Failure Prevention and recovery - PowerPoint Presentation

Slide1

Failure Prevention and recovery

Chapter -19 Slide2
Slide3

Summary

What is failure?

Why failures happen?

How do we measure failures?

Detection and analysis of failures.

How operations can improve their reliability?

How should the operations should recover from the failures? Slide4

Failure Slide5

Failure Slide6

Failure Slide7

Failure Slide8

What is failure?

At its simplest ‘failure’ is when something does not work as it should do. If the shop assistant who sells you an item of clothing ‘fails’ to inform you of the fact that it should be dry cleaned, it is technically a failure. Yet usually in operation management, we use the term failure to denote a more dramatic event. Usually we mean something stopping to do what it should do. So a piece of material fails, or a process fails.Slide9

Why do operations fail?

There are various reasons for the operations failures:

Design failures

Facilities failures

Supplier failures

Customer failures

Environmental failures Slide10

Design failures

A design may look fine on paper, but in real circumstances the limitations will become clearer.

Design failures happen due to two different situations:

Because miscalculating or overlooking a characteristic of demand – process fail to adjust with demand. For example a company process is designed to manufacture 3 televisions per hour, but the demand is to manufacture 7 televisions per hour. Slide11

Unexpected circumstances – product size on the design becomes different from demanded size. Slide12

Why systems fail

Design failures

Facilities failures

Staff failures

Failures inside the operation

Supply failures

Customer failuresSlide13

B. Facilities failure

Failures with machines, equipments, buildings, and fittings.

c. People failure

People failures come in two types:

Errors and Violations

Errors – are mistakes in judgments (run motorbike on reserve petrol)

Violations – are doing the things contrarily to the operating procedure. (driver avoiding changing the engine oil, causing major problems to engine)Slide14

D. Supplier failure

Failure in the delivery or quality of goods and services. (a music band of the hotel fails to turn – in)

E. Customer failure

Misuse of products and services from the production.

F. Environmental disruption-related failure

All the causes outside the

opration

. Example hurricanes, floods, lightning, temperature, fire, crime, theft, terrorism. Slide15

Measure failures

Failures are usual happening as human failure.

For example :

A machine failure may happen due to the poor design or maintenance .

A delivery failure by someone's errors to manage supply schedule.

Customers mistake, because no one to instruct the customer Slide16

So, failures can be controlled to an extent, again an organization learn from failures. Thereby we call failures as opportunities.

There are three main ways of measuring failure:

Failure rates – checking how often failure occurs.

Reliability - checking the chances of an occurrence of failure.

Availability – checking the amount of available useful operating time. Slide17

FR (Failure Rate) measuring

The number of failures occurring over a period of time. The failure of an airport security system can be measured by measuring the failure of security breaches.

FR=

number of failures

× 100

total numbers of products testedSlide18

Failure over-time – the ‘bath tub’ curve

Failure is a function of time. Different stages the probability for failing will be different.

The curve that describes failure probability is called ‘bath-tub’ curve. According to this curve the failure probability is high at beginning and end of the life cycleSlide19

There are three distinct stages.

The ‘infant-mortality’ or ‘early-life’ stage where early failures occurred by defective parts or improper use.

The ‘normal-life’ stage when the failure rate is usually low and constant.

The wear-out stage – when the failure rate increases as it reaching the end of its working life. Slide20

How

failure is measured

Time

Failure rate

‘Infant-mortality’ stage

Normal-life stage

Wear-out stageSlide21

Reliability measuring

It measures the ability of a system, product or service to perform as expected over time.

Rs = R1

×R2 ×R3 ×

Rn

…..

Rs = reliability of system

Here we consider that a single failure in a component of process causing failure to the whole components.

So the more the components in a system, the lesser will be the reliability. Slide22

MTBF (MEAN TIME BETWEEN FAILURES)

MTBF =

OPERAITNG HOURS

NUMBER OF FAILURES

Availability

The degree to which the operation is ready to work. An operation is not available if it has either failed or is being repaired followed by a failure. Slide23

Failure prevention and recovery

There are three sets of activities which relate to failure:

1. The first – understanding what failures are occurring in the operation and why they are occurring.

2.Second – examine or find the ways to reduce chances for failure and minimize consequences of failures.

3. Third – make plans and procedures to help the organization from recovering when they occur. Slide24

The three tasks of failure prevention and recovery

Failure detection and analysis

Finding out what is going wrong and why

Improving system reliability

Stopping things going wrong

Recovery

Coping when things do go wrongSlide25

Mechanisms to detect failure

There are six techniques to find out the failure:

In-process checks – employees check that the service is acceptable during the process itself (restaurants )

Machine diagnostic checks – a machine is tested by putting it through many activities. ( computer service)

Point of – departure – interviews - the staff may formally or informally check that the services has been satisfactory.

Phone surveys – used to solicit opinions about products or services.

