Failure Mode - DOE-HDBK-1100-20040064

DOE-HDBK-1100-2004

DEFINING THE PROCESS.

This step identifies the specific vessels, equipment, and

instrumentation to be included in the FMEA and the conditions under which they are

analyzed. Defining the problem involves establishing an appropriate level of resolution

for the study and defining the boundary conditions for the analysis.

The required level of resolution determines the extent of detail needed in a FMEA. The

choices for the level of resolution range from the subcomponent level to the system level.

To satisfy PSM Rule requirements, most FMEAs should be performed at the major

component level. This level provides the best trade-off between the time necessary to

perform the analysis and the usefulness of the information gained from it.

Defining the analysis boundary conditions requires the following.

Identifying the system or process to be analyzed.

Establishing the physical boundaries of the system or process.

Establishing the analytical boundaries of the system or process.

Documenting the internal and interface functions.

Documenting the expected performance of the system, process, or equipment

item; the system or process restraints; and the failure definitions of the

equipment items, the process, or the system.

Collecting up-to-date information identifying the process equipment and its

functional relationship to the system.

Functional narratives about the system or process should include descriptions of the

expected behavior of the system or process and the equipment components for each

operational mode. Narratives should describe the operational profiles of the components

and the functions and outputs of each.

To assist in the review, block diagrams should be constructed which illustrate the operation,

interrelationships, and interdependencies of functional components for each equipment item.

All interfaces should be indicated in these block diagrams.

PERFORMING THE ANALYSIS.

The FMEA should be performed in a deliberate, systematic

manner to reduce the possibility of omissions and to enhance completeness. All failure modes

for one component should be addressed before proceeding to the next component. A tabular

format is recommended for recording results. A FMEA worksheet is produced by beginning at

a system boundary on a reference drawing and systematically evaluating the components in the

order in which they appear in the process flow path. A worksheet such as that shown in Table

4.20 should be completed for each equipment item, as follows.

Failure Mode. The PrHA team should list all of the equipment item and interface failure

modes. Given the equipment's normal operating condition, the team should consider all

conceivable malfunctions.