Socket weld flanges are designed for small nominal pipe sizes (≤ 4 inches, ≤ 10cm) and are common for ½ to 2-inch pipe sizes (1.3 to 5cm pipe sizes). The mechanical strength of a socket weld flange is similar to that of a slip-on flange, but the slip-on flange may use two welds.
Socket weld flanges have only one fillet weld and this can be subjected to radiography to prove the weld, although in practice it is impractical. Magnetic particle inspection (MPI) and dye penetrant inspection (DPI) can be used to prove the weld.
