One of the world’s leading steel producers, Nucor Steel, has employed the latest technological advances from Wonderware to maintain its position at the forefront of
Steel production is a costly and capital-intensive process and the highly competitive nature of the steel industry intensifies the need to maximise asset utilisation, minimise downtime and remain flexible in order to respond to changing market conditions.
“We live in a worldwide economy now,” said Dennis Boyd, of Nucor. “So it is important that we stay on the leading edge of technology, both in how we control our furnaces and in how we collect data from them.” As supervisor of the melting area electrical systems at Nucor’s mill in Berkeley, South Carolina, Boyd helped revamp the mill’s control systems with Wonderware industrial control platforms.
Flexibility is critical
The melting area of a steel mill is one of the harshest industrial environments in the manufacturing world. As temperatures soar to 1700°C – almost one-third of the surface temperature of the sun – the manipulation of raw materials weighing hundreds of tons places severe strain on equipment and control systems.
The majority of the world’s carbon and alloy steel production uses electric arc furnaces, which are fired primarily with scrap steel. At Nucor’s Berkeley mill each load consists of 180 tons of metal, about 80% of which is recycled scrap. Once loaded into the furnace electric currents reaching 160 kA melts the raw material. Impurities float to the top and are removed, leaving 165 to 170 tons of pure liquid metal. Carbon and alloys are then added to the mixture to add tensile quality and produce the required grade of steel. Once it is determined to be perfect, the molten mass is transferred to the casters where it is moulded into sheets of differing thicknesses and widths to meet specific customer orders.
Flexibility in this environment is a key challenge as equipment disruptions occur frequently and components must be replaced. The organisation must also be prepared to respond to rapidly changing market conditions. By providing a clear picture of what is happening within the process, the chosen software solutions deliver this flexibility.
“One of the key issues is the need to make rapid adjustments,” said Mike Higgins, automation engineer, Nucor Steel. “We are always making changes to improve our process and we needed a system that would allow us to implement these as quickly as possible. The less time we spend doing programming the more time we have to focus on improvements and raising total profits for the company.”
According to Higgins, the Berkeley mill has relied on Wonderware’s industry-leading InTouch supervisory control and visualisation software, since it opened in 1997. But the mill outgrew the trending and analysis capabilities of the existing InTouch application and needed to take its data collection and analysis efforts to the next level. With the need for an advanced trending tool to help identify and eliminate problems that caused downtime becoming acute, Nucor managers turned to InSource Solutions – Wonderware’s regional Value Added Reseller – and asked for a better way to collect and trend data. InSource suggested updating and building on the InTouch application already in place with Wonderware’s IndustrialSQL Server historian and Application Server.
The IndustrialSQL Server realtime plant historian puts the intelligence in Wonderware’s plant intelligence solutions, delivering the data – both current and historical – that helps the melt shop team to do the detailed analysis and trending and has enabled them to identify and eliminate the problems that cause downtime.
The ArchestrA architecture enabled Nucor to centralise all the data from the different furnaces in the melt shop, providing tight integration regardless of its source. Of particular value, the use of standardised application objects means that new equipment can be added or removed from the system more easily than before. In an environment like the melting area of a steel mill, where equipment has a short life-cycle, this is of critical importance.
The Application Server provides a unified environment for visualisation, plant history, device communications and automation application integration. Additionally, it provides a common control and analysis capability and a facility for making rapid changes to improve production processes.
“Before we got up and running with Application Server and the IndustrialSQL Server historian, it would take days to add a new piece of equipment to the control system,” said Higgins. “Now I can do that in a matter of minutes.”
“One of the biggest benefits we saw was the elimination of downtime,” said Boyd. A common problem experienced in the melting area involved errors in the melting process that resulted in holes being burned in the sidewalls of the furnaces or the roof over them. These holes can be caused by a number of different failures, including an arc deflection, an arc flare or blowback from a co-jet – which blasts pure oxygen into the reaction to increase the temperature. Each of these errors causes the energy that should be passing through the scrap steel charge to be directed at the sidewall, blasting a fissure that will take hours – and possibly even days – to repair.
“We use sensors to track the temperatures on the side of the furnace,” added Boyd. “We were able to collect and track this much more accurately and come up with more sophisticated control processes.” Specifically, he said, this enabled Nucor to do two things: “Right off it allowed us to alarm and shut down before we got holes. We have all but eliminated the occurrence of these holes since we got enough trending data from the system that saved 2–5% productivity just through elimination of downtime. This also allowed us to power the furnace down rather than shutting it off altogether, resulting in a 5–10% gain in average power, which is directly proportional to productivity.”
Reduced downtime and increased productivity was only the start of the benefits experienced by Nucor Berkeley following the implementation. The new system has also had a dramatic impact on the quality of daily executive reporting. Prior to deploying the new system, operations data was fed directly from the PLCs on the shop floor into the centralised plant-wide data control system where a custom ‘C’ application would reformat it into the database. This meant that three disparate sets of the data were required and they were not always consistent.
The open .NET architecture of the Application Server allowed Mike Higgins and his team to completely bypass the old system and feed data directly from the InTouch control system into the IndustrialSQL Server historian and then into the plant-wide data collection system.
Metrics from the day-to-day operation, such as the number of tons charged into each load, the temperature in the furnace and the amount of time the furnaces take to operate are collected and analysed each day to identify opportunities to improve processes – and with the Application Server, managers are confident that the information they are using is accurate.
Higgins said that; “The IndustrialSQL Server historian is something we have been looking for. We had got to the point where we knew we needed to make improvements to our data collection and analysis. We would visit other mills and we were way behind what other people were doing and now we are light years ahead. We went from being the butt of the spear to being its tip.
“Almost immediately after introducing the IndustrialSQL Server historian, we were able to see rapid, immediate feedback on our data and processes. We started by collecting data which we used as a basis to predict failures such that we can now schedule preventive maintenance to minimise downtime. We are also able to track what happens at each step in the production process, sampling the steel at different stages to make sure that each batch is going to meet the grade and quality demands of our customers.”
Each year, the Nucor Steel mill in Berkeley, South Carolina, produces more than 2,5 million tons of rolled sheet steel and 1 million tons of steel beams and girders in 20 different grades, depending on customer requirements. The steel is then shipped to customers who either reprocess it and resell it or turn it into finished goods, such as refrigerators and automotive parts.
“The steel industry is a very harsh environment,” said Boyd. “Everything is temporary. Nothing is permanent. We see equipment destroyed and replaced on a daily basis. We needed a system that would enable us to make those changes without reinventing the wheel on a daily basis. Wonderware delivered that system and I would recommend it to anybody who is looking for a way to improve their process, speed up programming changes and increase profits.”
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