Maintainability Predictions
Last revised 01/14/2011
ASENT_MTTR.PPT
Slide 1
Introduction
ASENT_MTTR.PPT
Slide 2
Maintainability Manager Screen Layout
ASENT_MTTR.PPT
Slide 3
Maintainability Prediction Methodology
Hint: refer to the Maintainability Manager online help. Refer to
the ‘Using the Maintainability Manager’ help book.
ASENT_MTTR.PPT
Slide 4
Invoking the Maintainability Manager
The Maintainability
Manager is invoked from
the Session Manager.
Merely, right-click on
your project and select
the Maintainability
Manager from the dropdown menu.
ASENT_MTTR.PPT
Slide 5
Starting A New Maintainability Prediction
The first time that you
enter the Maintainability
Manager for a project, it
will prompt you to fill in
information for the
active scenario.
Fill in the scenario name,
description, and select a
toolkit. At this point, it
does not matter which
toolkit you select, as
these are intended for
future enhancements.
Once you have entered at
least the name and a
toolkit, click the Save
button.
ASENT_MTTR.PPT
Slide 6
The Scenario Tree
After the active
scenario has been
created the scenario
tree view will be
active. Initially, all that
exists is a top level,
project node.
ASENT_MTTR.PPT
Slide 7
Importing the Reliability Tree
Normally, when performing a Maintainability Prediction, 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 tool.
This is important, because normally the Reliability tree will not have
covers and other hardware that may be important to the
Maintainability Engineer. These items typically don’t impact the
failure rate much and are normally left off of the Reliability
Prediction.
ASENT_MTTR.PPT
Slide 8
Importing the Reliability Tree
In the Maintainability Manager you can import trees or sub-trees
from either the Reliability tree or other Maintainability scenario
trees. If you import the Reliability tree, then the Maintainability
scenario tree will be automatically linked to it.
If later, you need to modify descriptions or reference designator
values, modify these in the Reliability tree, and simply use the
Maintainability Update Links option, from the project node, to make
these changes in the Maintainability tree. You can sever the links or
re-link tree nodes anytime in the future.
ASENT_MTTR.PPT
Slide 9
Importing the Reliability Tree
To import the Reliability
tree, right-click on the
project node and select the
‘Import | Reliability’
option from the drop-down
menu.
ASENT_MTTR.PPT
Slide 10
Importing the Reliability Tree
Next, the Select a sub-tree to import
window appears. This window
displays the product tree structure
from the Reliability Manager. It is
collapsed initially and only shows the
project node. The ‘+’, ‘-’ symbols are
used to expand or collapse the tree.
To import the entire tree, select the
project node and click the OK button.
Click the Yes button when you are
asked if you want to overwrite the
MTTR tree.
ASENT_MTTR.PPT
Slide 11
The Maintainability Scenario Tree
This screen shows the
Maintainability
Scenario tree after the
import. It is a copy of
the Reliability tree.
The
icons next to
each item indicate that
they are linked to their
corresponding items in
the Reliability tree.
If changes occur in the
Reliability prediction,
updates to the
Maintainability tree can
be made by using the
Update Links or the
Update Failure Rates
options.
ASENT_MTTR.PPT
Slide 12
Reliability Data Tab
The Reliability
Data tab shows
the reliability
data that will be
used in the
Maintainability
and Availability
calculations.
ASENT_MTTR.PPT
Slide 13
Linked Data Tab
The Linked Data
Tab displays the
data for the
assembly in the
Reliability
Prediction for
Linked
Assemblies.
Linked
Assemblies are
blue. Unlinked
Assemblies
appear in gray.
ASENT_MTTR.PPT
Slide 14
Finding Assemblies
The ‘Find’ option
of the main menu
allows you to
quickly find any
assembly or
graphic in the
scenario.
Enter your search
string and select
the field for
ASENT to search,
then click the OK
button.
ASENT_MTTR.PPT
Slide 15
Assembly Menu Items
Clicking the Right
mouse button on
an assembly in the
tree opens a menu
that allows you to
import data, link
the assembly to
the reliability
prediction, attach
graphics to the
assembly,
generate reports or
copy the data
associated with an
assembly.
