(106b) Unexpected Low Temperatures in Systems and Equipment That Nearly Led to an Excursion below the MAT

Our Company conducts a program to evaluate, classify, and mitigate potential brittle fracture scenarios in its plants and units in accordance with API 579-1 FFS part 3. This program divided the Crackers and PE/PP and CS/PVC plants into systems that underwent Level 1 and Level 2 assessment, and in some cases, Level 3. This risk scenarios identification program was revised a few times based on the historical records of our process data, including specifically some equipment and systems in the identification flow that, in a Level 1 assessment, would not be considered candidates for low temperatures and, therefore, would not be susceptible to a brittle fracture scenario.

This paper presents these learnings that prompted the revisions in our brittle fracture risk identification process in some equipment or systems with C3 in the gas phase and C4 in the liquid phase, as well as unexpected and localized low temperature experiences in the inventory of liquids in previously gasified units. We also discuss how we address these events, whether through dissemination and training, change in procedures, or the installation of barriers, even though they not excursions below the MAT.

This paper is a complement to the AIChE 189b paper of 2024