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Answers to
frequently asked questions about ReliaSoft
software
products are presented next. If you have additional
questions, please contact ReliaSoft
for assistance.
Q: How can I find
out about your software validation
and QA practices?
A: Refer
to our Statement Regarding Standard
Software Validation & QA Practices, which presents our
software validation and quality assurance practices.
Q: How
do I get the latest software updates?
A: An integral
part of ReliaSoft's continuous improvement process involves
issuing updates for all of our products to address technology
changes, functionality requests and/or issue resolutions.
Same version software updates (i.e. same major version
number such as 6.X.X) are made available to all licensed
users free of charge. We encourage you to update your product
when a new update is released.
Service releases are available via the ReliaSoft.com
Web site. Consult the product home page for the product
of interest or consult the
Reliability
Software Downloads table for updated information.
Q:
Where
can I get information on the theory behind the calculations
and analyses being performed in ReliaSoft applications?
A: In addition
to the software User's Guide, ReliaSoft's
standard
software packages come with an additional reference
text that explains the theory and background of the
calculations being performed by the particular
application. Many users have found these reference texts
to be an invaluable tool for increasing their
understanding of the concepts behind the reliability
analyses they regularly perform. These texts can also be
purchased separately from the software.
Additionally, ReliaSoft provides free online versions
of some of these reference texts that can be accessed from
ReliaSoft's reliability engineering resources Web site at
http://www.weibull.com.
These include:
Q: Are special pricing options
available if I purchase ReliaSoft software and attend a
training seminar?
A: Yes. ReliaSoft provides special
"bundled" pricing options for users who purchase both software
and training. Complete details are available at
http://www.reliasoft.com/bundles.htm.
Q: Can
I share plots from ReliaSoft applications with colleagues
who do not have the applications installed on their computers?
A: Weibull++
and ALTA have a built-in graphics editing application called
RS Draw. RS Draw can be accessed by selecting the Edit
Plot command from the Plot Options menu, or by
clicking the RS Draw icon on the toolbar. You can edit and
annotate plots in RS Draw and then save them in the Windows
metafile format (*.wmf). In BlockSim, you can select Export
Plot Graphic from the Tools menu or Plot Sheet shortcut
menu to export the plot as a metafile. Metafile graphics
can be transmitted via e-mail or other mechanism and can
also be imported or pasted into other applications such
as Microsoft Word or PowerPoint.
You can also copy a plot in
Weibull++,
ALTA or
BlockSim and
paste it into another application like Microsoft Word or
Excel. In addition to copying the plot graphic, in some
cases, you have the option to copy/paste the data that was
used to create the plot. The data can then be pasted into
Excel with the Paste Special command.
Q: Can I speed up the data entry
process in Weibull++
and ALTA?
A: There
are some shortcuts available in Weibull++ and ALTA for speeding
up the data entry process.
In a Data Sheet that is configured for grouped data entry,
it is not necessary to enter a value for the "Number in
Group" if the value is 1. Weibull++ and ALTA will automatically
insert the value of 1 for the cells that are left blank
in the "Number in Group" column.
Another shortcut can be used when a "State F or S" column
is displayed in the Data Sheet. In this case, the cells
in the "Time Failed" column can be entered first. When a
positive value is entered, Weibull++ and ALTA automatically
insert an "F" in the corresponding "State F or S" column
position. When a negative value is entered, the applications
automatically insert an "S" in the "State F or S" column.
For example, for a right censored item at 100 hrs, type
"–100" in the "Time Failed" column. An "S" will automatically
be inserted into the "State F or S" column.
These applications also provide a variety of copy/paste
and import capabilities to obtain data from existing data
sources.
Q: Can
I display the locations of suspensions on my probability
plots?
A: Yes,
relative locations of suspensions can be displayed along
the x-axis of plots in
Weibull++ 7 or
ALTA 7 (Standard and
PRO). You can set this option by selecting Plot Setup
from the Plot menu or clicking the Plot Setup
icon in the Plot Sheet Control Panel and clicking the
Lines tab in the Plot Setup window. In the second drop-down
menu in the Name field, select Suspended Points
and then select the Show Points option in the area
to the right. With this option selected, the suspensions
will appear on the x-axis of of the plot. You can use the
other options on the Lines page to configure how the suspensions
are displayed.
