By | Apr 19, 2010
|Encapsulated system solution with special lifting elements is also suited for other applications in heavy industry|
|There is hardly any other workplace in which conditions are as harsh as they are in a steel mill. Surrounded by scorching heat and loads of grime, the hardest work is performed primarily by machines, and such equipment requires a particularly robust design. For the continuous casting plant operated by one of Germany’s largest steel producers, Pfaff-silberblau Hebezeugfabrik GmbH of Kissing, Germany, used its SHE 150 worm-gear screw jacks as a basis to develop a special push-tube construction for positioning ladle cars. Having passed its “trial by fire” in the foundry, this encapsulated system solution from the Southern German specialist in actuator technology is now available for other heavy-industry applications in which heavy loads have to be moved in harsh environments.
The steelmaker’s requirements for the ladle car positioning system from Pfaff-silberblau are derived from what might appear to be a simple process. However, the work requires great power and resilience: In continuous casting foundries, ladle cars are used to move molten steel from a furnace to casting molds. A lifting system moves the ladle car, which weighs up to 150 tons when filled, into its upper position. In this way, molten steel can then flow out of the furnace and into the ladle car via a ceramic tube. As it fills, the ladle car slowly lowers. A sensor on the other end of the shaft or on the jack’s motor determines its position, while a control unit in the foundry system guides the process.
With the system solution from Pfaff-silberblau, four lifting jacks, with a maximum lifting capacity of 500kN each, perform this hard work: They lift the ladle car at a maximum speed of approximately 2m/min – reliably, safely and precisely, even under the toughest production conditions. For this lifting system, the engineers from Pfaff-silberblau developed a special push-tube construction based on the company’s existing size-150 worm-gear screw jack.
Besides the reinforced mounts and the guide system, heavy-duty planetary roller screws were employed; they were required in order to be able to reach the maximum lifting speed. Each of these screws is housed in a tubular construction in which the screw’s traveling nut is integrated into a screw-nut housing, to which the hard-chrome plated push rod is attached. The tubular construction absorbs the lateral forces that arise when the ladle car starts moving and comes to a halt. As a result, there is no need for additional side guides for the ladle car. To protect the connecting rod against damage, it is also guarded by a cover that moves with the rod and protects it against grime from the outside. The foundry system receives the ladle car via screw threading on the end of the push tube.
Since this lifting equipment is highly efficient, it was possible to keep the requirements low for the power produced by the drive motors. Each of these lifting elements is pre-mounted on a shared base plate, thus forming a compact system together with the drive motor and 90° miter gear box. As a result, they are easy to mount and align within the on-site system.
To ensure high availability, the engineers at Pfaff-silberblau took maintenance requirements into considerations during the lifting element’s design phase. During the maintenance phase, all wear parts and seal-relevant components can be replaced without significant effort.
|Further information about Pfaff-silberblau is available at www.pfaff-silberblau.com.|
Columbus McKinnon Engineered Products GmbH, Kissing, launched, under the Pfaff-silberblau brand, a jacking system specially for the large-scale production of galvanized steel sheet, which is used in the packaging industry and in vehicle construction. Now, the specialist for drive technology has continued to perfect its system solution to meet the demanding requirements of the steel industry for short idle times. Thanks to a newly developed active cooling circuit, Pfaff-silberblau’s 500-ton lifting system can now be operated without cooling times imposing limits on its duty cycle; further, it does not require automatic relubrication devices. According to the specific requirements in use, this heavy-duty lifting system with 100 percent availability can also be realized for loads of 750 tons and more.