According to a first embodiment, a molten metal transferring system is provided. The system includes a device capable of lifting molten metal from a bath to a launder at varying quantity per unit of time. The system includes a sensor, such as a laser, arranged to monitor molten metal flow in the launder. The launder further includes a removeable insert facilitating, reversible modification of a cross-sectional area of the launder.

A measuring lance (1) for measuring a position (has) of an air-slag interface (2as) between an atmosphere (4) and a slag layer (2) sitting on top of a molten metal (3), and a position (hsm) of a slag-metal interface (2sm) between the slag layer (2) and the molten metal (3) in a single measurement run is provided that includes a carrier tube (5) extending along an axis (X) between a proximal end (5p) and a distal end (5d) located downstream of the proximal end, a measuring unit (6) coupled to the distal end (5d) of the carrier tube (5) and configured for passing through the slag layer (2). The measuring unit (6) includes an electric circuit (7) configured for detecting the air-slag interface (2as), a slag-metal interface detection unit (8) located downstream of the distal end (5d), a cap (10) enclosing the slag-metal interface detection unit (8).

A residual molten material amount detection method and detection apparatus that can detect a residual amount of molten material in a vertical furnace and a method for operating a vertical furnace by using the detection method. The residual molten material amount detection method detects a residual amount of molten material remaining in a bottom portion of a vertical furnace after end of discharge of the molten material. The method includes detecting the residual amount of the molten material by using a difference between a production speed of the molten material and a discharge speed of the molten material that is calculated by using a discharge acceleration, a discharge period, and an initial discharge speed of the discharge of the molten material through a taphole.