In the revamp of the Chiba No.6 blast furnace, a short revamp time of 62 days was achieved, reducing the period required for the conventional method by half. The main techniques employed were:For the dismantling and assembly of the furnace body, a large-block ring method was developed, in which the body was dismantled in large, ring-shaped blocks, and then assembled in a similar manner, using large sections that included the steel shell,staves and auxiliary equipment.In laying the hearth bricks, using large brick blocks reduced the number of bricks by half. An efficient continuous work system was also adopted.With the furnace top equipment, the bunkers were assembled as a single unit outside the supporting columns, while work was performed simultaneously inside the columns. The equipment was installed in large units wherever possible. Work, up to theinstallation of the piping and other auxiliary equipment, was performed in advance.Shop tests were made as complete as possible, to minimize testing in the field. Advance debugging by simulation tests was also completed as far as possible.To remove residual material from the furnace, conditions were created that permitted the efficient use of large equipment.Because the large-block ring method and large hearth bricks were used for the first time in this project, various investigations and experiments were carried out in advance. However, in a review after the revamp was completed, several points forimprovement were still found. In future revamps, attempts will be made to achieve a further reduction in the amount of work.Chiba No. 6 blast furnace was blown in for its second campaign on May 26, 1998, achieved a rapid ramp-up and is now functioning smoothly.
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