| Nominal Size | OD | Wall Thickness, SCH | |||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| NPS | DN | mm | 5S | 10S | 10 | 20 | 30 | 40S | STD | 40 | 60 | 80S | XS | 80 | 100 | 120 | 140 | 160 | XXS |
| 1∕8 | 6 | 10.3 | – | 1.24 | – | – | – | 1.73 | 1.73 | 1.73 | – | 2.41 | 2.41 | 2.41 | – | – | – | – | – |
| 1∕4 | 8 | 13.7 | – | 1.65 | – | – | – | 2.24 | 2.24 | 2.24 | – | 3.02 | 3.02 | 3.02 | – | – | – | – | – |
| 3∕8 | 10 | 17.2 | – | 1.65 | – | – | – | 2.31 | 2.31 | 2.31 | – | 3.2 | 3.2 | 3.2 | – | – | – | – | – |
| 1∕2 | 15 | 21.3 | 1.65 | 2.11 | – | – | – | 2.77 | 2.77 | 2.77 | – | 3.73 | 3.73 | 3.73 | – | – | – | 4.78 | 7.47 |
| 3∕4 | 20 | 26.7 | 1.65 | 2.11 | – | – | – | 2.87 | 2.87 | 2.87 | – | 3.91 | 3.91 | 3.91 | – | – | – | 5.56 | 7.82 |
| 1 | 25 | 33.4 | 1.65 | 2.77 | – | – | – | 3.38 | 3.38 | 3.38 | – | 4.55 | 4.55 | 4.55 | – | – | – | 6.35 | 9.09 |
| 1 1∕4 | 32 | 42.2 | 1.65 | 2.77 | – | – | – | 3.56 | 3.56 | 3.56 | – | 4.85 | 4.85 | 4.85 | – | – | – | 6.35 | 9.7 |
| 1 1∕2 | 40 | 48.3 | 1.65 | 2.77 | – | – | – | 3.68 | 3.68 | 3.68 | – | 5.08 | 5.08 | 5.08 | – | – | – | 7.14 | 10.15 |
| 2 | 50 | 60.3 | 1.65 | 2.77 | – | – | – | 3.91 | 3.91 | 3.91 | – | 5.54 | 5.54 | 5.54 | – | – | – | 8.74 | 11.07 |
| 2 1∕2 | 65 | 73 | 2.11 | 3.05 | – | – | – | 5.16 | 5.16 | 5.16 | – | 7.01 | 7.01 | 7.01 | – | – | – | 9.53 | 14.02 |
| 3 | 80 | 88.9 | 2.11 | 3.05 | – | – | – | 5.49 | 5.49 | 5.49 | – | 7.62 | 7.62 | 7.62 | – | – | – | 11.13 | 15.24 |
| 3 1∕2 | 90 | 101.6 | 2.11 | 3.05 | – | – | – | 5.74 | 5.74 | 5.74 | – | 8.08 | 8.08 | 8.08 | – | – | – | – | – |
| 4 | 100 | 114.3 | 2.11 | 3.05 | – | – | – | 6.02 | 6.02 | 6.02 | – | 8.56 | 8.56 | 8.56 | – | 11.13 | – | 13.49 | 17.12 |
| 5 | 125 | 141.3 | 2.77 | 3.4 | – | – | – – | 6.55 | 6.55 | 6.55 | – | 9.53 | 9.53 | 9.53 | – | 12.7 | – | 15.88 | 19.05 |
| 6 | 150 | 168.3 | 2.77 | 3.4 | – | – | – | 7.11 | 7.11 | 7.11 | – | 10.97 | 10.97 | 10.97 | – | 14.27 | – | 18.26 | 21.95 |
| 8 | 200 | 219.1 | 2.77 | 3.76 | – | 6.35 | 7.04 | 8.18 | 8.18 | 8.18 | 10.31 | 12.7 | 12.7 | 12.7 | 15.09 | 18.26 | 20.62 | 23.01 | 22.23 |
| 10 | 250 | 273.1 | 3.4 | 4.19 | – | 6.35 | 7.8 | 9.27 | 9.27 | 9.27 | 12.7 | 12.7 | 12.7 | 15.09 | 18.26 | 21.44 | 25.4 | 28.58 | 25.4 |
| 12 | 300 | 323.9 | 3.96 | 4.57 | – | 6.35 | 8.38 | 9.53 | 9.53 | 10.31 | 14.27 | 12.7 | 12.7 | 17.48 | 21.44 | 25.4 | 28.58 | 33.32 | 25.4 |
| 14 | 350 | 355.6 | 3.96 | 4.78 | 6.35 | 7.92 | 9.53 | – | 9.53 | 11.13 | 15.09 | – | 12.7 | 19.05 | 23.83 | 27.79 | 31.75 | 35.71 | – |
| 16 | 400 | 406.4 | 4.19 | 4.78 | 6.35 | 7.92 | 9.53 | – | 9.53 | 12.7 | 16.66 | – | 12.7 | 21.44 | 26.19 | 30.96 | 36.53 | 40.49 | – |
