IS 15550: Failure mode effects analysis

2005·2.2 MB·English

by  Bureau of Indian Standards

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IS 15550 (2005): Failure mode effects analysis [MSD 3:
Statistical Methods for Quality and Reliability]
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IS 15550:2005
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Indian Standard
FAILURE MODE, EFFECTS ANALYSIS
I(X 03.120.30

0 BIS 2005
BUREAU OF INDIAN STANDARDS
MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG
NEW DELHI 110002

April 2005 Price Group 10
Statistical Methods for Quality and Reliability Sectional Committee, MSD 3
FOREWORD
This Indian Standard was adopted by the Bureau of Indian Standards, after the dratl finalized by the Statistical
Methods for Quality and Reliability Sectional Committee, had been approved by the Management and Systems
Division Council.
FMEA is a problem prevention technique of identifying or investigating potential failure modes and related
causes. It can be:
a) applied in early concept selection or design phase and then progressively refined and updated as tbe
design evolves.
b) used to recognize and evaluate the potential failure of aproductiprocess and its effects.
c) helpful in identification of all possible causes, including root causes in some cases, and also helpful in
establishing the relationships between causes.
d) used as a tool to aid in the improvement of the design of any given product or process.
e) used to document the process.
It isone of the method of reliability analysis intended to identi~ failures having significant consequences on the
system performance in the application considered.
Starting from the basic element failure characteristics and the functional system structure, the FMEA determines
the relationship between the element failures and the system failures, malfunctions, operational constraints,
degradation of performance or integrity. To evaluate in addition to primary component failures, secondary and
higher order system and sub-system failures, sequence of events in time may have to be considered.
The FMECA iscomposed oftwo complementary analyses, one isFMEA and the other isCA (Criticality Analysis).
In the FMECA (Failure Modes, Effects and Criticality Analysis) there isassessment related to the failure modes
severity and probability of occurr ence.

The composition of the Committee responsible for the formulation of this standard is given in Annex R.
IS 15550:2005
Indian Standard
FAILURE MODE EFFECTS ANALYSIS
1 SCOPE 3.1.1 Design FA4EA — Design FMEA concentrates
effort on product itself, that is product design and
1.1This standard describes potential Failure Mode and
development, componentslpartslsub-sy stems/systems
Effects Analysis (FMEA) and provides generic
used based on design tolerance specified causing
guidelines in the application of the technique. There
catastrophic or critical failure.
are four basic types of FMEA, namely:
3.1.2 System FMEA — System FMEA can be
a) Design FMEA,
considered to be made up of various sub-systems. The
b) Process FMEA,
focus is to ensure that all interfaces and interactions
c) Programme/Project FMEA, and are covered among various sub-systems that make up
d) Machinery FMEA. the system aswell as interfaces toother product systems
and the customer. Interfaces and interactions as well
1.2 Process FMEA is of two types:
as items, functions and failure modes examples are
a) Manufacturing FMEA, and shown in Annex C.
b) Assembly FMEA.
3.1.3 Sub-system FMEA — Subsystem FMEA focus
The Machinery and Programme FMEA are not covered is to ensure that all interfaces and interactions are
by this standard. FMEA includes all requirements of covered among the various components that make up
FMECA as well. The typical Design FMEA and the subsystem.
Process FMEA Quality objectives are listed in
3.1.4 Component FMEA — Component FMEA is
Annex A and Annex B.
generally an FMEA focused on the sub-set of a sub-
system.
2 REFERENCES
3.1.5 Process FMEA — Process FMEA concentrates
The following standards contain provisions, which
effort onmanufacturing process with which the product
through reference in this text constitute provisions of
gets built.
this standard. At the time of publication, the editions
indicated were valid. All standards are subject to 3.1.6 Manufacturing FMEA — In manufacturing
revision and parties to agreements based on this FMEA’s, the failure modes are generally dimensional

standard are encouraged to investigate the possibility or visual.

of applying the most recent editions of the standards
3.1.7 Assembly FMEA — In assembly FMEA’s, the
indicated below.
failure modes are generally relational dimensions,
1SNo. Title missing parts, parts assembled incorrectly.
l1137(Part 2): Analysis technique for system
3.1.8 Program me/Project FMEA — Programmed
1984 reliability: Part 2 Procedures for
Project FMEA concentrates effort on resolving
failure mode and effects analysis
programme/project or workgroup problems.
(FMEA) and failure mode effects
and criticality analysis (FMECA) 3.1.9 Machinery FMEA — A machinery FMEA for
10645: 2003 Methods of estimation of process tooling and equipment is utilized for addressing
capability and process performance potential failure modes and their associated causes/
15280:2002 Quality function deployment mechanisms.
3.2 Function — A function could be any intended
3 TERMINOLOGY
purpose of aproduct or process. FMEA functions are
3.1 FMEA — FMEA is an analytical technique that best described in verb-noun format with engineering
combines the technology and experience of several specifications for example, delivery valve spring
engineering disciplines in identifying foreseeable controls unloading (inline Fuel Injection pump),
failure modes of aproduct or process and planning for assemble flywheel toengine, ream hole and fill inorder
its elimination or reduction in the likelihood of the form) Fuel Injection.
potential failure occurring. It is like defining what a
3.3 Potential Failure Modes — A potential failure
design or process must do to satisfy the customer.

