管道公称尺寸(NPS)历史与应用.doc

管道公称尺寸(NPS)历史与应用接触过ASME管道工程的工程师都应该知道NPS的意思，它的全称是Nominal Pipe Size。它是北美用于高、低压及温度的管道尺寸标准体系之一。其管道尺寸用两个非尺寸的编号来标识：即用以英寸单位的NPS和管表号（用Sched.或Sch.）表示。与NPT（national pipe thread）的简称来源相混淆有关，NPS常常被错误地叫做美国国家管道尺寸（National Pipe Size）。对于其它的管道尺寸标准请有兴趣的同行参见相应的管道（材料）尺寸标准，这里不作详细说明。欧洲的相当于NPS的术语是DN（diamtre nominal/nominal diameter），它的尺寸单位毫米表示。还有一个与NPS频繁相交互使用的术语是NB （nominal bore）。历史背景1927年3月，美国标准协会受权了一个委员会去标准化铸钢、铸铁钢和非标管（tube）的尺寸。当时只有一小部分的管壁厚系列被应用，即基于今天在使用的钢管尺寸IPS（iron pipe size）体系：标准重量（STD）、特加重壁厚（XS）和双倍特加重（XXS）管。但是这三个尺寸不满足应用的需要，于是此委员会在行业中进行了调查，制订了基于管壁厚分级差距更小的标识管壁厚的管表号系统（虽然IPS和NPS编号在意义上相同）。最初的目的是使每一个管表号编号与给定的压力等级相关联，但是通常使用中的此编号与管壁厚背离太大，当时的目的没有达到。曾在1939年希望将STD，XS和XXS三个壁厚标识逐步淘汰而采用管表号编号，但时至今日这三个仍在使用。自最初的管表号制订以来，基于行业应用和来自API、ASTM及其它标准，对管表号进行了多次修订和补充。不锈钢管的应用曾在20世纪中期很普遍，由于其抗腐蚀的优越性，更薄壁厚管被允许使用。截止1949年，基于压力要求修订的最接近BWG编号的薄壁厚管表号5S和10S被制订，后来又制订了加注“S”的此类其它管表号。由于它们薄壁性，此小尺寸的“S”管在ASME Standard 36.19M-2004规范上要求不能螺纹连接，只能采用电熔焊接连接。应用从NPS和管表号上不能看出相应的管外径（OD）和壁厚，只能通过ASME标准B36.10M 和B36.19M来获得。例如，NPS14 Sch40，通过查标准可知其OD为14英寸、壁厚为0.437英寸。但是，并不是所有的NPS和OD对应的值都是一样的，这样就产生的混乱。对于NPS1/8到NPS12英寸，其NPS和OD值是不相同的。例如，NPS12管的OD实际上是12.75英寸；要知道其真实的OD，只能通过标准查知。（注：对于Tube管，其NPS总是与实际的OD相同）NPS14及以上尺寸，NPS与OD值是相同的。换句话说，一个NPS14的管子，其真实的OD也正好是14英寸。NPS1/8到NPS12英寸的管子尺寸其NPS与OD不同的原因是，当时壁厚标准最初对这些管的NPS值用同一内径（ID）表示。后来经过发展，ID也有所变化，于是对这些尺寸的管用NPS既不与ID相同，也不与OD相同。对于一个给定的NPS，其OD总是保持不变，其壁厚随着管表号增大。对于一个给定的管表号，其OD随着NPS而增大，但壁厚保持不变或增大。如果应用ASME B31.3中的公式，可以发现随着NPS的增加而保持不变的管表号其压力等级是会降低。在有些规定书上使用的管表号为：标准壁厚（STD）、特加重（XS）、双倍特加重（XXS），尽管这种表示方法已属于一种老的被称为钢铁管尺寸（IPS）的标识方法。IPS编号与NPS编号方法是一样的。对于NPS1/8到NPS10（包括NPS10）之间的尺寸，STD与SCH40S是一样的；XS与SCH80S是一样的；不同的是XXS，其与SCH160通常更厚一些。管表号数字后加注的“S”，比如“NPS Sch 10S”最常用于不锈钢管的壁厚标识中，但也有一些不锈钢管的壁厚也用不加“S”的碳钢合金钢（对应标准ASME B36.10M）标准选用，因此说加注了“S”只是区别ASME B36.19M中不同于ASME B36.10M。对于PVC和CPVC管来说它们都采用NPS的尺寸标识。llljq2009-3-13 22:48:36Schedule TerminologyAn introduction to pipes and the schedule terminologyWelded and Seamless Wrought Steel PipeTo distinguish different weights of pipe, it is common to use the Schedule terminology from ANSI/ASME B36.10 Welded and Seamless Wrought Steel Pipe:Light WallSchedule 10 (Sch/10, S/10)Schedule 20 (Sch/20, S/20)Schedule 30 (Sch/30, S/30)Schedule 40 (Sch/40, S/40)Standard Weight (ST, Std)Schedule 60 (Sch/60, S/60)Extra Strong (Extra Heavy, EH, XH, XS)Schedule 80 (Sch/80, S/80)Schedule 100 (Sch/100, S/100)Schedule 120 (Sch/120, S/120)Schedule 140 (Sch/140, S/140)Schedule 160 (Sch/160, S/160)Double Extra Strong (Double extra heavy, XXH, XXS)Note that many of the schedules are identical in certain sizes.Stainless Steel PipeFor stainless steel pipes thru 12-inch, schedule numbers from Schedule 5S to schedule 80S are used as published in ANSI/ASME 36.19M Stainless Steel Pipe.Schedule 5S (Sch/5S, S/5S)Schedule 10S (Sch/10S, S/10S)Schedule 40S (Sch/40S, S/40S)Schedule 