nominal pipe size

Nominal Pipe SizeFrom Wikipedia, the free encyclopedia

Nominal Pipe Size (NPS) is a North American set of standard sizes for pipes used for high or low pressures and temperatures.[1]

Pipe size is specified with two non-dimensional numbers: a nominal pipe size (NPS) for diameter based on inches, and a schedule(Sched. or Sch.) for wall thickness. NPS is often incorrectly called National Pipe Size, due to confusion with national pipe thread(NPT). The European designation equivalent to NPS is DN (diamètre nominal/nominal diameter), in which sizes are measured inmillimetres.[2] The term NB (nominal bore) is also frequently used interchangeably with NPS.

Contents

1 History2 Application3 NPS tables for selected sizes

3.1 NPS ⅛ to NPS 3½3.2 NPS 4 to NPS 83.3 NPS 10 to NPS 24

4 See also5 Sources6 References7 External links

History

In March 1927, the American Standards Association authorized a committee to standardize the dimensions of wrought steel andwrought iron pipe and tubing. At that time only a small selection of wall thicknesses were in use: standard weight (STD), extra-strong (XS), and double extra-strong (XXS), based on the iron pipe size (IPS) system of the day. However these three sizes did notfit all applications. The committee surveyed the industry and created a system of schedule numbers that designated wallthicknesses based on smaller steps between sizes,[3] although IPS and NPS numbers remain equivalent.

The original intent was that each schedule would relate to a given pressure rating, however the numbers deviated so far from wallthicknesses in common use that this original intent could not be accomplished.[3][4] Also, in 1939, it was hoped that thedesignations of STD, XS, and XXS would be phased out by schedule numbers, however those original terms are still in common usetoday (although sometimes referred to as standard, extra-heavy (XH), and double extra-heavy (XXH), respectively). Since theoriginal schedules were created, there have been many revisions and additions to the tables of pipe sizes based on industry use andon standards from API, ASTM, and others.[3]

Stainless steel pipes, which were coming into more common use in the mid 20th century, permitted the use of thinner pipe wallswith much less risk of failure due to corrosion. By 1949 thinner schedules 5S and 10S, which were based on the pressurerequirements modified to the nearest BWG number, had been created, and other "S" sizes followed later. Due to their thin walls,the smaller "S" sizes can not be threaded together according to ASME code, but must be fusion welded.[5]

Application

Based on the NPS and schedule of a pipe, the pipe outside diameter (OD) and wall thickness can be obtained from reference tablessuch as those below, which are based on ASME standards B36.10M and B36.19M. For example, NPS 14 Sch 40 has an OD of14 inches and a wall thickness of 0.437 inches. However the NPS and OD values are not always equal, which can create confusion.

For NPS ⅛ to 12 inches, the NPS and OD values are different. For example, the OD of an NPS 12 pipe is actually12.75 inches. To find the actual OD for each NPS value, refer to the tables below. (Note that for tubing, the size is alwaysthe actual OD.)

Nominal Pipe Size - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Nominal_Pipe_Size

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For NPS 14 inches and up, the NPS and OD values are equal. In other words, an NPS 14 pipe is actually 14 inches OD.

The reason for the discrepancy for NPS ⅛ to 12 inches is that these NPS values were originally set to give the same inside diameter(ID) based on wall thicknesses standard at the time. However, as the set of available wall thicknesses evolved, the ID changed andNPS became only indirectly related to ID and OD.

For a given NPS, the OD stays fixed and the wall thickness increases with schedule. For a given schedule, the OD increases withNPS while the wall thickness stays constant or increases. Using equations and rules in ASME B31.3 Process Piping, it can beshown that pressure rating decreases with increasing NPS and constant schedule.[4]

Some specifications use pipe schedules called standard wall (STD), extra strong (XS), and double extra strong (XXS), althoughthese actually belong to an older system called iron pipe size (IPS). The IPS number is the same as the NPS number. STD isidentical to SCH 40S, and 40S is identical to 40 for NPS 1/8 to NPS 10, inclusive. XS is identical to SCH 80S, and 80S is identicalto 80 for NPS 1/8 to NPS 8, inclusive. XXS wall is thicker than schedule 160 from NPS 1/8" to NPS 6" inclusive, and schedule 160is thicker than XXS wall for NPS 8" and larger.

The "S" designation, for example "NPS Sch 10S", most often indicates stainless steel pipes. However some stainless steel pipes areavailable in steel designations, so strictly speaking the "S" designation only differentiates B36.19M pipe from B36.10M pipe.[1]

Both polyvinyl chloride pipe (PVC) and chlorinated polyvinyl chloride pipe (CPVC) are made in NPS sizes.

