study of failure of critical equipments

8/13/2019 Study of Failure of Critical Equipments

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Study of Failures of Critical Equipments ofUnit 5/6/7/8

Under Guidance of

MR. M.K. VAIDYA

Chief Manager, EMD

TPCL

By

1

PRESENTATION ON

JAYET MOON NAVDEEP S. BAGGA REEMA KUMARI SANTOSH K. NAIK



Click to edit section divider master title

2



Critical Equipments



Failure Analysis

3

.

CURRENT TECHNIQUES:8D,Why-Why,RCA etc

PROPOSED TECHNIQUES:

FAILURE MODE EFFECT ANALYSIS

FAILURE REPORTING ANALYSIS

& CORRECTIVE ACTION SYSTEM

FAULT TREE ANALYSIS



Failure Analysis(Contd.)

MAINTENANCE TECHNIQUES

REACTIVE

PREVENTIVE

PREDICTIVE

PROACTIVE



EXAMPLE-BEARING FAILURE

REACTIVE

MAINTENANCE

MAINTENANCE

APPROACH :

KEEP SPARE

STOCK, WHEN

FAILURE

OCCURS ,

REPLACE

UNPLANNED

DOWNTIME &

REVENUE LOSS

PREVENTIVE

MAINTENANCE

MAINTENANCE

APPROACH :

REPLACEMENTS

BASED ON

PREVIOUS

HISTORY

PREMATURE

FAILURES,OR

PERFECT

CONDITION

PREDICTIVE

MAINTENANCE

MAINTENANCE

APPROACH :

AILING BEARING

WILL PRODUCE

SYMPTOMS

OF POTENTIALFAILURE.

TECHNIQUES SUCH

AS THERMAL,OIL

VIBRATION ANALYSIS

ARE USED.

IMMINENT FAILURESCAN BE PREDICTED

AND MAINTENANCE

TEAM IS NOT

CAUGHT BY

SURPRISE

PROACTIVE

MAINTENANCE

MAINTENANCE

APPROACH :

DEVELOP A

CROSS

FUNCTIONAL

TEAM TOSTUDY BEARING

AND DO OIL

ANALYSIS.

E.G

RELATIONSHIP

FOUNDBETWEEN

CONTAMINANTS

AND BEARING

LIFE.



FRACAS



FMEA



Comparison



Fault Trees

Offer a “Top-down”structured way

Allow multiple causes using gates

Effective combination with FRACAS and FMEA



Failure Mode Effect Analysis

Description:

• FMEA is a systematic method by which potential failures of a

component or process are identified, analyzed and documented.

• Once identified, the effects of these failures on performance and

safety are recognized, and appropriate actions are taken to

eliminate or minimize the effects of these failures.

• An FMEA is a crucial reliability tool that helps avoid costs incurred

from product failure and liability.



Main Elements of FMEA

• Failure Mode: A failure mode is defined as the manner in which acomponent, subsystem, system, process, etc. could potentially fail to

meet the design intent.

• Failure Effect: A failure effect is defined as the result of a failure

mode on the function of the product/process.

• Failure Cause: Failure Cause indicates all the things that may be

responsible for a failure mode.



FMEA Variables

• Severity: is an index corresponding to the seriousness of an effect ofa potential failure mode.

• Occurrence: is an index defined as function of the number of failure

occurrences.

• Detection: is an index constructed based on the probability

estimative that a failure can be detected, assuming that it has

occurred.

These variables are normally measured in a scale of 1 – 10



Classification Criteria of the Variables



Risk Probability Number

• The RPN is a step that is used to help prioritise failure modes foraction.

• It is calculated for each failure mode by multiplying the numerical

ratings of the severity, probability of occurrence and the probability

of detection (effectiveness of detection controls)

RPN=S x O x D



FMEA Worksheet

ITEM FUNCTION FUNCTION

FAILURE

FAILURE

MODE

FAILURE CAUSE FAILURE EFFECT

SEVERITY OCCURRENCE DETECTION RPN NO.

FACTORS FOR FAILURE MODE EVALUATION

STEP 1 STEP 2 STEP 3 STEP 4 STEP 5 STEP 6 S 7

STEP 8: Prioritize failure modes for action.

STEP 9: Take action to eliminate or reduce failure modes with high RPN.

