Avaliação de integridade estrutural de um tanque de concentrado de minério de ferro através do método dos elementos finitos

Abstract

This paper presents the methodology for evaluating the structural integrity of an iron ore concentrate tank at the Minas-Rio system. The structural integrity assessment methodology is based on ISO 55001, 2014 asset management standard. The operational and maintenance risks related to structural integrity of the concentrate tank during this life cycle were assessed based on ISO 55001, 2014 asset management standard. It is presented an application proposal of structural integrity management of significant structures based on the ISO 55001, 2014 standard throughout the life cycle of a concentrate tank. The tank design has been evaluated based on API 650, 2011 standard and by the finite element method (FEM). Based on API 650, 2011 standard, two gaps was found in the project. Those gaps are related to the dimensions of the cleanout fitting and to the wind girder. The use of the FEM made possible to evaluate the dynamic behavior through the natural frequencies and vibration modes. It has been found the need for a second wind girder due to two natural frequencies below 1 Hz. During the assessment of stresses and displacements it was possible to evaluate the influence of having cleanout fitting dimensions above the specification of API 650, 2011 standard. It was found a region of high stress concentration around the cleanout fitting overcoming the utilization rate and a small region with localized plastic strain. Through these analyzes it was identified the need for a secondary wind girder and for annual inspections of the cleanout fitting region in order to monitor cracks. The annular plates thicknesses were measured using ultrasound predictive technique in order to create a database. Based on the first measurement a periodic inspection plan was created for monitoring the wear caused by corrosion and abrasion of iron ore slurry, through ultrasound test. It was evaluated through the FEM the influence of thickness loss on the annular plates and the impact on the distribution of stresses, displacements, natural modes and frequencies. A significant increase in the number of vibration modes was identified on the minimum and intermediate tank levels of the analyzed filling conditions. There was a small reduction in the overall utilization rate, but an increase of regions with utilization rate greater than one.