NPS tables for selected sizes

NPS ⅛ to NPS 3½

NPS[6] DNmm

ODinches

(millimeters)

Wall thicknessinches (millimeters)

SCH 5 SCH 10 SCH 30 SCH40/STD SCH 80 SCH 120 SCH 160 XXS

⅛ 6 0.405 in (10.29mm)

0.035 in(0.889mm)

0.049 in(1.245mm)

0.057 in(1.448mm)

0.068 in(1.727mm)

0.095 in(2.413mm)

— — —

¼ 8 0.540 in (13.72mm)

0.049 in(1.245mm)

0.065 in(1.651mm)

0.073 in(1.854mm)

0.088 in(2.235mm)

0.119 in(3.023mm)

— — —

⅜ 10 0.675 in (17.15mm)

0.049 in(1.245mm)

0.065 in(1.651mm)

0.073 in(1.854mm)

0.091 in(2.311mm)

0.126 in(3.200mm)

— — —

½ 15 0.840 in (21.34mm)

0.065 in(1.651mm)

0.083 in(2.108mm)

—0.109 in(2.769mm)

0.147 in(3.734mm)

— —0.294 in(7.468mm)

¾ 20 1.050 in (26.67mm)

0.065 in(1.651mm)

0.083 in(2.108mm)

—0.113 in(2.870mm)

0.154 in(3.912mm)

— —0.308 in(7.823mm)

1 25 1.315 in (33.40mm)

0.065 in(1.651mm)

0.109 in(2.769mm)

—0.133 in(3.378mm)

0.179 in(4.547mm)

— —0.358 in(9.093mm)

1¼ 32 1.660 in (42.16mm)

0.065 in(1.651mm)

0.109 in(2.769mm)

0.117 in(2.972mm)

0.140 in(3.556mm)

0.191 in(4.851mm)

— —0.382 in(9.703mm)

1½ 40 1.900 in (48.26mm)

0.065 in(1.651mm)

0.109 in(2.769mm)

0.125 in(3.175mm)

0.145 in(3.683mm)

0.200 in(5.080mm)

— —0.400 in(10.160mm)


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2 50 2.375 in (60.33mm)

0.065 in(1.651mm)

0.109 in(2.769mm)

0.125 in(3.175mm)

0.154 in(3.912mm)

0.218 in(5.537mm)

0.250 in(6.350mm)

0.343 in(8.712mm)

0.436 in(11.074mm)

2½ 65 2.875 in (73.02mm)

0.083 in(2.108mm)

0.120 in(3.048mm)

0.188 in(4.775mm)

0.203 in(5.156mm)

0.276 in(7.010mm)

0.300 in(7.620mm)

0.375 in(9.525mm)

0.552 in(14.021mm)

3 80 3.500 in (88.90mm)

0.083 in(2.108mm)

0.120 in(3.048mm)

0.188 in(4.775mm)

0.216 in(5.486mm)

0.300 in(7.620mm)

0.350 in(8.890mm)

0.438 in(11.125mm)

0.600 in(15.240mm)

3½ 90 4.000 in(101.60 mm)

0.083 in(2.108mm)

0.120 in(3.048mm)

0.188 in(4.775mm)

0.226 in(5.740mm)

0.318 in(8.077mm)

— —0.636 in(16.154mm)

NPS 4 to NPS 8

NPS[6] DNmm

ODinches

(millimeters)


SCH 5 SCH10

SCH20

SCH30

SCH40/STD

SCH60

SCH80

SCH100

SCH120

SCH140

SCH160

4 100 4.500 in(114.30 mm)

0.083 in(2.108mm)

0.120 in(3.048mm)

—0.188 in(4.775mm)

0.237 in(6.020mm)

0.281 in(7.137mm)

0.337 in(8.560mm)

—0.437 in(11.100mm)

—0.531 in(13.487mm)

4½ 115 5.000 in(127.00 mm) — — — —

0.247 in(6.274mm)

—0.355 in(9.017mm)

— — — —

5 125 5.563 in(141.30 mm)

0.109 in(2.769mm)

0.134 in(3.404mm)

— —0.258 in(6.553mm)

—0.375 in(9.525mm)

—0.500 in(12.700mm)

—0.625 in(15.875mm)

6 150 6.625 in(168.27 mm)

0.109 in(2.769mm)

0.134 in(3.404mm)

— —0.280 in(7.112mm)

—0.432 in(10.973mm)

—0.562 in(14.275mm)

—0.719 in(18.263mm)

8 200 8.625 in(219.08 mm)

0.109 in(2.769mm)

0.148 in(3.759mm)

0.250 in(6.350mm)

0.277 in(7.036mm)

0.322 in(8.179mm)

0.406 in(10.312mm)

0.500 in(12.700mm)

0.593 in(15.062mm)

0.718 in(18.237mm)

0.812 in(20.625mm)

0.906 in(23.012mm)

NPS 10 to NPS 24

NPS[6] DNmm

ODinches

(millimeters)


SCH 5s SCH 5 SCH 10s SCH 10 SCH 20 SCH 30

10 250 10.75 in (273.05mm)

