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Welding Neck Flange Explained

A welding neck Flange (also known as a ‘weld neck or flange’) is well recognised by its long-tapered hub which gives mechanical strength (useful to ward off bowing and ‘dishing’). Welding neck flanges have high-quality flanges that are offered with all dimensions, as well as all faces that are commonly used (flat raised, flat, and RTJ) and all types. Because of the durability of the hub and the integrity of the welding the 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 groove weld, is a single weld penetration. It can be utilized to connect the neck of the welding flange to an appropriate pipeline or fitting. The single weld opening makes this type 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. Excellent stress-distribution along the tapered.

Unrestricted flow, with a very low drop in pressure across the valve (low delta P).

The ability to load cyclically is high.

It causes minimal Turbulence.

Low rates of erosion.

It is a method of connecting directly with elbows, tees or reducers.

For flanges with larger diameters, there is more space for non-destructive tests to be conducted on the weld (difficult on certain design flanges because of 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 properties 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 bore is identical to the bore of the pipe. The rate of erosion is also related with the drop in pressure across the flange however, the rate of erosion is dependent greatly on what flows across the.

This flange type has one major disadvantage in comparison to other types of flanges, it’s more expensive (a important factor in the selection of firms).

Non-Destructive Testing (NDT) Techniques

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

The magnetic particle inspection (MPI) as well as dye permeant inspection (DPI) Radiographic testing (RT) and/or ultrasonic tests (UT) are all options to test the weld on the butt.

ASME Standards

Standards ASME B16.5 as well as ASME B31.3 define the specifications for welding neck flanges maintenance, testing, and installation.