A new damping system from Siemens Metals Technologies was brought into operation recently at the Steel Making Plant North of the Chinese producer, Taiyuan Iron & Steel. The Simetal Drive Damper is installed on the tilting drive of the AOD converter. It reduces vibrations caused by the blowing processes, and thus the mechanical loads acting on the entire system from the converter down to the foundations. The patented system reduces wear and maintenance costs while also extending lifetime of service parts. It can be installed in new plants as well as an upgrade onexisting converters.

The AOD (argon-oxygen decarburisation) refining process is used in the production of stainless and high-alloy steels. Large quantities of oxygen, argon and nitrogen are injected laterally to mix the bath thoroughly and minimise the unwanted slagging of alloying elements. This process-related injection during the refining process sets the bath and the several hundred tonnes of the AOD converter in vibration. This causes additional dynamic loads, which reduce the service life of the mechanical components of the converter plant, and increase the amount of maintenance required. So far vibrations lead to premature wear on bearings and gears of the tilting drive.

HYDRAULIC DAMPERS

The Simetal Drive Damper developed and patented by Siemens reduces the induced vibrations and the associated mechanical load on the converter mechanism by more than 50 per cent. The system consists of two hydraulic dampers developed in cooperation with Hainzl, an Austrian company, as well as measuring devices, evaluation software and automation system. The dampers are installed in parallel to the torque support of the converter tilting drive, and are driven independently of it. The design ensures highest availability and makes it easy to upgrade existing plants. Each damper has a closed hydraulic circuit, making an additional, external hydraulic system superfluous. The damping effect is achieved by means of an electrohydraulic proportional throttle valve, and is therefore continuously adjustable. The thermal energy generated by the damping is dissipated by an integrated water cooling system.

The dampers are equipped with a position measuring system as well as pressure and temperature sensors. All process data – such as vibration displacement, temperature, pressure and damping force – are recorded and evaluated by software developed by Siemens. This facilitates a fast, effective response to the momentary vibration state of the AOD converter.

The development of the system was preceded by comprehensive measurements made on existing converter plants along with various experiments, as well as the numerical simulation of the fluid dynamics in the steel bath and the interaction between the fluid and the mechanical structure.