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 (7.798mm)

12 300 12.75 in (323.85mm)

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 (8.382mm)

14 350 14.00 in (355.60mm)

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 (9.525mm)


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16 400 16.00 in (406.40mm)

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 (9.525mm)

18 450 18.00 in (457.20mm)

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)

20 500 20.00 in (508.00mm)

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)

24 600 24.00 in (609.60mm)

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)

NPS[6]Wall thickness

inches (millimeters)SCH 40s SCH 40 SCH 60 SCH 80s SCH 80 SCH 100 SCH 120 SCH 140 SCH 160

10 0.365 in(9.271 mm)

0.365 in(9.271 mm)

0.500 in(12.700mm)

0.500 in(12.700mm)

0.593 in(15.062mm)

0.718 in(18.237mm)

0.843 in(21.412mm)

1.000 in(25.400mm)

1.125 in(28.575mm)

12 0.375 in(9.525 mm)

0.406 in(10.312mm)

0.500 in(12.700mm)

0.500 in(12.700mm)

0.687 in(17.450mm)

0.843 in(21.412mm)

1.000 in(25.400mm)

1.125 in(28.575mm)

1.312 in(33.325mm)

14 0.375 in(9.525 mm)

0.437 in(11.100mm)

0.593 in(15.062mm)

0.500 in(12.700mm)

0.750 in(19.050mm)

0.937 in(23.800mm)

1.093 in(27.762mm)

1.250 in(31.750mm)

1.406 in(35.712mm)

16 0.375 in(9.525 mm)

0.500 in(12.700mm)

0.656 in(16.662mm)

0.500 in(12.700mm)

0.843 in(21.412mm)

1.031 in(26.187mm)

1.218 in(30.937mm)

1.437 in(36.500mm)

1.593 in(40.462mm)

18 0.375 in(9.525 mm)

0.562 in(14.275mm)

0.750 in(19.050mm)

0.500 in(12.700mm)

0.937 in(23.800mm)

1.156 in(29.362mm)

1.375 in(34.925mm)

1.562 in(39.675mm)

1.781 in(45.237mm)

20 0.375 in(9.525 mm)

0.593 in(15.062mm)

0.812 in(20.625mm)

0.500 in(12.700mm)

1.031 in(26.187mm)

1.280 in(32.512mm)

1.500 in(38.100mm)

1.750 in(44.450mm)

1.968 in(49.987mm)

24 0.375 in(9.525 mm)

0.687 in(17.450mm)

0.968 in(24.587mm)

0.500 in(12.700mm)

1.218 in(30.937mm)

1.531 in(38.887mm)

1.812 in(46.025mm)

2.062 in(52.375mm)

2.343 in(59.512mm)

See also

British standard pipe thread sizesPipe sizes

Sources

Oberg, Erik; Franklin D. Jones, Holbrook L. Horton, and Henry H. Ryffel (2000). ed. Christopher J. McCauley, RiccardoHeald, and Muhammed Iqbal Hussain. ed. Machinery's Handbook (26th Edition ed.). New York: Industrial Press Inc..ISBN 0-8311-2635-3.Nayyar, P.E., Mohinder L. (2000). "A1". In Mohinder L. Nayyar, P.E.. Piping Handbook (7th ed.). New York:McGraw-Hill. ISBN 0-07-047106-1.Engineering Department (1988). Flow of Fluids Through Valves, Fittings, and Pipe (Technical Paper No. 410) (25thPrinting—1991 ed.). Joliet, IL: Crane Co..ASME B36.10M - Welded and Seamless Wrought Steel Pipe.ANSI/ASME Standard 36.19M - Stainless Steel Pipe.ANSI/ASTM Reference R0036 - Stainless Steel Pipe.


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References

^ a b ASME B36.10M-2004, p. 11.^ NPS - "Nominal Pipe Size" and DN - "Diamètre Nominale" (http://www.engineeringtoolbox.com/nps-nominal-pipe-sizes-d_45.html) , EngineeringToolbox.com

2.

^ a b c ASME B36.10M-2004, p. iv3.^ a b This is contrary to the McGraw Hill Piping Handbook, which says that the schedule number can be converted topressure by dividing the schedule by 1000 and multiplying by the allowable stress of the material. [Nayyar and Mohinder,2000.]

4.

^ ASME Standard 36.19M-2004, p. iv5.^ a b c d Table of Pipe Schedules (http://www.engineersedge.com/pipe_schedules.htm) from EngineersEdge.com. Tableshows additional schedules, sizes and sizes greater than 24".

6.

External links

Schedule 40 Pipe (http://www.profenceworks.com/schedule_40.html)Notes on Pipe (http://www.gizmology.net/pipe.htm) -- PVC Pipe weights and max PSI

Retrieved from "http://en.wikipedia.org/wiki/Nominal_Pipe_Size"Categories: Piping | Mechanical standards

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