Weld Neck Flanges

weld neck flange


Weld neck flanges stand as the most favored among flange types due to their extended neck featuring a weld bevel at its tip. This particular flange design is crafted for seamless butt welding to pipe, creating a remarkably robust and inherently smooth connection.

As dimensions grow larger and pressure requirements become more demanding, the weld neck flange takes center stage as the preferred choice for forging these connections. If solitary bored flange style were to govern modern applications, the weld neck would undoubtedly claim its position as the prime selection.


The weld neck flange also boasts a notable feature in the form of its tapered hub. This design characteristic facilitates a gradual distribution of pressure forces, ensuring a smoother transition from the pipe to the flange’s base. This structural advantage is particularly beneficial in environments characterized by elevated pressure and temperature conditions, helping to absorb some of the impact associated with such usage. The presence of extra steel material along the hub transition further mitigates mechanical stresses.

Given the prevalence of higher pressure classes, weld neck flanges are predominantly manufactured with a ring type joint facing, often referred to as an RTJ face. This specific sealing surface accommodates the use of a metallic gasket that can be compressed within the grooves of the connecting flanges. This arrangement forms an exceptional seal, supplementing the robust weld bevel connection to the pressurized pipe assembly. In scenarios where utmost reliability is imperative, an RTJ weld neck flange coupled with a metallic gasket emerges as the primary preference.



Frequently referred to as nozzle flanges or “long neck” flanges, these components were meticulously crafted to cater to the requirements of the pressure vessel and tank fabrication sector. Typically fashioned as a unified construction, their purpose is to serve as a substitute for the conventional combination of a weld neck and pipe weld. The distinctive hallmark of this flange style is its elimination of the obligatory weld connection.

As indicated in ASME B16.5 subsection 2.8, these flange configurations are alternatively recognized as “straight hub welding flanges.” They receive limited elaboration within the governing specification, primarily because the design specifics of long weld necks are tailored to individual applications, aligning with the specific engineering prerequisites of a particular pressure vessel or tank. The operational pressure, temperature, and substance contained within the vessel collectively play a pivotal role in determining the precise form of long weld neck flange connection essential for the given scenario.


Typically, long weld neck flanges feature a single straight bore with a squared termination (in contrast to the customary weld neck bevel). The diameter of the bore for the long weld neck usually matches the nominal pipe size precisely, although adjustments can be made as needed.

The overall length of the nozzle flange is also determined by the end user, and the nozzle’s body can be adapted to conform to existing sizes or tailored for custom dimensions, enhancing its reinforcement. The junction between the neck’s base and the flange’s base is subtly rounded, addressing the abrupt perpendicular connection between these components and enhancing the concept of a unified and strengthened single-piece construction.