A flat welding flange is a type of flange that is connected to a vessel or pipe using an angular weld. It belongs to the arbitrary type of flange. During design, it is checked as a monolithic or loose flange based on the degree of integrity between the flange ring and the straight tube section. Flange rings come in two types: with neck and without neck. Compared to necked butt-welding flanges, flat welding flanges have a simpler structure, use less material, but are not as rigid or sealed as necked butt-welding flanges. Flat welding flanges are widely used for connecting medium and low-pressure vessels and pipes.