Piping of NPS how many inches should have welded pipe joints?

Welded pipe joints are generally required for piping systems over a certain size to ensure structural integrity and safety. In the context of piping with nominal pipe sizes (NPS), when the size is 2 1/2 inches or greater, welded joints are mandated due to the significant pressures and stresses that may be exerted on larger diameter pipes.

The requirement for welded joints in these larger sizes helps to prevent leaks and potential failures that could occur at flanged, threaded, or other types of connections that may not provide the same level of strength and reliability as a welded joint. This is especially critical in applications involving gas, where safety and containment are of utmost importance.

Smaller pipe sizes, on the other hand, often utilize different connection methods that are adequate for their lower pressure ratings and mechanical stresses. Therefore, the specification for welded joints being required for pipes 2 1/2 inches or greater reflects a balance of safety, performance, and construction standards in the gas industry.