ASENT_MTTR.PPT
Slide 16
Maintainability Data Manager
Working with Task Time
Libraries
ASENT_MTTR.PPT
Slide 17
Maintainability Data Manager
The Maintainability Data Manager is the tool in ASENT that
allows you to manage your remove/replace task library. It
comes pre-populated with tasks from both Mil-Hdbk-472
and RADC -TR-84-165. You can also add new task
categories and tasks to any projects that you are assigned to.
These other tasks could be preventive maintenance tasks,
preparation tasks, troubleshooting tasks, verification tasks or
anything else that you need.
ASENT_MTTR.PPT
Slide 18
Maintainability Data Manager
To invoke the
Maintainability
Data Manager,
select the
Maintainability
Data option, and
select the
Maintainability
Data Manager.
ASENT_MTTR.PPT
Slide 19
Editing Task Time Libraries
Here, we are viewing
the data associated
with a Captive Screw
in the Mil-Hdbk-472
task library.
The brown folder icon
next to this project
library indicates that
we can use the data,
but we are not able to
edit it.
Yellow folder icons
indicate that we have
editing privileges.
ASENT_MTTR.PPT
Slide 20
Displaying task images
Images exist for many of
the tasks, and are
displayed when the user
selects the View button.
ASENT_MTTR.PPT
Slide 21
Toolkits and Tools
Data associated
with maintainer
toolkits and
tools can also be
captured in the
Maintainability
Data Manager.
At this point this
data is not tied
to specific tasks,
but that is a
planned future
enhancement.
ASENT_MTTR.PPT
Slide 22
Maintainability Manager
Working With The
Maintainability Scenario Tree
and Assembly Times
ASENT_MTTR.PPT
Slide 23
Definitions of Assembly Times
FDI Times – Represents the time that corresponds to all of the tasks and judgments
associated with localizing the failure. This would include any tasks associated with Fault
Detection and Isolation. Sometimes tasks that are associated with preparing the item for
maintenance are also included here.
Disassembly Times – This includes all of the equipment that must be removed or gotten out
of the way so that you can actually remove and replace the item of interest. This could
include removing covers, circuit cards, and other pieces of equipment so that you can get to
the item of interest. Here, you will select the items from a list that is made up of items found
in the Maintainability scenario tree.
Remove Times – Represents the time that corresponds to all of the tasks and judgments
associated with removing the item of interest. This could involve removing screws,
connectors and other items. It could also incorporate judgments that add extra time to account
for working in cramped or adverse conditions.
Replace Times – Represents the time that corresponds to all of the tasks and judgments
associated with replacing the item of interest. This could involve replacing screws,
connectors and other items. It could also incorporate judgments that add extra time to account
for working in cramped or adverse conditions.
ASENT_MTTR.PPT
Slide 24
Definitions of Assembly Times
Reassembly Times – This includes all of the equipment that must be replaced or put back on
after you have removed and replaced the item of interest. This could include replacing
covers, circuit cards, and other pieces of equipment that were removed to get to the item of
interest. Here, you will select the items from a list that is made up of items found in the
Maintainability scenario tree
Align/Adjust Times – This includes all of the tasks or judgments involved in aligning and
adjusting the equipment after the item of interest has been repaired.
Verification Times – This includes all of the tasks or judgments involved in testing the
equipment and verifying that it is functioning normally after the repair was made.
Preventive Times – This includes all of the tasks or judgments involved in performing
preventive maintenance on the equipment. Maintenance intervals in hours are entered for
each task.
Maintenance Interval – A calculated value based on the Preventive Maintenance tasks and
intervals that were added. It tells you what the maintenance interval is between tasks, in
hours, during 1 million hours.
ASENT_MTTR.PPT
Slide 25
Editing / Viewing the Tasks & Times
Detailed remove and
replace tasks can be
specified for each
assembly by clicking
on the selection
button next to each
time.
ASENT_MTTR.PPT
Slide 26
Remove and Replace Tasks
Here, the user
specifies 8
Machine screws
need to be
removed. The
time needed to
remove each
screw is
automatically
supplied by the
task time
database.
