Long weld neck flange (LWN flange) is also called integral flange, it means a welding neck flange has a very long neck.
Commonly, the welding neck flange has a tapered neck and a bevel end which is going to butt welding with the matching pipe. But the long weld neck flange, has a straight short pipe as the neck of a long weld neck flange. Long weld neck flange (LWN flange), is used for high pressure situations, integral hub weld neck flanges are used and for very high pressure cases Long Welding Neck flanges are preferred. In this case, the weld are far from the ring to avoid bending stresses and weld stress being combined.
The Long Weld Neck Flanges are the best designed butt-welded flange of those currently available because of its inherent structural value. It is expensive because of the design.
Long welding neck flange, LWN flanges are similar to a standard Welding Neck flanges, but the “Neck” is considerably longer than other flanges. LWN flange is often used as a nozzle for a barrel or column. In addition, there are the type LWN Heavy Barrel (HB) and the Equal LWN Barrel (E); they have a different shape and a thicker “Wall”.
The long weld neck flange should be butt welded with the pipes, it means the neck dimensions is same with the matching pipe, same diameter and wall thickness , commonly the long weld has a plain end, not a bevel end for welding . Except the neck, the LWN flange has a same dimensions with the welding neck flange. In addition, there are also the type LWN Heavy Barrel (HB) and the Equal LWN Barrel (E); they have a different shape and a thicker “Wall” which name is Nozzle.
Tube OD sizes: 3/8 to 2 inches
The Long Weld Neck Flange is normally referred to as the high hub flange. It is designed to transfer stresses to the pipe, thereby reducing high stress concentrations at the base of the flange.
The Long Weld Neck Flange is the best designed butt-welded flange of those currently available becuase of its inherent structural value. It is expensive because of the design.