NPS 18 Schedule 120 Pipe
18.000 in (457.2 mm) outside diameter on a 1.375 in (34.9 mm) wall, giving a 15.250 in (387.3 mm) bore and 244.14 lb/ft (363.32 kg/m) empty. ASME B36.10M.
- Nominal size
- NPS 18 (DN 450)
- Schedule
- Schedule 120
- Outside diameter
- 18.000 in (457.2 mm)
- Wall thickness
- 1.375 in (34.9 mm)
- Inside diameter
- 15.250 in (387.3 mm)
- Weight, empty
- 244.14 lb/ft (363.32 kg/m)
- Weight, water filled
- 323.33 lb/ft (481.16 kg/m)
- Flow area
- 182.654 in² (117841 mm²)
No other designation in NPS 18 shares this wall thickness, so Schedule 120 is unambiguous in this size.
Every schedule in NPS 18
Dimensions are given in inches, with the millimetre equivalent beneath in grey.
| Schedule | Wall thickness | Inside diameter | Weight, empty | Water (US gal/ft) |
|---|---|---|---|---|
| Sch 5 | 0.1654.19 mm | 17.670448.82 mm | 31.4346.77 kg/m | 12.739 |
| Sch 10 | 0.1884.78 mm | 17.624447.65 mm | 35.7653.22 kg/m | 12.673 |
| Sch 20 | 0.3127.92 mm | 17.376441.35 mm | 58.9487.71 kg/m | 12.319 |
| Sch 30 | 0.43811.13 mm | 17.124434.95 mm | 82.15122.26 kg/m | 11.964 |
| Sch 40 | 0.56214.27 mm | 16.876428.65 mm | 104.67155.76 kg/m | 11.620 |
| STD | 0.3759.52 mm | 17.250438.15 mm | 70.59105.05 kg/m | 12.141 |
| Sch 60 | 0.75019.05 mm | 16.500419.10 mm | 138.18205.63 kg/m | 11.108 |
| Sch 80 | 0.93823.83 mm | 16.124409.55 mm | 170.93254.37 kg/m | 10.607 |
| XS | 0.50012.70 mm | 17.000431.80 mm | 93.45139.07 kg/m | 11.791 |
| Sch 100 | 1.15629.36 mm | 15.688398.48 mm | 207.96309.48 kg/m | 10.041 |
| Sch 120 this page | 1.37534.92 mm | 15.250387.35 mm | 244.14363.32 kg/m | 9.489 |
| Sch 140 | 1.56239.67 mm | 14.876377.85 mm | 274.23408.09 kg/m | 9.029 |
| Sch 160 | 1.78145.24 mm | 14.438366.73 mm | 308.51459.11 kg/m | 8.505 |
Weight is plain-end carbon steel, w = 10.6802 × t × (OD − t) lb/ft.
Flanges for NPS 18 pipe
Flange dimensions are set by NPS and pressure class, not by schedule, so every flange below fits this pipe. The exception is the weld neck: its bore is machined to the pipe it is welded to, which for Schedule 120 means 15.250 in (387.3 mm). Order the flange to the schedule or the bores will not line up at the weld.
| Class | Flange OD | Thickness | Bolt circle | Bolting |
|---|---|---|---|---|
| Class 150 | 25.00635.00 mm | 1.5639.62 mm | 22.75577.85 mm | 16 × 1 1/8 in |
| Class 300 | 28.00711.20 mm | 2.3860.45 mm | 24.75628.65 mm | 24 × 1 1/4 in |
| Class 400 | 28.00711.20 mm | 2.6266.55 mm | 24.75628.65 mm | 24 × 1 3/8 in |
| Class 600 | 29.25742.95 mm | 3.2582.55 mm | 25.75654.05 mm | 20 × 1 5/8 in |
| Class 900 | 31.00787.40 mm | 4.00101.60 mm | 27.00685.80 mm | 20 × 1 7/8 in |
| Class 1500 | 36.00914.40 mm | 6.38162.05 mm | 30.50774.70 mm | 16 × 2 3/4 in |
Fittings for NPS 18 pipe
ASME B16.9 dimensions come from NPS alone, so these figures hold for Schedule 120 exactly as they do for every other schedule in the size. Only the wall thickness has to be ordered to match.
| Fitting | Dimension | NPS 18 |
|---|---|---|
| 90° Long Radius Elbow | Centre-to-end A | 27.00685.80 mm |
| 90° Short Radius Elbow | Centre-to-end A | 18.00457.20 mm |
| 45° Long Radius Elbow | Centre-to-end B | 11.25285.75 mm |
| Straight Tee | Centre-to-end C and M | 13.50342.90 mm |
| Reducing Tee | Run centre-to-end C | 13.50342.90 mm |
| Concentric Reducer | End-to-end H | 15.00381.00 mm |
| Eccentric Reducer | End-to-end H | 15.00381.00 mm |
| Cap | Length E | 8.00203.20 mm |
Common questions
What is the inside diameter of NPS 18 schedule 120 pipe?
15.250 in (387.3 mm). The outside diameter is fixed at 18.000 in (457.2 mm) by ASME B36.10M, and the 1.375 in (34.9 mm) wall takes 2.750 in off it — 1.375 in from each side — leaving that bore.
How much does NPS 18 schedule 120 pipe weigh?
244.14 lb/ft (363.32 kg/m) empty, as plain-end carbon steel. Full of water it comes to 323.33 lb/ft (481.16 kg/m), because the bore holds 9.489 US gallons per foot. One short ton of this pipe is about 8 ft.
Does NPS 18 schedule 120 pipe use special flanges or fittings?
No. Flanges and buttweld fittings are dimensioned from NPS, so NPS 18 hardware fits this pipe in any schedule. The one thing that does follow the schedule is the bore of a weld neck flange or a fitting end prep, which has to be 15.250 in (387.3 mm) to match.