C2024-20970 Ammonia Stress Corrosion Cracking Of Admiralty Brass Heat Exchanger Tubes In Refinery Cooling Water System.

Sudharsanan Soundararajan - Instrument air (IA) system is one of the critical systems in the utilities section of a refinery complex. IA system of this refinery consists of compressor package and dryer package to supply air to refinery header at 9 kg/cm2 (128 psi) with dew point less than -20degC (-4degF). The 3 stage compressors have intercoolers with extended plate surface fin type tubes. The metallurgy of the tubes is Admiralty brass SB-111 C44300. In this cooler, compressed air is in the shell side and fresh cooling water on the tube side. All 8 intercoolers in the compressor package leaked in a period of 1 month. A failed sample tube was analyzed using Optical Emission Spectroscopy, Stereo Microscope, SEM/EDS and XRD.This paper discusses the findings and the methodology used to identify the reason for failure as Ammonia Stress Corrosion Cracking. Process parameter analysis revealed that the leak from a recycle gas cooler in Hydrocracker unit as the possible source for ammoni