Q: How
do I remove the Program ID from the plots in
Weibull++ and
ALTA?
A: The
Program ID, or upper title, appears in the upper left corner
of plots in Weibull++ and ALTA, and contains information
about the software and ReliaSoft. This text, along with
the other titles on the plot, can be altered or removed
via the Plot Setup. Select Plot Setup from the
Plot menu or click the Plot Setup icon in the
Plot Sheet Control Panel and clicking the Titles
tab in the Plot Setup window. Select or deselect the
Show box next to each input box to determine whether
the title will be shown on the plot. Each asterisk (*) represents
the title defined in the Set Default Plot Titles window.
If you type new text in an input box, either instead of
or in addition to the asterisk, the text you type will be
displayed on the plot instead of or in addition to the default
text. To use your changes as the default for all subsequent
plots, click the Set as Default button on the right
side of the window. To change the default text for the current
plot type or another plot type, click the Default
button at the bottom of the Titles page to open the Set
Default Plot Titles window.
Q:
How can I show information from
more than one data set on one plot in
Weibull++
and ALTA?
A:
Weibull++ or ALTA Folios that contain more than one data
set can easily display data from multiple sources using
the MultiPlot feature. Once the data sets of interest have
been entered and analyzed, you can add a MultiPlot to a
Standard Folio or to the project. To add a MultiPlot to
a project, select Add Additional Plot then Add
MultiPlot from the Project menu. You will be prompted
to select the Folios/Data Sheets that will appear in the
plot. To add a MultiPlot to a Standard Folio, select
Insert MultiPlot Sheet from the Folio menu. In this
case, the Data Sheets in the Standard Folio will be automatically
selected for inclusion in the MultiPlot. You can change
this selection using the Select Data Sheets button
in the MultiPlot Control Panel.
Once you have selected the Data Sheets that
will appear in the plot, specify the rest of the plot properties.
In order to be available for inclusion in a MultiPlot, the
Data Sheet must have been calculated and, for probability
plots and contour plots, the Data Sheets must have been
calculated with the same distribution. For example, if you
have a data set that has been analyzed using the lognormal
distribution, it cannot be displayed on a Weibull probability
plot. This is because probability plots are constructed
specifically for one type of distribution.
Note that in Weibull++, Warranty Folio Data Sheets can also
be included on MultiPlots.
Q: How do I avoid having
borders on my printed plots in
Weibull++ and
ALTA?
A: You can set this
option by selecting Plot Setup from the Plot
menu or clicking the Plot Setup icon in the Plot
Sheet Control Panel and clicking the Appearance tab
in the Plot Setup window. Select or clear the checkbox beside
the Border option in the Plot area to show or hide
the outline on the plot.
In addition, when printing the plot from the RS Draw
utility, you can de-select the Print Border option
in the RS-Draw Graphic Print window. Note that the setting
in the Plot Setup has no effect on graphs printed from RS
Draw, and vice versa.
Q: Is there a way that I can
display probability scales on the probability plots in
Weibull++ and
ALTA?
A:
Probability scales allow the user to read parameter estimate
values directly from the probability plot. To toggle this
feature on or off in Weibull++ or ALTA, select Show/Hide
Items from the Plot menu or the Plot Sheet
shortcut menu (accessible by right-clicking inside the plot
area). In the Show/Hide Plot Items window that appears,
select the Scales checkbox beside the Probablility
Scales option in the Other area and then click OK.
This will show the probability scales appropriate to the
selected distribution on the probability plot.
Q: How can I determine the confidence
bounds on parameter estimates in
Weibull++ and
ALTA
A:
Confidence bounds on parameter estimates
in Weibull++ and ALTA can be obtained through the Quick
Calculation Pad (QCP). Once a data set has been entered
and analyzed, open the QCP, go to the Confidence Bounds
tab and select Show Confidence Bounds then select
the type of confidence bounds you wish to display for the
parameter estimates. Once you have selected the type of
confidence bounds, go to the Parameter Bounds tab
and click the Calculate Bounds button. This will
display the parameter estimates as well as the selected
confidence bounds.
Q: What is the DRT (Design of
Reliability Tests/Testing) utility in
Weibull++
and ALTA and how
can it be used?
