ITEM TOOLKIT

Chapter 5 Predictions 119
4. Derating Components
Most equipment failures are precipitated by stress. When applied stress exceeds the inherent strength of the part, either a
serious degradation or a failure will occur. To assure reliability, equipment must be designed to endure stress over time
without failure.
Design stress parameters must be identified and controlled. Parts and materials must be selected which can withstand these
stresses. Derating is the selection and application of parts and materials so that the applied stress is less than rated for a
specific application.
For example, derating is the negative slope of a power-versus-temperature graph. It shows that as the operating ambient
temperature increases, the output power of a particular component drops to ensure reliable system operation. Derating
curves provide a quick way to estimate the maximum output power of a device at a given temperature.
Following are several derating standards that are included within ToolKit:
NAVSEA TE000-AB-GTP-010
Parts Derating Requirements and Application Manual for Navy Electronic Equipment.
MIL-HDBK-1547
Electronic parts, materials, and processes for space and launch vehicles.
MIL-STD-975M (NASA)
Part selection for electrical, electronic, and electromechanical parts used in the design and construction of space flight
hardware in space missions as well as essential ground support equipment (GSE).
NAVAIR-AS-4613 Class A/B/C
Application and Derating requirements for electronic components, General specification F.
For all ToolKit prediction modules, you can choose a derating standard to use for the components in the system. Once a
standard has been chosen, each component indicates if its current stress levels are within the derating standard or not.
Graphical displays of the situation are available for ease in identifying problem areas. Parametric displays are also available
to show the temperature vs. stress situation of the component.
User defined derating “standards” can also be created. They are saved as .itd files, and are associated with the project file.
When a project is opened, if the components are being derated, the associated derating file is applied. If the derating file is
not available, the project will still open normally, but you are presented with a warning window, and can search for the
derating file if desired.
A derating file manager is also included to help manage the different derating files, whether included with ToolKit or user
defined.