Process Validation, Part 1

Ship of Theseus

Published: Tuesday, July 11, 2017 - 12:02

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, sail by sail, and oar by oar. Finally, no part of the original ship remained. Now the paradox is this: Is the ship the 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, 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, many of the parts get worn down and replaced. 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
2. Revalidation criteria

Maintaining the validation state includes proper monitoring of the process, once it is qualified, to ensure that it 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:
• Major parts of the equipment replaced
• Equipment relocated to a new facility
• Equipment not in use for more than a year
• Significant changes to the process, such as raw material change
• Negative trends in quality

Both maintaining the validated state and revalidation requirements must be part of a process validation protocol. In tomorrow’s column we’ll look at the problem of induction.

About The Author

Harish Jose

Harish Jose has more than seven years experience in the medical device field. He is a graduate of the University of Missouri-Rolla, where he obtained a master’s degree in manufacturing engineering and published two articles. Harish is an ASQ member with multiple ASQ certifications, including Quality Engineer, Six Sigma Black Belt, and Reliability Engineer. He is a subject-matter expert in lean, data science, database programming, and industrial experiments, and publishes frequently on his blog Harish’s Notebook.