). It can be described as the percentage of failures among the total number of products tested (FR(%)) or as the number of failures during a period of time (FR(N)). Firms producing high-technology equipment often provide failure-rate data on their products. Perhaps the most common term in reliability analysis is the mean time between failures (MTBF), which is the reciprocal of FR(N). This slide provides the formulas for all three measures. Slide 16 presents Example 2 from the text illustrating all three measures. Notice how the Operating time in the FR(N) calculation subtracts out the downtime during the two failures that occurred. Slide 17 converts the FR(N) value into a failure rate per trip, by multiplying the operating hourly failure rate by the length of a trip (24 hours times 6 days).

Failure Rate Example (1 of 2)

20 air conditioning units designed for use in NASA space shuttles operated for 1000 hours One failed after 200 hours and one after 600 hours

Failure rate per trip

FR = FR(N)(24 hrs)(6 days/trip)

FR = (.000106)(24)(6)

FR = .153 failures per trip

17 – #

Providing Redundancy

Provide backup components to increase reliability

17 – #

While it may be possible to increase the reliability of individual components, a more cost-effective approach may be to provide a backup for certain components. This is called redundancy, and the components are said to be operating in parallel. Interestingly, the reliability of the backup does not even need to be particularly high (say 50%) to improve overall component reliability substantially. Slide 18 provides the formula along with a sample problem. (Note that for this example, even if the backup had been only 50% reliable, the new reliability with redundancy would still have jumped from 80% to 90%.) Slide 19 (Example 3) provides a reliability example that combines components in series with components in parallel. Perform all of the backup calculations first for each component; then multiply all of the revised component reliabilities together.

Redundancy Example

A redundant process is installed to support the earlier example where Rs = .713

Reliability has increased from .713 to .94

= [.9 + .9(1 ? .9)] × [.8 + .8(1 .8)] × .99

= [.9 + (.9)(.1)] × [.8 + (.8)(.2)] × .99

= .99 × .96 × .99 = .94

17 – #

Slide 19 (Example 3) provides a reliability example that combines components in series with components in parallel. Perform all of the backup calculations first for each component; then multiply all of the revised component reliabilities together.

Maintenance

Two types of maintenance

Preventive maintenance routine inspection and servicing to keep facilities in good repair

Breakdown maintenance emergency or priority repairs on failed equipment

17 – #

This slide describes the two basic types of maintenance. Performing more of the first usually mean having to perform less of the second.

LO 4: Distinguish between preventive and breakdown maintenance.

Implementing Preventive Maintenance

Need to know when a system requires service or is likely to fail

High initial failure rates are known as infant mortality

Once a product settles in, MTBF generally follows a normal distribution

Good reporting and record keeping can aid the decision on when preventive maintenance should be performed

17 – #

Slide 21 identifies issues surrounding the implementation of preventive maintenance. Reliability and maintenance are of such importance that most systems are now computerized. Slide 22 (Figure 17.3) presents a schematic of a computerized maintenance system.

Computerized Maintenance System

Figure 17.3

17 – #

Maintenance Costs (1 of 3)

The traditional view attempted to balance preventive and breakdown maintenance costs

Typically this approach failed to consider the true total cost of breakdowns

Inventory

Employee morale

Schedule unreliability

17 – #

These slides address the traditional vs. an enlightened view regarding the amount of preventive maintenance to perform. Since the full cost of a breakdown may involve so much more than the repair cost itself (e.g., extra safety stock, safety, morale, customer relations, etc.), the implication is that the cost curve looks more like Slide 25 than Slide 24, implying that sufficient preventive maintenance should be performed to ensure that the system almost never breaks down.

Maintenance Costs (2 of 3)

Figure 17.4a

17 – #

LO 6: Compare preventive and breakdown maintenance costs.

Maintenance Costs (3 of 3)

Figure 17.4b

17 – #

Maintenance Cost Example (1 of 4)

Should the firm contract for maintenance on their printers?

Number of Breakdowns Number of Months That Breakdowns Occurred
0 Blank 2
1 Blank 8
2 Blank 6
3 Blank 4
Blank Total : 20
Average cost of breakdown = $300

17 – #

These slides (Example 4) illustrate a cost analysis for preventive maintenance. No preventive maintenance would cost the firm $480 per month in breakdown costs. Purchasing a service contract for preventive maintenance would reduce the expected number of breakdowns per month from 1.6 to 1. Even after adding the cost of the service contract, the preventive maintenance option in this example was more cost effective, saving an estimated $30 per month.

LO 6: Compare preventive and breakdown maintenance costs.

Maintenance Cost Example (2 of 4)

Compute the expected number of breakdowns

Number of Breakdowns Frequency Number of Breakdowns Frequency
0 2/20 = .1 2 6/20 = .3
1 8/20 = .4 3 4/20 = .2
Copyright © 2020 Pearson Canada Inc.

