Which standard governs the form of NPT pipe threads used in gas piping?

• A. ANSI B7.1
• B. NFPA 54
• C. ASTM A53
• D. ASME B1.20.1

Answer: (D)

The form of NPT pipe threads is defined by ASME B1.20.1. This standard specifies the geometry of standard pipe threads used for tapered connections, including the taper, pitch, and thread profile, ensuring that mating male and female threads seal properly when assembled with appropriate sealing methods. In gas piping, you need compatible thread forms to achieve a leak-free connection, and that compatibility is established by this standard. NFPA 54 governs how gas piping systems are installed and operate, but it does not define the thread form. The other standards listed cover unrelated topics (grinding wheels safety, steel pipe material, etc.). Therefore, the standard governing NPT thread form is ASME B1.20.1.