Equal Allocation Model

When you select the Equal allocation model in the Allocation utility, you must enter the following information on the control panel:

The Reliability Goal is the overall desired reliability for the system, expressed as a decimal from 0 to 1, excluding 0.
The Operating Time is the length of time that the system will operate, in hours.

In addition, the Elements field will be 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).

Once you have entered all required information and clicked the Calculate icon, the following information will be displayed in the table for each block selected to be included in the analysis:

Reliability Allocated displays the reliability goal for the block, expressed as a decimal value from 0 to 1, excluding 0.

Allocated Failure Rate displays 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) displays 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 displays the current failure rate for the block based on the current reliability prediction so you can compare with the recommended value.

About the Equal Allocation Model

Description:

Assumes a series of n sub-elements, each of which is assigned the same reliability figure of merit.
The weakness is that the elements are not assigned reliability design goals in accordance with the degree of difficulty associated with achieving the goal.

Model:

or:

where:

Rproduct = Product reliability requirement/goal.
= Reliability allocated to the ith element.
i = 1, 2, ..., n elements.

where λ can be obtained by:

(failures per hour).