Transcript No Slide Title

Failure Mode, Effects, and Criticality Analysis (FMECA)
Last revised 08/14/2014
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Introduction
The FMECA toolkit provides most of the analyses commonly
associated with a FMECA analysis. It supports the
accomplishment of Task 101 (FMEA) and Task 102 (Criticality
Analysis). In addition, you can use the toolkit to perform
Testability Analysis and Reliability Centered Maintenance for
each failure mode in the system.
ASENT’s FMECA Manager supports functional, hardware, or
combined FMECAs, and its methodology allows you to do topdown or bottom-up FMECAs. Assemblies, boards, functions,
parts, and signals can be modeled along with related failure
modes and effects. The relationship between failure modes and
effects and the tree structure are automatically tracked by the
toolkit so that updates can easily be made at any time.
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FMECA Manager Screen Layout
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FMECA Manager Icons and Menu Bar
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Recommended Methodology
Hint:
refer
to the
FMECA
Manager
online help.
Refer to the
‘Using the
FMECA
Manager’
help book.
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Starting A New FMECA
The FMECA Manager is the tool in ASENT that is used to
perform FMECAs. From the ASENT Session Manager, rightclick on your project and select the FMECA Manager from the
drop-down menu.
The first time that you enter the FMECA Manager for a project
it will ask you to select a project to copy libraries from.
This gives you the ability to start your
FMECA by leveraging off of FMECA
data that may already exist for other
projects. This can be very helpful when
performing an analysis on equipment that
is similar, where a FMECA already
exists.
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Initializing FMECA Libraries
If in doubt, just select the COMMON_FMD97 project. This
should be highlighted as the default. This project is empty
except it contains part types and their failure mode distributions.
This is particularly helpful if you are performing a piece-part
level FMECA.
Select what data you want
copied from the selected
project library to your
FMECA project. If in doubt,
leave everything checked
and click the OK button.
If you want a totally blank
library, then uncheck all of
the boxes and click the OK
button.
User selects the COMMON_FMD97
project to use as their default starting
point.
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Defining A Function/Phase
Next, you will create the
function/phase for your
FMECA. ASENT allows you
to have as many
function/phase combinations
as you want. These are
treated like separate projects
within a project.
These are used to keep track
of the data associated with
different modes of operation.
For example, you may have
a FLIR with a function of
Surveillance Mode. Maybe it
has a Daytime phase and a
Nighttime phase that need to
be analyzed separately.
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Importing the Reliability Tree
Normally, when performing a FMECA, a good starting point is to
import the Reliability tree. Once imported, the user can add or
delete items, and modify the data, since you have full tree editing
capability in the FMECA. This is important, because often, there
will be portions of your system that you may want to model
functionally in the FMECA.
In the FMECA tool you can import trees or sub-trees from either
the Reliability tree or other FMECA trees. If you import the
Reliability tree then the FMECA tree will automatically be linked
to it. If later, you have to modify descriptions or reference
designator values, modify these in the Reliability tree, and simply
use the FMECA Update Links option, from the project node, to
make these changes in the FMECA. You can sever the links or relink tree nodes anytime in the future.
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Importing the Reliability Tree
To import the Reliability
tree, right-click on the
project node and select the
‘Import’ option from the
drop-down menu. When the
Import window appears,
select ‘Reliability Manager
Trees’ and click the OK
button.
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Importing the Reliability Tree
Next, a list of projects
appear. Locate your
project name in the list
and select it, then click
on the OK button.
After the project has been selected, a window will
be displayed showing the product tree. Initially, the
tree is collapsed and only the project node is shown.
Select the project node and click on the OK button.
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Importing the Reliability Tree
Once you have selected the project node of the Reliability tree and clicked OK,
then you will be prompted for some additional data.
First, you will be asked whether or not to overwrite the existing FMECA tree.
Answer ‘Yes’ so that the FMECA tree becomes a copy of the Reliability tree. If
you answer ‘No’ it will append it off the project node of the FMECA tree.
Next, you will be asked whether or not to import parts. If you are doing a piecepart level FMECA then you should answer ‘Yes’. If not, then select ‘No’.
Finally, if you chose to import parts, then you will be asked whether or not to
default the failure modes for each of the parts. ASENT does this by using the Part
Type/Failures library, which is built into the FMECA. Normally, if you are
importing parts, then you would want the failure modes automatically defaulted
for these parts, so answer ‘Yes’ to this prompt.
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Extensive use of libraries reduces data entry and errors
Data entry and errors are
significantly reduced by the
extensive use of libraries in
the tool.
The FMECA Library Editor
contains data tabs to access
various types of library data.
Libraries exist for failure
modes and effects, signals,
part types and their
corresponding failure modes,
and detection or test codes.
The navigation buttons and
their meanings are shown
below.
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Part Types/Failures Library
Here, the default
failure modes and
their failure
distributions are
displayed for a
Bipolar Digital
Microcircuit. The
user can select
either the FMD-97,
MIL-HDBK-338,
or their own library
for part type
failures. This
feature virtually
eliminates the need
to enter failure
modes for parts
when doing a piecepart level FMECA.
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Adding Failure Modes
To add failure
modes for an item,
right-click on its
corresponding FMs
container and
select the ‘Add’
option from the
drop-down menu.
Here, we are
adding failure
modes for the
PWRCNV.
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Adding Failure Modes
Failure modes can
be added by either
selecting a failure
mode that exists in
the library, or it can
be added on the fly.
