New VAI descaling philosophy by use of variable speed pumps

Abstract

The VAI Variable Speed Descaler takes full advantage from the use of variable speed pumps powered by inverter driven AC motors. Integration with strip tracking and feed forward pump control, together with direct application, allow to optimize the energy savings, to improve pumps life and to simplify the layout. Integration with flow and pressure feedback measurements at headers allows headers pressure tuning, nozzle wear compensation, process control with different “descaling recipes” as function of steel grade and main strip parameters, bar-to-bar adaptation of descaling parameters in case in-line surface inspection is present. Specific “descaling recipes” and pumping station design, together with proper mill scheduling, result in a new maintenance concept allowing to run the system without a stand-by pump, saving investment cost. First two references of this new system are at the hot strip mills of Ilva Taranto (HSM No. 1) (Italy) and of Duferco La Louvière (Belgium).