System FMEAs are designed to understand the overall
reliability of the system and the adverse effects of failures at a system/subcomponent level on the customer.
In our reliability department, we use System FMEAs in conjunction with boundary diagrams, QFD, and reliability schematics (AND/OR relationships). All of these tools help us understand which systems or subsystems must be redesigned to obtain the necessary system reliability.
Using the System
FMEA, a team can better understand how failure modes in the component levels FMEAs will effect the overall product performance. From there, a better understanding of failures in the process FMEAs can be understood.
FMEAs should be used as a system to better understand how to plan/execute a robust part and process. Always attack the highest RPN on the most critical components/subsystems.