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What Are Welding Neck Flanges?

A welding neck Flange (also called a ‘weldneck or flange’) is well recognised for its long-tapered hub which gives mechanical strength (useful to ward off bowing and ‘dishing’). Welding necks are high integrity flanges , and are offered at all lengths, as well as all faces that are commonly used (flat raised, flat, and RTJ) and in all classes. Because of the robustness of the hub as well as the strength of the weld this type of flange is suitable to high pressure and temperature applications.

A Welding Neck Flange Cross Section

A butt weld, also referred to as V-weld or a groove weld, is a single weld penetration. It can be utilized to connect the neck of the welding flange to the tube or fitting. The single weld penetration makes this kind of flange appropriate for harsh operating conditions like extreme pressure systems, temperatures below zero as well as elevated temperatures. Other benefits of welding neck flanges include:

Great stress distribution throughout the tapered hub.

Unrestricted flow and very low drop in pressure across the valve (low delta P).

The ability to load cyclically is high.

Causes very little Turbulence.

Low rates of erosion.

A direct connection with elbows, tees or reducers.

For flanges with larger diameters, there is more room for non-destructive tests to be conducted on the weld (difficult on certain designs of flanges due to the position on the location of the welding).

A high resistance to bending forces because of the long hub.

Welding Neck Flange

The flow is unrestricted and the low turbulence of a flange with a welding neck are related to that the pressure drops are low across the flange. this is due to the fact that the flange bore is identical to the bore of the pipe. The rates of erosion are also tied by the volume of pressure that flows across the flange however, the rate of erosion is dependent greatly on what flows across the.

This type of flange comes with one disadvantage that is significant compared with other types of flanges: it’s pricey (a important factor in the selection of firms).

Non-Destructive Testing (NDT) Techniques

The phased array (ultrasonic NDT technique) inspection of the flange’s face is possible on flanges that are welding necks and the results will show any damage that is internal to the face of sealing.

The magnetic particle inspection (MPI) Dye permeant inspection (DPI) radiographic testing (RT) or ultrasonic testing (UT) are all options to verify the weld.

ASME Standards

These standards ASME B16.5 ASME B16.5 and ASME B31.3 provide the necessary requirements for welding neck flanges maintenance, as well as testing.