| 18 | 450 | 457.2 | 4.19 | 4.78 | 6.35 | 7.92 | 11.13 | – | 9.53 | 14.27 | 19.05 | – | 12.7 | 23.83 | 29.36 | 34.93 | 39.67 | 45.24 | – |
| 20 | 500 | 508 | 4.78 | 5.54 | 6.35 | 9.53 | 12.7 | – | 9.53 | 15.09 | 20.62 | – | 12.7 | 26.19 | 32.54 | 38.1 | 44.45 | 50.01 | – |
| 22 | 550 | 558.8 | 4.78 | 5.54 | 6.35 | 9.53 | 12.7 | – | 9.53 | – | 22.23 | – | 12.7 | 28.58 | 34.93 | 41.28 | 47.63 | 53.98 | – |
| 24 | 600 | 609.6 | 5.54 | 6.35 | 6.35 | 9.53 | 14.27 | – | 9.53 | 17.48 | 24.61 | – | 12.7 | 30.96 | 38.89 | 46.02 | 52.37 | 59.54 | – |
| 26 | 650 | 660.4 | – | – | 7.92 | 12.7 | – | – | 9.53 | – | – | – | 12.7 | – | – | – | – | – | – |
| 28 | 700 | 711.2 | – | – | 7.92 | 12.7 | 15.88 | – | 9.53 | – | – | – | 12.7 | – | – | – | – | – | – |
| 30 | 750 | 762 | 6.35 | 7.92 | 7.92 | 12.7 | 15.88 | – | 9.53 | – | – | – | 12.7 | – | – | – | – | – | – |
| 32 | 800 | 812.8 | – | – | 7.92 | 12.7 | 15.88 | 17.48 | 9.53 | 17.48 | – | – | 12.7 | – | – | – | – | – | – |
| 34 | 850 | 863.6 | – | – | 7.92 | 12.7 | 15.88 | 17.48 | 9.53 | 17.48 | – | – | 12.7 | – | – | – | – | – | – |
| 36 | 900 | 914.4 | – | – | 7.92 | 12.7 | 15.88 | 19.05 | 9.53 | 19.05 | – | – | 12.7 | – | – | – | – | – | – |
| 38 | 950 | 965.2 | – | – | – | – | – | – | 9.53 | – | – | – | 12.7 | – | – | – | – | – | – |
| 40 | 1000 | 1016 | – | – | – | – | – | – | 9.53 | – | – | – | |||||||
From the above data chart, pipe sizes are determined by NPS and Schedule Number based on ASME/ANSI B 36.10 Welded and Seamless Wrought Steel Pipe and ASME/ANSI B36.19 Stainless Steel Pipe, some points should be noted below:
- For a given NPS, the outside diameter stays constant and the wall thickness increases with a larger schedule number. The inside diameter will depend upon the pipe wall thickness specified by the schedule number.
- From NPS ⅛ to 12 inches, the NPS and OD values are different.
- For NPS 14 inches and above, the NPS and OD values are equal, and the NPS pipe size is the actual outside diameter.
- From NPS 12 to NPS 22 the wall thicknesses in some cases are different. Pipes with the suffix “S” have in that range of thinner wall thickness.
- For NPS ≥ 4, the related DN is equal to the NPS number multiplied by 25.
Pipe Schedule
Pipe Schedule is a method of expressing the wall thickness of the pipe, usually expressed in numbers, such as 5, 5S, 10, 10S, 20, 20S, 30, 40, 40S, 60, 80, 80S, 100, 120, 140, 160 and so on. These numbers followed by ‘S’ indicate that the stainless steel pipe. There is also an earlier method of expressing the wall thickness of tubes called WGT Class, which includes STD (Standard), XS (Strong), XXS (Extra Strong), and so on.