A: The DRT utility allows you to
determine the required numbers of units and/or test time
required to demonstrate a certain reliability result. It
is a useful tool when you need to evaluate the number of
units, the test time required under a certain testing scenario
or the reliability and confidence that can be demonstrated
if such a scenario is actually implemented. The utility
uses the binomial distribution
(and in Weibull++ version 6 or later, the
reliability equation) to perform
the required calculations. There is also
functionality for test design for units with an assumed
exponential distribution.
Q: When using the Tests of Comparison
utility (Comparison Wizard) in
Weibull++
and ALTA, is it
appropriate to change the lower limit to something other
than zero on the Setup tab?
A: No, the lower limit should be
equal to zero. The tests of comparison utility has been
designed to compare data sets over their entire life spans,
starting at time t=0.
Q:
How are the points on the probability plot determined
in Weibull++?
A:
Weibull++ 5.0 uses median ranks
to calculate the points for the plot. Weibull++ 6 and 7
use median ranks or
Kaplan-Meier estimates. For
a more detailed discussion of the use of median ranks for
plotting, see ReliaSoft's Life Data Analysis Reference
on the following topics. The reference is also available
in an online
version on weibull.com.
|
Topic |
Weibull++ 7
Revision |
Weibull++ 6
Revision |
Weibull++ 5.0
Revision |
|
Median ranks and
complete data |
Pages
38-44,
529-531 and
121-127 |
Pages 31-37, 367-369
and
97-103 |
Pages 34-39,
76-77, 113-117 |
|
Median ranks and
right censored data |
Pages
65-69 |
Pages 52-56 |
Pages 61-66 |
|
Median ranks and
left and interval censored data |
Pages
532-539 |
Pages 370-376 |
Pages 69-75 |
|
Kaplan-Meier estimates |
Pages
43-44 and
478-480 |
Pages 36 and 323-325 |
N/A |
Q:
Why doesn't the calculated MLE
line track the data points on my probability plot in
Weibull++?
A:
The reason that the
fitted MLE model does not track the data points is due to
differences in the way the plot and the MLE model are generated.
The probability plot incorporates estimates of the unreliability
in order to provide y-axis values to go with the failure
times on the x-axis. In Weibull++, these unreliability estimates
are provided by median ranks or Kaplan-Meier estimates.
The maximum likelihood estimator (MLE) method of parameter
estimation only uses the failure and suspension (x-axis)
data when generating the unreliability model. Consequently,
the fitted model may not necessarily track the data points
on the plot. However, this does not mean that the model
or the plot is "wrong," just that they were generated using
two different methods.
Q: In
Weibull++, what
does the "Use True 3-P MLE on Weibull" option do?
A: When the Use True 3-P MLE on Weibull option
is selected on the Calculations tab of the User Setup window
in Weibull++, the software will use
maximum likelihood estimation (MLE)
to determine the parameter estimates for all of the parameters
in the three-parameter Weibull distribution. By default,
this option is not selected and Weibull++ first determines
the estimate of the location parameter,
γ
(gamma), by nonlinear regression.
Once this estimate has been determined, Weibull++ uses MLE
to estimate the other two parameters. It has been found
that this methodology is generally more appropriate for
the analysis of life data. With the Use True 3-P MLE
on Weibull option selected, the results of the analysis
may not make sense in the context of life data analysis
(e.g. very large negative values for
γ
, etc.).
Q:
When entering temperature values into
ALTA, on what temperature
scale should the values be based?
A:
If you are entering temperature values for the stress, you
should enter the values in an absolute scale, i.e.
Kelvin or
Rankine. If the values are
not in absolute scale, proper results will not be returned.
Q:
How is thermal cycling handled in
ALTA?
A:
All of the models available within the ALTA Standard software
deal with constant stress, i.e. stress that does
not change over time. However, in temperature cycling you
can cautiously use the change in temperature per cycle as
the stress level in a constant stress model as defined by
the Coffin Manson relationship.
For a more detailed discussion, consult ReliaSoft's Accelerated
Testing Reference, which is also available in an online
version on weibull.com. The Coffin Manson relationship
is covered on pages
182-185 of the reference (revised March 2007 and distributed
with ALTA 7 -- pages 164-167 in the version distributed
with ALTA 6 and pages 155-158 in the original reference
distributed with ALTA 1.0).
