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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
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Click to edit section divider master title
2
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Critical Equipments
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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
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Failure Analysis(Contd.)
MAINTENANCE TECHNIQUES
REACTIVE
PREVENTIVE
PREDICTIVE
PROACTIVE
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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.
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FRACAS
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FMEA
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Comparison
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Fault Trees
Offer a “Top-down”structured way
Allow multiple causes using gates
Effective combination with FRACAS and FMEA
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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.
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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.
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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
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Classification Criteria of the Variables
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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
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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
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FMEA Flow Diagram
ITEM FUNCTION FUNCTION FAILURE FAILURE CAUSE FAILURE EFFECT FACTORS FOR FAILURE MODE EVALUATION
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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
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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.
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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.
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Diagramatic Representation
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FRACAS Worksheet
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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).
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Steps for FRACAS(Contd.)
3. Correct ive Act ions:
• Develop corrective actions.
• Assign owners for action items.
• Track actions to completion.
• Measure results
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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.
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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.
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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
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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.
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• IDENTIFY• EVALUATE
• DEFINE
• PRIORITIZE
• DOCUMENT
• TRACK
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Value Addition
• Improved Failure reporting methodology with relevant examples to
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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.
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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.