What is Weld Neck Flange?

What is Weld Neck Flange?

Among the most used flanges are those known as Weld Neck or Welding Neck (WN). As with the others, the characteristics of this flange are very specific, differentiating it from the rest by its use and application. The WN flange is very durable and forms a good seal. It is often used on high-pressure pipes and pipelines.

A weld neck flange, also called a tapered hub flange or high-hub flange, is a kind of flange that can relocate stress to the pipes, ensuring a decrease in high-stress concentration at the bottom of the flange. There are two welding neck flanges designs – the first type is used with wipes while the second, longer type cannot be used with pipes but with a process plant. The weld neck flange comprises of a round fitting that extends beyond the rim of the circumference. These flanges, typically manufactured from forging, are actually welded to pipes.

The rim has numerous holes drilled into it that enables the flanged to be attached to a bolted flange. This design is far better because of the structural valve.

Long weld neck Flange

Long WN flange looks like the typical welding neck flange, but is considered to be elongated. It’s usually used as a nozzle for a column or barrel. You can also choose between the Equal LWN Barrel and LWN Heavy Barrel, which have a thick wall and their own shape.

Reducing Weld Neck Flange

It is also called reducing welding neck flange, because the flange neck has a reducing diameter that to weld to a smaller diameter pipe.

Weld Neck Flange Dimensions

Below we list some sizes of weld neck flanges (Class 150) under ASME B16.5 (1/2” to 24”).

· The 1/2” NPS weldneck flange has inside diameter of 0.62” and outside diameter of 3.50”. The raised face’s thickness is 1.88” with four holes for bolts.

· The 3/4” NPS flange has inside diameter of 0.82” and the outside diameter of 3.88”. The raised face’s thickness is 2.06” with four bolt holes.

· The 1” NPS weldneck flange has inside diameter of 1.05” and outside diameter of 4.25”. The raised face’s thickness is 2.19” and the standard bolt holes are four in a number.

· 2” NPS weldneck Flange has inside diameter of 2.07” and outside diameter of 6.00”, The raised face’s thickness is of 2.50”.

· The 5” NPS Flange has 5.05” of inside diameter and the outer diameter is of 10.00”. The thickness of the raised face is 3.50”.

· The 6” NPS Flange has 6.065” of inside diameter and the outer diameter is of 11.00”. The thickness of the raised face is 3.50”.

· The 10” NPS flange has inside diameter dimension of 10.02” and the outer diameter of 16”. The thickness of the raised face is of 4.00”.

· The 20” NPS flange has inside diameter of 19.25” and the outer diameter of 27.50”. The thickness of the raised face is 5.69”.

· The 24” NPS Weld neck flange gets the interior diameter of 23.25” and the outer diameter of 32.00”.

Characteristics of welding neck flanges

These flanges are distinguished by having a long conical neck, the end of which is welded to the connecting pipe. The inside diameter of the pipe is equal to that of the flange, providing a conduit of generally constant cross-section and no interruptions or turbulence in the gases/liquids flowing through the pipe. Welding neck flanges provide high load strength along with even stress distribution.

Attention must be paid to the junction between the flange and the pipe to be welded on in order to avoid possible interruptions in high speed flows.

Why use a welding neck flange?

WN flanges are intended for activities involving high pressure and extreme conditions (cold or heat), flammable or corrosive contents, etc., and, above all, environments where leakage must be minimal or almost non-existent. They are used in order to minimize the number of welds on small parts while helping to reduce corrosion of the junction itself.

These benefits make weld neck flanges a preferred choice in demanding applications, ensuring safety and long-term performance.

They are used in steam lines; oil, natural gas and refined hydrocarbon lines; fire networks; petrochemical facilities, etc.