Choosing suitable Reliability Prediction Method

RAM Commander supports more than 30 different reliability prediction methods. Different methods use different calculation models and assumptions, use different input data and may give different results for the same component. Some metods are suitable for mechanical components only, some for electronic, some methods can't provide prediction results for some temperature ranges, some old methods do not provide results for new component types (like 64-bit microprocessors in old MIL-217) etc. All these characteristics should be taken into consideration during the method selection.

ALD Ltd. does not invent the reliability prediction methods - we just implement and computerize the calculation models described in officially published standards. That's why RAM Commander user manual does not provide help and detailed instructions to specific reliability methods usage - you have to be a reliability engineer, you have to obtain, read and understand the specific reliability prediction standard book you are going to use. Only then there will be a confidence in results you get from RAM Commander.

Classification of reliability prediction methods and some short description for the most popular methods is given in the table below - it may help to choose the required reliability prediction method for your project:

Method	Mode	Supported components	Features	Description
ALCATEL	Operating	Electronic
BELLCORE Issue 5	Operating	Electronic		Document reference TR-NWT-000332
BELLCORE Issue 6	Operating	Electronic
BRITISH TELECOM HRD4	Operating	Electronic
BRITISH TELECOM HRD5	Operating	Electronic
CNET RDF93 rev 02/95	Operating	Electronic	French	Based on CNET, French reliability prediction method for commercial applications
FIDES 2004	Operating	Electronic	Mission-profile based	The latest reliability prediction standard created by FIDES Group - a consortium of leading French international defense companies: AIRBUS, Eurocopter, Giat, MBDA and THALES.
FIDES 2009	Operating	Electronic	Mission-profile based, New	New version of FIDES 2004, Edition A, September 2010
GJB/Z 299B P. count	Operating	Electronic	Chinese
GJB/Z 299B P. stress	Operating	Electronic	Chinese
GJB 299C P. count	Operating	Electronic	Chinese, New	Both import and Chinese parts
GJB 299C P. stress	Operating	Electronic	Chinese, New	Both import and Chinese parts
GPRD	Operating and Non-operating	All		General Part Reliability Data - suitable for storage of temperature-dependent failure rates (see Specify known temperature-dependent FR)and also time-to-failure statistics and Weibull parameters calculation
HDBK-217Plus	Operating	Electronic	Mission-profile based, New	Published in May 2006 by Reliability Information Analysis Center (RIAC)
HRD5 TELECOMM	Operating	Electronic
IEC 62380	Operating	Electronic	Mission-profile based	RDF 2003. New version of UTE C 80-810.
ITALTEL IRPH93	Operating	Electronic
MIL-217E-1 P. stress	Operating	Electronic		by Department of Defence, USA
MIL-217F-1 P. count	Operating	Electronic
MIL-217F-1 P. stress	Operating	Electronic
MIL-217F-2 P. count	Operating	Electronic
MIL-217F-2 P. stress	Operating	Electronic
NPRD-95	Operating and Non-Operating	Mechanical and Electro-Mechanical	Library of aggregated historical failure rates data.	A library of failure rates for a large number of non-electronic components under various environments. The source of this data is the document NPRD-95, "Non-electronic Parts Reliability Data", released by RAC. Part category which provides a rough classification of parts (e.g., actuators, batteries, pumps, etc.) should be selected for each device. Next, the user selects a certain subtype (e.g., for batteries - Carbon Zinc, Lithium, etc.).
NSWC-98/LE1 Mechanics	Operating	Mechanical		US NAVY, Carderock Division of the Naval Surface Warfare Center. Nineteen basic mechanical components have been identified for which reliability prediction equations have been developed. All mechanical equipment is composed of some combination of these nineteen components. A designer can utilize the equations to determine individual component reliability and then combine the results in accordance with the system reliability diagram to determine total system reliability in its operating environment.
Telcordia Issue 1	Operating	Electronic		Telcordia SR332, Issue 1, May 2001
Telcordia Issue 2	Operating	Electronic		Reliability Prediction Procedure for Electronic Equipment, SR-332, Issue 2, September 2006
Telcordia Issue 3	Operating	Electronic	New	Reliability Prediction Procedure for Electronic Equipment, SR-332, Issue 2, January 2011
Siemens SN 29500-1	Operating	Electronic
Siemens SN 29500-2005-1	Operating	Electronic
Stress/Strength Analysis	Operating	All	Calculates Unreliability, not Failure Rate	Calculation of Failure Probability (Unreliability) by distribution parameters of Stress and Strength.
UTE C 80-810	Operating	Electronic	Mission-profile based, French	RDF 2000. Provides complex models that can handle permanent working, on/off cycling and dormant applications
MIL-217E-1 draft	Non-operating	Electronic
RADC-TR-85-91	Non-operating	Electronic
Reliability Toolkit (1995)	Non-operating	Electronic		Translates operating Failure Rates to Non-operating using coefficients.

When the decision is taken, you may set the default reliability prediction method for the whole project (see paragraph Project Configuration) or/and set different method for each particular component (see Item FR Calculation paragraph later in this chapter).