Equipment Efficiency: Availability, P erformance and M aintenance

1/80

Equipment Efficiency:Availability, Performance

and MaintenanceOperations Analysis and Improvement

2010 Fall

Dr. Tai-Yue WangIndustrial and Information Management Department

National Cheng Kung University

2/80Dr. Tai-Yue Wang IIM Dept. NCKU

Presentation

The role of maintenance is to insure the survivability and proper functioning of all company hardware. Most maintenance departments are considered “a

necessary evil”. Investments required to improve production processes

usually take on a low priority.


Presentation

Maintenance evolution, as well as maintenance technique evolution, has developed in parallel for many companies. Remediate hardware failures. Prevent future problems with the equipment. Incorporate basic maintenance tasks into their daily

production routine. Predicting equipment breakdowns.


Introduction

Maintenance’s primary objective is to maintain, at a high operative level, the productive resources in order to assure their service at an expected cost.

Maintenance is the “machine’s medicine”. Determine the right moment to replace the

equipment. It may be better to simply unplug it.


Introduction Elements that need maintenance.

Machines and tools. Facilities (compressed air, heating,

…) Buildings (walls, illumination,…) Information and transportation

systems.

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Introduction Some companies subcontract

maintenance. Is contemplated in both the

Just-in-time and the 20 keys (key number 9) for lean. Improves the availability and

performance rates of the equipment.

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Types of maintenance Corrective -> All industrial equipment is

exposed to transitory (wear) or definitive breakdowns (catastrophic failure). Affecting its functionality and performance. Can represent high costs for enterprises.

Preventive -> The maintenance mission cannot only be repairing the breakdowns. They should be able to get ahead of the breakdowns.


Corrective maintenance Also called breakdown maintenance.

Up to the 1950s it was virtually the only maintenance.

Machine stoppages hardly affected productive time. Repairs were carried out in an effective way.

Equipmentperformance Substitution

Repair

Time until failure

Repair time

Time


Types of corrective maintenance

Urgent repairs. Reestablishing the equipment into service. Repair is carried out is temperally. The remainder of the tasks will/can be

scheduled for a future time.


Types of corrective maintenance

Scheduled corrective. Appears as a result of urgent repairs.

Determine an appropriate time to repair the machine completely.

After repairing the damaged component As good as new. At least as it was before.


Repair problems

Repair tasks are performed quickly and under pressure, which can cause future problems.

Repair time can be very high because replacement part(s) may have to be ordered from a supplier.


Repair problems Accidents can take place because of poor maintenance

safety measures. Corrective maintenance policy implies higher labor

costs. This policy can be justified in some cases.

Equipment with a frequent replacement policy. Like personal office computers.

When breakdown costs are small. Light bulbs fail.


Types of preventive maintenance

The preventive maintenance has two variants. Systematic preventive maintenance. Conditional preventive maintenance or predictive

maintenance.


Systematic preventive maintenance

1960s -> the General Electric Corporation systematized a new type of maintenance called planned maintenance.

Equipmentperformance

Substitution

Theoretical time until failure

Intervention duration

Time


Repair

Time until failure

Repair time

Time



Planned maintenance arrived to Japan. The bases of this systematic

preventive maintenance process were established.

Systematic substitution of some machine components.


Substitution



Time


Repair

Time until failure

Repair time

Time



Applied to general wear or use components. Know with precision the

component’s performance characteristics.


Substitution



Time


Repair

Time until failure

Repair time

Time



Replacement policy might call for a component to be replaced every week or in other ways such as, every 300 working hours or every 1000 parts produced. Equipment

performanceSubstitution



Time


Conditional preventive maintenance

Also called predictive maintenance.

Systematic preventive maintenance can become very expensive.


Substitution



Time

Inspections


Substitution



Time



Conditional preventive maintenance is used to change components depending on their current state. The useful life for costly

components can be extended. This type of maintenance best

fits components where performance can be monitored.


Substitution



Time

Inspections


Substitution



Time



ISO 14000 (environmental norm) requires that industry avoid systematic preventive maintenance when working with environmentally harmful products.


Substitution



Time

Inspections


Substitution



Time



Predictive maintenance. Look for correlations between

multiple parameters and the degradation of a component.

Temperature (thermocouples), Noises (phonometer). Cracks (X-rays machine). Pressure losses (manometer).

QS9000 recommends predictive maintenance.


