Corrosion investigation of a steam turbine after power generator failure onboard a vessel: A case study

Abstract Steam turbines for power generation installed on vessels are designed to operate for over 30 years. However, there are some cases of untimely failures. In this paper, we are reporting a case of a deeply damaged turbogenerator, with several visible corrosion/erosion attacks, such as ‘pit-shaped’ defects, rust, and drains. While significantly widespread, they were almost only observed on the inlet steam flow side. Also, their extension and size were not such as to affect the integrity of the failed rotor, especially if we consider the size of its blades and discs. Some chemical elements not included in the alloy composition of the turbogenerator are detectable on the surface of the turbine components. Their presence could be due to passivation layers and/or material oxidation, in the case of oxygen, or, in the case of other elements detected in very low amounts and contained in the steam, to their deposition during standard turbine operations. However, turbogenerator storage conditions at the shipyard workshop before analysis might also be involved. Based on our data, we would rule out that a damage such as detachment of all blades from the sixth disc in the intermediate-pressure stage was caused by material corrosion/erosion. This conclusion was further supported by reports by the crew on how the failure had occurred. Other turbogenerators similar to the one described in our paper are currently operating on vessels. Therefore, this paper can be useful to better manage steam turbines for power generation and prevent corrosion/erosion damage.