25 Cr super duplex stainless steel (SDSS) centrifugal pumps have found vast applications in the Oil & Gas industry for produced water injection systems. An important factor in water injection pump material selection is the need to provide adequate corrosion resistance throughout the operating life cycle. Presence of solids and/or other contaminants in the pumped fluid (e.g. traces of solids, water cut percentage, hydrogen sulphide, chlorides, oxygen, and carbon dioxide content) can impact the corrosion resistance of water injection pumps. SDSS material is used in critical pump components such as casing body, impellers, shafts, balancing lines etc. The main focus of this paper is to present two cases of SDSS centrifugal pump component failures associated with a casing body and balancing line. Pitting corrosion mechanism was found to be the root cause of the both pump component failures. The factors contributed to these two failures will be discussed, in addition lessons learned & mitigation measures will be proposed.
The application of corrosion resistance alloys such as 25% Cr super duplex stainless steel (25Cr SDSS) has expanded in the oil & gas industry recently as new technologies made it feasible for Oil and Gas operators to invest in high sour and corrosive fields. 25Cr SDSS material is often used in critical applications such as piping, rotating equipment, coolers, and instrument components etc. SDSS materials are well known for the 50/50 austenite (γ) and ferrite (α) microstructure which provides the combination of corrosion resistance and high-performance mechanical properties.1,2
The selection of SDSS material for produced water systems is normally driven by many factors, such as presence of high chlorides levels, high H2S partial pressure and presence of containments (e.g. oxygen). Premature failures of this equipment can be very costly, not only from repair and maintenance cost point of view but also the business implications, such as oil deferment, safety and environment aspects.3,4 Therefore, it is very critical for the oil & gas operators to proactively incorporate learnings from premature materials failures to prevent re-occurrence.
