F121: Premature Failure of Newly Constructed Heat Exchanger TubeSheet

In harsh environments like urea and ammonia, carbamate corrosion is the most common cause of failure. A newly installed heat exchanger experienced a premature failure in the tubesheet resulting in a complete plant shutdown. The new heat exchanger was in service for less than a year. The material of construction of the tubesheet is carbon steel overlaid with a special stainless steel grade. A sample from the tubesheet was collected to investigate and identify the damage mechanism. A detailed metallurgical failure analysis for the tubesheet sample was performed using optical microscope, SEM, XRF, and mechanical testing to determine the damage mechanism. In addition, recommendations were provided to be considered during any fabrication of a new heat exchanger especially for the tubesheet.