Application Solutions
DRIVE to a Digital Future - Smorgon Steel
Rockwell Automation Drive Systems takes up the challenge to replace an existing steel rolling mill drive control system with minimal downtime.
Product obsolescence, reduced technical support and diminishing availability of spares presented Melbourne-based steel producer Smorgon Steel with a tough choice to replace its first-generation digital/analog bar mill process control system and mill stand drive DC converters, or risk increasing down time and reduced plant efficiencies.
The challenge was to find a product and engineering team that fitted the bill; one that could provide both an excellent product and sound local technical support, plus minimal changeover downtime.
Smorgon Steel’s 16-stand/20-drive bar mill manufactures over 90 different products in round, flat, angle and channel profiles. These are usually to specific order and around the clock, 52 weeks per year, ensuring optimal speed and efficiency in filling customer orders. Mill downtime is a critical issue.
A Smorgon Steel team headed up by the rolling mill manager Alan Armitage and bar mill electrical superintendent Andrew Thomas, set out on an international search for a replacement system. The tender selected a Rockwell Automation Drive Systems solution based around the AUTOMAX Distributed Power System (DPS), a purpose-built multiple drive digital control system.
The entire system changeover would be designed and technically supported by a team of local and international Drive Systems, Global Technical Services (GTS) and IAS Engineering experts.
Unique solution
The DPS presented a unique solution for this challenging upgrade, as its highly modular construction permitted Smorgon Steel to retain its original drive thyristor power stacks and enclosures. By simply replacing the existing regulators with the AUTOMAX Power Module Interface (PMI), a staged ‘drive-by-drive’ changeover could be realised with minimal downtime, rather than one requiring a drawn out total-plant shut.
The system’s fibre optic-based digital communications, plus Remote I/O field and control room links would dramatically simplify the site’s existing discrete I/O cabling network.
Drive Systems would also provide an entirely new control room ‘pulpit’ console, complete with SIGMA and Mill Manager control screens. The PC-based SIGMA server would connect into the controller network, providing both a powerful real-time system database and a screen-based control room operator interface. This, in turn, would be linked to the Drive Systems’ Mill Manager system a Visual Basic ‘front-end’ on an SQL Server application providing total mill product recipe support and production recording.
After struggling with technical support during its first 15-years, local service and support were high on the Smorgon Steel wish list.
The team was handpicked from the Australian Drive Systems, GTS and IAS Engineering crews. For the all-important commissioning engineering role, GTS Drive Systems engineer Darryl Peterson was nominated a veteran of 35 years and a world bar mill expert.
To provide the digital to thyristor system interface, the Drive Systems team designed and manufactured a number of thyristor isolator boards. Each was custom-built to suit the unique firing voltage requirements of the specific thyristor stack.
‘Down days’ turnaround
The mill scheduled extended ‘down days’ to provide tight but achievable time windows for the regulator changeovers. To ensure a problem-free changeover, Smorgon Steel sent a complete legacy system converter panel to Drive Systems’ Sydney works, to trial a complete ‘dry run’ changeover.
On the day of the first changeover the team stripped out the existing regulator, installed the PMI and thyristor isolator board, cabled to the power stacks, then connected across the speed reference from the legacy controller to the new PMI.
This first changeover took the entire 36 hour shut. During subsequent shutdowns the team changed over two and sometimes three drives in less than 24 hours.
"We ended up getting 14 stands done out of 16 this way before the main mill shutdown," remembers bar mill electrical superintendent Thomas. "The advantage of having these stands done was they’d all been tuned and proven to run. As a result, we had very few problems with the final changeover."
Pre-shutdown prep
The project team worked intensely for some months prior to the three week total plant shutdown, as it finalised the SIGMA Server, Mill Manager and control pulpit development.
On completion of the new pulpit desk, Thomas, two supervisors and four Smorgon operators visited Drive Systems, to step through the design screen-by-screen, item-by-item. Full SIGMA and Mill Manager systems were trialed live on line, with all the DPS racks, the clients, server and the Mill Manager.
Each SIGMA point was individually checked, including scaling and point allocation. The 30-screen Smorgon SIGMA system (which includes process and drive overviews, line control, tracking, setpoint management and trending and alarm screens) supports around 4000 variables, including 1500 alarms and around 500 trending variables.
Fieldwork was also completed prior to the shutdown, including the installation and cabling of the Remote I/O enclosures mounted beneath each mill stand.
The final shut work was ultimately rationalised down to the removal of the legacy controller and pulpit, installation and connection of the new pulpit and connection of mill floor field devices to the Remote I/O panels on the drive control floor.
The speedy shutdown changeover allowed the site team plenty of time to run ‘ghost rolls’ a system operation trial without material. "We made the shears cut, brought up all the loopers and so on. We did this over and over, so we were pretty confident when the first bar went through," says Thomas.
In fact, the first bar went through without a hitch. GTS commissioning engineer and world bar mill expert Darryl Peterson described the start-up as "one of the smoothest I’ve ever seen in 35 years."
The mill now runs with an improved availability, along with improved product quality and line throughput. "Our old system normally experienced component failures once or twice a week, particularly the converter cards and optical encoders," Thomas says. "We’ve had no control system component failures at all since commissioning, and we’re enjoying a two hours per week reduction in downtime due to electrical faults."
The Mill Manager/SIGMA Server combination also makes for speedy product changeovers. The legacy system required the 200 parameter of each product recipe to be manually selected item-by-item a process that could often take longer than 40 minutes, and a potential source of difficult-to-find errors.
The new system involves a simple ‘scroll and select’ activity at the Mill Manager’s recipe page; a single fault-free operation taking only seconds.
The powerful SIGMA server database will also ultimately afford Ethernet communication with the Smorgon site’s administration computing system. This will allow on-line downloads of production schedules to the shop floor, plus real-time production data availability at management level true ‘shop floor to top floor’ data transfer.
The Smorgon bar mill upgrade is a Drive Systems success, where preparation and planning played a major part. The Rockwell Automation/Smorgon site team integration and hands-on approach were also crucial factors in the project’s success. "To go from complete shut to start-up with zero downtime was this project’s greatest success," concludes Drive Systems Asia Pacific manager Michael Day. "It’s a credit to all involved a great team effort."
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