In the front end of the olefins unit, liquid or gaseous feed stock is cracked and quenched. The front end consists of cracking furnaces and quench sections. From here, the gas goes to the back end for further processing. In the front end of an olefins plant, damaging mechanisms include carburization and hot corrosion of radiant tubes, thermal fatigue, Inter Granular Stress Corrosion Cracking-IGSCC, graphitization of carbon steel tubes and caustic cracking.

In the back end of an olefins unit, the process gas is compressed and separated into products. The entire stream is caustic washed. Then, it is separated in a series of distillations. Distillations of the lightest fractions are done at cryogenic temperatures. The common materials of construction and the potential process-related damage mechanisms will be identified and discussed. They include caustic SCC, brittle fracture, mercury liquid metal attack of aluminum and hydrogen cracking of nickel steels.

Examples of plant failures and solutions will be provided and discussed.