The ALTA PRO software provides the
cumulative damage (cumulative
exposure) life-stress relationship model for analysis of
data with time-varying stress profiles.
Q:
What life-stress relationships and life distributions
are available in ALTA?
A:
All versions of the ALTA software provide the
Weibull,
lognormal and
exponential life distributions.
ALTA 7, ALTA 6 Standard and ALTA 1.0 provide five
life-stress relationship models: Arrhenius,
Eyring,
Inverse
Power Law, Temperature-Humidity
and Temperature-NonThermal.
The Arrhenius, Eyring and Inverse Power Law models are single
stress models. Temperature-Humidity and Temperature-NonThermal
are combination models, which allow you to analyze the effect
of two stresses simultaneously.
ReliaSoft's ALTA 7 PRO and ALTA 6 PRO provide three additional,
more complex, models that support the analysis of data with
up to eight simultaneous stress types or with stress profiles
that vary with time: Proportional
Hazards, General Log-Linear
and Cumulative Damage. Transformations
available for the general log-linear model or the cumulative
damage model include the power, exponential and, new in
version 7, Arrhenius relations.
The life distributions
and life-stress relationships available in the ALTA software
are discussed in more detail in ReliaSoft's Accelerated
Testing Reference, which is also available in an online
version on weibull.com.
Q:
What do I need to know before analyzing data from an
accelerated life test with more than one type of stress
in ALTA?
A:
Before analyzing data with more than one stress type (e.g.
temperature and humidity), there must be an "overlap" of
the stress levels in order to be able to fit a multiple
stress life-stress relationship. This is because a relationship
between the stress levels and the failure behavior of the
product needs to be established. For example, consider a
situation where Stress 1 has levels A and B and Stress 2
has levels X and Y. If the failure information is only collected
where the stress levels are at A and X and at B and Y, a
mathematical relationship between the two stress types and
reliability cannot be obtained. The same failure data will
have to be collected at a stress combination of A and Y
or B and X in order to obtain a solution for the data set.
If you attempt to analyze a non-cross-referenced data set
in ALTA with a multiple stress model (such as the
temperature-humidity and
temperature-nonthermal models
in ALTA 7 and the generalized Eyring,
proportional hazards, general
log-linear and cumulative damage
models in ALTA 7 PRO), a message box will inform you that
such an analysis is not possible.
Q:
What do the parameters B and C represent in
ALTA?
A:
The parameters B and C are used by ALTA for the
Arrhenius and
temperature-nonthermal life-stress
relationships. The application returns values for these
variables along with the shape parameter for the selected
distribution (beta for
Weibull or
standard deviation for
lognormal). However, it is
much more difficult to glean information about the test
items from the B and C parameters than from the shape parameter.
Essentially, B and C are just variables
for which ALTA solves in order to determine the relationship
between stress and life; it is difficult to draw any conclusions
about the behavior of the products based on the values of
these parameters. However, you can get an indication of
the nature of the relationship between life and stress from
the parameter B. The sign of the B parameter indicates in
which direction the life-stress relationship lies. If B
is positive, the life of the product decreases with increasing
stress. If B is negative, the life of the product increases
with increasing stress (an unusual but by no means impossible
situation). Similarly, the magnitude of the B parameter
can indicate how quickly the life of the product changes
with stress; values with larger magnitudes indicate that
the life of the product is more sensitive to the stress.
However, all of this is relative and one cannot draw any
conclusions based on the value of B alone. The parameter
C does not impart any useful information at all, it is merely
a variable that ALTA solves for in order to complete the
analysis.
Q:
Is there a quick way to specify stress profiles in
ALTA PRO?
A:
With the cumulative damage
life-stress relationship selected in ALTA 7 PRO, right-click
a cell in the stress column to display a list of the stress
profiles that have been defined in the project. You can
select a profile from the list and click Add. Stress
profiles are added to the project in much the same way as
Folios.
Note that this feature is available
only with the cumulative damage model in ALTA PRO.
In ALTA 6 PRO, stress profiles are
managed in libraries, which can be attached to projects.
Q:
Does
BlockSim handle
k-out-of-n parallel redundancy configurations?