Substitution



Time

Inspections


Substitution



Time


Maintenance program implementation

Almost all machines follow a similar lifecycle. Hidden small defects.

Difficult to detect and to observe -> It does not interfere with functionality.

Increase of friction in an axle.

Apparent small defects. Are more noticeable -> They are normally not

repaired. Small vibrations on a machine.



Execution under expectations. The defects affect the equipment productivity. the standards of quality will be violated.



Almost all machines follow a similar lifecycle. Intermittent stops.

The machine intermittently produces defect parts. Small repairs are performed.

Stops and breakdowns. Breakdowns are frequent.

Production equipment may not be as new as we would like them to be. “Stops and breakdown” stage.



Production equipment typically becomes more sophisticated/complex. More expensive every year. It has greater economic impact.

Repairs should be done at a faster rate.

Working shifts can also represent an obstacle for maintenance interventions. Limits possible maintenance tasks and scheduling.



The objective of maintenance is to efficiently oversee equipment throughout the equipment life cycle. Cover the entire lifecycle

Implementing an effective corrective maintenance. Preventive maintenance tasks. Implementing predictive maintenance strategies.


Getting started

Become familiar with the resources that will require maintenance. Each maintained resource should be coded (resource

id#). Code the types of breakdowns and maintenance

tasks. In a historical data study -> Group failure causes.


Getting started

Maintenance should have the following two documents. Facility Inventory.

Lists all equipments and their principle characteristics. Code, record number, equipment type,…

Equipment History Files. Data given by the equipment manufacturer. Information about the location in the plant. Types of spare parts needed. …


Corrective maintenance implementation

Organize, in an effective way, the corrective maintenance procedures and actions. Breakdown occurs -> Fill out a breakdown work

order. If the worker can solve it -> fill a report. If not -> the work order will be sent to the maintenance

department. Work request order will be issued. Maintenance workers will either repair the machine immediately

or will schedule the repair. The repair can be provisional or definitive.


Scheduled corrective maintenance

Variability in the corrective maintenance tasks duration can be problematic. Corrective orders and flow diagrams for repetitive repairs

must be developed. Materials and spare parts that should be utilized.

Maintenance workers’ tasks do not end with the equipment repair. They should gather all the breakdown information. Describe the process that was performed.



Each machine should have its own file with breakdown records. Analyze breakdown causes. Anticipate future problems. This file must be upgraded with each maintenance

intervention.



Corrective maintenance tasks do not only consist on changing the broken or malfunctioning components. Study the causes and the frequency of the

breakdowns.


Preventive maintenance implementation

Avoid a breakdown of any resource, while keeping maintenance cost as low as possible.

Two types of actions. Inspections.

Observe and detect possible anomalies. Frequent checkups that follow a specific inspection plan.

Revisions. Scheduled equipment stops.

Systematic substitution of several machine components. Carried out during the weekend.



Preventive maintenance tasks’ scheduling is mandatory in the ISO norms.



These tasks can be planned daily, weekly, monthly or even annually. Scheduled at times when they do not affect the

factory’s production plan. Daily working problems force us to continuously

reschedule these tasks.



Equipment preventive maintenance tasks are also called PM orders. Each PM order should be based on a study of the

equipment breakdown causes. FMEA tool described at the tools section.


Autonomous maintenance

PM orders carried out by the production workers. Known as user maintenance orders.

They should be simple and graphically represented. Many inspection tasks should be carried out every

day.



Significant amount of notices that could be easily handled by the production worker. It takes more time to fill out the request order than to

fix the problem



Autonomous maintenance includes these small tasks and three daily preventive measures. Cleaning, lubricating and checking.


Autonomous maintenance. Safety

Safety is one of the most important restrictions. Autonomous tasks apply only for simple repair

operations. Repair or maintenance should never be

performed if the knowledge required to fix the machine is high.


Autonomous maintenance. Safety

It can be very challenging to convince production workers about the importance of maintenance tasks. They do not consider their responsibility.



Autonomous maintenance implementation process has a specific methodology.

Initial cleaning1

Countermeasures to Sources of Contamination

2

Cleaning and Lubricating Standards

3

Overall inspections4

Autonomous Maintenance Standards5

Process Quality Assurance6

Autonomous Supervision7


TPM - Total Productive Maintenance

In the 1970s, Nakajima developed in Japan TPM. New maintenance management philosophy.

English translation was not published until 1988. JIPM – Japanese Institute of Plants Maintenance.

