Blast furnace and stove control systems see a retrofit
A control system upgrade to the main blast furnace and stove at a major Midwest steel producer was completed in 18 months without downtime or production delays, according to the system integrator involved. The legacy distributed control system (DCS) was transitioned to a programmable automation controller system from one automation vendor and a human-machine interface (HMI) platform from another supplier.
The system integrator termed its protocol on the project the System Transition Execution Plan (STEP). During the implementation of STEP, the client experienced no interruption in blast-furnace or stove-control system operations. The new system was designed and installed by engineers working on-site at the steel mill with client personnel.
Zero downtime during the changeover was the core of the strategy, according to those involved. Using a building-block operation, each control input/output (I/O) point on the old system was upgraded with parallel monitoring of performance values and system readouts. Only when each new component was functioning properly and the signals were in line with the existing monitored values were the control strategies changed and integrated loop-by-loop into the new process local area network (LAN).
The STEP upgrades included: replacement of legacy programmable logic controller (PLC), replacement of DCS/PLC interface, movement of I/O from DCS to a programmable automation controller (PAC), deployment of HMI, movement of control from DCS to PAC, historian integration, and, finally, Level 2 interface via HMI. Essentially, the control scheme for each system element was installed in parallel to the legacy control, then connected to the new processor, and monitored on a channel of the client’s overall process control LAN for comparison to the older output.
Using this STEP approach, minimal process impact occurred, and there were savings realized for the client, both in operational expense and total project cost. Because it happened in steps, the project could be categorized as a maintenance expense and not as a capital expense, because it happened in steps. The major capital expenditure diminished. Client benefits included a gradual weaning away from the legacy system, which eased training for plant operational and maintenance personnel with the new hardware and software, as the changeover progressed.
The determination to upgrade this system had resulted from numerous factors, according to the client. The I/O had become obsolete, and the legacy system was UNIX-based, so many of the client’s current engineering staff on-site were unfamiliar with it. However, because a need existed to retain the overall control strategies and functional client knowledge of system operations, the consulting firm devised this STEP protocol to make the transition more gradual and self-teaching.
According to the client’s plant production and technologies manager on the project, "The blast furnace and stove control systems needed to be upgraded from a legacy DCS to a PLC platform, with an HMI and historian. The consulting firm was challenged with cost-effective project deliverables requiring a proven transition plan, zero production outages, minimal risk implementation with no impact to production or product quality, improved technology with future expansion capabilities, improved process controls, enhanced operator interface, improvements to system reliability, and stringent budgetary guidelines. This project required verification and movement of some 2,000 I/O points, installation of new workstations, network communication upgrades, development of more than 60 HMI screens with built-in diagnostics and alarms, extensive PLC programming, system functional documentation development and drawing approval, historian upgrades, and on-site training. Finally, total project implementation and completion were required within a two-year period."
The plant production and technologies manager on the project said, "The upgraded control systems have been in operation for nearly a year now, with reliable and efficient operations. Our plant now has the technology to further enhance the automation strategies and drive flexibility and productivity that were not available with the legacy automation platform."
– Marc L. Hunter is Synergy Systems vice president. Edited by Eric R. Eissler, editor-in-chief, Oil & Gas Engineering, email@example.com.
- System Transition Execution Plan (STEP) attempts to minimize downtime and allow consulting engineers to work alongside the client engineers to get the job done without causing downtime.
- STEP protocol makes transitioning more gradual and self-teaching.
When upgrading equipment or processes, how do you minimize downtime?
– See related stories linked below.