A: Yes. This functionality
is controlled by the use and configuration of the nodes
in BlockSim. Lines going out from units in parallel can
end in a node. A node is a block that usually has no failure
characteristics (although they can be assigned failure characteristics
in BlockSim). Double-click the node block to open the Node
Properties window, where you can assign how many paths out
of the parallel units must be functioning in order for that
part of the system to operate. In this way, k paths out
of n units can be assigned.
Q:
How can I repeat the results I get when performing
simulations in BlockSim?
A: The reliability and maintainability
simulations in BlockSim rely on a random number generator
to perform the analyses. Consequently, if you perform consecutive
analyses on the same system without specifying a
seed for the random number
generator, the results will differ each time you run the
simulation. If repeatable results are desired, be sure to
select the Use Seed option on the Maintainability
or Reliability tab of the Reliability/Maintainability Simulation
window and specify the value to be used as the seed.
Q: In
BlockSim, how
can I simultaneously change the values of more than one
block in the RBD?
A: In order to change the values
in more than one block, highlight the collection of blocks
of interest. This can be accomplished either by dragging
a box around the group of blocks you want to change, or
by clicking the individual blocks while simultaneously holding
down the Ctrl key. Double-click the highlighted blocks
to begin editing (a message box will pop up to inform you
that you are changing the values of more than one block).
Note that once the changes have been entered, the blocks
will have the same values for all parameters, even parameters
that were not changed during the editing process.
Q:
How do
I obtain component failure and repair information for RBD
blocks in BlockSim?
A: The recommended way to obtain
failure and repair information is through empirical testing.
This may be through in-house testing of components and parts
or from information supplied by the vendor. ReliaSoft takes
the position that this type of directly-obtained component
information is the best way to represent the failure and
repair characteristics of the components, and consequently
will produce the best results for the system-level analysis.
However, ReliaSoft recognizes that this information may
not always be available for those who wish to perform a
system reliability analysis. This may be due to a lack of
affordable parts for testing early in the development process
or simply due to the desire to "blue sky" and play around
with potential design configurations without having to undergo
costly testing procedures. Consequently, BlockSim can also
import generic failure rates from the PRISM database. The
PRISM software has the next generation of electronic component
failure rate models and a comprehensive searchable database
of observed field failure rates modeled after the successful
NPRD and EPRD data book series. The PRISM concept accounts
for the myriad of factors that can influence system reliability,
combining all those factors into an integrated system reliability
assessment resource. For more information about BlockSim's
integration with PRISM, see
http://www.reliasoft.com/blocksim/prism.htm.
Q: How can I quickly insert identical
units in series in a
BlockSim reliability
block diagram?
A:
Identical blocks in series can be inserted automatically
using BlockSim's Add Block to Diagram command. Simply select
an existing block in the diagram and select Add Block
to Diagram from the Diagram menu or click the
icon.
A new block, with the same style and properties as the
selected block, will be created in the diagram. The new
block will be placed to the right of the original block
and connected with a relationship line.
Q: How can I copy a portion of
a reliability block diagram (RBD) into the same diagram
sheet in BlockSim?
A:
Entire RBDs or sections of RBDs can be copied and pasted
into the same diagram sheet in BlockSim simply by clicking
the diagram sheet outside the blocks and dragging an outline
around the section of interest. This will highlight a group
of blocks that can be copied by selecting Copy from
the Edit menu or by pressing Ctrl+C. By selecting
Paste from the Edit menu or pressing Ctrl+V,
the entire section of blocks (with connections) will be
pasted back into the same diagram sheet and additional blocks
and connections can be inserted to link this portion of
the diagram with the original section of blocks.
Q: Is there an easy way to align
the blocks in BlockSim?
A:
BlockSim's Align Objects tool allows you to align
selected blocks in relation to the top, middle, bottom,
left, center or right sides of the blocks.
In addition, the Diagram Setup window provides the
Snap to Grid option, which automatically aligns the
blocks in the diagram sheet to a grid. To access the Diagram
Setup, press Ctrl+D or select Diagram Setup
from the Diagram menu or Diagram Sheet shortcut
menu. The Diagram Setup also allows you to hide or display
grid lines in the diagram sheet and change other aspects
of the appearance of the diagram.
Q: Can I have circular references
in my BlockSim
reliability block diagram (RBD)?
