More Thoughts on POD’s and Penetrant Inspection

Our recent article about penetrant POD brought this response from Brian MacCracken, now retired, but an important figure in the penetrant
using community:

“I enjoyed this month’s Pen Prof, as I usually do. However, I would like to add my two cents about POD’s for FPI and if you want to quote me, feel free to do so. In fact, I am sure my opinion may stir up a hornets nest but since I am retired, I no longer have to be worried about being censored or politically correct.

In regards to last month’s Pen Professor, I would first like to say that I was involved in POD’s from the very beginning when POD’s were
just hitting the airline industry and that I was heavily involved with POD’s for over 28 years. I went around the world performing POD’s because my company was contractually required to do so. I was even involved in writing a specification for my company on the “how to”
perform POD’s for FPI”. As you can see, I am very experienced, well versed and have a lot of knowledge when it comes to POD studies
or evaluations for FPI. With all this being said, all I want to say is, “POD’s for FPI are the biggest façade that there ever was”. It truly
is a joke and can be scary to think that engineering people use these so called POD numbers to sink their teeth into. Regardless of what this number comes out to be, people will apply this number as gospel. Now that they have a number, or POD, they can now answer the old
proverbial question, “how small of a crack can I find?” I wish I had a dime for every time I was asked this question during my almost 41 years on the job. If I did, I could have retired earlier. I could go on and on with my opinion and the wisdom I have gained over so many years of doing countless POD studies, but I would likely have many people disputing my words, and it wouldn’t be worth it. However, I can support and back up my claims and in fact, I have always wanted to write a paper and entitle it, “The façade of POD’s for Fluorescent Penetrant”. I think if I had done this paper, there would be a lot of people who would show up and thank me for speaking out, and then there will be the ones that would still argue that these POD numbers are real numbers and are the true probability and detectability
of the FPI process.

As I stated before, feel free to quote me in your next Pen Prof.or just file it all away.” We thank Brian for his input on this and we are sure he is not alone in his view.