New in RWB Version 10.2
A whole host of new features have been added to Reliability Workbench 10.2. These features are described below.
Integrated Parts Libraries
The IsoLib NPRD, IAEA and Electronic Parts Libraries have now been integrated into Reliability Workbench. These libraries may now be accessed directly from the Prediction, FMECA, RBD, Fault Tree and Event Tree modules. There are three libraries available – the Electronic Parts Library, the IAEA library (IAEA-TECDOC-508) and the NPRD library (NPRD-95). The Electronic Parts Library contains tens of thousands of common electronic parts and must be used in conjunction with a prediction standard to provide failure rate data. The IAEA and NPRD libraries contain failure rate data for mechanical components and may be used in conjunction with the Prediction, FMECA, RBD, Fault Tree and Event Tree modules. The large parts database may be quickly searched by part category or by text filters and selected parts may be transferred to a Reliability Workbench project using drag and drop.
Import Free Format FMEA/FMECA Data
The new version provides a facility to import FMEA data from typical FMEA standard formats that have been recorded, or transferred to, an Excel ‘csv’ file. A common feature of this type of format is that FMEA data for a single item or failure mode may flow over many rows of the spread-sheet. For example, a failure mode may be assigned multiple causes. In effect the spreadsheet represents a tree structure. The new facility can handle such formats and does not require the failure mode to be repeated for each individual cause (as would be the case when importing from a database).
FMECA Configuration Templates
Configuration templates may now be created and used to initialise new FMEA or FMECA projects. The template files contain information such as the text field header settings, grid layout settings and ranking descriptions. Template files may be passed on to users to ensure the FMEA or FMECA configuration is consistent within an organisation.
Up to 60 Text Custom Text Fields for FMECA System, Blocks and Failure Modes
Users may now utilise up to 60 custom text fields for the system, blocks and failure modes in a FMECA project.
FMECA Text Field Custom Headers Used in Report Designer Dialogs
Custom text fields are now referred to by their user-specified header names rather than Text1, Text2 etc. in the Report Designer dialogs.
FMECA Text Grouping, Lists and Non-Null Fields
FMECA system, block and failure mode text fields may now be grouped to provide easy navigation to the required text field when entering data. Custom text field headers are specified by selecting one of the ‘Text Field Headers’ options on the ‘Edit’ pull-down menu. By entering a group name at the beginning of a text field header (enclosed by special parentheses), the user can indicate a group name. For example, entering
<Notes>Data Source
will indicate that the text field header belongs to a group called ‘Notes’.
Users may also now indicate that a text field may only be populated by selecting from a phrase list. This may be done by adding the special character ~ before the text field header.
The special character ^ may be used to indicate that a text field cannot have a null value.
FMECA Function Blocks
The FMECA module now allows users to add function blocks to a project as well as the standard blocks that represent hardware failures. Function blocks and hardware blocks may be added at any level in the same project. Failure modes may be added below a function block in the same way as they may be added below a hardware block. In this way a single project could potentially represent the interaction of functional and hardware failures at any level of the FMEA structure.
FMECA Root Causes
Users may now optionally assign root causes at the lowest levels of the FMEA or FMECA structure. Root causes are directly connected to the lowest level failure modes in the FMEA or FMECA structure. A root cause can only be attached to a single failure mode at the lowest level whereas failure modes may be assigned multiple effects. If you choose to define root causes in a project then failure rate data or occurrence rankings and detection data must be entered at the root cause level.
FMECA Custom Ranking Descriptions
Reliability Workbench now allows users to specify descriptions to be associated with each of the 10 severity, occurrence and detection rankings associated with process and design FMEAs. In addition, users may specify equivalent failure rates and detection probability values for occurrence and detection rankings respectively. This allows the program to calculate ranking values through the FMECA hierarchy. This new facility is accessed through the ‘Edit, Ranking Descriptions’ pull-down menu option.
FMECA Display Rankings as Preference
Users may now set up custom FMEA or FMECA formats that display rankings in dialogs rather than failure rates and detection probabilities. This may be done by selecting ‘Display rankings as preference’ in the ‘Project Options’ dialog.
FMECA Text Level Categories
In previous versions of Reliability Workbench users could specify different text field headers and phrases depending on the level in the hierarchy of a block or failure mode. This level value started at zero for the system level and increased in value according to the position in the tree control displayed in the left window of the FMECA module. Now users can specify a different scheme as an alternative. Setting the ‘Use text level categories’ check-box in the ‘Project Options’ dialog will mean that a block or failure mode will be assigned a level value of 0, 1, 2 or 3 depending on the following criteria:
Blocks and failure modes attached directly to the system block will be assigned a level of 0. Blocks and failure modes at the root of the visible FMECA structure in the left hand window will be assigned a level of 2. Root causes will be assigned a level of 3. All other blocks and failure modes will be assigned a level of 1. This new facility allows users to control the text headers to be displayed in flexible FMECA structures with many hierarchical levels.