A:
Circular references are not allowed in BlockSim. The software
uses a methodology called the Path
Tracing Method in order to evaluate the reliability
of the system in the RBD. The Path Tracing Method requires
that each RBD has one starting block and one ending block.
It then calculates all of the "paths" from the starting
block to the ending block that would allow the system to
function. For this reason, circular references are not allowed,
as it would result in an infinite number of paths through
the system. Note:
Issue 2 of the Reliability HotWire eMagazine presents
a more detailed discussion of methods to determine the reliability
of complex systems.
In some circumstances, it may be possible to work around
the problem of circular references by splitting blocks,
or creating an input block and an output block, which represent
two different functions of the same component.
Q: Why do I receive an error
message when I export my
Xfmea project to
an XML file and then try to open the XML file in
BlockSim?
A:
This question is answered under Xfmea and
FMEA/FMECA Analysis.
Q: In
RGA 7, can a fixed
effectiveness factor be used throughout the analysis instead
of specifying individual effectiveness factors for each
BD mode?
A:
Yes. In the Effectiveness Factor window, click the Use Fixed
Effectiveness Factor button on the toolbar. If effectiveness
factors are defined in the Spreadsheet area of the window,
then when you click this button, the input box will display
the average effectiveness factor, which is also displayed
in the status bar at the bottom of the window. You can use
this value or enter a new value into the input box. This
value must be less than 1.
Q:
What are the requirements for defining
system configurations in
MPC 3?
A:
MPC 3's System Hierarchy has
been designed to fit the Air Transport Association (ATA)
definitions for aircraft groups, systems and subsystems
(described in the document ATA iSpec 2200: Aircraft Systems).
Therefore, the following constraints apply:
- There is a maximum of four levels in the system
hierarchy: system, subsystem, sub-subsystem and part.
- The system numbers are intended to be based on the
ATA iSpec2200 where, for example, 21 represents Air
Conditioning, 23 represents Communications, 34 represents
Navigation and so on.
- The subsystem numbers are intended to be identified
in multiples of ten (i.e. 10, 20, 30, 40, etc.)
based on the ATA iSpec2200 where, for example, 21-10
represents the Compression subsystem of the Air Conditioning
system and 34-30 represents the Landing and Taxiing
Aids subsystem of the Navigation system and so on.
- The subsubsystem numbers are intended to be defined
within the range specified by the subsystem. For example,
for any subsystem #10, the numbers 11 through 19 are
valid to define the sub-subsystems.
- The "ATA Number" that is presented in the print-ready
reports will consist of four (or more) numbers, in which
the first two numbers are determined by the system,
the third number is determined by the subsystem, the
fourth number is determined by the sub-subsystem. Two
or more additional numbers may be used to represent
parts. For example, the ATA# 231500 represents the following
system configuration:
- System = 23 Communications
- Subsystem = 10 Speech Communications
- Sub-Subsystem = 15 SATCOM
- In CRV 3.0.11, ReliaSoft added the ability to use
the "extended" MSI number format in print-ready report
output. If this option is selected on the Report Properties
page of the User Setup, the first two numbers are determined
by the system, the third and fourth numbers are determined
by the subsystem and the fifth and sixth numbers are
determined by the sub-subsystem. For the example given
above, this would be 231015.
Q: Why are the MSI selection
questions disabled in
MPC 3?
A:
In
MPC 3, the MSI selection questions are available only at the lowest
level of the system hierarchy; answers made at that level
are then "rolled up" to the higher levels. If, for example,
you have a hierarchy with a system, a subsystem and a sub-subsystem,
MSI selection questions will be available only for the sub-subsystem.
If you have assigned one or more parts below that sub-subsystem,
however, the selection questions will be available only
for those parts and the answers to the questions will apply
at all levels above the parts. This is based on the assumption
that if any component of an assembly poses, for instance,
a safety risk, then the entire assembly also poses a safety
risk, and so on. A Yes answer for any question for any part
will identify the subsubsystem as a Maintenance Significant
Item in the software and in the report output.
Q:
When using a Standard database in Xfmea
or RCM++, why are the Add and Delete
buttons disabled in the Profiles/Libraries Management window?
I am also unable to edit any of the profiles.