While the Nominal Pipe Size identifies the outside diameter of the pipe, more information is needed to identify specific pipes. A pipe’s schedule is the thickness of the pipe wall, which directly affects the interior dimension and weight of the pipe. Wall thickness is important because it determines the amount of internal pressure that the pipe can withstand. The schedule number is roughly calculated as Schedule = 1000 x (P/S) where P is the internal service pressure of the pipe (psig) and S is the ultimate tensile strength of the pipe material (psi).
In practice, the selection of Pipe Schedule is based on factors such as working pressure, fluid properties, and the environment in which it is used. For example, where high-pressure fluids are to be handled, a Pipe Schedule with a larger wall thickness, such as Schedule 80, is often chosen, while in some applications where cost is a factor, a smaller wall thickness, such as Schedule 40, may be preferred.
Nominal Pipe Size (NPS)
Nominal Pipe Sizing (NPS) is a North American standard for identifying pipe sizes, it gives the approximate inside diameter or nominal bore of a pipe. The European designation equivalent to NPS is DN (diamètre nominal/nominal diameter/Durchmesser nach Norm). All pipes are specified using the NPS (or DN) and schedule numbers, it is the schedule number that determines the approximate inside diameter.
Technically, the NPS is non-dimensional and only roughly refers to the diameter of the pipe. However, from NPS 14 and above, the NPS value matches the outside diameter of the pipe. Nominal Pipe Sizes apply to all materials of pipe. When specific pipes are specified, the NPS, Schedule, and material are required.
Pipe Inside Diameter
The inside diameter of the pipe is determined by NPS and pipe schedule, while the standardized NPS outside diameters are unchanged, the Schedule number is increased, inside diameter is reduced.
Pipes are designed to carry fluid, therefore their internal diameter is a critical dimension in determining how much fluid they can carry. This critical dimension is often referred to as the nominal bore, commonly abbreviated as NB. Obviously, for pipes containing pressurized fluids the wall thickness, and by implication the pipe’s strength, is important – too thin and the pipe could rupture.
For all steel pipes with the same NB (nominal bore), the outside diameter remains relatively constant. Therefore any variation in piping schedule i.e. wall thickness, affects only the inside diameter. As the pipe schedule number increases, the wall thickness increases, and the actual bore is reduced. For a given schedule, the outside diameter (OD) increases with nominal pipe size (NPS) while the wall thickness stays constant or increases. Using equations and rules in ASME B31.3 Process Piping, it can be shown that pressure rating decreases with increasing NPS and constant schedule.
Pipe Size vs Tube Size
Pipe dimensions consist primarily of outside diameter (OD), inside diameter (ID), and wall thickness (WT). The most important dimensions of a pipe are the outer diameter (OD) and wall thickness (WT), with the OD minus twice the wall thickness equaling the inner diameter (ID), which determines the capacity of the pipe.
Standard systems for pipe size include the [NPS (National Standard Pipe Size) system. The NPS system shows some of the typical thicknesses that exist under the IPS and introduces new thicknesses (e.g., Sch. 5, 10, 20, 30, 40, 60, 80, 100, 120, 140, 160). For pipes with NPS less than 12, the OD is larger than the size indicator; for pipes larger than 14 inches, the OD matches the NPS. Pipes with the same NPS have different inside diameters, depending on the wall thickness. For example, NPS 6 pipe Sch. STD and NPS 6 pipe Sch. XXS has the same OD, but the former has a larger ID.
Tube size is generally expressed in inches (inch) or millimeters (mm). The following are common ways of expressing steel tube diameters.
- inches (inch) that: usually use imperial units to indicate the outer diameter or inner diameter of steel tube, common inch units are 1/8, 1/4, 1/2, 3/4, etc., of which 1 inch is equal to 25.4 mm.
- millimeter (mm) the use of millimeters as a unit to indicate the outer diameter or inner diameter of steel pipe. Common millimeter single 6mm, 8mm, 10mm and so on. In the identification or specification of steel pipe, the stock will be marked in both inches and millimeters units, so that the user can choose and use it. For example, the size of a steel tube may be 2 inches (50.8 mm) or 20 mm.
Pipe Schedule For Stainless Steel Pipe
Stainless steel offers superior corrosion resistance to carbon steel allowing thinner stainless steel pipe wall thickness to be used. ASME introduced different schedule numbers for stainless steel pipe and fittings. Under ASME B36.19 four new pipe schedules with an “S” suffix were introduced for stainless steel pipe. These stainless steel pipe schedules are: 5S, 10S, 40S and 80S.
