A method of determining a carburisation model of a coil of a steam cracking furnace, the method comprises the steps of: determining reference temperature values at reference positions of a wall of a reference coil during operation of a reference steam cracking furnace comprising a reference coil; determining reference carburised portion values of a depth at a reference point in time; determining the at least one material specific constant in dependence of the first relation and the second relation; and determining the carburisation model of the coil in dependence of the determined at least one material specific constant and further in dependence of the first relation and the second relation.