(40f) Cracked Gas Compressor Balance Line Failures

Walker, E., Sasol North America Inc.

On January 3, 2006, multiple cracks were discovered on the balance line on the high pressure case of the cracked gas compressor. This balance line balances the pressure from the balance drum to the third stage suction. The mode of failure was believed to be fatigue failure and the ethylene unit was shut down and repairs were made to this balance line. Following the repairs, the unit was again started up. Four days later, another crack was observed on the repaired balance line. This crack was monitored until its propagation warranted another unit shut down for repairs. It was determined that long term fatigue failure, as previously diagnosed, was not the mode of failure.

This paper will focus on the unique mode of failure associated with the balance line cracks, the analysis performed to determine the cause of the cracks, and the repairs that were made to implement a safe and effective solution.