What is the ANSI pipe schedule？
The ANSI pipe schedule is a standard for pipe sizes that establishes the relationship between pipe wall thickness and outer diameter. It helps to identify the thickness and strength of the pipe by dividing the wall thickness into different grades, such as Schedule 10, Schedule 40, and Schedule 80. Each grade has a specific wall thickness and outer diameter. The choice of grade depends on the application requirements and the pressure the pipe needs to withstand. For instance, a thicker wall grade would be chosen for a pipe system that needs to handle high pressures.
The parameters in the ANSI pipe schedule
Let’s talk about the ANSI pipe schedule, which is quite intriguing. It consists of several important parameters that are essential to understand when dealing with pipes:
1. NPS (Nominal Pipe Size): This is the nominal diameter of the pipe, often expressed in inches as NPS 1, NPS 2, and so on. It’s important to note that NPS is a nominal value and doesn’t directly indicate the inner or outer diameter.
2. Schedule Number: The schedule number indicates the wall thickness of the pipe. Common wall thickness numbers are Schedule 10, Schedule 40, and Schedule 80. As the schedule number increases, so does the wall thickness of the pipe. It’s crucial to remember that the wall thickness number is a relative indicator and doesn’t directly represent a specific thickness value.
3. Outside Diameter (OD): This refers to the diameter of the outside of the pipe. The outside diameter is fixed for a specific NPS. For example, the outside diameter of an NPS 2 pipe is usually about 2.375 inches (60.3 mm).
4. Inside Diameter (ID): The inside diameter depends on the outside diameter and the wall thickness. Therefore, pipes of the same NPS can have different inside diameters based on the schedule number.
5. Wall Thickness: This indicates the thickness of the pipe wall, usually in millimeters or inches. The schedule number of the pipe determines the wall thickness. For instance, a Schedule 40 pipe has thicker walls than a Schedule 10 pipe.
6. Weight: The weight of a pipe is typically expressed as weight per unit length, such as kg/m or lb/ft. It depends on the pipe’s outer diameter, wall thickness, and material density.
7. Pressure Rating: This refers to the maximum working pressure that the pipe can withstand at a specific temperature. The pressure rating is related to the wall thickness and pipe material. Each schedule number corresponds to different pressure ratings.
Understanding these parameters is crucial when working with pipes, and it’s truly fascinating how each aspect plays a significant role in determining the characteristics and capabilities of the pipes.
Relationship between NPS and OD
For pipes from NPS 1/8 to NPS 12, the NPS number does not directly represent the actual inside diameter of the pipe, but rather is an approximate nominal value. For pipes from NPS 14 and above, NPS usually refers to the outside diameter.
When dealing with pipes from NPS 1/8 to NPS 12, it’s important to note that the NPS value is nominal and doesn’t directly correspond to the inner diameter of the pipe. The inner and outer diameters are determined by the wall thickness number (Schedule Number).
For example:
NPS 2 (2-inch pipe)
– Schedule 40 (common wall thickness number)
– Outer diameter (OD): 60.3 mm (about 2.375 inches)
– Inner diameter (ID): 52.5 mm (about 2.067 inches)
– Wall thickness: 3.68 mm (about 0.145 inches)
It’s important to understand that even though this example is referred to as an NPS 2 pipe, its actual inner diameter is slightly less than 2 inches.
For pipes in the size range of NPS 14 and above, the NPS value corresponds to the outer diameter of the pipe, while the inner diameter still depends on the wall thickness. The table below illustrates this pattern.
