With many millions of dollars of obsolete control systems still in operation in mills and plants across the county, the following situation may be more common than people are willing to admit. A 40+-year-old ductile pipe mill had a control system for their annealing operations based on a platform of disparate and obsolete PLCs. The company was experiencing unplanned down time and increased time to repair because of the difficulty finding spares or finding individuals with appropriate knowledge. This resulted in missed schedules, increased overtime costs, and greater rework expenses. Add in the challenges of a legacy HMI system that employed equally disparate navigation and command functions, and you have real problems serving the customer base. Sound familiar? Once the decision makers overcame their hesitancy to fund an upgrade, recognizing that there would be a significant return on investment if unplanned down time could be reduced or eliminated, they turned to us to design and implement their process system upgrade.
Lean Workshop
A key aspect of the project was to have our engineering manager attend their 3-day lean workshop, an event that involved all system stakeholders in developing a system that would address operability, safety, and maintenance elements. Also included in the workshop were domain experts with deep knowledge of the operating environment, the processes, and the controls. The current situation was audited and the findings summarized for the group of stakeholders. The decision was made to use a ControlLogix* PLC platform and a Factory Talk* HMI platform. This gave our project team a tremendous head start in the area of system design.
From the information gathered at the lean workshop event, the team was able to develop a scope of work. One of the challenges identified by the audit was that existing drawings were either missing or inaccurate, including P&IDs and schematics, and O&M manuals were nowhere to be found. But the audit also identified materials that could be reused to help expedite design and programming.
Tight Timeline
Normally, a project of this magnitude would require about 12 weeks to complete. Our team was able to compress the schedule into seven weeks, from project award to ship date. One of the factors in this achievement was development of a panel template, speeding completion of CAD drawings. A second factor was making extensive use of our CNC automated cutting system for panel enclosures. This system shaves about 40% of the labor off the panel production time compared to manually punching, cutting, and tapping the panels.
Design
The four disparate PLCs were replaced by two ContolLogix systems communicating on an Industrial Ethernet I/P, device level ring. The first system, with a GuardLogix*-based integrated safety system, sequenced the annealing processes and tracked production. The second system was dedicated to the burner management system. Rockwell’s Factory Talk View SE, with three clients, served as the HMI platform. The system had approximately 1,000 I/O points. The final system consisted of seven control panels and one PanelView Plus that could meet temperature specifications.
Two-Week Startup
Our project team performed the on-site commissioning during a planned two-week service outage, the critical reason for the necessary schedule compression. The first week was set aside for removal of the old equipment and installation of the new panels. In order to stay on schedule on such a large system, the team spent numerous very late nights at the site, sometimes catching a few hours of sleep in their vehicles in order to be ready for the 4am oven lighting schedule the plant maintained.
Results
With the new system in place, the customer is experiencing very few unplanned downtime events. They also are experiencing considerably less overtime costs associated with make-up production, thereby maintaining schedule shipments to their customers. The new platform provides numerous improvements to the on-screen diagnostics, simplifying maintenance. It also provides the data basis for on-going optimization of the overall annealing process. And they now have a complete and accurate set of drawings and manuals.
For more information on implementing legacy control system migration, check out our white paper on the subject.
* ControlLogix, GuardLogix, Factory Talk, and PanelView are registered trademarks of Rockwell Automation