The description above matches that found in Mil-Hdbk-472, but
a more descriptive narrative can also be entered by the user.
ASENT_MTTR.PPT
Slide 27
Adding a remove task for an item
To specify additional remove
tasks for an item, merely
right-click from the Edit
Remove Tasks window. The
user can select a task from
the entire task library or be
presented a list of the 20
most recently used tasks.
Judgments can also be entered, which apply to specific
tasks or all tasks. These are typically used as difficulty
factors to compensate for working in cramped or adverse
conditions.
ASENT_MTTR.PPT
Slide 28
Selecting tasks from the library
List of projects
Here, the user selects a
Captive Screw
fastener from the
MIL-HDBK-472 task
library.
ASENT_MTTR.PPT
Slide 29
Editing remove / replace tasks
After the user adds the
Captive Screw fastener
the updated list of remove
tasks is displayed.
ASENT_MTTR.PPT
Slide 30
Entering replace tasks
Since, normally the
list of replace tasks is
just the list of remove
tasks displayed in
reverse order, the user
can accomplish this
with the mere click of
a mouse.
ASENT_MTTR.PPT
Slide 31
Maintainability Predictions
Performing a Maintainability
Prediction
ASENT_MTTR.PPT
Slide 32
Maintainability Predictions
We have just covered some of the steps involved in
working with the Maintainability Scenario tree to
define remove/replace times and
disassembly/reassembly times. Now, it is time to add a
prediction and begin working with this data.
ASENT_MTTR.PPT
Slide 33
Maintainability Prediction - defaults
The user can
specify default
values to be
used when
creating new
predictions.
Click on the
Predictions tab
and click on
the Predictions
folder to
edit/display the
prediction
defaults.
ASENT_MTTR.PPT
Slide 34
Adding a new prediction
To add a new
prediction make sure
that the Predictions tab
is selected, then rightclick on the word
Predictions and select
the Add option.
If SMR Codes were
entered for assemblies,
you can use these as a
filter, so that ASENT
will only populate the
prediction with items
matching the specified
SMR code.
ASENT_MTTR.PPT
Slide 35
Maintainability Predictions
Once a prediction has been
created then the prediction
results screen is displayed.
Both corrective and
preventive maintenance can
be analyzed. This information
can be displayed in manminutes, man-hours or both,
and is controlled by selecting
the Display Options tab.
(Refer to the Maintainability
lab for more information)
ASENT_MTTR.PPT
Slide 36
Maintainability Predictions
Here, the user
includes the
Chassis, Mother
Board, and
Sound Card in
their prediction.
By clicking on
the slider bar in
the middle of the
screen, ASENT
displays the
spreadsheet in
full screen. Click
it again and the
screen will
assume its
original display.
ASENT_MTTR.PPT
Slide 37
Corrective maintenance prediction spreadsheet
Here, the
corrective
maintenance
prediction
spreadsheet is
displayed fullscreen. As you
scroll to the
right you will
see additional
fields
displayed.
ASENT_MTTR.PPT
Slide 38
Adding or Deleting Prediction Items
Prediction items
can be added or
deleted by
right-clicking
on an item and
selecting either
the Add or
Delete option.
Adds will be
inserted below
the row that is
selected.
ASENT_MTTR.PPT
Slide 39
Corrective maintenance prediction spreadsheet
The user can either use calculated values or enter user set values.
Above, the 3.20 minutes displayed for the Motherbd interchange
time is the sum of the times for all of the remove and replace
tasks associated with this item. By clicking the user set checkbox
next to Interchange Time, the user can directly enter a value.
Here, are
some of the
times that
contribute to
the Mean
Corrective
Time (MCT)
for each item.
ASENT_MTTR.PPT
Slide 40
Copying Predictions
The ‘Copy’
feature of the
prediction
menu make it
easy to create
alternatives or
other
maintenance
level
predictions
using the
existing
prediction as a
starting point.
ASENT_MTTR.PPT
Slide 41
Maintainability Reports
A comprehensive
set of reports is
readily available
in the
Maintainability
Manager.
ASENT_MTTR.PPT
Slide 42