Ansi Pipe Schedule Table in Inch
| Pipe Size |
OD | Sch 5 |
Sch 10 |
Sch 20 |
Sch 30 |
Sch 40 |
Std | Sch 60 |
Sch 80 |
XH | Sch 100 |
Sch 120 |
Sch 140 |
Sch 160 |
XXH | |||
| 1/8 | 0.405 | 0.035 0.140 |
0.049 0.190 |
0.068 0.240 |
0.068 0.240 |
0.950 0.310 |
0.950 0.310 |
|||||||||||
| 1/4 | 0.54 | 0.049 0.260 |
0.065 0.330 |
0.088 0.420 |
0.088 0.420 |
0.119 0.540 |
0.119 0.540 |
|||||||||||
| 3/8 | 0.675 | 0.049 0.330 |
0.065 0.420 |
0.091 0.570 |
0.091 0.570 |
0.126 0.740 |
0.126 0.740 |
|||||||||||
| 1/2 | 0.84 | 0.065 0.540 |
0.083 0.670 |
0.109 0.850 |
0.109 0.850 |
0.147 1.090 |
0.147 1.090 |
0.187 1.300 |
0.294 1.710 |
|||||||||
| 3/4 | 1.05 | 0.065 0.680 |
0.083 0.860 |
0.113 1.130 |
0.113 1.130 |
0.154 1.470 |
0.154 1.470 |
0.218 1.940 |
0.308 2.440 |
|||||||||
| 1 | 1.315 | 0.065 0.870 |
0.109 1.400 |
0.133 1.680 |
0.133 1.680 |
0.179 2.170 |
0.179 2.170 |
0.250 2.840 |
0.358 3.660 |
|||||||||
| 1-1/4 | 1.66 | 0.065 1.110 |
0.109 1.810 |
0.140 2.270 |
0.140 2.270 |
0.191 3.000 |
0.191 3.000 |
0.250 3.770 |
0.382 5.210 |
|||||||||
| 1-1/2 | 1.99 | 0.065 1.270 |
0.109 2.090 |
0.145 2.720 |
0.145 2.720 |
0.200 3.630 |
0.200 3.630 |
0.281 4.860 |
0.400 6.410 |
|||||||||
| 2 | 2.375 | 0.650 1.600 |
0.109 2.640 |
0.154 3.660 |
0.154 3.660 |
0.218 5.030 |
0.218 5.030 |
0.344 7.470 |
0.436 9.040 |
|||||||||
| 2-1/2 | 2.875 | 0.083 2.480 |
0.120 3.530 |
0.203 5.800 |
0.203 5.800 |
0.276 7.670 |
0.276 7.670 |
0.375 10.02 |
0.552 13.71 |
|||||||||
| 3 | 3.5 | 0.083 3.030 |
0.120 4.340 |
0.216 7.580 |
0.216 7.580 |
0.300 10.26 |
0.300 10.26 |
0.438 14.34 |
0.600 19.60 |
|||||||||
| 3-1/2 | 4 | 0.083 3.480 |
0.120 4.980 |
0.226 9.120 |
0.226 9.120 |
0.318 12.52 |
0.318 12.52 |
0.636 22.87 |
||||||||||
| 4 | 4.5 | 0.083 3.920 |
0.120 5.620 |
0.156 7.240 |
0.188 8.670 |
0.237 10.80 |
0.237 10.80 |
0.337 15.00 |
0.337 15.00 |
0.438 19.02 |
0.531 22.53 |
0.674 27.57 |
||||||
| 5 | 5.563 | 0.109 6.630 |
0.134 7.780 |
0.188 10.80 |
0.258 14.63 |
0.258 14.63 |
0.375 20.80 |
0.375 20.80 |
0.500 27.06 |
0.625 32.99 |
0.750 38.59 |
|||||||
| 6 | 6.625 | 0.109 7.590 |
0.134 9.300 |
0.156 10.79 |
0.188 12.94 |
0.219 15.00 |
0.250 17.04 |
0.280 18.99 |
0.280 18.99 |
0.432 28.60 |
0.432 28.60 |
0.562 36.43 |
0.719 45.39 |
0.864 53.21 |
||||
| 8 | 8.625 | 0.109 9.920 |
0.156 14.12 |
0.148 13.41 |
0.188 16.96 |
0.250 22.38 |
0.219 19.68 |
0.277 24.72 |
0.322 28.58 |
0.322 28.58 |
0.406 35.67 |
0.500 43.43 |
0.500 43.43 |
0.594 51.00 |
0.719 60.77 |
0.812 67.82 |
0.906 74.76 |
0.875 72.49 |
| 10 | 10.75 | 0.134 15.21 |
0.188 21.23 |
0.165 18.67 |
0.219 24.65 |
0.250 28.06 |
0.279 31.23 |
0.307 34.27 |
0.365 40.52 |
0.365 40.52 |
0.500 54.79 |
0.594 64.49 |
0.500 54.79 |
0.719 77.10 |
0.844 89.38 |
1.000 104.23 |
1.125 115.78 |
1.000 104.23 |
| 12 | 12.75 | 0.165 22.20 |
0.188 25.25 |
0.180 24.19 |
0.219 29.34 |
0.250 33.41 |
0.312 41.48 |
0.330 43.81 |
0.406 53.57 |
0.375 49.61 |
0.562 73.22 |
0.688 88.71 |
0.500 65.48 |
0.844 107.42 |
1.000 125.61 |
1.125 139.81 |
1.312 160.42 |
1.000 125.61 |
| 14 | 14 | 0.219 32.26 |
0.250 36.75 |
0.312 45.65 |
0.375 54.62 |
0.438 63.50 |
0.375 54.62 |
0.594 85.13 |
0.750 106.23 |
0.500 72.16 |
0.938 130.98 |
1.094 150.93 |
1.250 170.37 |
1.406 189.29 |
||||
| 16 | 16 | 0.219 36.95 |
0.250 42.09 |
0.312 52.32 |
0.375 62.64 |
0.500 82.85 |
0.375 62.64 |
0.656 107.60 |
0.844 136.74 |
0.500 82.85 |
1.031 164.98 |
1.219 192.61 |
1.468 228.05 |
1.594 245.48 |
