(26e) Aluminum Core Coldbox Failure Case Study

This paper addresses the failures of the aluminum coldbox cores due to thermal stresses coupled with internal pressure stresses from the process and determination of likely future failure locations.

Ineos Olefins and Polymers operates numerous aluminum core coldbox units globally. The coldbox units operate at temperatures ranging from +90 °F to -150 °F, with adjacent streams experiencing differential temperatures greater than the manufacturers recommended limit of 50 °F.

Failure of a coldbox core unit occurred with subsequent investigation determining the leak was from a crack between passes of the coldbox core upper section. Investigation into the process data, core construction factory records and similar failures globally, indicated that a combination of the factory repairs and thermal cycling led to a crack forming in a weld bead near the end of a repaired section. Open areas in the core illustrate areas of inadequate or non-fusion between the plates and side bars, resulting in a reduced cross section weld repair being the main pressure boundary. Similar failures have occurred in units globally with new acceptance criteria and inspection hold points determined to understand the effect of factory repairs on core life.

Revisions to the initial inspections and acceptance criteria from the manufacturer have been determined along with new inspection hold points and documentation criteria.