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IS 15550:2005
Mode describes the way inwhich aproduct or process to reduce rankings in the following order: Severity,
could fail to perform itsdesired ti.mction (design intent Occurrence and Detection.
or performance requirements) as described by the
3.13 Responsibility for the Recommended Actions
needs, wants and expectations of the internal and
— Specify departments and individuals responsible for
external customers (for example, fatigue/erosion/wear,
each recommendation with target date.
flywheel not perpendicular to crank, hole oversized,
wrong information used). 3.14 Actions Taken — Brief description of the actual
action and effective date.
3.4 Potential Effect(s) of Failure — The effects of
the failure mode on the function, as perceived by the 3.15 Revised Ratings — After the preventive/
customer. The customer could be: the next operation, corrective action has been taken, estimate and record
the assembly line, and the end user (for example, loss resulting Severity, Occurrence and Detection ratings.
of engine performance, smoke, engine vibration, oil Calculate and record resulting RPN. All revised
leakage, delay in processing). ratings should be reviewed for further necessary
actions.
3.5 Severity (S) — Severity is an assessment of how
serious the effect of the potential Failure Mode is on 4GENERAL
the customer.
4.1 Purpose
3.6 Classification — Classify any special product
The primary objective of FMEA is to improve the
or process characteristics (for example, critical, key,
major, significant) for components, sub-systems, or design of the product and/or process that is being
systems that may require additional design or analyzed. Higher risk failure modes are identified
through the analysis, and their effects are either
process controls.
eliminated or mitigated by recommending design,
3.7 Potential Causes/Mechanisms of Failure — A
process and allied improvements.
cause is the means by which a particular element of
the design or process results in a failure mode (for 4.2 Application
example, hydraulic duty, dirt on crank flange, bushings
FMEA’s are generally done where a level of risk is
worn on spindle, catalog information incorrect).
anticipated inaprogramme early inproduct or process
3.8 Occurrence (0) — Occurrence is the assessment development. Some of the factors considered in
of likelihood that a particular cause will happen and deciding to do FMEA’s are: new technology, new
result in the failure mode during the intended life and processes, new designs, orchanges inthe environment,
use of the product. It is how frequently the specific loads, or regulations. FMEA’s can be done on
failure cause/mechanism is projected to occur. components or systems that make up products,
3.9 Current Controls (Preventio n, Detection) — processes or manufacturing equipment. They can also
Current Controls (design and pr o cess) are the be done on software systems and processes involved
in service industry.
mechanisms that prevent the cause of the failure mode
from occurring, or which detect the failure before it
4.3 Key Elements
reaches the customer (for example, fail-sating used for
flywheel assembly, SPC used to monitor hole size, a The FMEA analysis generally follows these steps:
cross checking by a printing company).
a) Identification of how the component of
3.10 Detection (D) — Detection is an assessment of system orpart ofthe process should perform;
the likelihood that the current controls (applicable) will
b) Identification of potential failure modes,
detect the cause ofthe failure mode orthe failure mode
effects and causes;
itself, thus preventing it from reaching the customer.
c) Identification of risk related to failure modes
3.11 Risk Priority Number (RPiV) — The Risk and effects;
Priority Number is the mathematical product of the
d) Identification of recommended actions to
numerical Severity (S’),Occurrence (0), and Detection
eliminate or reduce the risk;
(D) ratings. RPN =($ x (0) x (D). This number can
e) Follow upactions toclose outtherecommended
be used torank order the concerns inthe designlprocess
actions; and
requiring additional quality planning.
f-) Documentation and archiving.
3.12 Recommended Actions — Engineering assessment
for preventive/corrective action should be first directed The analysis must be completed in time for the
athigh severity, high RPN, and other items designated recommended actions to be implemented into the final
by the team. The intent of any recommended action is design or process.

