NPS 外径壁厚参照.pdf

NPS (Nominal Pipe Size) Nominal Pipe Size (NPS) is a set of standard pipe sizes used for pressure piping in North America. The same pipe dimensions are used with different names in Europe Pipe size is specified with two non-dimensional numbers: a Nominal Pipe Size (NPS) and a schedule (SCH). The relationship of these numbers to the actual pipe dimensions is a bit strange. The NPS is very loosely related to the inside diameter in inches, but only for NPS 1/8 to NPS 12. For NPS 14 and larger, the NPS is equal to the outside diameter (OD) in inches. For a given NPS, the OD stays constant and the wall thickness increases with larger SCH. For a given SCH, the OD increases with increasing NPS while the wall thickness increases or stays constant. Pipe sizes are documented by a number of standards, including API 5L, ANSI/ASME B36.10M in the US, BS 1600 and BS EN 10255 in the United Kingdom and Europe, and ISO 65 internationally. For NPS of 5 and larger, the DN is equal to the NPS multiplied by 25 (not 25.4). The most commonly used schedules today are 40, 80, and 160. There is a commonly held belief that the schedule number is an indicator of the service pressure that the pipe can take. For example, the McGraw Hill Piping Handbook says the schedule number can be converted to pressure by dividing the schedule by 1000 and multiplying by the allowable stress of the material. However, this is not true Pressure rating actually goes down with increasing NPS and constant schedule. The various standards for pipe schedule are not identical. Frequently some sizes—or even entire schedules—are present in some standards but not others. When different standards do overlap, they usually have the same dimensions. For this reason, the source of the schedules is not distinguished in the table below. Beyond NPS 8, however, there are differing version of schedules 5, 10, 40, and 80. One variation is the presence or absence of an S suffix after the schedule number