80S (Sch/80S, S/80S)NPS tables for selected sizesNPS to NPS 3NPSDNmmODinches (millimeters)Wall Thicknessinches (millimeters)SCH 5SCH 10SCH 30SCH 40SCH 80SCH 120XXS60.405 in (10.29 mm)0.035 in (0.889 mm)0.049 in (1.245 mm)0.057 in (1.448 mm)0.068 in (1.727 mm)0.095 in (2.413 mm)-80.540 in (13.72 mm)0.049 in (1.245 mm)0.065 in (1.651 mm)0.073 in (1.854 mm)0.088 in (2.235 mm)0.119 in (3.023 mm)-100.675 in (17.15 mm)0.049 in (1.245 mm)0.065 in (1.651 mm)0.073 in (1.854 mm)0.091 in (2.311 mm)0.126 in (3.200 mm)-150.840 in (21.34 mm)0.065 in (1.651 mm)0.083 in (2.108 mm)0.095 in (2.413 mm)0.109 in (2.769 mm)0.147 in (3.734 mm)0.170 in (4.318 mm)0.294 in (7.468 mm)201.050 in (26.67 mm)0.065 in (1.651 mm)0.083 in (2.108 mm)0.095 in (2.413 mm)0.113 in (2.870 mm)0.154 in (3.912 mm)-0.308 in (7.823 mm)1251.315 in (33.40 mm)0.065 in (1.651 mm)0.109 in (2.769 mm)0.114 in (2.896 mm)0.133 in (3.378 mm)0.179 in (4.547 mm)-0.358 in (9.093 mm)1321.660 in (42.16 mm)0.065 in (1.651 mm)0.109 in (2.769 mm)0.117 in (2.972 mm)0.140 in (3.556 mm)0.191 in (4.851 mm)-0.382 in (9.703 mm)1401.900 in (48.26 mm)0.065 in (1.651 mm)0.109 in (2.769 mm)0.125 in (3.175 mm)0.145 in (3.683 mm)0.200 in (5.080 mm)-0.400 in (10.160 mm)2502.375 in (60.33 mm)0.065 in (1.651 mm)0.109 in (2.769 mm)0.125 in (3.175 mm)0.154 in (3.912 mm)0.218 in (5.537 mm)0.250 in (6.350 mm)0.436 in (11.074 mm)2652.875 in (73.02 mm)0.083 in (2.108 mm)0.120 in (3.048 mm)0.188 in (4.775 mm)0.203 in (5.156 mm)0.276 in (7.010 mm)0.300 in (7.620 mm)0.552 in (14.021 mm)3803.500 in (88.90 mm)0.083 in (2.108 mm)0.120 in (3.048 mm)0.188 in (4.775 mm)0.216 in (5.486 mm)0.300 in (7.620 mm)0.350 in (8.890 mm)0.600 in (15.240 mm)3904.000 in (101.60 mm)0.083 in (2.108 mm)0.120 in (3.048 mm)0.188 in (4.775 mm)0.226 in (5.740 mm)0.318 in (8.077 mm)-0.636 in (16.154 mm)NPS 4 to NPS 9NPSDNmmODinches (millimeters)Wall Thicknessinches (millimeters)SCH 5SCH 10SCH 20SCH 30SCH 40/STDSCH 60SCH 80SCH 100SCH 120SCH 140SCH 16041004.500 in (114.30 mm)0.083 in (2.108 mm)0.120 in (3.048 mm)-0.188 in (4.775 mm)0.237 in (6.020 mm)0.281 in (7.137 mm)0.337 in (8.560 mm)-0.437 in (11.100 mm)-0.531 in (13.487 mm)41155.000 in (127.00 mm)-0.247 in (6.274 mm)-0.355 in (9.017 mm)-51255.563 in (141.30 mm)0.109 in (2.769 mm)0.134 in (3.404 mm)-0.258 in (6.553 mm)-0.375 in (9.525 mm)-0.500 in (12.700 mm)-0.625 in (15.875 mm)61506.625 in (168.27 mm)0.109 in (2.769 mm)0.134 in (3.404 mm)-0.280 in (7.112 mm)-0.432 in (10.973 mm)-0.562 in (14.275 mm)-0.719 in (18.263 mm)82008.625 in (219.08 mm)0.109 in (2.769 mm)0.148 in (3.759 mm)0.250 in (6.350 mm)0.277 in (7.036 mm)0.322 in (8.179 mm)0.406 in (10.312 mm)0.500 in (12.700 mm)0.593 in (15.062 mm)0.718 in (18.237 mm)0.812 in (20.625 mm)0.906 in (23.012 mm)NPS 10 to NPS 24NPSDNmmODinches (millimeters)Wall Thicknessinches (millimeters)SCH 5sSCH 5SCH 10sSCH 10SCH 20SCH 301025010.75 in (273.05 mm)0.134 in (3.404 mm)0.134 in (3.404 mm)0.165 in (4.191 mm)0.165 in (4.191 mm)0.250 in (6.350 mm)0.307 in (7.798 mm)1230012.75 in (323.85 mm)0.156 in (3.962 mm)0.165 in (4.191 mm)0.180 in (4.572 mm)0.180 in (4.572 mm)0.250 in (6.350 mm)0.330 in (8.382 mm)1435014.00 in (355.60 mm)0.156 in (3.962 mm)0.156 in (3.962 mm)0.188 in (4.775 mm)0.250 in (6.350 mm)0.312 in (7.925 mm)0.375 in (9.525 mm)1640016.00 in (406.40 mm)0.165 in (4.191 mm)0.165 in (4.191 mm)0.188 in (4.775 mm)0.250 in (6.350 mm)0.312 in (7.925 mm)0.375 in (9.525 mm)1845018.00 in (457.20 mm)0.165 in (4.191 mm)0.165 in (4.191 mm)0.188 in (4.775 mm)0.250 in (6.350 mm)0.312 in (7.925 mm)0.437 in (11.100 mm)2050020.00 in (508.00 mm)0.188 in (4.775 mm)0.188 in (4.775 mm)0.218 in (5.537 mm)0.250 in (6.350 mm)0.375 in (9.525 mm)0.500 in (12.700 mm)2460024.00 in (609.60 mm)0.218 in (5.537 mm)0.218 in (5.537 mm)0.250 in (6.350 mm)0.250 in (6.350 mm)0.375 in (9.525 mm)0.562 in (14.275 mm)NPSWall Thicknessinches (millimeters)SCH 40sSCH 40SCH 60SCH 80sSCH 80SCH 100SCH 120SCH 140SCH 160100.365 in (9.271 mm)0.365 in (9.271 mm)0.500 in (12.700 mm)0.500 in (12.700 mm)0.593 in (15.062 mm)0.718 in (18.237 mm)0.843 in (21.412 mm)1.000 in (25.400 mm)1.125 in (28.575 mm)120.375 in (9.525 mm)0.406 in (10.312 mm)0.500 in (12.700 mm)0.500 in (12.700 mm)0.687 in (17.450 mm)0.843 in (21.412 mm)1.000 in (25.400 mm)1.125 in (28.575 mm)1.312 in (33.325 mm)140.375 in (9.525 mm)0.437 in (11.100 mm)0.593 in (15.062 mm)0.500 in (12.700 mm)0.750 in (19.050 mm)0.937 in (23.800 mm)1.093 in (27.762 mm)1.250 in (31.750 mm)1.406 in (35.712 mm)160.375 in (9.525 mm)0.500 in (12.700 mm)0.656 in (16.662 mm)0.500 in (12.700 mm)0.843 in (21.412 mm)1.031 in (26.187 mm)1.218 in (30.937 mm)1.437 in (36.500 mm)1.593 in (40.462 mm)180.375 in (9.525 mm)0.562 in (14.275 mm)0.750 in (19.050 mm)0.500 in (12.700 mm)0.937 in (23.800 mm)1.156 in (29.362 mm)1.375 in (34.925 mm)1.562 in (39.675 mm)1.781 in (45.237 mm)200.375 in (9.525 mm)0.593 in (15.062 mm)0.812 in (20.625 mm)0.500 in (12.700 mm)1.031 in (26.187 mm)1.280 in (32.512 mm)1.500 in (38.100 mm)1.750 in (44.450 mm)1.968 in (49.987 mm)240.375 in (9.525 mm)0.687 in (17.450 mm)0.968 in (24.587 mm)0.500 in (12.700 mm)1.218 in (30.937 mm)1.531 in (38.887 mm)1.812 in (46.025 mm)2.062 in (52.375 mm)2.343 in (59.512 mm)Note: - = size not designated.PipePipe is a tube with round cross section conforming to the dimensional requirements ofASME B36.10M Welded and Seamless Wrought Steel PipeASME B36.19M Stainless Steel PipePipe SizeInitially a system known as iron pipe size (IPS) was established to designate the pipe size. The size represented the approximate inside