Auto-Refrigeration & Flashing and Cold Ambient Exposures
We see around a half dozen pressure vessels in a “service” they were not initially designed for. There are literally hundreds of excuses as to why we find these issues, but they are simply excuses. It was not uncommon for us to find a PV in an NH3 refrigeration process with an MDMT of -20°F being operated in the -40°F range, and the facility would say, “We’ve been operating like that for X years, and nothing has failed.” So let’s talk about what the Minimum Design Metal Temperature (MDMT) means and how it plays a crucial role in process safety when the chemical we’re covering is a gas at standard temperature and pressure.