Failure Analysis of API 5L (Grade B) Oil Field Separator Flowline Pipe

This paper presents the root cause failure analysis of an API 5L (Grade B) pipe that failed while in full well stream service in the oil and gas industry. The operating temperature ranged from 120 to 190 °F and was exposed to hydrogen sulfide (H2S) concentrations of 350–1000 ppm. Visual inspection, hardness test, metallography, Fourier transform infrared spectrophotometry, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were carried out to investigate the pipe failure. This study revealed that an extremely localized pitting corrosion due to chloride attack was the main mode of the failure.