invited talk nccm 2013

8/12/2019 Invited Talk NCCM 2013

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Reliability ofEngineered Systems

By

Dr. Edwin Vijay Kumar

Assistant General Manager (Technical Services)

VIZAG STEEL


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Lecture Outline

Engineer Society Expectations

Why Reliability is important?

How is Reliability affected?

Reliability Degradation Maintenance

Strategies for Reliability

Condition Monitoring Reliability Relation


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Expectations of Society fromEngineering Fraternity

Less struggle more comfort

Health

Clean environment

Secure world

Longer & Happy life


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Business Values

Essentially, there are three kinds ofbusiness values to look for whenconsidering Engineered Systems:

Making Human Life Comfortable

Making more money

Saving money


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Examples:

Making Life Comfortable :

Driver less car

Making More Money:

Mobile Communication systems

Saving Money:Energy efficient Home Appliances


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Backbone for achieving BusinessValues

Technology:

User Friendly

Effectiveness:Doing the right task, completingactivities and achieving goals.

Reliability:

Delivering Intended Functionalitywhen

needed


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Engineering Managers Role

Managing engineering assets to deliver

maximum outputwith effectiveuse of

resources with assured reliability


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Constraints to Engineering Manager

Uncertaintyin assets performance

Shortageof resources

Assets degradation


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Cost of Unreliability

Industry Specific

Product Specific

User Specific

Location Specific


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Degradation Asset/EquipmentPerformance Characteristic

t1 tn

Stressor

tf

1.0

Minimal Repair

UnacceptablePerformance

Degradationpattern

Time (Age/Usage)

Performance

Major Overhaul

ReducedPerformance

0


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Performance Failure Characteristic

Pattern 2

Pattern 3Alert Level

Alarm Level

Time (Age/ Monitoring period)

IndicatorLevel(Normalized)

Operating Level

t11t0

1t1t0

Degradation pattern 1

1.0Reliability

P-F Interval

P-F Interval


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Classical Belief on Equipment Failures

All equipment fail after using forsome time.

Early replacement of componentsprevent failures.

Regular Inspection/Maintenanceactivities help to identify impending

failures.

More maintenance - Less failures.


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Basis for development of RCM

Classification of Component Failures


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Stanley NowlanHoward Heap

By 1985 it was a well established system & applied to nuclear stations.

History of RCM

RCM developed in the airlineindustry during the late 60s

-------MSG-1 applied to BOEING 747

------MSG-2 applied to Lockheed 1011,

Douglas DC 10, Airbus A-300, Concorde.

Nowlan & Heaps 1978 book, Reliabi l i ty-Centered Maintenance, showed that a

strong correlation between age and failure rate did not exist, thus the basic

premise of time-based preventive maintenance was false for the majority of

equipment.In 1978 for aviation industry

1970s

-----RCM--Stanley Nowlan & Howard Heap

[MSG-3 applied to BOEING 757 & 767]

1990s RCM-II --- Applied in more than 1000 industries

in 50 countries

Pioneers


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RCMs foundation lies on

Failure Mode Identification

Failure Mode Progression Monitoring

Root Cause analysis of Failure

Elimination/Mitigation of Failure Mode

Review of Maintenance Strategy


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RCM Definition

RCM is an analytical process used to

determine the maintenance

requirements of plant equipment intheir operating context.

Reliability is the probability that an asset

will perform its intended function for aspecified period of time under specified

operating conditions.


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Location

Temperature

Salinity

Humidity

SpeedAcceleration

Pressure

Depth

Altitude

Operating Context:

Systems operate in environment consisting of

Atmosphere


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Operating Context Influence on Motor Failures

Failure ModeFailure Causes

Motor A ( Indoor) Motor B ( Cellar)

1 Bearing Seizure Lack of LubricantBearing Defect

Lack of Lubricant

Ingress of water

Bearing defect

High humidity

2 Winding burnt Over loadInsulation damage

Under voltage

Fluctuating load

Over load

Insulation damage

Under voltage

Water logging

Damp surroundings

High ambient Temperature

Corrosive vapors

Fluctuating load3 Coupling Failure

(Rubber Bushes)Worn out

Fatigue failureWorn out

Fatigue Failure

Chemical action

Thermal stresses

High humidity


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Some Frequently asked questions

Is there any cost incurred if Run-to-Failuremaintenance ispracticed on a certain equipment?

What is the cost of performing Preventive Maintenanceonan equipment?

What type of condition monitoring technologies are

available? How much do they cost to install and maintain?What is the cost of Predictive Maintenance?

