ASTM A182 F1 F5 F9 F11 F12 F22 F91 ANSI B16.5/B16.47 WN Alloy Steel Weld Neck Flange

Alloy steel weld neck flanges are made from various alloy steel grades, such as ASTM A182 F5, F9, F11, F22, or F91. Alloy steel offers high strength, excellent corrosion resistance, and enhanced temperature resistance, making it suitable for applications in high-pressure and high-temperature environments.

Flanges made of alloy steel are widely used in water lines, oil, and gas, chemical plants, food production systems, etc. where high corrosion resistance, high temperature resistance and high pressure resistance are required.

The weld neck flange has a long tapered hub with a neck that is welded to the pipe, providing reinforcement and preventing leakage. The tapered hub also facilitates smooth flow transition and reduces stress concentration in the joint.

Product Information

Chemical Composition of Alloy Flange Material

Flange Type: Weld Neck (WN)

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 pipes 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.

Long Weld Neck Flanges (LWN)

This flange type is regarded as high-hub flanges, which were created so stress could be transferred to the pipe and decreasing the stress concentration at the bottom of the flange.

The long welding neck flange is mainly applied to the construction of pressure vessel functioning as a nozzle (such as a thermowell nozzle). To attach a common welding neck flange to a pressure vessel, a piece of pipe is required with additional welding. A LWN flange on the other hand attaches directly to the vessel, hence, it can be viewed as an integrally reinforced nozzle. It avoids making a weld seam at pipe to flange and provides self-reinforcement.

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.

The reducing weld neck flange is used to make a reduction in the diameter of the pipe. A reducing flanged joint consists of a reducing flange and a standard flange, functioning like a reducer fitting. As illustrated in Figure-1, the larger end of reducing flange A, which is in contact with the standard flange B, is known as “the size from which the reduction is being made”; the smaller end of the reducing flange A, which will be welded to a pipe, is known as “the size to which the reduction is being made”. The flow should travel from the smaller size to the larger. If the flow direction were reversed, severe turbulence could develop.

In order to make a reduction in the pipe line with two standard welding neck flanges, an additional reducer shall be used as illustrated in Figure-2. The overall length of this configuration is 2L+H, which is much longer than L+M of a reducing flanged joint as illustrated in Figure-1. It means that the use of reducing flanges can effectively save space in crowed situation. In fact, the reducing flange is most frequently used in installations with limited space.

Manufacturing Process