Rockwell Automation has successfully designed and delivered an Allen-Bradley® Guardmaster® ProsafeTM trapped key interlocking system for a chrome smelter, located in Steelpoort in the Mpumalanga Province (seen left). The system is being employed across the smelter's four furnaces to improve safety and sequential operation of the furnace power switching and access control.
According to Roy Plotz, commercial engineer, Rockwell Automation, three of the existing systems needed to be replaced due to problems caused by operating in the harsh environment, while the fourth system, an existing Prosafe solution, was still performing well. "This is one of the largest systems of its kind that has been installed in southern Africa, from the number of keys used to the actual size of the installation," he says.
"Improved safety and durability were the two main requirements of the system. We worked closely with our distributor in the region, Supplytech and the client to design and deliver a system that precisely met their requirements. Once we'd confirmed the specification requirements, the four systems were completed. From design to delivery, the project was completed in 12 weeks.
"Initially the customer wanted four identical systems. However, two of the furnaces were different so we altered the design specifications accordingly."
Plotz notes that the Prosafe system was the ideal choice because of its reputation of quality, robustness and performance in harsh environments where heat, dust, and continuous use are important considerations. "In addition, the Prosafe system caters to more complex operating sequences and assists with safety requirements. It is typically used in applications where sequential access into potentially hazardous areas is required."
The Prosafe system helps prevent secondary keys being removed from the unit in question until all of the primary keys have been inserted, rotated and trapped. In the same vein, the primary keys remain trapped until all secondary keys have been re-inserted, rotated and trapped.
The system itself eliminates the need for a lot of keys that can be misplaced or misused. The keys are manufactured from 316L grade stainless steel, are specially coded, and can only be manufactured by Rockwell Automation to help ensure the safety integrity of each system. The system can be configured as mechanical or electro-mechanical, depending on the customer's requirements. In the case of the smelter, a combination of both methods was used which allows for the monitoring of individual keys and integration into the existing control system.
"We completed this project in conjunction with the client and Supplytech, who also performed the majority of the installation. Installation was done in stages, as the furnaces within the smelter went offline, to ensure a minimum of downtime," concludes Plotz.
www.rockwellautomation.com
