Aluchemie is situated in the Botlek part of Rotterdam’s port area. They produce and supply anode blocks to aluminium smelters worldwide. These blocks later serve as an electrical contact with the aluminium smelting bath and weigh approximately 1 tonne each. The anode blocks are made from petroleum coke and coal tar pitch. Multiple anode blocks are baked simultaneously in large carbon bake furnaces. When the anode blocks have been baked, they are cooled slightly and removed from the furnaces at a temperature of up to 400 degrees Celsius. Large jaw grabbers press six blocks together at a time from the sides and prise them a little until loosened enough to be lifted and removed from the furnace.

There is limited space between the anode blocks and the furnace wall for the jaw grabber to operate, usually less than fifteen centimetres. Anode blocks are produced in multiple sizes and tend to shrink somewhat during the baking process. Stacking them effectively in the furnace is an art in itself and to then lift and remove them out of the furnace keeping them completely intact is also a great challenge. Sometimes this does not go as planned. For example, it could be a scenario that the jaw grabber no longer fits between the furnace wall and the anode blocks. Also, the blocks can sometimes break out of the jaw grabber due to the occurrence of instability.
 

Iv-Consult has developed a method to calculate the correct clamping force in combination with the sufficient release force required for removing the anode blocks from the furnace. The trend in recent years has been to make the clamping jaws much thinner, due to accessing the furnace easier and the increasingly limited space that is available between the anode blocks and the furnace wall. Where previously the strength of the hoisting tool was normative, now the rigidity of the hoisting tool and the clamping jaws (in combination with the stiffness of the blocks themselves) is increasingly becoming the normative factor. A critical limit is reached when the anode blocks can break (fall) due to symptoms of instability. If this happens in the furnace, the jaw grabber and the anode blocks become jammed or lodged in the furnace, with serious consequences.

LEGO building bricks also came into play when calculating the clamping force. As it turned out, the problems that arose with the clamping jaws were exactly the same as those experienced with the LEGO bricks. Because of this, we were able to easily visualise the problems experienced by both the customer and the colleagues who were dealing with the issue.
 

The greatest challenge for Iv-Consult is to select a material for the clamping jaws that has a sufficiently high yield point and E-modulus at an elevated temperature and combines these properties with a minimum thickness. The material must be applied in such a way that six anode blocks (approximately 5 tonnes), with a clamping distance of approximately five metres, remain clamped between the clamping jaws in an elastically stable manner. Iv-Consult has developed various hoisting tools for different types of anodes and has plans to develop a universal hoisting tool for all types of anodes.