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When you select the Feasibility of Objectives allocation model in the Allocation utility, the Elements field in the control panel will update automatically to display the number of blocks that you have selected to include in the analysis (i.e., the number of check boxes that are selected in the Include column of the table).
In the Reliability Goal field in the control panel, enter the desired overall reliability for the system (expressed as a decimal from 0 to 1, excluding 0). Then enter the following information for each selected block in the table:
The Intricacy Factor represents how intricate the element is, expressed as a number from 1 to 10 where 1 is simple and 10 is very complex.
The State of the Art factor represents how technologically up-to-date the element is, expressed as a number from 1 to 10 where 1 is mature and 10 is new.
The Operating Time Index factor represents how continuously the element is in operation, expressed as a number from 1 to 10 where 1 is a low duty cycle and 10 is continuous operation.
The Environment factor represents how harsh the element's environment is, expressed as a number from 1 to 10 where 1 is benign and 10 is severe.
Once you have entered all required information, click the Calculate icon. The control panel displays the following totals calculated for all blocks in the analysis:
Failure Rate displays the total failure rate, expressed in failures per million hours (FPMH) for MIL-217 and NSWC, and in failures per billion hours (FITS) for Bellcore/Telcordia and FIDES.
MTBF displays the total MTBF, expressed in hours.
Composite Rating (Wfk) displays the total weighting factor.
In addition, the following results will be displayed in the table for each block selected to be included in the analysis:
The Weighting Factor is the calculated weighting factor for the block, which is the product of the four input factors (i.e., Intricacy Factor, State of the Art, Operating Time Index and Environment).
The Percent Ck is the normalized weight for the block, based on the weighting factors for all blocks in the analysis.
Allocated Failure Rate is the recommended failure rate for the block, based on the allocation analysis. This calculated result is expressed in failures per million hours (FPMH) for MIL-217 and NSWC, and in failures per billion hours (FITS) for Bellcore/Telcordia and FIDES.
Allocated MTBF (hrs) is the recommended mean time between failures for the block, based on the allocation analysis. This calculated result is always expressed in hours.
Current Failure Rate is the current failure rate for the block based on the current reliability prediction so you can compare with the recommended value.
Description:
Does not require detailed failure history of product elements.
Applicable to all repairable electromechanical products.
Element allocation factors are computed as a function of numerical rating of:
Product complexity (1 - simple to 10 - very complex)
State-of-the-art (1 - mature to 10 - new)
Operating time (1 - low duty cycle to 10 - continuous operation)
Environment (1 - benign to 10 - severe)
The four criteria ratings are multiplied together to get an overall weighting and normalized so that the product sum is 1.
The element allocation is then based on the normalized part of the product reliability goal.
Model:
and:
where:
Ck = normalized weight of element:
Wfk = composite rating for element k
and where:
λs = Product failure rate.
T = Operating duration.
λk = Allocated element k failure rate.
N = Number of elements.
rik = ith rating result for a factor for element k.
© 1992-2017. HBM Prenscia Inc. ALL RIGHTS RESERVED.
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