When creating a welded outlet on sprinkler piping, a hole is cut into the run of the pipe. The piece of metal removed, known as a disc or coupon, can fall into the pipe. NFPA 13 explicitly requires that these discs be retrieved. This is a critical step to prevent the disc from traveling through the piping system and causing an obstruction at a fitting, valve, or sprinkler head, which could critically impair system performance during a fire. This requirement ensures the waterway remains clear and unobstructed.

B. Steel plates shall be welded to the ends of piping or fittings: This describes one method for creating a welded cap, but it is not a general requirement applicable to all welding performed on sprinkler systems.

C. Fittings shall be modified: Modifying listed fittings is expressly prohibited. Field modifications can compromise the structural integrity and hydraulic characteristics of the fitting, voiding its listing and approval for use.

D. Fittings can penetrate the internal diameter of the piping: This is incorrect. Welded outlet fittings are explicitly forbidden from penetrating the internal diameter of the pipe, as this would create a flow obstruction and a potential snag point for debris.

1. NFPA 13, Standard for the Installation of Sprinkler Systems (2022 Edition).

Section 7.5.2.4.2: "Discs shall be retrieved." (Supports Answer A)

Section 7.5.2.4.4: "Fittings or shaped nipples shall not penetrate the internal diameter of the pipe." (Refutes Answer D)

Section 7.5.2.5: "Fittings shall not be modified." (Refutes Answer C)

2. SFPE, Handbook of Fire Protection Engineering (5th Edition).

Chapter 20, "Automatic Sprinkler Systems," Section 20.5.1, "Piping." This section discusses installation standards and adherence to NFPA 13, which includes the specific welding requirements for maintaining a clear waterway, such as the retrieval of welding coupons (discs) to prevent system obstruction. (DOI: https://doi.org/10.1007/978-1-4939-2562-420)