Hazards of high oxygen concentration, mixing incompatible materials, and more in process safety newsletters

From AIChE’s “Process Safety Beacon” newsletters:

Hazards of high oxygen concentration – “Autoignition temperature (AIT) and minimum ignition energy (MIE) are lowered markedly by higher oxygen content. Substances ignite more readily, burn faster, generate higher temperatures, and are difficult to extinguish.”

Mixing incompatible materials in storage tanks – “Understand potential hazardous interactions among different materials that you unload into your plant’s storage tanks. The July 2016 “Beacon” describes the “Chemical Reactivity Worksheet,” a tool which your engineers and chemists can use to help understand chemical interactions.”

…but the temperature was below the flash point! – “Because the vessel was operating below the flash point of the contents, the concentration of fuel vapor in the vessel atmosphere was too low for ignition. There should not have been an explosion hazard. But the fuel may not only be present as a vapor (remember dust explosions). The investigation determined that the vessel agitator created a fine mist of liquid droplets (Fig. 2). The tiny droplets were estimated to have an average size of about 1 micron. … Flammability testing demonstrated that the mist could be ignited at room temperature in air – and the mist would be ignited even more easily in a pure oxygen atmosphere.”

Are you sure that vessel is empty? – “When returning equipment to service following maintenance, make sure that it is completely clean and does not contain anything that could be incompatible with process materials or operating conditions.”

Corroded tanks! – “Holes in tanks can allow toxic or flammable vapors to escape into the surrounding environment. Corrosion can weaken tanks, pipes, or other equipment so they can fail under normal operating conditions.”

Incident investigation of a steam pipe failure – “There is a reason for including a team of people with different expertise in an incident investigation… In this incident, the engineers and other experts did not recognize the machine tool marks on the failed pipe, and yet it was immediately obvious to the expert, experienced machinist. His knowledge completely changed the conclusions of the investigation, and was essential for understanding the cause of the incident.”

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