Hangers used for the support of piping, NPS how many inches and larger, shall be designed to permit adjustment after erection?

The correct answer is based on the requirements established for pipe support systems. In this case, hangers designed for piping that is 2 1/2 inches in nominal pipe size (NPS) and larger must incorporate features that allow for adjustment after installation. This is essential because it provides flexibility to account for thermal expansion and contraction, alignment corrections, and any other adjustments that may be necessary once the piping system is fully operational.

Adjustable hangers help maintain the integrity and functionality of the piping throughout its lifecycle, allowing for necessary modifications without requiring significant dismantling of the system. This is particularly important in large-scale installations where precise alignment and support are critical to avoid stress and potential damage to both the pipes and surrounding structures.

The other options do not meet the requirement for hangers designed for adjustment; hangers for smaller diameter pipes, such as those under 2 1/2 inches, typically do not require the same level of flexibility due to their size and the associated lower stresses experienced. Hence, the emphasis on 2 1/2 inches and larger highlights the need for these adjustable features in larger piping systems.