Recently presented Pfaff Silberblau a lifting system especially for the large-scale production of galvanized sheet steel, as it is used in the packaging industry or in vehicle construction. Now the drive technology specialist has further optimized its system solution so that it meets the high demands of the steel industry after a short service life.
The lifting system can now be operated by means of a newly developed active cooling circuit without limiting the duty cycle by cooling down and dispenses with automatic relubrication. Depending on the application requirements, this heavy load lifting system with 100-percent availability is also feasible for loads of 750 t or more.
Four screw jacks for 500 t load
Galvanized steel sheet is produced in Continuous Galvanizing Line (CGL). At the heart of these plants are zinc hearth furnaces, in which the zinc is melted and kept in the liquid state. Most CGLs have two furnaces with different zinc alloys that can be used as needed. For this purpose, the required kiln with a weight of 500 t is moved from its parking position one floor below the production line via a rail system to the lifting system and lifted by around 2 m directly into the production line. For this system, which not only has to reliably lift a huge load, but also withstand high heat and dirt, four SHE200.1 hoisting elements are used, which are driven by a central motor via transfer boxes and cardan shafts.
Unlimited duty cycle
Depending on the ambient temperature, load and stroke, the previously used mechanically operated lifting systems required a cooling time after each double stroke of up to 6 h to bring the spindle and worm gear back to ambient temperature - an unacceptable service life for many steelworks operators had to resort to hydraulic solutions.
A new development now combines the best of both worlds: The use of an active cooling circuit for the worm gear and the spindle makes the system as unlimited as a hydraulic solution. At the same time, the mechanical lifting system from Pfaff-silberblau retains all of its advantages: high reliability and absolute safety of the system even in the event of a break in the nut.
Active cooling circuit tempered lubricant
In the optimized lifting system, the heat resulting from the power loss of the spindle and worm gear is completely dissipated to the lubricant. This is led via a return to a surge tank and then cooled by an oil cooler to ambient temperature. With the help of a pump, the oil is constantly circulated and kept at a constant low temperature level. The container is necessary to compensate for the difference in volume within the gearbox and the protective tube when retracting and extending the spindle. A feed line then leads the cooled lubricant to the lowest point on the protective tube of the spindle. Here it enters again, flows through the protective tube and the worm gear and ensures reliable again for the necessary cooling.
Another innovation is that the lubricant for spindle and gearbox are identical and thus automatic relubricating devices are superfluous. As with the SHE200 with sensors, the temperature of the spindle and gearbox is monitored by means of temperature sensors in the advanced SHE200.1.