STEP 10: Calculate the resulting RPN



FMEA Flow Diagram

ITEM FUNCTION FUNCTION FAILURE FAILURE CAUSE FAILURE EFFECT FACTORS FOR FAILURE MODE EVALUATION



ITEM FUNCTION FUNCTION

FAILURE

FAILURE

MODE

FAILURE CAUSE FAILURE EFFECT

SEVERITY OCCURRENCE DETECTION RPN NO.

moto r trips so

pump sto ps

working

over heating

of moto r

1)overloading

2) Increasing motor

current d ue to high

voltage3) One phase broken or

faulty contact

4) Short circuit or

grounded windings

5)overvoltage

1) Insulation failure

2) motor may trip

3) load drop

5 1 1 5

moto r trips so

pump sto ps

working

winding

failure

1) weakening and

damage of insulation

due to rubbing o f

mechanical part on

winding and lo oseness

because of impact on

bearing

2) thermo mechanical

stress

3)vol tage surges

4) overload

5) short

circuit/grounded

windings

1) winding damage

2) moto r trip

3) load drop

5 2 1 10

vibrat ion 1) single phase

operation or volt age

unbalance

2) broken coil of rot or

or uneven contact brush

3) uneven loading

1)can accelarate bearing

failures

2)mechanical damage to

insulation

3)brush sparking

5 1 1 5

no ise 1)Sing le p hase o perat io n

or vo ltage unbalance

2)unbalanced air g aplengt h due to wearing of

bearing

1)bearing damage

2)may result in vibration

5 1 1 5

FACTORS FOR FAILURE MODE EVALUATION

C o n d e n s a t e E x t r a c t i o n P u m

p m o t o r

to drive

condensate

extraction

pump whichpumps

condensate

from condenser

to bo iler



Compatibility Analysis

•FMEA addresses potential errors, yet can also accommodateobserved errors, whereas FRACAS is intended only for observed

errors.

• There are a huge number of observed errors and there is the

possibility to pay insufficient attention to potential errors if oneperforms only FMEA. Hence, one should perform both FMEA and

FRACAS.

• This reduces the likelihood of ranking problems since the FMEA will

focus on potential problems and the FRACAS will focus on observedproblems.



FRACAS

• Failure Reporting and Corrective Action System is a procedure

by which testing and process anomalies as well as any failure or

noted deviation from standards, the cause and corrective action are

reported, properly investigated and documented.

• FRACAS is a powerful method for making the organization a“learning organization” i.e. to learn from mistakes.



Diagramatic Representation



FRACAS Worksheet



Steps for FRACAS

1. Failure Reportin g:

• Established procedure that includes collecting and recording corrective

maintenance information and times.

• Data should be submitted on simple, easy-to-use format.

• Consolidate all the data into a central data logging system.

• Failures should also be ranked in terms of the criticality or severity of

the error.

2. Failu re Analy sis :

•Review, in detail, the failure reports.

•Capture historical data from the database of any related or similar

failures.

•Do a root cause analysis (RCA).

•Obtain the failed items for analysis required beyond your resources for

external support (as needed).



Steps for FRACAS(Contd.)

3. Correct ive Act ions:

• Develop corrective actions.

• Assign owners for action items.

• Track actions to completion.

• Measure results



Benefits

• Saving of direct and indirect costs by the proper handling and

investigation of problems followed by appropriate corrective action.

• Visibility of reliability performance problems Initiation of continuousreliability improvement process.

• Effectiveness of corrective actions control and linkage to results.

• Expedient engineering effort to resolve problems.

• Root Cause Analysis.

• Knowledge base of a history of problems and lessons learnedhelping to avoid similar occurrences.



Fault Tree Analysis

• A technique by which many events that interact to produce other

events can be related using simple logical relationships

• Fault trees allow multiple causes for an event and use “AND” and

“OR” gates to distinguish between error types

• Fault trees can contain both potential and observed errors.

• Because of this, they are ideal to contain the knowledge expressed

in both FMEA and FRACAS.



Fault Tree Logic and Symbols• Logic gates are used to show how top event occurs.

• Higher gates are the outputs from lower gates in the tree

• Top event is output of all the input faults or events that occur

Basic Event

Conditioning Event

Undeveloped Event

External Event

Primary Event Symbols

Gate Symbols

AND

OR

Intermediate Event Symbol



FTA Procedure

• Define the system of interest.

• Define the top event for the analysis.

• Explore each branch in successive levels of detail.

• Solve the fault tree for the combinations of events contributing to

the top event .

•Identify important dependent potential failures and adjust themodel appropriately.

• Use the results in decision making.



• IDENTIFY• EVALUATE

• DEFINE

• PRIORITIZE

• DOCUMENT

• TRACK



Value Addition

• Improved Failure reporting methodology with relevant examples to



Key Learning

• Familiarization with the various departments, units and equipments

of the Trombay plant.

• Compilation of critical equipment list of various units.

• In depth study of failure analysis methods currently used viz.RCA,8D form, Why-Why Analysis, Is-Is not analysis.

• Ground study of other analysis methods and brainstorming about

efficiency and suitability of various methods and their advantages

and disadvantages over current practices.



Conclusion

• The methods of FMEA, FTA and FRACAS were selectively studied

and evolved to suit the technical fault and failure logging

requirements of the power plant.

• An integrated failure reporting form was conceived consisting of the

most essential and technically relevant details in line with six sigmaprinciples.

• Proactive maintenance has been studied and analysed as a

practically viable maintenance technique and as a companion

technique to preventive and reactive maintenance.

• FMEA has been analysed as a flagship tool of proactive

maintenance which covers the entire spectrum of possible faults and

remedies occurring in any system or equipment.

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