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IS 15550:2005
The FMEA to be revisited through product life cycle f) Key Date — Enter the initial FMEA due date,
and on changes in product or process design. which should not exceed the scheduled
production design release date.
NOTE — Ageneric flow chart for FMEA Process is included
inAnnex D. .!4 FMEA Date — Enter the date, the original
FMEA was compiled and the latest revision
5 DEVELOPMENT OF A DESIGN FMEA
date.
5.1 The process of preparing the design FMEA begins h) Core Team — Listthe names ofthe responsible
with listing the design intent. Customer needs and individuals and departments.
wants determined from Quality Function Deployment
(QFD) (see IS 15280), product requirements, and/ 6 THE DESIGN FMEA PROCESS
or manufacturing/as sembly/service/re cycling FMEA Process Sequence is shown in Annex K.
requirements should be incorporated. The steps in
6.1 Identify Functions
preparation of design FMEA includes:
Enter asconcisely aspossible, the function of the item
a) Define the part/sub-system/system to be
being analyzed to meet the design intent. Include
analyzed;
information (metrics measurable) regarding the
b) Obtain Equipment and Material requirements;
environment inwhich this system operates. Ifthe item
c) Select FMEA team members;
has more than one function with different potential
d) Identify information that may be needed such modes of failure, list all the functions separately.
as: drawings, sketches, standards, layouts,
6.2 Identify Potential Failure Modes
system structure, system environment, system
initiation, operation, control and maintenance List each potential failure mode associated with the
etc; particular item and item function. The assumption is
e) Plan what will be done with the results; such made that the failttre could occur but may not
as who will coordinate the action plan; and necessarily occur. Potential failure modes that could
occur only under certain operating and usage
9 Schedule first meeting.
conditions should beconsidered. Typical failure modes
5.2 Adesign FMEA should begin with ablock diagram examples may include:
for the system, sub-system, and/or component being
Premature operation, Failure to operate at a
analyzed. Examples of block diagrams are shown in
prescribed time, Failure to cease operation at a
Annex E, F and G.
prescribed time, Failure during operation,
5.3 A blank design FMEA form that maybe used for Cracked, Loosened, Sticking, Fractured, Slips
documentation of the analysis of potential failures and (does not hold full torque), Inadequate support,
their effects is available in Annex H. Disengages too fast, Intermittent signal,

Deformed, Leaking, Oxidized, Does not transmit
5.4 An example of a completed for m is contained in

torque, No support (structural), Harsh
Annex J. The. necessary header information may be
engagement, Inadequate signal, No signal, Drift.
recorded indicated as below:
a) FMEA Number — Enter document number 6.3 Identify Potential Effects of Failure
used for tracking. Describe the effects of the failure in terms of what the
b) Item — Enter the name ofsystem, sub-system, customer (internal or external) might notice or
or component for which the design is being experience. State clearly ifthe failure mode could impact
analyzed. safety or non-compliance to regulations. The effects
c) Design Responsibility — Enter the Original should always bestated interms ofspecific system, sub-
Equipment Manufacturer (OEM), department system or component being analyzed. A hierarchical
and group. Also include the supplier name, if relationship exists between component, sub-system and
applicable. system levels. Typical failure effects may include:
d) Prepared by — Enter the name, telephone Noise, Erratic operation, Poor appearance,
number and company of the engineer Unstable, Intermittent operation, Leaks, Rough,
responsible for preparing the FMEA. Inoperative, Unpleasant odour, Operation impaired,
e) Mode[ Year(s)/Programme (s) — Enter the Thermal event, Regulatory non-compliance.
intended model year(s)/programme(s) that
6.4 A failure effect may also impact the next higher
will use and/or be affected by the design being level and ultimately may affect the highest level under
analyzed (if known). analysis. Therefore the failure effects on each higher
level should be evaluated.

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IS 15550:2005
6.5 Determine Severity (S’) Typical failure mechanisms may include:
Severity istherank associated with the most serious Yield, Fatigue, Material instability, Creep, Wear,
effect for a given failure mode. Severity is a relative Corrosion, Chemical oxidization, Electro
ranking within the scope of the individual FMEA. A migration.
reduction in the severity ranking can be effected only
6.8 Determine Occurrence (0)
through adesign change. Suggested severity are given
in Table 1. Occurrence is the likelihood that specific cause/
mechanism will occur during the design life. It has a
6.6 Identify Special Chara&eristics (Classification)
relative meaning rather than an absolute value.
Identify special characteristics requiring additional Preventing or controlling the causes/mechanisms of
design or process controls at system, sub-system and the failure mode through a design change or design
component level using standardized appropriate symbols process change is the only way a reduction in
for critical, key, major, significant characteristics. occurrence ranking can be effected. Occurrence can
be estimated using Table 2.
6.7 Identify Possible Causes/Mechanisms of Failure
6.9 Identify Current Design Controls
List concisely and completely every potential cause
and/or failure mechanism for each failure mode sothat List the prevention, design validation/verification, or
remedial efforts can be aimed at pertinent causes. other activities that have been completed or committed
Typical failure causes may include: to and that will assure the design adequacy for the
failure mode and/or cause/mechanism under
Incorrect material specified, Inadequate design
consideration. Typical current controls may include:
life assumption, Over-stressing, Insufficient
lubrication capability, Inadequate maintenance Design reviews, Fail/Safe designs such as
instructions, Incorrect algorithm, Improper pressure relief valve, Mathematical studies, Rig/
software specification, Improper surface finish Lab testing, Feasibility review, Prototype tests,
specification, Inadequate travel specification, Road testing, Fleet testing.
Improper friction material specified, Excessive 6.9.1 There are two types of design controls to
heat, Improper tolerance specified. consider:
Table 1Suggested Design FMEA Severity Evaluation Criteria ~
(Clause 6.5)
Effect Criteria: Severity ofEffeet Ranking
(1) (2) (3)
Hazardous without Very high severit y ranking when apotential failure mode affeefs safe item operation and/or involves 10
warning non-compl iaoce with Government regulation without warning