Will it really improve the bottom line result of ProactiveMaintenance?

The general questions above dont have simple

answers. Each of these general questions need to be

answered individually with reference to criticality of

the equipment...


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Maxim

OLD

Maintenance is about preservingphysical assets

NEW

Maintenance is about preserving thefunctions the of assets


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Safety and environment are to be given utmostimportance in defining function

Crux of RCM Strategy


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Q.1 What is a Function?

Any physical asset is put into service because it is

intended to do something.

So it follows that when we maintain an equipment, the

state must be preserved to continue its intended

function.


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Q.2 In what ways does it fail to fulfill itsfunctions? (Functional Failure)

Q.2 What is Functional Failure?

Functional failure : A functional

failure is the inability of an itemto fulfill a function to a standard

of performance acceptable to theuser.


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RCM divides functional failures in to two

categories

evident failures

hidden failures

Evident failure: a failure that, by itself, becomes

obvious to the crew or operator while they are

performing their normal duties.

Hidden failure: a failure that is not evident to the

crew or operator while performing normal duties


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Potential Failure


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Q.3 What causes its functional failure?

(Failure Modes )

Q.3 What are Failure Modes?

FAILURE MODES: is a specific physical condition

that causes a functional failure.

Failure modes represent the primary focus of the

RCM analysis.

RCM analysis seeks to identify maintenance tasks

that will prevent the consequences that result when

failure modes are allowed to occur.


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CMMS

Faithful recording of data

Technical manuals

OEM recommendations

Hands - on experience

History data

Documentation MTBF data from OEM.(for new eqpt. )

Sources for identifying Failure Modes:


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RCM FMEA

Failure modes are to be analyzed down to a level where the root cause is found


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Q.4 What happens when each failureoccurs ? (Failure Effects)

Q.4 What are Failure Effects?

Failure effect: is the impact that a functional

failure has on the item under analysis, the

surrounding items, and the functional

capability of the end item.

A failure effect should be described in terms ofphysical damage, including both primary and

secondary damages that may occur.


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Q.5 In what way does each failure matter ?(Failure Consequences)

Q.5 What are Failure Consequences?

Failure consequences stem from functional

failures. They are of f ive categor ies:

Safety

Environmental

Operational

EconomicNo effect


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Q.6 What are Proactive Tasks?

Task selection is the last major step in the

RCM analysis process. It looks at each

output from the task evaluation process

andallows selection of the optionthat best

reduces the probability of failure

consequences to an acceptable level.

Applicability and Effectiveness:

A maintenance task to be selected and must satisfy two criteria:

It must be Technically Feasible and must be Worth Doing

Q.6 What can be done to predict or preventeach failure ? (Proactive Tasks)


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They embrace what is traditionally known asPredictive or Preventive Maintenance

RCM uses the terms

proactive tasks :Tasks undertaken before failureoccurs, in order to prevent the item from getting intoa failed state.

scheduled restoration,scheduled discard and

on-condition maintenanceFailure Finding Tasks


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Q.7 What should be done if a suitable proactive task

cannot be found ? (Default Actions)

Q.7 What are Default Actions?

Default actions:

These deal with the failed state, and

are chosen when it is not possibleto identify an effective proactivetask. Default actions includeredesign and run-to-failure.


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Question: Proactive MaintenanceWill it really improve the bottom line result of Proactive Maintenance?

Is it that a symptom treated over and over again? Thesame equipment keeps breaking down andreplaced/maintained?

How much money it costs (Loss) due to treating justthe symptom - and not the root cause - of theproblem?

These questions on proactive maintenance are toughto answer, so lets just table them (we will get back to

them) and take a look at Predictive Maintenancetechnologies.


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Predictive Maintenance Data

What data needs to be collected on each piece ofequipment? How to collect this data? What kind ofhardware it needs?

More data is better. Do not fall into this trap!

Collecting too much data costs money, obscures theproblem, & is a pain.

What data would provide a quick indication of thecondition of the equipment?

Just as a doctor takes a patients temperature and pulse

to get a quick indication of that patients health, whatwould give a quick indication of the health of anequipment?

The answer to this question depends on the type ofequipment complexity, criticality and operating context


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Some Predictive Maintenance Technologies

Vibration Analysis

Bearing Shock pulse analysis

Laser Alignment & ShaftBalancing

Thermography

Ultrasonic Testing

Motor Current SignatureAnalysis

Oil Analysis

Wear Debris Analysis


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Questions Please


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Thanks

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