Relief valves distillation towers

In 1974,1 was promoted to the position of operating supervisor at the Amoco Refinery in Texas City. I had four tall distillation towers on my alkylation unit. The towers had relief valves at the top of the tower. These relief valves vented to the atmosphere. Over-pressuring was common and I saw the white plume blowing from the valves on many occasions. Never did I stop and think, "What will happen if a relief valve opens when a tower is in fully developed flood "... 

I have never seen or heard about tray failure due to a relief valve opening. However, in a packed distillation tower, I am aware of at least one such incident, also at the Whiting Refinery. 

Relief valves are often placed toward the bottom of distillation towers. In particular on crude oil fractionators, relief valves are commonly located in the flash zone (i.e., at the feed elevation). 

Air Point source emission stack, vent (e.g., laboratory hood, distillation unit, reactor, storage tank vent), material loading/unloading operations (including rail cars, tank trucks, and marine vessels). Fugitive emissions pumps, valves, flanges, sample coUection, mechanical seals, relief devices, tanks. Secondary emissions waste and wastewater treatment units, cooling tower, process sewer, sump, spill or leak areas. Equipment wash solvent or water, lab samples. 

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