I have written about this topic several times, but in reading the newest edition (2015) of NATIONAL BOARD INSPECTION CODE I came across some actual language that must be considered when establishing our Safe Upper Design Limits for our pressure vessels. I feel like I must state the obivious once again – a relief valve is NOT a pressure control valve! It should ONLY lift as a LAST RESORT to protect the vessel from being over pressurized. Any time we have an event where a RV has lifted, it MUST BE investigated as a serious incident! I have highlighted the language that is most critical…