Page 126 - Safety Risk Management for Medical Devices

Risk Analysis Techniques 105

the PFD with the stakeholders, e.g., manufacturing engineers and technicians, to
debug the PFD. Perform the process using the PFD to verify the PFD. Add any dis-
covered missing steps.

12.7.1.4 Analyze
Cite each step of the process that was described in the PFD, in the PFMEA template.
• Example process step: rinse casing.
For each process step, describe the purpose or intent of the step.
• Example purpose: to remove debris from machined casing.
For each process step, identify the ways in which it could fail. If there is more than
one way to fail, enter each Failure Mode in a separate row.

Failure Modes of a process step could be:
• Complete failure
• Partial failure
• Intermittent failure
• Process drift, which could lead into failure

Process step failures can have one of four types of potential outcomes:
1. Desired outcome is achieved.
2. Desired outcome is not achieved.
Example: rinse is incomplete.
3. Desired outcome is achieved but some deleterious unintended outcomes are
also achieved. Example: rinse is complete, but rinse-head impacts casing.
4. Desired outcome is not achieved, and some deleterious unintended outcomes
are achieved. Example: casing becomes contaminated due to use of wrong
rinse solution.

Process step Failure Modes with outcomes 2, 3, or 4 are cited in the PFMEA.
In the “Causes/Mechanisms of Failure” column, describe realistic potential Causes of
failure. Example: rinse timer drifts. Avoid highly imaginative but improbable Causes.
While they may be interesting, or even entertaining, they don’t add real value to the
product development process and waste valuable engineering time in endless discussions.
The next two columns are End Effect and Local Effect. Each Failure Mode has an
End Effect. An End Effect is that which is visible at the boundary of analysis. That is
the impact of the Failure Mode which is perceivable on the product of the process.
Example: metal debris on casing causes short circuit in the electronics. A Local Effect
is not perceivable on the product of the process. It may be something internal that