What method is commonly used to join black iron and stainless steel pipe sections with diameters of 2" in newer fuel systems?

Welds and welded flanges are commonly utilized for joining black iron and stainless steel pipe sections in newer fuel systems primarily due to their strength and reliability. Welding creates a strong, permanent bond between the pipe sections, which is essential in fuel systems that may experience high pressure and fluctuating temperatures. This method minimizes the potential for leaks that could occur with other joining methods.

In addition, welded connections are particularly effective when working with different materials, such as black iron and stainless steel, as they can accommodate the differing thermal expansion rates and other material properties. This is a significant factor in maintaining the integrity of a fuel system, ensuring safety and efficiency.

While other methods like threaded connections or compression fittings might be used in certain applications, they do not offer the same level of strength or resistance to high-pressure environments as welded connections do. Additionally, hub and spigot connections are generally more suited for certain types of piping and are not as commonly used in the context of fuel systems compared to welded connections.