Pharma glass defects - Part 20. Broken general

Hello everyone – welcome to an ongoing series of posts covering visual defects in pharmaceutical glass vials.? While it feels great to hit Part 20, I still have a long way to go if the goal is to make it through the entire lexicon covered by PDA TR 43.? So without further ado, I’d like to introduce the “Broken General” defect.? It perhaps reads a little odd – we’re considering breakage of a general nature in which a vial is fully separated into two or more distinct pieces.? We use the term “general” to differentiate this defect from two specific failure modes – i.e., the Broken Detached Bottom and Broken Ring Off defects (to be covered in future posts).? This sounds straightforward enough, but there are potential sources of confusion. ?For example, the Chip defect is also a form of breakage in which the glass vial has now been separated into two distinct pieces (a small fragment and the rest of the container).? However, the wall of the container is still presumably intact because the Chip is a relatively shallow feature.? Similarly, the Crack defect occurs when the container wall has been compromised, but the vial is still one piece.

The Broken General defect is considered a Major A defect because it renders the container unusable.? No tools are needed for classification – a simple visual assessment should be sufficient.? However, knowing that the container is broken is very different from knowing why it is broken.? Let’s also remember that breakage is the result of a sufficiently large tensile stress acting upon a sufficiently large flaw in the glass container (refer back to my post on glass strength for more information).? So where is the stress and/or damage coming from?? The “Root Cause” column within PDA TR 43 indicates that the tubular conversion process is one potential source because of thermal shock, but it also states that handling is the more likely source.? Handling-related events that can result in glass breakage is a big category.? A discussion of the tools and procedures needed to identify the root cause of glass breakage is beyond the scope of this discussion, although I hope to address them in future posts involving topics such as fractographic analysis.? I’ll just note for now that what is identified as a Broken General defect will often have its origins connected to another defect type – e.g., Stones, Metal Marks, etc.

Another detail of the Broken General defect’s definition that’s worth considering is the phrase “…two or more distinct pieces”.? There’s no upper limit to that statement – how many pieces of glass might be generated during breakage?? As is often the case, it depends.? The amount of fragmentation that occurs during breakage is related to the creation of new glass surfaces as a way to release stored strain energy within the material. ?We can therefore generally conclude that a small amount of glass fragments indicates a relatively low stress break while significant fragmentation indicates a large applied stress at the time of failure.? Just understanding this level of information can put you on useful path towards identifying the root cause of breakage.

Questions or comments?? Please leave them below or feel free to directly contact me.