A:
If you are using a Standard
database in
Xfmea
or
RCM++, the Add and Delete buttons will be
disabled in the Profiles/Libraries Management window if the active
library is Read-Only for the user. To test this, determine the location/filename
for the active library file. Then determine whether
the user has Read/Write access to this file. If not, give
the user Read/Write access (e.g. place the file in
a directory that the user has Read/Write access to and/or
open the Properties window for the file and de-select the
Read-only option) or choose a different library to be active.
Q:
Why do I receive an error message when
I export my Xfmea
project to an XML file and then try to open the XML file
in BlockSim?
A:
You will receive an error message
in
BlockSim when you try to open an XML file that was created
in
Xfmea if at least two higher level items in the Xfmea
project have the same name. This is because any item that
has one or more sub-items is represented as a subdiagram
in BlockSim and the diagram names in BlockSim must be unique.
This will also occur if the project and a higher level item
have the same name because the project is also represented
as a diagram in BlockSim.
When you receive this error message in BlockSim, you
will be asked if you want to see the error report. Click
Yes so you can identify the errors in the XML file.
You may be prompted to enter a path for the word processor
that will display the error report. Type the pathname for
an application on your computer that can open a text file
(e.g. Notepad, WordPad, etc.). For example, enter
C:\Windows\System32\Notepad.exe. (Please note that if this
is not a valid pathname/filename on your computer, then
the report will not open.) Click OK. The report will
automatically open in the specified application with a list
of the errors that have been found in the XML file. You
can then go back to your Xfmea project and correct these
errors, export the revised project to XML and then open
the XML file in BlockSim.
Q:
How do I replace the logins
for existing Xfmea Enterprise user accounts if my company's
domain name changes?
A: SQL Server databases in
Xfmea Enterprise use Windows NT Authentication.
Therefore,
if the company's "domain" changes, the administrator will
need to replace the SQL Server Logins for existing Xfmea
Enterprise database users to reflect the new domain name. See Technical
Support document # RS40001 for
detailed instructions.
Q:
How can I print column headings
on every page of a report generated by Xfmea or RCM++?
A: If you want to print column
headings on every page of a report generated by
Xfmea
or
RCM++, there is an option to set this
automatically for reports generated in Microsoft Excel and
a workaround to apply this to reports generated in Microsoft
Word. See Technical Support document #
RS40003 for detailed instructions.
Q:
What are the
minimum database maintenance recommendations
for my Xfmea Enterprise or RCM++ Enterprise database?
A: With enterprise-wide,
database-driven software applications such as
Xfmea
Enterprise and
RCM++ Enterprise, it is important to have established
procedures to assure that proper database maintenance
and backup activities are being performed. Technical
Support documents # RS40005
(SQL Server) and # RS40006
(Oracle) present ReliaSoft's
recommendations for the minimum database backup and
maintenance activities that should be performed in SQL Server
and Oracle to protect the organization's data and keep the system running
smoothly.
Q:
What should I do to protect my data in
an Xfmea or RCM++ Standard database?
A:
ReliaSoft's
Xfmea and
RCM++
software products work with Microsoft Access databases
in the back end for storing analysis data. These database
and library files (e.g. *.rx4, *.lb4, *.rx5,
*.lb5) will be subject to the
same limitations and vulnerabilities as any other Access
database. Therefore, Technical Support document #
RS40010 provides some recommendations
for standard precautions that all users can take to protect
the data in their Xfmea/RCM++ Standard databases from
this type of corruption and reduce the impact of the data
loss if corruption is unavoidable.
Q:
Why don't Xfmea and RCM++ provide a Save command?
A:
ReliaSoft's
Xfmea and
RCM++
software products are database-driven applications that
store data in a relational database on the back end and
have the potential for simultaneous access by multiple users.
Therefore, the software behaves somewhat differently than
a Microsoft Word document or Weibull++ project file that
can be edited by only one user at a time. One of the differences
is in how the analysis data is saved. In Xfmea and RCM++,
your changes are saved whenever you click OK to close
a properties window and, when working in the FMEA Worksheet
View, whenever you navigate away from the cell you were
typing into. The software does not provide a separate
Save command in the File menu (like Word or Weibull++)
because in Xfmea/RCM++, your changes are saved automatically
while you're updating the analysis.
