Steel furnace upgrade benefits from easier wiring

The steel plants of Saarstahl at Völklingen, Burbach and Neunkirchen have been producing steel products in the Saarland region of Germany since the late 19th century and specialise in the production of wire rod, steel bars and semi-finished products of various grades. Saarstahl is considered one of the most important manufacturers of long steel products in the world. The product range also includes open die forgings. These products are important preliminary products for the automotive industry and its suppliers, the construction industry, power industry engineering, the aerospace industry, general mechanical engineering and other steel-using industries.

Industrial service provider schütz engineering PLT was engaged in a modernisation project at the Saarstahl Burbach plant and was looking for a suitable connectivity solution for signal distribution. In the end the PRV PUSH IN marshalling terminal blocks from Weidmüller were selected.

The 92 MW walking-beam furnace in Saarstahl’s Burbach plant places very high demands on the process control system with its 14 control zones. Saarstahl contracted schütz engineering to modernise the Contronic 3 measurement and control system made by Hartmann and Braun in 1996. The industrial service provider was able offer Saarstahl a complete package, using its experts for furnace systems, that was tailored to the customer’s requirements. For the area of marshalling, the maintainers had a clear wish: the use of terminal blocks.

“During maintenance and servicing, terminals are simply easier to operate,” stated Peter Altmeyer, leader of EM maintenance and power supply at Saarstahl. “So that we could wire both securely and quickly, we wanted a connection solution with screwless direct insertion technology. The PRV marshalling terminal block from Weidmüller which schütz engineering presented to us met these requirements exactly. It impressed us, not just with its push-in connection method, but also with its compact design. Its shape means that it is ideally suited for installation into the existing space in our electrical cabinets. There was even enough space for spare inputs, so that any future expansions can be directly incorporated into the system.”

To avoid downtime, the conversion of the measurement and control system was to take place during the summer holidays, when there was a 14-day shutdown of the walking-beam oven. The PRV terminals also had benefits when it came to the tight time period for conversion, signal testing, recommissioning and control circuit optimisation.

“The existing wiring to the electrical cabinets had to be reinstalled one for one. Instead of the standard web-like colour variants, Weidmüller delivered us terminals with striped colour markings. As the existing connection elements were also constructed with a white-red striped colour scheme, the rewiring could be carried out quickly and without complications. The re-wirers were almost able to work without a circuit diagram,” recalled Franzjosef Haas from schütz engineering about the seamless project flow. “We connected 5600 terminal points in 32 hours from the start of disassembly to the beginning of signal testing.”

For running operations, the PRV terminals offer an operating and maintenance friendly solution. Thanks to the high connection density, there was always a danger in the TERMI-POINT versions used previously that a short circuit could be caused during maintenance work in a running plant. This was because the terminals in the measurement system circuits were constructed in such a way that these short circuits could lead to false measurements and even shutdowns for plant components; this could lead to major damage in the worst cases. The PRV PUSH IN marshalling terminal blocks, on the other hand, prevent wiring errors successfully and do not need special tools for the re-wiring. The previously prepared conductors are simply inserted into the terminal points and a vibration-proof and gas-tight connection is made. A normal screwdriver can be used to release the connections.

“The colour coding of the connections was tailor made to meet our requirements. This and the simple operation of the connection technology in the PRV system made a major contribution to us being able to meet the 14-day deadline for the customer without any problems,” Haas went on. “The additional improvement in plant security meant that we were able to offer our customers a solution which was suitable all round.”