There is a great Greek paradox/puzzle called the Ship of Theseus. There are multiple versions and derivations to it. My favorite version is as follows (highly watered down);
Theseus bought a new ship. Each day he replaced one part of the ship. Plank by plank, and sail by sail and finally oar by oar. Finally no part of the original ship remained. Now the paradox is this – is the ship same as the original ship now that every part has been replaced? This is a great thought experiment about identity and understanding of self. If we go one step further and build a new ship with all the parts that were replaced from the original ship, is the new ship the same as the original ship?
When I read about this great paradox, somehow my mind started thinking about process validation. We get a new piece of equipment, say a pouch sealer, and during the course of multiple years, the equipment gets many of the parts replaced and many of the parts get worn down. Is the sealer the same as the original sealer? Is the original validation still valid?
This is where two main aspects of the process validation are important.
1) Maintaining the validated state; and 2) Revalidation Criteria.
Maintaining the validation state includes proper monitoring of the process, once it is qualified, to ensure that the process is in a state of control. For example, for a sealer validation, we might perform seal strength testing and visual inspection based on a frequency and defined criteria. Any adverse results shall be reviewed and rectified.
The revalidation criteria can be based on predetermined criteria as well. Some examples are below.
1) Major parts of the equipment replaced.
2) Equipment relocated to a new facility.
3) Equipment not in use for more than a year.
4) Significant changes to the process like raw material change.
5) Negative trends in Quality.
Both maintaining the validated state and revalidation requirements must be part of a process validation protocol.
Keep on learning…