Q:
How do I turn off the RPNs in the DRBFM
Utility?
A:
The Design Review Based on Failure Mode (DRBFM) utility
in Xfmea and
RCM++ includes Risk Priority Number
(RPN) columns if those columns have been activated for the
associated FMEA. The workaround for users who wish to use
the RPN columns for FMEAs but not for DRBFMs is to disable
the RPN options in the Project's Interface Style when you
are working with DRBFMs and then enable the RPN options
again when you are working with the FMEA. See Technical
Support document # RS40009 for
detailed instructions.
Q:
How can I distribute the
same User Setup settings to other
Xfmea
or
RCM++
users?
A: When using the
Xfmea
or
RCM++ software, an organization may want to standardize
certain elements for all users, such as the priority colors
and the displayed math precision. In these cases, you can
have one user set the preferences on his/her machine and
then export the settings so that other users can import
them to their machines. See Technical Support document #
RS40011 for detailed instructions.
Q:
How can I import the AIAG
4th Edition Automotive DFMEA and PFMEA Rating Scales into
an Xfmea 4 or RCM++ 4 Library?
A: ReliaSoft's
Xfmea
and
RCM++ are shipped with a default library that includes
predefined settings that you can use to configure the software
to fit the column names, rating scales and other details
from the major published standards for FMEA (such as SAE
J1739, AIAG and MIL-STD-1629A).
In June 2008, the AIAG released the new Fourth Edition
of their Potential Failure Mode and Effects Analysis
guidelines, which includes modifications to the Severity,
Occurrence and Detection rating scales recommended for automotive
industry Design FMEAs and Process FMEAs. ReliaSoft has updated
the default library for Version 4 to contain the rating scales from AIAG
4th Edition. See Technical Support document #
RS40012 for detailed instructions.
Q:
How does ReliaSoft's Criticality Analysis
calculation method differ from the original MIL-STD-1629A
and why?
A:
The original MIL-STD-1629A approach to quantitative criticality
analysis assumes that the failure behavior of each item
follows an exponential distribution and can therefore be
defined with a failure rate (λ)
that does not vary with time. However, in reality, the constant
failure rate assumption is not valid for many types of components
that will be analyzed with the FMECA methodology, including
components that exhibit infant mortality, wearout or other
types of non-random failure behavior. See Technical
Support document # RS40008 for
a discussion of the quantitative criticality analysis method
used in ReliaSoft's
Xfmea and
RCM++ software.
Q:
Why don't Xfmea and RCM++ record a separate
Detection rating for each Control?
A: There is no benefit to calculating
a separate RPN for each Control, since there is no need
to prioritize Controls for corrective action. If there are
multiple Controls in place for a single Cause then even
if each Control is rated separately, there must be some
way to select a single Detection rating that will be used
to calculate the RPN for the Cause, which is the actionable
level of the analysis. Some analysts may choose to rate
each Control and select the lowest rating but many will
choose to take all Controls into account and assign a single
overall rating. See Technical Support document #
RS40007 for a detailed explanation
of the approach taken in Xfmea and RCM++.
Q:
Why does RCM++ place Effects
before Causes?
A: The
RCM++ software
supports all 7 questions required for an RCM analysis but
it considers the questions in a different sequence than
the SAE JA1011 and JA1012 guidelines recommend. The reasons
for this include 1) consistency with FMEA/FMECA and MSG-3
analyses, 2) intuitiveness and convenience of placing the
Cause (Failure Mode) adjacent to applicable actions/tasks
and 3) efficiency of defining and categorizing an Effect
one time when it is the same for multiple Causes (Failure
Modes). See Technical Support document #
RS40002 for a more detailed discussion
of this issue.
Other FAQs for RCM++ are presented under
Xfmea and FMEA/FMECA Analysis listed
above.
Q:
What are the
minimum database maintenance recommendations
for my database?
A: With enterprise-wide systems
such as XFRACAS, it is important to have established procedures
to assure that proper database maintenance and backup activities
are being performed. Technical Support documents #
RS40005 (SQL Server) and RS40006
(Oracle) present ReliaSoft's
recommendations for the minimum database backup and
maintenance activities that should be performed in SQL Server
or Oracle to protect the organization's data and keep the system running
smoothly.
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