An inadvertent mixing of hot and volatile fluids can result in overpressure if the volatile fluid is vaporized and sufficient volumetric accumulation occurs.  Hot fluid temperatures exceeding the bubblepoint temperature of the volatile fluid is the common criterion for establishing applicability of the scenario, and cases in which that hot fluid temperature exceeds what is known as the superheat limit of the volatile fluid are usually identified as requiring a refocus of engineering effort to prevention rather than mitigation.  For cases involving distillation systems immediately downstream, an additional screening for the scenario applicability can be made based on the capacity of the cooling system.  Read more in our white paper Mixing of Hot and Volatile Fluids.