If you want a spirited process safety debate, simply mention the practice of having “intervening valve(s)” before or after a Pressure-Relieving Device (PRD). There are some who swear that it is not allowed, but in fact, it is. This is how I learned about the “Car-Seal” program early in my career. ASME B31.12 is one of those RAGAGEPs that allows this practice WHEN it meets certain criteria, such as a Car-Seal Program.