17 – #

Maintenance Cost Example (3 of 4)

Compute the expected breakdown cost per month with no preventive maintenance

17 – #

Maintenance Cost Example (4 of 4)

Compute the cost of preventive maintenance

Hire the service firm; it is less expensive

17 – #

Increasing Repair Capabilities

Well-trained personnel

Adequate resources

Ability to establish repair plan and priorities

Ability and authority to do material planning

Ability to identify the cause of breakdowns

Ability to design ways to extend MTBF

17 – #

A good maintenance facility should have the six features identified in this slide.

How Maintenance is Performed

Figure 17.5

17 – #

Since not all repairs can be performed in the firms facility, managers must decide where repairs are to be performed. This slide (Figure 17.5) provides a continuum of options and how they rate in terms of speed, cost, and competence. Moving to the right may improve the competence of the repair work, but at the same time it increases costs and replacement time.

Autonomous Maintenance

Employees accept responsibility for

Observe

Check

Adjust

Clean

Notify

Predict failures, prevent breakdowns, prolong equipment life

17 – #

Autonomous maintenance is consistent with employee empowerment (Chapters 6 and 10). System performance is enhanced when operators take ownership in their equipment and help to prevent breakdowns.

LO 7: Define autonomous maintenance.

Total Productive Maintenance (TPM) (1 of 2)

Designing machines that are reliable, easy to operate, and easy to maintain

Emphasizing total cost of ownership when purchasing machines, so that service and maintenance are included in the cost

17 – #

Many firms have moved to bring total quality management concepts to the practice of preventive maintenance with an approach known as total productive maintenance (TPM). This strategic view of maintenance includes the points described on these two slides.

Total Productive Maintenance (TPM) (2 of 2)

Developing preventive maintenance plans that utilize the best practices of operators, maintenance departments, and depot service

Training for autonomous maintenance so operators maintain their own machines and partner with maintenance personnel

17 – #

Techniques for Enhancing Maintenance (1 of 2)

Simulation

Computer analysis of complex situations

Model maintenance programs before they are implemented

Physical models can also be used

17 – #

The techniques described in this slide have proven beneficial to effective maintenance. An example of a physical simulation model would be vibrating an airplane to simulate thousands of hours of flight time to evaluate maintenance needs.

Techniques for Enhancing Maintenance (2 of 2)

Expert systems

Computers help users identify problems and select course of action

Automated sensors

Warn when production machinery is about to fail or is becoming damaged

The goals are to avoid failures and perform preventive maintenance before machines are damaged

17 – #

Summary

Reliability improvements can be made through the use of preventive maintenance

Firms should give employees ownership of their equipment to enhance preventive maintenance

Reliability of equipment will drive out variability of systems and leads to that customers can rely on products and services to be carried out to specifications and on time

17 – #

Number of failures

FR(%)100%

Number of units tested

=´

Number of failures

Number of unit-hours of operating

)

(

MTBF

)

(

FR(%)(100%)10%

FR.000106 failure/unithr

20 0001200

()

–

MTBF 9434hrs

.000106

(

)

(

)

(

)

ProbabilityProbabilityProbability

of firstof secondof needing

second

componentcomponent

workingworkingcomponent

.8.81.8

.8.16.96

éù

æöæöæö

êú

ç÷ç÷ç÷

+´

êú

ç÷ç÷ç÷

êú

èøèøèø

ëû

+´

(

)

(

)

(

)

(

)

(

)

(

)

(

)

(

)

éù

æöæö

=´

ç÷

èøèø

ëû

+++

Number ofCorresponding

Expected number

of breakdowns

breakdownsfrequency

0.11.42.33.2

1.6 breakdowns per month

(

)

(

)

æöæö

=´

ç÷ç÷

èøèø

ç÷

èø

ExpectedExpected numberCost per

breakdown costof breakdownsbreakdown

1.6$300

$480 per month

(

)

(

)

æö

ç÷

èø

æö

ç÷

èø

Cost of expected

PreventiveCost of

breakdowns if service

maintenance costservice contract

contract signed

1 breakdown/month$300$150/month

$450 per month

Applied Sciences
Architecture and Design
Biology
Business & Finance
Chemistry
Computer Science
Geography
Geology
Education
Engineering
English
Environmental science
Spanish
Government
History
Human Resource Management
Information Systems
Law
Literature
Mathematics
Nursing
Physics
Political Science
Psychology
Reading
Science
Social Science
Home
Homework Answers
Blog
Archive
Tags
Reviews
Contact
google+twitterfacebook
Copyright © 2021 HomeworkMarket.com

Operations Management: Sustainability and Supply Chain Management

Operations Management: Sustainability and Supply Chain Management

Our Service Charter

Format and Features

Our Advantages

Useful Links

Recent Posts

Recent Comments

Archives

Categories

Search

Meta