Taking the confusion out of slab stores

Radar positioning system keeps track of steel slabs and smooths rolling mill operations
Hoesch Hohenlimburg is a steel refiner with a long tradition and a very special product: the (PresseBox) (Neubiberg, ) Greatly improved process stability and a 20 percent increase in inventory turnover result as the main benefits of an innovative inventory management system implemented by Hoesch Hohenlimburg for the steel slab store of their hot-rolling mill plant. Now the solution has demonstrated its reliability and effectiveness, plans are to extend it to a second slab store one step backward in the logistics chain. Symeo Local Positioning Radar forms a key component of this system, continuously tracking crane trolley positions down to a few inches.

Hoesch Hohenlimburg is a steel refiner with a long tradition and a very special product: the "Hohenlimburg medium strip", hot-rolled steel strip for use in the automotive and similar industries. Long and unwieldy steel slabs are delivered via road and rail to Hoesch’s site in Hagen, Westphalia and then stored in irregular stacks where they then wait to be processed in the mill.

And although those slabs all look more or less alike, they are not. Each steel strip has to be rolled from one and only one kind of slab to meet its unique property requirements. This requires knowing the exact whereabouts of each and every slab waiting in store all the time. Traditionally, the slabs were identified by marking them with coloured chalk. This was arguably not the safest method and confusing two slabs was usually a near disaster, affecting two different orders at once as likely as not.

In contrast, the new IT based inventory management system (IMS) keeps an exact record of where each steel slab waiting to be milled is stored and how deep down in which stack the crane operator has to go to get hold of it when it is needed. Keeping track of the exact position of every stored slab this way is crucial for the inventory management system to work. This is done by following every movement of the trolley cranes used for moving the slabs across the rolling mill site.

And here, Symeo’s Local Positioning Radar (LPR) comes in: Each of the six crane trolleys on the site is fitted with an LPR base receiver unit. Radar transponders are distributed over the site and between them, these radar devices continuously keep track of the cranes’ movements down to an accuracy of 5cm (2 inches).

The Symeo radar positioning system is complemented by laser scanning equipment which is used for recording the height profile of the slab stacks in regular intervals. As a result, Hoesch has a continuously updated, detailed three-dimensional image of the slab store available at all times. This serves, e.g., to show the crane operators exactly where to find the next slab to be picked up and moved to the furnace for heating and rolling.

The IMS also identifies optimal storage positions for newly delivered slabs and supplies the crane operator with detailed instructions including a 3D view of the storing operation. Furthermore, based on the scheduled furnace operating sequence, the IMS calculates the time needed to clear the required slabs for access first and then supply them to the furnace roller conveyors in time. The resulting transport operations are distributed among the six crane systems in a time and priority controlled fashion.

Hoesch’s new inventory control system started normal operations in the course of year 2006. Since then, the solution has delivered outstandingly on its promise: The risk of confusing two steel slabs has dropped to less than 0.001 percent.

The benefits of the IT controlled warehouse logistics are quite evident, as Marcus Bleck, factory manager in charge at Hoesch Hohenlimburg, readily confirms. "We have reduced crane movements by about 20 percent with the new system. And lowering the risk of confusing slabs has significantly raised our process stability. In all, we managed to increase the store turnover by about 20 percent", he states.

In the meantime, the outstanding effectivity of the inventory control system has encouraged plans to extend it beyond the Hohenlimburg location. The intention is to employ the logistics solution featuring Symeo’s Local Positioning Radar at a slab store in Duisburg-Huckingen from where most of the slabs for Hohenlimburg come from. So in future, when the slabs arrive at Hohenlimburg, their logistics data will already be sent over and ready for further processing.

More information at www.symeo.com.

About Hoesch Hohenlimburg GmbH

Based in Hagen, Westphalia, Germany, and part of the ThyssenKrupp Steel Group, Hoesch Hohenlimburg GmbH, takes pride in more than 150 years of steel processing history and today stands out as a niche supplier of special hot rolled steel strip. This Hohenlimburg medium strip finds its use as input stock for the cold rolling industry as well as in direct processing largely in the automotive industry. Hoesch Hohenlimburg employs a staff of 900 and last reported annual sales of 683m Euro.

Website: www.hoesch-hohenlimburg.de

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