Failure analysis on cracking of 4130 steel casing of an offshore platform water injection pump

Author of the article:YANG Zhongna1, ZHAO Jieying2, MENG Qiang1, XIA Minglei1, JIN Lei1, YANG Yang1

Author's Workplace：1. CNOOC (Tianjin) Pipeline Engineering Technology Co., Ltd., Tianjin, 300452, China; 2. Zhanjiang Branch of CNOOC (China) Co., Ltd., Zhanjiang, Guangdong, 524000, China

Key Words：Water injection pump; Cracking; Failure analysis; Corrosion fatigue

Abstract：An offshore platform injection pump casing cracked after 3 months of operation. In order to find out the cause of the casing cracking, failure analysis was conducted by macroscopic morphology analysis, Non-Destructive Testing (NDT), anatomical analysis, microscopic analysis (SEM), corrosion products analysis (XRD & EDS), physical and chemical performance analysis and finite element analysis. The analysis results showed that the injection pump had excessive carbon content, poor seawater corrosion resistance, and severe stress concentrations at the intersection of the horizontal and vertical inner bore (6 oclock and 12 oclock location). The failure of water injection pump was due to fatigue corrosion caused by a combination of corrosion and alternating stress In this paper, recommendation is made to avoid or mitigate such incidents in future, which is of great significance to ensure the safe operation of the platform water injection system.