What is the maximum size limitation for NPS class 600 socket welded flanges according to ASME power piping code B311?

According to ASME B31.1, which covers power piping, the maximum size limitation for NPS (Nominal Pipe Size) class 600 socket welded flanges is indeed 3 inches. This standard specifies the design, installation, and maintenance of piping systems, and includes guidelines for various types of flanges and joint connections.

The limitation for socket welded flanges is primarily due to considerations related to the structural integrity and the capabilities of socket welding processes. As pipe diameters increase, the challenges of maintaining a consistent and strong weld also increase, which makes larger sizes less practical for socket welding. Therefore, class 600 socket welded flanges are restricted to a maximum size of 3 inches to ensure safety, reliability, and ease of installation in power piping systems.

Understanding these limitations helps in making appropriate selections for piping components based on their intended application and operating conditions.