Stainless Steel Pipe Weight Chart, KG Per Meter
| Nominal Pipe Size (inches) | Outside Diameter | Schedule | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 5S | 10S | 40S | 80S | |||||||
| (mm) | (inches) | Wall Thickness and Weight | ||||||||
| mm (in) | kg/m | mm (in) | kg/m | mm (in) | kg/m | mm (in) | kg/m | |||
| 1/8 | 10.3 | 0.405 | – | – | 1.25 (0.049) | 0.28 | 1.73 (0.068) | 0.37 | 2.42 (0.095) | 0.47 |
| 1/4 | 13.7 | 0.540 | – | – | 1.66 (0.065) | 0.49 | 2.24 (0.088) | 0.63 | 3.03 (0.119) | 0.80 |
| 3/8 | 17.2 | 0.675 | – | – | 1.66 (0.065) | 0.63 | 2.32 (0.091) | 0.85 | 3.20 (0.126) | 1.10 |
| 1/2 | 21.3 | 0.840 | 1.65 (0.065) | 0.81 | 2.11 (0.083) | 1.00 | 2.77 (0.109) | 1.27 | 3.74 (0.147) | 1.62 |
| 3/4 | 26.7 | 1.050 | 1.65 (0.065) | 1.02 | 2.11 (0.083) | 1.28 | 2.87 (0.113) | 1.68 | 3.92 (0.154) | 2.20 |
| 1 | 33.4 | 1.315 | 1.65 (0.065) | 1.30 | 2.77 (0.109) | 2.09 | 3.38 (0.133) | 2.50 | 4.55 (0.179) | 3.24 |
| 1 1/4 | 42.2 | 1.660 | 1.65 (0.065) | 1.66 | 2.77 (0.109) | 2.69 | 3.56 (0.140) | 3.39 | 4.86 (0.191) | 4.47 |
| 1 1/2 | 48.3 | 1.900 | 1.65 (0.065) | 1.91 | 2.77 (0.109) | 3.11 | 3.69 (0.145) | 4.06 | 5.08 (0.200) | 5.41 |
| 2 | 60.3 | 2.375 | 1.65 (0.065) | 2.40 | 2.77 (0.109) | 3.93 | 3.92 (0.154) | 5.45 | 5.54 (0.218) | 7.49 |
| 2 1/2 | 73.0 | 2.875 | 2.11 (0.083) | 3.69 | 3.05 (0.120) | 5.26 | 5.16 (0.203) | 8.64 | 7.01 (0.276) | 11.4 |
| 3 | 88.9 | 3.500 | 2.11 (0.083) | 4.52 | 3.05 (0.120) | 6.46 | 5.49 (0.216) | 11.3 | 7.62 (0.300) | 15.3 |
| 3 1/2 | 101.6 | 4.000 | 2.11 (0.083) | 5.18 | 3.05 (0.120) | 7.41 | 5.74 (0.226) | 13.6 | 8.08 (0.318) | 18.6 |
| 4 | 114.3 | 4.500 | 2.11 (0.083) | 5.84 | 3.05 (0.120) | 8.37 | 6.02 (0.237) | 16.1 | 8.56 (0.337) | 22.3 |
| 5 | 141.3 | 5.563 | 2.77 (0.109) | 9.46 | 3.41 (0.134) | 11.6 | 6.56 (0.258) | 21.8 | 9.53 (0.375) | 31.0 |
| 6 | 168.3 | 6.625 | 2.77 (0.109) | 11.3 | 3.41 (0.134) | 13.9 | 7.12 (0.280) | 28.3 | 10.98 (0.432) | 42.6 |
| 8 | 219.1 | 8.625 | 2.77 (0.109) | 14.8 | 3.76 (0.148) | 20.0 | 8.18 (0.322) | 42.5 | 12.70 (0.500) | 64.6 |
| 10 | 273.1 | 10.750 | 3.41 (0.134) | 22.7 | 4.20 (0.165) | 27.8 | 9.28 (0.365) | 60.4 | 12.70 (0.500) | 81.5 |
| 12 | 323.9 | 12.750 | 3.97 (0.156) | 31.3 | 4.58 (0.180) | 36.1 | 9.53 (0.375) | 73.9 | 12.70 (0.500) | 97.4 |
Dimensions, wall thickness and weights of stainless steel pipes according to ASME B36.19 Stainless Steel Pipe.