Serial Replacement (which is also called prioritized replacement) is an approach to maintaining a system in which all items that have been isolated by diagnostics (i.e., all items in an isolated fault group) are replaced in prioritized order with the system being re-diagnosed after each replacement. Some contracts allow some amount of serial replacement to be assumed when evaluating the diagnostic capability of a design. Lambda Search is a commonly used method of prioritizing serial replacement based on failure rate. Compare with Block Replacement.
In the eXpress, the following fault resolution metrics assume the serial replacement of isolated faults.
Probability of Isolating Items in Category to Fault Group of Size 1 Using Only Testing
Subset FD/FI Statistics Report
When considering whether or not Serial Replacement is suitable for a particular design, bear in mind that this approach will tend to reduce the number of False Removals, possibly at the expense of a longer Mean Time to Repair (since the system is re-diagnosed after each replacement). Serial Replacement may actually improve the Mean Time to Repair, however, when the collective time to replace isolated items greatly exceeds the time to isolate the failure. The Analyst should also bear in mind the risk of maintenance-induced failures when considering the use of Serial Replacement.
In addition to Serial Replacement, eXpress diagnostic assessments support Block Replacement.
