The Differences Between Socket Weld Flanges (SW) And Weld Neck Flanges (WN)

The differences between socket weld flanges (SW) and weld neck flanges (WN) are significant in terms of structure, welding, performance, and application scenarios.

In terms of structure and connection, SW flanges involve inserting pipes into the flange socket followed by external fillet welding, with a short neck. In contrast, WN flanges are butt-welded to pipes via their necks, which are longer and gradually thicken.

From the perspective of welding and inspection, SW flanges use fillet welds, featuring low welding difficulty and simple inspection (visual inspection). WN flanges, however, require butt welds with full penetration, which is more challenging and demands strict non-destructive testing (such as RT and UT).

In terms of performance, SW flanges have lower strength and rigidity, moderate sealing (with potential medium accumulation), poor fatigue resistance, and low cost. WN flanges, on the other hand, offer high strength (equivalent to that of the pipe), excellent sealing (no retention dead corners), superior fatigue resistance, and higher cost.

SW flanges are suitable for medium and low pressure (PN2.5~PN40), small to medium diameters (DN15~DN100), weakly corrosive media (such as water and air), and scenarios requiring quick installation or with limited space (e.g., chemical and food industries). WN flanges are applicable to high-pressure and high-temperature conditions (PN10~PN100), full diameters (DN15~DN2000), and hazardous/high-parameter media (such as steam and LNG), and are widely used in harsh working conditions like petroleum and nuclear power industries.