Final answer:
Pipes that are 2.5 inches NPS or larger are generally required to be welded, with welding being favored for larger pipes like 4-inch, 8-inch, and 16-inch pipes due to the need for strong and secure joints. Option A) 2.5" NPS is the correct answer, informed by common industrial practice and considerations of economies of scale in the chemical industry.
Step-by-step explanation:
The size of the pipe that necessitates welding can vary depending on the codes, standards, and practices of a particular industry or project. However, commonly in the industry, pipes that are 2.5 inches NPS (Nominal Pipe Size) or larger are typically welded. This is due to the increased strength and reliability that welding offers for larger diameter pipes, which may be subjected to higher pressures or more demanding service conditions.
Given the options provided, option A) 2.5" NPS is generally the threshold at which piping must be welded. It is important to note that this is a general rule, and specific requirements can vary. For instance, in the chemical industry, economies of scale might come into play when selecting pipe sizes and joining methods for cost efficiency and operational effectiveness, as implied by 'Table 7.15 Comparing Pipes: Economies of Scale in the Chemical Industry'.
For larger pipes, such as a 4-inch pipe, 8-inch pipe, or 16-inch pipe, welding is preferred because it ensures a strong and secure joint capable of handling the pipes' operational needs. In this context, 'Table 7.15 Comparing Pipes: Economies of Scale in the Chemical Industry' likely relates to the comparative costs and benefits of using larger pipes in chemical processes, where welding is part of the cost and efficiency considerations.