When we presented our Profile Mill Fingerprint service to a prominent customer in India, they expressed an interest in applying it to one of their high speed wire rod mills, run on legacy 3rd party control system and drives. We were asked to investigate a specific problem in the laying head, where an inconsistent coil laying pattern, due to issues with positioning of the coil front ends, was having a negative effect on productivity in the downstream section, and therefore, on the productivity of the entire high speed mill (100m/s).
Profile Mill Fingerprint – an advanced service from ABB
The Profile Mill Fingerprint service is designed to do a process & control health check-up for any long product mills, running on either ABB or non-ABB control systems. This study can be conducted for the entire mill or limited to a specific area, as long as the mill is equipped with a fast and reliable data logging system such as IBA. The outcome is a detailed analysis of any problem areas identified and recommendations on how they can be overcome with the help of ABB products and/or services.
Analyses and actions
The customer agreed to carry out a Profile Mill Fingerprint service for the laying head of the wire rod mill. The plant runs on GE Rx 7i control system, and Nelco Drives, with a high speed data logger system (IBA) installed. The customer wanted to run the fingerprint for some specific material grades, where they face major issues. Accordingly, we collected plant running data from the data logging system, and control code back up from the GE system.
A detailed analysis was carried out to find out the root cause of the problem and our findings were as follows:
- The control concept for synchronization, length measurement and prediction was not sufficient enough to achieve consistent performance in this kind of high speed mill
- The positioning control was an open loop control, whereas it should ideally be of closed loop type in order to achieve better accuracy.
As the analysis related to a 3rd party system, we offered two alternatives aimed at addressing the issues in question:
- Explain the correct control concept to customer so that they could implement it into their running control system by themselves or,
- Provide our own technological control (controller, IOs, interfaces & application program) limited to the problem area, which would interface with mill control system.
At first the customer was skeptical to these findings, and doubted how the basic control philosophy could be the reason for the inconsistencies they had experienced, since the existing control system has been running for such a long time. We were, however, able to present our findings in such a comprehensive manner, with supporting data and recordings, and could convince the customer that action based on our recommendations was necessary. At the same time, being a legacy system, the customer did not feel confident about implementing the suggested modifications on their own and, after much deliberation, they agreed to place an order for a technological control upgrade for the laying head only.
Recommendations reap results
ABB provided a PEC controller with fast XF801 IOs for this scope, and the GE system was communicated over Modbus for slow signals, and hardwired for fast signals. The change-over included the following:
- Detailed signal exchange between the mill controller and the new ABB system
- Certain critical field signals were multiplied to both systems through hardwired
- Prior testing of interface between the GE and ABB PEC controllers was done onsite
- Complete system shadowing for one week prior to the change-over, where output from the ABB system was monitored in the data logging system together with the inputs connected to both the systems.
- Performance of the 3rd party laying head drive was validated by ABB drives expert
Control of the laying head was successfully upgraded to a new ABB control system within the 6 hour window provided by the customer during their weekly shutdown. Front end positioning is now much more consistent, plant operators are satisfied with performance and the customer has expressed an interest in upgrading the rest of the mill with ABB control systems with a detailed proposal in progress.