Análise de confiabilidade de um sistema de transporte e resfriamento de bobinas de aço laminadas a quente

Abstract

The hot strip mill transforms the steel plates into strips through a lamination process, when the steel plates are heated to average temperatures of 1200ºC. Once the ideal temperature is reached, the plates are transferred to the mills, where the plates pass through cast iron cylinders. The process is repeated so the thickness of the material is successively reduced. After that, the steel strip is cooled down in a controlled process in the cooling table, where it is striked with water in a laminar flow. This study proposes the modeling of a cooling system for a hot strip mill in order to obtain quantitative data of reliability and analysis of improvements and modifications in the components with the objective of increasing the reliability and availability of the system. This system was elected for this study due to the direct impact it has on the productivity and quality of the coils produced in the mill, and also because it has, among the other systems, the largest quantity of equal components working in series. This allows, through the concentrated analysis of a subsystem, here called drive unit, the modeling of the entire laminar cooling system. The development of the study is based on the Reliability-Centered Maintenance Methodology, using software tools for handling historical data of subsystem failures and components and also the experience of employees who work in the coil cooling and transfer process. Based on the quantitative reliability analysis, specific improvements will be proposed in some components of the system for the reduction or even elimination of the main identified failure modes, and above all, the quantitative analysis performed points out to a mindset change in maintenance managing and waste reduction in the employment of the available resources and materials, improving cost control for maintenance and spare parts acquisition.