Click here to select
a failure mode
from the library.
Click here to add a
new failure mode
on the fly.
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Adding Failure Modes that exist in the library
This screen shows
the user selecting a
failure mode from
the library. This
picklist has an
active search
capability, so if you
start typing, it will
immediately jump
down to the first
failure mode that
contains your
string.
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Adding Failure Modes on the fly
When the user is adding failure modes for an item and they
select the
button, then the following screen appears.
The Description
field is normally left
blank. Only use it if
you need more than
255 characters.
This screen allows the user to enter a failure mode that
was not previously defined in the failure mode library.
The name field will handle 255 characters. Enter the
failure mode in the Name field and click OK. Then, click
on the Save button to add the failure mode.
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Working with Failure Modes
Individual failure modes or groups of failure modes can be
copied and moved from one location to another. The CTRLDrag-and-Drop accomplishes a copy and the Drag-and-Drop
accomplishes a move.
Always drop the item to be copied on the next biggest item.
For example, individual failure modes should be dropped on a
FMs container and entire FMs containers dropped on items.
Hint: Refer to the FMECA Manager online help for
detailed instructions on working with failure modes.
Refer to the ‘Working with Failure Modes’ help book.
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Entering Failure Mode Ratios
Failure Mode Ratios should only be entered at the lowest level
in the tree structure. For example, if you are doing a piece-part
level FMECA, then failure mode ratios should be filled in for
each failure mode at the part level. If ASENT was told to
default the failure modes for the parts, then this will happen
automatically.
If the lowest level in your tree structure is a function or a
circuit card, then at this level the failure mode ratios need to
be filled in. The failure mode ratios for all of the failure modes
associated with intermediate nodes should be left blank.
Right-click on the project node and select the ‘Roll-up
Failure Mode Ratios’ option to calculate these values.
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Evenly Distribute Failure Mode Ratios
ASENT has the ability
to evenly distribute the
failure mode ratios
among all of an item’s
failure modes.
To do this, merely
right-click in the grey
area above the
Description, and select
the ‘Distribute FM
Ratios’ option.
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Defining Next Higher Effects
The failure
mode that we
are assigning
Next Higher
Effects for.
Use these buttons
to Add or Remove
Next Effects.
List of modes at
the NHA that have
not been selected.
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FMECA Manager product tree display
Here, the
FMECA
Manager displays
the product tree
structure for the
Radar / Operating
phase that is
being analyzed.
By selecting the
Failure Mode
(FMs) container
on the project
node the user is
able to view or
edit the system
level (End)
effects.
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User selects a single effect to analyze
Notice, when the user
selects a single failure
mode or effect the
data for that item is
displayed on the right
side. Also, the user
can select the Causes
tab to view the failure
causes, enter
compensating
provisions, remarks,
the detection method,
or perform testability
analysis. At the RIU or
PWRCNV levels in
the tree the user would
also be able to view /
edit the Next Higher
Effects.
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Viewing the causes of a system level effect
The user views the
failure causes for the
highlighted system
level effect by
clicking on the
Causes tab. Here, a
bit circuit failure on
the RIU causes a bit
circuit failure on the
system.
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Viewing the End Effects of a Failure Mode
The user can easily
view all the End
Effects for a failure
mode by selecting the
End Effects Tab. This
informs him if the
Criticality
Calculations are
current and shows the
criticality, severity
and conditional
probability.
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Adding & Viewing Graphics
The user can add graphics
or supporting documents to
the tree, or view this
information for an
assembly by selecting
‘Graphics’ from the pop
up menu.
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FMECA Manager Menus
Failure rates in the FMECA
can easily be updated with
new prediction results from
the Reliability Manager. The
tool calculates Criticality and
Fault Detection / Isolation.
Extensive reporting
capabilities exist, including a
user defined report feature.
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Built-in Completeness Checker
The Check
FMECA utility
checks your
analysis and
pinpoints any
areas where
needed data is
missing. This
time saving
feature helps
ensure that your
analysis is
complete. In
spreadsheets and
many other tools
this is usually
performed
manually by the
user.
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Completeness Checker Results
Here, the completeness
checker reports that the
LOSS OF 5 VOLTS A
failure mode does not have
a Next Higher Effect, and
that the Criticality numbers
have not been calculated.
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Finding Data in the FMECA
The Find menu
makes it easy to
find items within
your FMECA.
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Fault Detection / Isolation
Here, the user
defines the
detection /
isolation groups
to determine test
coverage. For
example, the
SRA TEST
group uses test
points to isolate
failures to the
component level.
The Isolation
Group sizes are
defined as <=4,
<=8, and <=10
components.
Refer to the Testability Analysis tutorial for more details.
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Leverage the existing Failure Mode Analysis
The user enters
detection /
isolation
information at
the lowest
level, and then
intermediate
values are
calculated.
Here, an
Improper
Config
Resistor failure
is detected by
the SRA TEST
group using
testpoint J1-92.
It isolates the
failure to the
R0005
component.
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Importing / Exporting Data
Data from the FMECA
can easily be exported to
Logan for Fault Tree
Analysis, creating
significant savings of
time and money in
performing this analysis.
Failure Mode data may
also be imported to the
library from an Excel
spreadsheet.
In addition, entire
FMECAs can be
imported using the
FMECA Import.xls
template found in the
\ASENT\Data folder.
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