What type of welds are required for the attachment of slip on flanges according to ASME B311 power piping code part six?

The requirement for double fillet welds for the attachment of slip-on flanges, as specified by ASME B31.1, power piping code, is grounded in ensuring the integrity and strength of the joint. Double fillet welds provide a more robust connection than single fillet welds, as they encircle the joint on both sides, effectively distributing stresses and preventing potential failure points.

When considering other types of welds, such as butt welds, they are typically used for joining two pieces of pipe end-to-end, rather than for flanged connections. Socket welds are intended for fittings and are not applicable for slip-on flanges which require the flanges to be welded both above and below to ensure a secure fit. Single fillet welds, while still providing some level of attachment, do not offer the same enhanced support and safety that double fillet welds give in high-pressure applications or dynamic environments.

Therefore, the choice of double fillet welds aligns with best practices in pipeline construction and design, enhancing the reliability of the piping system.