An apparatus for processing a molten material comprising: a vessel (102; 144; 202; 302; 402; 502; 702) comprising a wall (104; 204; 304; 404; 504; 704), the vessel (102; 144; 202; 302; 402; 502; 702) arranged to convey the molten material; and a flange (100; 140; 200; 300; 400; 500; 600; 700) attached to the vessel (102; 144; 202; 302; 402; 502; 702) and configured to deliver an electric current to the vessel wall (104; 204; 304; 404; 504; 704), the flange (100; 140; 200; 300; 400; 500; 600; 700) comprising a first ring (112; 216; 316; 416; 516; 616; 712) extending completely around the vessel (102; 144; 202; 302; 402; 502; 702) in a closed loop, the first ring (112; 216; 316; 416; 516; 616; 712) comprising a first portion (118; 222; 322; 522) including a first thickness and a second portion (128; 228; 328; 528) including a second thickness different from the first thickness, the first portion (118; 222; 322; 522) and the second portion (128; 228; 328; 528) comprising overlapping edges in a plane of the flange (100; 140; 200; 300; 400; 500; 600; 700) such that the first portion (118; 222; 322; 522) is positioned between the second portion (128; 228; 328; 528) and the vessel wall (104; 204; 304; 404; 504; 704), and neither the first portion (118; 222; 322; 522) nor the second portion (128; 228; 328; 528) extends completely around the vessel (102; 144; 202; 302; 402; 502; 702), wherein the first thickness of the first portion (118; 222; 322; 522) and the second thickness of the second portion (128; 228; 328; 528) extend in a direction parallel to the longitudinal axis (108; 208; 408; 508; 708) of the vessel (102; 144; 202; 302; 402; 502; 702). a vessel (102; 144; 202; 302; 402; 502; 702) comprising a wall (104; 204; 304; 404; 504; 704), the vessel (102; 144; 202; 302; 402; 502; 702) arranged to convey the molten material; and a flange (100; 140; 200; 300; 400; 500; 600; 700) attached to the vessel (102; 144; 202; 302; 402; 502; 702) and configured to deliver an electric current to the vessel wall (104; 204; 304; 404; 504; 704), the flange (100; 140; 200; 300; 400; 500; 600; 700) comprising a first ring (112; 216; 316; 416; 516; 616; 712) extending completely around the vessel (102; 144; 202; 302; 402; 502; 702) in a closed loop, the first ring (112; 216; 316; 416; 516; 616; 712) comprising a first portion (118; 222; 322; 522) including a first thickness and a second portion (128; 228; 328; 528) including a second thickness different from the first thickness, the first portion (118; 222; 322; 522) and the second portion (128; 228; 328; 528) comprising overlapping edges in a plane of the flange (100; 140; 200; 300; 400; 500; 600; 700) such that the first portion (118; 222; 322; 522) is positioned between the second portion (128; 228; 328; 528) and the vessel wall (104; 204; 304; 404; 504; 704), and neither the first portion (118; 222; 322; 522) nor the second portion (128; 228; 328; 528) extends completely around the vessel (102; 144; 202; 302; 402; 502; 702), wherein the first thickness of the first portion (118; 222; 322; 522) and the second thickness of the second portion (128; 228; 328; 528) extend in a direction parallel to the longitudinal axis (108; 208; 408; 508; 708) of the vessel (102; 144; 202; 302; 402; 502; 702).