Hazardous with Very high severity ranking when apotential failure mode affects safe item operation and/or involves 9
warning non-compliance with Government regulation with warning
Very Iligh item inoperable (loss ofprimary function) 8
High Item operable but atreduced level ofperformance, Customer very dissatisfied 7
Moderate Item operable but comfoticonvenience item(s) inoperable customer dissatisfied 6
Low Item operable convenience/convenience item(s) operable at a reduced level of performance. 5
Customer somewhat dissatisfied
Very Low Fit and Finish? Noise and vibration item does not conform. Defect noticed by most customers 4
(greater than 75 percent)
Minor Fit and Finish? Noise and vibration item does not conform. Defect noticed by about 50 percent of 3
customers
Very Minor Fit and Finish? Noise and vibration item does not conform. Defect noticed by discriminating 2
customers (less than 25 percent)
None No discernible effect 1
NOrES
1 Making design revisions that compensate ormitigate the resultant severity offailure can sometimes reduce high severity rankings.
Forexample “seat belts” can mitigate the severity of avehicle crash.
2Ranking tables for SOD (Severity, Occurrence and Detection inTables 1,2 and 3) given inthis standard are most appropriate for
use inAutomotive Industry. Similar ranking scales can be developed or formed on similar lines or found inpublished literature for
FMEA speciiic to other industries.

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IS 15550:2005
Table 2 Suggested Design FMEA Occurrence Evaluation Criteria
(Clause 6.8)
Probability ofFailure Possible Failure Rates per Million Items Ranking
(1) (2) (3)
Very High: Pcrsisteot failures > 105items 10
5I ]04it~ms 9
}Iigh: Frequent failures 2 x 104items 8
I04items 7
Moderate: occasional failures 5X103items 6
2 x 103 it~ms 5
103items 4
Low: Relatively few failures 5 x 102items 3
102items 2
Remote: Failure isunlikely < 10items 1
—
a) Prevention: Prevent the cause/mechanism of control listed in the design control. Detection is a
failure or the failure mode from occurring, or relative ranking within the scope of the individual
reduce their rate of occurrence. FMEA. In order to achieve a lower ranking generally
the planned design control has to improve. Detection
b) Detection: Detect the cause/mechanism of
can be estimated using Table 3.
failure orthe failure mode, either by analytical
or physical methods, before the item is After making the detection ranking, the team should
released for production. review the occurrence ranking for still being
appropriate.
The preferred approach is to first use prevention
controls. Once the design controls have been identified, 6.11 Determine Risk Priority Number (RPN)
review all prevention controls to determine if any
~~ = (S) x (0) x (D)
occurrence rankings need to be revised.
Within the scope of the individual FMEA this value
6.10 Determine Detection (D)
(between 1and 1000) can be used to rank order the
Detection isthe rank associated with the best detection concerns in design.
Table 3 Suggested Design FMEA Detection Evaluation Criteria

(Clause 6.10)

Detection Criteria: Likeliboort ofDetection by Design Control Ranking
(1) (2) (3)
Absolute [Jocertainty Design control will not and/or can not detect a potential cause/mechanism and subsequent 10
failure mode; orthere isno design control
Very Remote Very remote chance the design control will detect a potential cause/mechanism and 9
subsequent failure mode
Remote Remote chance the design control will detect a potential cause/mechanism and subsequent 8
failure mode
Very Low Very low chance the design control will detect apotential cause/mechanism and subsequent 7
failure mode
I.OW Low chance the design control will detect apotential cause/mechanism and subsequent failure 6
mode
Moderate Moderate chance the design control will detect apotential cause/mechanism and subsequent 5
failure mode
Moderately High Moderately high chance the design control will detect a potential cause/mechanism and 4
subsequent failure mode
IIigh High chance the design control will detect apotential cause/mechanism andsubsequent failure 3
mode
Very High Very high chance the design control will detect apotential cause/mechanism and subsequent 2
Pailcrremode
Almost Certain Design control will almost certainly detect a potential cause/mechanism and subsequent 1
failure mode

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