List each potential failure mode for the particular subsystem function. The assumption is made the failure could occur, but may not necessarily occur. A recommended starting point is a review of maintenance logs, downtime reports, field service reports, warranty documents, scrap reports and group “brainstorming.”
The task of identifying subsystem failure modes can take either of two approaches:
Functional approach: involves listing each subsystem, its functions, and the failure modes leading to the loss of each function. The functional approach is used most often in the preliminary design stages when machinery design detail is not complete. When taking a functional approach, it may be necessary to list the cause(s) in column 14 before listing the effect(s) first in column 11. This could assist in selecting the appropriate severity rating.
Hardware approach: involves listing each part, and its probable failure modes. The hardware approach is used most often when detailed part design information is available.