diameter of the pipe in inches. An IPS 6 pipe is one whose inside diameter is approximately 6 inches (in).Users started to call the pipe as 2-in, 4-in, 6-in pipe and so on. To begin, each pipe size was produced to have one thickness, which later was termed as standard (STD) or standard weight (STD.WT.). The outside diameter of the pipe was standardized.As the industrial requirements demanded the handling of higher-pressure fluids, pipes were produced having thicker walls, which came to be known as extra strong (XS) or extra heavy (XH). The higher pressure requirements increased further, requiring thicker wall pipes. Accordingly, pipes were manufactured with double extra strong (XXS) or double extra heavy (XXH) walls while the standardized outside diameters are unchanged.With the development of stronger and corrosion-resistant piping materials, the need for thinner wall pipe resulted in a new method of specifying pipe size and wall thickness. The designation known as nominal pipe size (NPS) replaced IPS, and the term schedule (SCH) was invented to specify the nominal wall thickness of pipe.Nominal pipe size (NPS) is a dimensionless designator of pipe size. It indicates standard pipe size when followed by the specific size designation number without an inch symbol. For example, NPS 2 indicates a pipe whose outside diameter is 2.375 in. The NPS 12 and smaller pipe has outside diameter greater than the size designator (say, 2, 4, 6, . . .). However, the outside diameter of NPS 14 and larger pipe is the same as the size designator in inches. For example, NPS 14 pipe has an outside diameter equal to 14 in. The inside diameter will depend upon the pipe wall thickness specified by the schedule number. Refer to ASME B36.10M or ASME B36.19M. Refer to App. E2 or E2M.Diameter nominal (DN) is also a dimensionless designator of pipe size in the metric unit system, developed by the International Standards Organization (ISO).It indicates standard pipe size when followed by the specific size designation number without a millimeter symbol. For example, DN 50 is the equivalent designation of NPS 2. Refer to Table A1.1 for NPS and DN pipe size equivalents.TABLE A1.1 Pipe Size Designators: NPS and DNNPSDNNPSDNNPSDNNPSDN863290225504411004841002460048120041051252665052130021561502870056140042082003075060150012510250328006416001432123003485068170012401435036900721800250164003895076190022651845040100080200038020500421050Notes:1. For sizes larger than NPS 80, determine the DN equivalent by multiplying NPS size designation number by 25.Pipe Wall ThicknessSchedule is expressed in numbers (5, 5S, 10, 10S, 20, 20S, 30, 40, 40S, 60, 80, 80S, 100, 120, 140, 160). A schedule number indicates the approximate value of the expression 1000 P/S, where P is the se