Failure analysis of 101-C ammonia plant heat exchanger

Long-term overheating is a major cause of failures in boiler tubes of different designs and operation conditions. These failures are usually related to the formation and growth of internal oxide scales or deposits at areas of high heat flux. Deposits might have different sources; poor water treatment and general corrosion in the system are two common types of these sources. Thickening of the deposit layer hinders heat transfer and local spots of high metal temperature are created in the tube wall. With increasing metal temperature, creep becomes much faster leading to tube failure under internal pressure. In this paper, a case history involving this type of failure is presented. Using finite element modeling the failure are analyzed and some methods to prevent this type of failure are recommended.