Manually Setting FMECA Results Severity Rankings
Users now have a choice of how to set results severity rankings in a process or design FMEA. By default severity rankings for results will be assigned by tracing the standard severity ranking down from the top level to the root failure modes or causes. By setting the ‘Manually set results severity rankings’ flag in the ‘Project Options’ dialog users can directly enter these values at any level of the FMECA.
Setting the FMECA Default Effect Level
By default immediate effects are assigned to the next level in the FMECA hierarchy. That is, an effect at one level is a failure mode at the next level up. In some circumstances users may wish to assign effects directly at the system level. Although this was possible with previous version of Reliability Workbench, users had to assign the effect via the ‘Failure Mode’ dialog if there were more than two levels in the FMECA structure. By setting the ‘Default effect level’ to ‘Level 0’ in the ‘Project Options’ dialog users can now instruct the program to assign effects at the system level by default.
FMECA Grid Options by Level
FMECA grid options may now be set by level. In the ‘Grid Options’ dialog users may now specify the level for which the display options apply. Users may set different grid options for up to 8 levels.
FMECA RPN History
Reliability Workbench now allows users to record a history of calculated system RPN and action results RPN values. A system’s RPN and RPNR values will change as the system design changes and the appropriate changes are made to the design FMEA. Users can choose to save calculated RPN values at any time by selecting the ‘Results, RPN History’ pull-down menu option. Recorded values may be displayed in graphical format together with extrapolated future values using the ‘RPN History’ graph type. This facility is only available if the ‘Display rankings as preference’ flag is selected in the ‘Project Options’ dialog.
New in RWB Version 10.1
For reference, here are the new features added to Reliability Workbench Version 10.1.
Reliability Allocation Module Added
The new ‘Allocation’ module may be accessed by selecting the appropriate tab in the right-hand window.
The new Reliability Allocation methods provide the means of assigning reliability targets to sub-systems and equipments based on a system reliability goal. Reliability allocation is normally applied during the design and development stages of a system.
Reliability allocation methods may recommend redundancy configurations to meet reliability targets as well as assigning reliability requirements of individual sub-systems and equipments. Some reliability allocations methods employ constraints on the system (such as cost and weight) whereas others employ grading (weighting) factors.
The new Allocation module allows the user to choose one of six methods for Reliability Allocation:
- Non-restricted equal allocation
- Non-restricted graded allocation
- Non-restricted proportional allocation
- Non-restricted redundancy proportional allocation
- Non-restricted reliability re-allocation
- Restricted direct research allocation
Reliability Workbench allows a system hierarchy to be constructed where sub-systems (defined directly below the system block) may be resolved into their components. There is no limit to the number of levels that may be defined.
Workbench will allocate reliability parameters on a top-down basis. First reliability allocation will be performed on the level directly below the system. Then the allocated parameters will be used as targets at the next level down.
217Plus™ Prediction Standard Added
217Plus™ is a methodology developed by the Reliability Information Analysis Center (RIAC) to aid in the assessment of system reliability.
It is the next generation of the PRISM® software tool initially released by the Reliability Analysis Center (RAC) in 1999 (which became RIAC in 2005) and contains twice the number of models as the original PRISM® tool.
The primary element of the 217Plus™ prediction module of Reliability Workbench is the component reliability prediction models. A system failure rate estimate is made by using the component models to estimate the failure rate of each component. These failure rates are then summed to estimate the system failure rate.
Telcordia Prediction Standard Upgraded to Issue 2
The Telcordia failure rate prediction models have been upgraded to Issue 2 (released by Telcordia in September 2006). A large proportion of the basic failure rate data has been revised in this issue (failure rates are generally reduced compared to the previous issue of the standard). In addition a number of new devices have been added.
Users can request Reliability Workbench to provide prediction data based on the new Issue or the previous 2 issues of the standard (by selecting the appropriate option in the ‘Prediction’ tab of the ‘Project Options’ Dialog.
Prediction Data Transfer Changes
The copy and transfer of prediction data to the RBD or fault tree modules would previously result in the RATE/MTTR model being created. In version 10.1, the RATE/MTTR model will only be chosen if the ‘Transfer Prediction Repair Data’ flag is set on in the ‘Data Link Options’ Dialog. If MTTR values are not transferred the RATE model is now created with a zero repair rate.
FMECA Module Severity Graph Ordering
The FMECA severity matrix graph now orders severity categories according to their weight values. The order is in increasing weighting from left to right.
Extend FMECA Memo-to-Text Fields in Reports
An ‘Extend memo-to-text fields in reports’ check box has been added to the FMECA project options Tab. If this check box is not checked, the program will truncate special FMECA ‘text’ fields in reports that are copies of ‘memo’ fields. This facility has been provided to ensure that record lengths do not exceed limits imposed by Access.
IEC 61508 Diagnostic Coverage Models Implemented in FMECA
The diagnostic coverage models described in IEC61508-6 have been implemented. Users may now categorize failures as safe or dangerous and assign a diagnostic coverage % to both safe and dangerous failures. The program calculates safe, dangerous, detected and undetected failure rates through the system hierarchy together with the ‘safe failure fraction’ as specified in the standard.