Grants the PM prize to the TPM top excellent companies. 60% of the winning companies during the first 17 years are now part

of the Toyota Group or suppliers of this Group.


TPM - Total Productive Maintenance

Nakajima combined preventive maintenance theories with the total quality concept. Nakajima developed the Overall Equipment

Efficiency ratio.


TPM keys

Maximize the Overall Equipment Efficiency. Eliminating the six big losses.

Autonomous maintenance implementation. In order to terminate the “I operate, you repair”

mind set. Preventive engineering.

Improving the equipments’ maintainability.


TPM keys

Training workers for maintenance improvements. Propose methods for increasing the equipment

availability. Initial equipment management. The objective of the TPM -> Zero Breakdowns.

Utilize tools such as the P-M analysis -> Explained in tools section.


RCM - Reliability Centered Maintenance

RCM was created in the United States in the 1960s, to optimize the reliability of aeronautical equipment. RCM was not utilized in nuclear power stations

until the 1980s. Recently has been implemented in the industrial

world.


RCM - Reliability Centered Maintenance

Needs a complete maintenance and breakdown record for each item of equipment. RCM objective is to determine the maintenance

tasks that are more effective for the critical components.

FMEA, reliability analysis, statistical techniques. It is necessary to have a preventive maintenance

program implemented and running properly.


FMEA for equipment

All defects have a root cause, and to eliminate future defects an action must be carried out. Defect -> Gap between two elements Cause -> Lack of lubrication or a loose fastener. Action -> Grease or tighten the lose element.


FMEA for equipment

To determine a good preventive maintenance plan, all the possible breakdowns, their causes and their corrective actions must be analyzed. The main tool to carry out this type of analysis is the

FMEA for equipment (Failure Mode and Effects Analysis).

Is a guide to analyze, in an organized manner, causes of possible equipment breakdowns.

A group of workers is gathered to study the problems and failures


EQUIPMENT CARRIED OUT BY DATE

PAGE OF

Equipmentfunctions Failure modes Faiulre efects Failure causes

Actualcontrols

Recommendedactions Responsible

FMEA for equipment


FMEA for equipment

Equipment functions. The functions that the equipment carries out.

Provides compressed air during specific conditions.

Failure modes. All the possible ways that the equipment can be

forced to stop. Breaks, blockage, leaks, etc.


PAGE OF


Actualcontrols



FMEA for equipment

Failure effects. All possible consequences of each failure are

analyzed in detail. Severity (S).

1 being not very serious. 4 very serious or 10.


PAGE OF


Actualcontrols



FMEA for equipment

Failure causes. The origin of the failure is analyzed. Identify the anomaly that can lead to the failure.

Probability (P). 1 not very frequent. 4 very frequent or 10.


PAGE OF


Actualcontrols



FMEA for equipment

Actual controls. If, at the present time, some kind of control is carried

out. Detection (D)

1 if the control does not always detect the cause 4 if it always detects or 10.


PAGE OF


Actualcontrols



FMEA for equipment

After the first part of the FMEA table has been completed, the Risk Priority Number (RPN) is calculated. The product of the three quantified variables (S,

P and D). Ranking failures by RPN.

Analyze the causes that do not represent any threat. Special attention must be paid to those effects that

have been considered critical.


FMEA for equipment

The chosen plan of action and the employee responsible for carrying out this plan are registered in the same table utilized in the FMEA. After a FMEA application arises, the necessity

of developing a preventive maintenance plan is recommended.


FMEA for equipment

Preventive maintenance intervention periods (T). Know the component damage/wear behavior

curve. Breakdowns and the time when the breakdowns

occurred -> Mean Time Between Failures (MTBF). T is based on the corrective percentage that the

company would like to support (K).


Substitution

MTBF

MTTR

Time

T = K·MTBF


Reliability

Reliability is defined as the probability that an equipment will work satisfactorily, during a certain period of time under some specific working conditions.

Reliability is a probability. Relative frequency of breakdowns.


Reliability

All production equipment should work satisfactorily. Failure can be triggered by an abrupt change in the

component characteristic or by progressive damage. Work satisfactorily for a specific period of time.

Maintain quality standards during a reasonable period of time.

RELIABILITY = QUALITY + TIME


Reliability

The component life or equipment life duration depends on working conditions. Environmental (temperature or humidity). Operational (continuous starts and stops,

electrical strain).


Reliability

The system state depends on the primary group of elements that makes it work properly. Each element has a random lifetime.

Estimate the lifetime of the components.