Focus groups - group of customers are brought together to discover problems or finding out attitude towards products or services . Slide26

Complaint feed back cards and questionnaires

Many organizations using them for collecting views about products or services.

Failure Analysis

Understand why its has occurred.

Accident investigation – specifically trained staff analyze the cases of accident.( airplane, road accident)

Failure traceability - making sure an operation can trace (

fing

proof or evidence)

Complaint analysis – analyze the complaints.

Slide27

CIT or critical incident analysis

Finding out the satisfying and non – satisfying factors from customers. Slide28

How failure is detected and analyzed

–

in-process checks

–

accident investigation

–

failure mode-and-effect analysis

–

fault-tree analysis

Failure detection mechanisms include:

Failure analysis procedures include:

–

point-of-departure interview

–

machine-diagnostic checksSlide29

Failure mode and effect analysis

Identify the product or service or process that are important in determining the effect of failures. Or identifying failures before they happen by providing checklist procedures.

It has three steps

What is likelihood that failure will occur?

What would the consequence of failures be?

How likely a failure to be detected before affecting customers?. Slide30

Based on the above questions, we use the RPN or Risk Priority number and find out the cause of failure.

There are seven steps involved in this

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Failure

Severity of consequence

Effect on customer

Normal operation

Probability of failure

Degree of severity

Likelihood of detection

Risk priority number

Failure modes effects analysisSlide32

Fault-tree analysis

It is a logical procedure starting from a failure or potential failure and works back- wards to indentifying all possible causes and origins. Slide33

Fault-tree analysis for below-temperature food

being served to customers

Food served to customer is below temperature

Key

AND node

OR node

Cold plate used

Plate taken too early from warmer

Plate warmer malfunction

Oven malfunction

Timing error by chef

Ingredients not defrosted

Plate is cold

Food is coldSlide34

Improving process reliability

The responsibility of this step of operational managers is to prevent failures, we can do it by following 4 steps.

Design out fail points.

Build redundancy

Fail-

safeing

Maintenance Slide35

a. Design out fail points

We can do it by proper product/service designing, by quality planning and control, by process controlling.

b. Redundancy

Building redundancy to an operation means, having a back-up system. (airplane, kidney, two red lights in cars) Slide36

c.fail-safeing

Coming from Japanese methods of operations improvement. It is known as

Poka

-yoke in Japan, which means prevent. So the

Poka

-Yoke are devices used against failures. Slide37

3.5 inch diskette cannot be inserted unless it is orientated correctly. This is as far as a disk can be inserted upside-down. This feature, along with the fact that the diskette is not square, prohibits incorrect orientation. It is a control method.

Warning lights and chimes alert the driver of potential problems. These devices employ a control method

and

a warning method.

Poka-yoke (fail-safing)Slide38

Filing cabinets can fall over if too many drawers are pulled out. For some filing cabinets, opening one drawer locks all the rest, reducing the chance of the filing cabinet tipping. It is a control method.

The window in the envelope is not only a labour saving device. It prevents the contents of an envelope intended for one person being inserted in an envelope address to another. It is a control method.

Poka-yoke (fail-safing)Slide39

Examples for Poke-yoke techniques

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Maintenance

Maintenance is how organizations try to avoid failure by taking care of their physical facilities.

Benefits of maintenance

1. it enhances safety

2.It enhances reliability

3. It enhances quality

4. Low operation cost

5. Longer life

6. Higher end value ( can be sued as second hand)Slide40

Three basic approaches for maintenance

Run to breakdown ( RTB) - operate till something fails and do maintenance.

Preventive Maintenance – eliminate or reduce chances of failure by servicing the facilities.

Condition-based maintenance – perform maintenance only when facilities required. It is

appliccable

for expensive facilities. Slide41

Mix of maintenance approaches Slide42

A mixture of maintenance approaches is often used –

in a motor car, for example

Use condition-based monitoring maintenance

Use run-to-breakdown maintenance

Use preventive maintenanceSlide43

Total productive maintenance

Means the productive maintenance carried out by all employees through small group activities. So TPM means maintenance management.

Five goals of TPM

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Reliability-centered maintenance

It is another method of maintenance where different types of maintenance for different parts of a process. Slide45

One part in one process can have several different failure modes, each of which requires a different approach

Cutters

Shredding process

Failures

Time

Cutter ‘wear out’ failure pattern

Solution

Preventive maintenance before end of useful lifeSlide46

One part in one process can have several different failure modes, each of which requires a different approach

Cutters

Shredding process

Failures

Time

Cutter ‘shake loose’ failure pattern

Solution

Ensure correct fitting through trainingSlide47

Recovery

The activities designed to adjust with the failures are known as recovery.

Failure planning

The procedures which allow the operation to recover from failure is called failure planning Slide48

What’s happened

What consequences

Inform

Contain

Follow up

Find root cause

Engineer out

Analyze failure

Plan recovery

The stages in failure planning

Discover

Act

Learn

PlanSlide49

Procedures of business continuity

Avoid or recover from failures and keep business going.

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