The flange end connection defines the way in which it is attached to the pipe. The following are commonly available standard flange end types:
Weld-Neck (WN) Flange. Weld-neck flanges are distinguished from other types by their long, tapered hub and gentle transition to the region where the WN flange is butt-welded to the pipe. The long, tapered hub provides an important reinforcement of the flange, increasing its strength and resistance to dishing. WN flanges are typically used on arduous duties involving high pressures or hazardous fluids. The butt-weld may be examined by radiography or ultrasonic inspection. Usually, the butt-welds are subject to visual, surface, or volumetric examinations, or a combination thereof, depending on the requirements of the code of construction for piping or a component. There is, therefore, a high degree of reliability in the integrity of the weld. A butt-weld also has good fatigue performance, and its presence does not induce high local stresses in the pipework.