The Volume Control System from INITEK
The system that accurately track and supervise the amount of molten metal in tilt-able
casting furnaces, troughs, filters and launders.
- The remains of molten metal in the furnace after
casting is the start of the next cast.
It is important to be able to determine the volume
of molten metal accurately to be able to achieve
correct volume and alloy analysis.
- It is important to supervise the amount of molten
metal during casting to be able to determine
whether there is enough molten metal to achieve
the specified casting length, particularly during
casting of long billets.
- In order to stop molten metal transfer at a given
metal volume when transferring from a melting
furnace to a casting furnace.
Traditional methods to handle these tasks has been to
either maintain good metal accounts manually when
charging the casting furnace or to install furnace
weighing systems. By keeping manual track of the
metal volume, results will vary from person to person.
Most weighing systems have considerable problems:
- The total weight of the furnace is often 2-3 times
the molten metal weight when fully charged.
- The furnace is exposed to major mechanical and
- The furnace will only be weighed at one position
at one time, what then happens before the next
weighing is out of control.
- How do you keep track of refractory wear or metal
build-up inside the furnace.
- A weighing system only gives the amount of metal
in the furnace and does not handle the molten
metal in the casting system outside the furnace.
The Norwegian consultant company, INITEK, has developed a computer based system for supervision and con-trol
of the molten metal volume in a casting station based on information and measurements that are already
available in the casting station or that easily can be established. The system measures the volume of molten metal
in the furnace before and during the entire cast as well as the amount of metal in launders, troughs, filters and
casting table. The total amount of molten metal is available for the ongoing cast. Furthermore, the remains of
metal in the furnace after casting is estimated as well.
The patented method is based on the fact that there is a relation between furnace volume, tilt angle and the
metal level in the furnace tap-out. This relation is called the Furnace Volume Profile (FVP).
When the FVP is known (calculated by the system) the actual molten metal volume in the furnace is calculated
using the tilt angle and the metal level in the furnace tap-out. The volume profile for a furnace will change over
time due to phenomena like fouling, wear and tear etc. The system will automatically generate and store a new
furnace curve for each cast. These stored curves will be the input for a generation of a new volume profile.
The most important reason why the method works in practice, is the fact that there are separate functions in the
system for generation and maintenance of the volume profile. Figure 2 shows an example of a volume profile for
a 60 ton casting furnace at Elkem Aluminium Mosjøen, Norway which is generated by the system in daily opera-tion.
In determining the metal volume available before casting,
the metal volume in troughs, filters and casting table has
to be taken into account. A casting station often has
various courses for the metal from the furnace to the
casting table, depending on metal treatment to be given.
This means that the metal volume on its way between
furnace and casting table can vary quite a lot from casting
to casting. See figure 3. The system takes into account the
metal´s course in the station in question to be able to
correct these deviations. The system automatically
calculates the different volumes at different courses.
Since the system continuously estimates the available metal volume for the cast, the operator can be warned
during casting if there is too little metal in the system to achieve the desired casting length. The early warning
enables the operator to shut off a few molds early in the casting instead of all the billets becoming too short.
At the end of the process, the remains of metal in the furnace is determined. This is the start of the next charge.
The remains of metal is an important parameter to achieve the correct metal volume and metal analysis when the
next charge is to be alloyed.
When the metal volume in a casting furnace is to be measured, there will be a need for tarring and calibration
functions regardless of measurement system used, due to the fact that the furnace itself change over time, e.g. the
lining is being worn. If tarring and calibration cannot be executed at sufficient frequency, the performance of any
measurement system will gradually be reduced and the measurement accuracy will be lowered over time.
INICast emphasizes the parts of the system which optimize the measurement accuracy over time, with a minimum
of disturbance of operations. In addition, the system has functions which indicate if the measurement inaccuracy
These elements are decisive factors for maintaining accuracy over time.
Assuming that the measurements and parameters are accurately fed into the system, the inaccuracy is roughly
proportional to the remains of metal in the furnace at any given time, i.e. the accuracy increases at the end of the
The absolute accuracy for a casting station can only be estimated when the station´s parameters are known.
Typically, for a 60 ton furnace the accuracy will be approximately +/- 500 - 700 kg at full furnace.
System overview/ System Structure
- The system is contained on a PC located in the control room. It will cover the furnaces that are served from
this control room. The system structure is shown in figure 4.
- A high resolution tilt angle sensor must be installed on the furnace.
- At least one good level sensor (SLS5000) must be installed per furnace on the casting station measuring the
metal level in the launder (in practice directly after the furnace tap-out).
- The interface between the casting station control system and the INICast System must be defined. Operator
displays may be added or changed.