||||
| 18 | 18 | 0.250 47.44 |
0.312 58.99 |
0.438 82.23 |
0.562 104.76 |
0.375 70.65 |
0.750 138.30 |
0.938 171.08 |
0.500 93.54 |
1.156 208.15 |
1.375 244.37 |
1.562 274.48 |
1.781 308.79 |
|||||
| 20 | 20 | 0.250 52.78 |
0.312 65.66 |
0.375 78.67 |
0.500 104.23 |
0.594 123.23 |
0.375 78.67 |
0.812 166.56 |
1.031 209.06 |
0.500 104.23 |
1.281 256.34 |
1.500 296.65 |
1.750 341.41 |
1.969 379.53 |
||||
| 22 | 22 | 0.250 58.13 |
0.375 86.69 |
0.500 114.92 |
0.375 86.69 |
0.875 197.60 |
1.125 251.05 |
0.500 114.92 |
1.375 303.16 |
1.625 353.94 |
1.875 403.38 |
2.125 451.49 |
||||||
| 24 | 24 | 0.250 63.47 |
0.312 79.01 |
0.375 94.71 |
0.562 140.81 |
0.688 171.45 |
0.375 94.71 |
0.969 238.57 |
1.219 296.86 |
0.500 125.61 |
1.531 367.74 |
1.812 429.79 |
2.062 483.57 |
2.344 542.64 |
||||
| 26 | 26 | 0.250 68.82 |
0.312 85.68 |
0.500 136.3 |
0.375 102.72 |
0.500 136.30 |
||||||||||||
| 28 | 28 | 0.250 75.16 |
0.312 92.34 |
0.500 146.99 |
0.625 182.90 |
0.375 110.40 |
0.500 146.99 |
|||||||||||
| 30 | 30 | 0.250 79.51 |
0.312 99.02 |
0.750 234.51 |
0.500 157.68 |
1.000 310.01 |
0.625 196.26 |
0.375 118.76 |
0.500 157.68 |
|||||||||
| 32 | 32 | 0.250 84.85 |
0.312 105.99 |
0.500 168.37 |
0.625 209.62 |
0.688 230.29 |
0.375 126.78 |
0.500 168.37 |
||||||||||
| 34 | 34 | 0.250 90.20 |
0.344 123.77 |
0.500 179.06 |
0.625 222.99 |
0.688 245.00 |
0.375 134.79 |
0.500 179.06 |
||||||||||
| 36 | 36 | 0.250 95.54 |
0.312 119.13 |
0.500 189.75 |
0.625 236.35 |
0.75 282.62 |
0.375 142.81 |
0.500 189.75 |
||||||||||
| 42 | 42 | 0.375 166.70 |
0.500 221.60 |
|||||||||||||||
| 48 | 48 | 0.375 190.70 |
0.500 253.60 |
|||||||||||||||
| 52 | 52 | 0.375 206.95 |
0.500 275.27 |
Difference between NPS and DN
| Aspect | NPS (Nominal Pipe Size) | DN (Diameter Nominal) |
| Unit | Inches | Millimeters (mm) |
| Nominal Diameter Representation | Nominal pipe size (not directly corresponding to actual size) | Nominal diameter (close to actual outside diameter) |
| Primary Usage Region | North America and related regions | International standards (ISO) and most other regions |
| Representation | NPS 1/2, NPS 2, NPS 4, etc. | DN 15, DN 50, DN 100, etc. |
| Actual Size Meaning | Typically refers to nominal inside or outside diameter, actual size depends on wall thickness (Schedule) | Typically refers to nominal outside diameter |
| Common Range | NPS 1/8 to NPS 36+ | DN 6 to DN 900+ |
| Standard Reference | ASME B36.10M, ASME B36.19M | ISO 6708 |
| Size Conversion | No direct conversion formula, needs to check standard tables | No direct conversion formula, needs to check standard tables |
| Common Applications | Industrial piping systems, water treatment, oil, etc. | Building, manufacturing, chemical, oil, etc. |
Can NPS and DN Be Converted?
While NPS and DN cannot be directly converted using a simple formula, standard pipe size tables can be used to find the corresponding sizes. These tables list the actual dimensions, such as the outside and inside diameters of pipes of different NPS and DN. Here’s an example to demonstrate this correspondence more clearly:
| NPS (inches) | DN (mm) | OD (mm) |
| 1/8 | 6 | 10.3 |
| 1/4 | 8 | 13.7 |
| 1/2 | 15 | 21.3 |
| 1 | 25 | 33.4 |
| 2 | 50 | 60.3 |
| 3 | 80 | 88.9 |
| 4 | 100 | 114.3 |
| 6 | 150 | 168.3 |
| 8 | 200 | 219.1 |
| 10 | 250 | 273.1 |
| 12 | 300 | 323.9 |
| 14 | 350 | 355.6 |
| 16 | 400 | 406.4 |
| 18 | 450 | 457.2 |
| 20 | 500 | 508.0 |
| 24 | 600 | 609.6 |
