Loose flange is also known as lap joint (LJ) flange which is actually achieved by welding, it has a curved radius at the bore and face to house a lap joint stub-end, and then use the bolts and gaskets to achieve sealing, The stub end and the pipe connections can be either flat welding or butt welding. The advantage of this flange is that the flange itself is not welded or fixed in any way. It is free to spin for proper alignment with whatever it is joining to. Also lap joint flanges and stub-end assemblies are typically used in situations where frequent dismantling is required for cleaning or inspection.