Which are the most common types of flanges used in piping? How do they look like? The key types of flanges are the welding neck, long welding neck, slip-on flanges, socket weld, lap joint, threaded and blind flanges. In addition to these standard flanges, some special ones exist, called Weldoflange/Nipoflange and Elboflange, swivel flange, expander/reducer flange, and orifice flanges. STANDARD TYPES O | 0 | 145 | haiquene119 |