The situation

A large Gulf Coast refiner experienced a series of corrosion failures on the atmospheric overhead line, resulting in significant refinery downtime and repair costs. Prior to the equipment failures, routine sampling suggested periods of very low pH (pH less than 3) in the condensed water for 12+ hours, but the root cause was still yet to be identified.

the solution

A root cause failure analysis highlighted a key action to increase the amount of sampling to further clarify the possible cause(s).  3D TRASAR™ Technology for Crude Overhead Systems (3DTCOS) was installed and connected to the DCS for improved understanding of the real time behavior of their overhead. The 3DTCOS outputs were set to alarm both Nalco Water and refinery operations of process conditions with high corrosion risk.

the results

The 3DTCOS tracked pH dips and chloride spikes, linking back to mud washing on the desalters. Each pH/chloride event caused short-term pressure fluctuations and a drop in caustic dosage. This lead to a mechanical survey on the unit that identified mud wash piping pressure interferences and operational differences between the desalter trains as the root cause, which was fixed at the next TAR.

The 3DTCOS was critical to understand the mechanical, operational, and chemical causes of this corrosion event, and the estimated reliability savings calculated by the refiner was greater than $6.7M per year.