Reliability -> MBTF (Mean Time Between Failure)

failuresof Number time Operating

MTBF


Reliability and Maintainability

Maintainability -> probability that it must be repaired in a predetermined time following a specific repair procedure.

failuresof Number time total Failures

MTTR


Reliability and Maintainability

Maintainability depends on different factors. Machine factors.

Accessibility or interchangeability among components. Organizational factors.

Maintenance staff knowledge, documentation availability,… Operative factors.

Ability of the manpower.

Is quantified through the MTTR (Mean Time To Recovery).

failuresof Number time total Failures

MTTR


Reliability and Statistical availability

Average between the middle time used in the equipment and the required production time

If the different times between breakdowns as well as each repair duration time are graphically represented this process.

tTBF1 TBF2 TBF3

TR1 TR2 TR3

MTTR MTBFMTBF

ty availabili lstatistica


Reliability - the Bathtub curve

Is a graphic representation of the failure rate (t). Probability that an element fails depending on its

life use stage or status. ZONE I. Infant period. ZONE II. Useful period. ZONE III. Waste period.

time

(t)

ZONEI

ZONEII

ZONEIII


Reliability – The bathtub curve: Zone I

Equipment set up and debug process. Goes downhill because, as time moves

forward, the probability of a component failure decreases.

The problems in this area can be avoided by making intensive tests or by exchanging troublemaker elements at an early stage adjustment period.

time

(t)

ZONEI

ZONEII

ZONEIII


Reliability – The bathtub curve: Zone II

Zone II. Failures randomly appear. Electronic systems.

The curve formed is virtually horizontal.

In mechanical systems. The curve normally has a slightly

positive slope.

time

(t)

ZONEI

ZONEII

ZONEIII

time

(t)

ZONEI

ZONEII

ZONEIII


Reliability – The bathtub curve: Zone III

Zone III. Failures come from components far

more quickly. Critical components replacement is

strongly recommended.

time

(t)

ZONEI

ZONEII

ZONEIII

time

(t)

ZONEI

ZONEII

ZONEIII


P-M Analysis

Defects reasons. Sporadic(零星 ) losses. Chronic(慢性 ) losses.

Sporadic losses can be corrected using tools already studied.

Defects

Time

sporadic losses

zero losses

chronic losses


P-M Analysis

The P-M analysis is responsible for eliminating chronic losses. Considered “natural” according to their root sources. P - > Phenomenon. M - > Mechanism.

Defects

Time

sporadic losses

zero losses

chronic losses


P-M Analysis

Reliability that has been studied has two aspects to consider. Intrinsic reliability.

Due to the design and production of the component. Operative reliability.

Due to the component use and the maintenance process.

Defects

Time

sporadic losses

zero losses

chronic losses


P-M Analysis

P-M analysis should be applied after conventional improvement.

Six sigma is also suitable to carry out this type of study.

Defects

Time

sporadic losses

zero losses

chronic losses


Maintenance management

A maintenance department should properly manage and control their costs.

Unlimited number of indicators that can be used for maintenance department performance. Manpower performance, hours dedicated to urgent

work, repair cost, availability,...


Maintenance management

Maintenance management is a difficult task because it frequently does not have management’s support. As long as the maintenance department does not

exceed its assigned budget, no one pays much attention to the maintenance department activities or expenses.


Maintenance costs

Using economic terms, maintenance management helps to control deviations in the firm’s budget and also to determine investment needs to reduce the costs.


Maintenance costs

There are two alternatives or opposing costs. Non-maintenance costs.

Opportunity costs, quality costs, production manpower cost, etc.

Maintenance costs. Breakdown prevention costs, anomalies detection cost,

inspection resources costs, etc.


Maintenance costs

(1) -> Maintenance investment increases the equipment availability and at the same time

(2) -> An increase of the availability, supposes large investments.

Cost

Availability

Non-maintenancecosts

Maintenance costs

Total costs

0 % 100 %

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Summary

This chapter has provided an overview of maintenance activities, a critical aspect of Lean Manufacturing. Maintenance planning and monitoring activities are critical factors for Lean Enterprise efficiency.


Summary

Unfortunately, maintenance is normally perceived as a necessary evil, and is not always seen as a critical engineering activity. This chapter has outlined some of the maintenance policies and procedures that can be used to obtain the goal for any production system: operate as efficient as possible at the lowest cost.

Equipment Efficiency: Availability, P erformance and M aintenance

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