The letters 'NPT' used in the notation 1/8-27 NPT as shown in the illustration, indicates the __________. GS-0010

Correct Answer: Option A — thread series

NPT stands for National Pipe Taper, which defines the thread series used for tapered pipe threads. This standard, governed by ASME B1.20.1, ensures mechanical sealing in marine piping systems. The '1/8-27' denotes the nominal pipe size and the number of threads per inch, respectively.