Downtime in the steel industry can be a very costly experience, so minimizing the completion time for major overhauls and repair projects is a prime objective. For one steel manufacturing site in Brazil, a large, integrally-geared compressor needed two impellers replaced quickly. Through reverse engineering, their client delivered a solution in 6 months that was also more cost-effective.
Steel production is a very competitive industry that requires a tight control on costs and a constant effort to improve productivity. In order to achieve cost-effective manufacturing, any maintenance or repair project that will affect productivity needs to be carefully assessed for the impact on production. The large-scale steel manufacturing facility in Brazil has a capacity to produce over 7 million tons per year and the associated industrial gas plant forms an integral part of the production process. Throughout the site, large pieces of rotating equipment require monitoring as well as remedial maintenance in order to minimize downtime.
In many cases, the steel plant operator had retained the maintenance services of the original equipment manufacturers (OEMs) to ensure that all the necessary work was completed by engineers with sufficient expertise and access to the spare parts. However, this arrangement came under review as part of a rationalization process aimed at reducing repair costs and improving the timescales involved. The first step was to establish the exact condition of the compressor and then establish a plan of action that would deliver the most cost-effective solution.
A field team was deployed to carry out detailed inspections and diagnostics to identify potential areas of concern. The results of the inspection showed several issues, including a reduction in wall thickness of the third stage impeller and cracks in the fourth stage. Based on this, and the lack of operational reliability, the decision was made to take the compressor out of service until the impellers could be replaced.
The process to reverse engineer two new impellers began with extensive measurements using portable coordinate measuring machines (CMM) and laser scanning to create a true 3-D drawing. Positive material identification highlighted the potential to improve the corrosion resistance of the components by upgrading the base material.
The impellers were designed and manufactured at a service center where the vane sections were manufactured from a solid piece of chrome molybdenum vanadium steel using a 5-axis vertical milling machine. These were then welded to the outer casing to create the finished impellers. The completed impellers were shipped to the field service engineers where the installation and commissioning process was completed before the compressor was returned to the customer.
- Edited by CFE Media. See more Control Engineering CNC and motion control stories.