Drives and control system upgrade for a 350,000 ton/yr bar mill

Gerdau awarded Russula a contract to upgrade the 350,000 tpy bar mill, located in Charlotte, NC, USA. The previous mill control system was a hybrid of several different systems, which contained numerous hardware platforms, several computer generations, and involved different programmers with varying programming methods. The mill was controlled by four main systems; powered by three different processors and six unique interface systems on five different platforms. This system became obsolete and the manufacturer advised the plant’s management that they would terminate equipment support.

Scope of Supply

Russula provided a complete solution for the modernization of the 15-stand in line rolling mill at Gerdau in Charlotte. The modernization consisted of a new rolling mill automation system and the modernization of existing drives for the furnace change, mill entry, mill, cooling bed, cold shear and bundle discharge. The scope of supply included project management, engineering, erection, start-up support and training.

“The Russula rolling mill control system has greatly improved our mill set-up and has provided consistent rolling”

Casimiro Liborio, Mill Superintendent, Gerdau Charlotte

Project Execution

Russula implemented the rolling mill control automation using standard ABB AC800M Modular Controllers. A high speed data acquisition system from IBA, along with networked drives and controller software provided single point monitoring and diagnostics; as well as remote support capabilities to the upgraded systems.

Results

The complete system upgrade for the bar mill was completed in 240 hours, exactly 10 days. After the upgrade the plant experienced yield and availability improvements.

Yield improvements were due to more accurate and consistent operations throughout the rolling mill:

Reduction in mill crop ends, due to more accurate cut control.
Reduction in short end waste - cut optimization based on customer lengths.
Reduction in cobbles and mill rejects, due to more accurate speed and cascade control, a repeatable mill method of operation, analysis tools needed for continuous improvement.
Plant availability increased because of faster transitions, less cobbles and less electrical failures with the new equipment.
Reduction of delays in the finishing end previously caused by poor control methods.