One of the most used secondary recovery methods in mature oil production fields is the injection of water. Multi-stage mixed flow centrifugal pumps are usually used in order to achieve the required high pressures and flow rates. However, the material of this equipment can suffer high damage when it is in contact with the high chemical complexity of the reservoirs water. Even if a 50-micron filtration and chemical dosing processes are applied to improve the fluid quality, it is still a very harmful fluid for equipment.This paper proposes a case study referring to the effects of erosion-corrosion in an injection pump that operated in an oil production company in mature fields located in Brazil for six months. The equipment has its rotors and diffusers manufactured in Ni-Resist 1. According to the Nickel Institute, this material has a high resistance to corrosion in sea water and in other salt solutions.Initially, twelve samples of the water were collected at two different points (suction and discharge of the pump) and several components were analyzed, among them we can highlight the salinity tests that showed an average value of 40.36% measured in the suction of the pump, i.e. , almost nine times greater than the reference salinity of sea water which is 3.5% [1] and the suspended solids that presented an average value of 236.58 mg/L which is a value considered high for the operation of this equipment.Continuing the study, the equipment was teared down and a visual inspection of all 40 stages was done. In this analysis, it was possible to identify an excessive wear and the damage form. The diffusers showed a mass loss at the blades leading edges, in the sealing region, in the coupling region between stages and it kept the blades rear edges in good condition. The impeller showed excessive wear, losing about 80% of the blades and 100% of the skirt, the hydraulic balancing holes showed little wear on their edges.After visual inspection, Brinell hardness, micrography and chemical analysis by Optical Emission Spectrometry (OES) were performed reaching values consistent with the Nickel Institute, thus not affecting the type of damage.In the semi-quantitative chemical analysis by Energy Dispersive Spectrometry (EDS) we were able to evaluate the distribution of the main elements in the base metal and in the impeller decomposition residues, highlighting the low concentration of nickel in the affected region and the presence of oxygen.Finally, it can be concluded that the greatest wear occurred at the points where the fluid follows almost perpendicularly to the metal surfaces, as in the impeller and diffuser blades leading edges. According to a simulation using ANSYS erosion mode performed by Bahadir Basaran [2] for a pump similar to the one in this paper, the greatest erosion is noticed at the impeller leading edge, coinciding with the shape of the wear presented in the analyzed impeller and diffuser samples proving that erosion was responsible for the constant removal of the oxide passive layer, leaving the base metal exposed to the high salinity of the medium and suffering corrosion at high levels. Thus, even if the solids and the speed were not enough to become the main wear cause, they were sufficient to not allow the Ni-Resist 1 surface to repassivate.

Wear Analysis of a Ni-Resist 1 Mixed Flow, Multi-Stage Centrifugal Pump: An Erosion-Corrosion Case Study

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.