ASME B36.10M (welded and seamless wrought steel pipe) · DN 350
Outside diameter 14.000" (355.60 mm), wall 0.312" (7.92 mm), inside diameter 13.376" (339.76 mm), 45.65 lb per foot.
| Trade size | NPS 14 · DN 350 |
|---|---|
| Schedule | Schedule 20 |
| Standard | ASME B36.10M (welded and seamless wrought steel pipe) |
| Outside diameter | 14.000" · 355.60 mm |
| Wall thickness | 0.312" · 7.92 mm |
| Inside diameter | 13.376" · 339.76 mm |
| Weight, plain end | 45.65 lb/ft · 67.91 kg/m |
Cross-check: the standard plain-end weight formula W = 10.6802 x t x (OD - t) gives 45.61 lb/ft here, 0.1% from the published 45.65 lb/ft. The published figure is the one printed above.
NPS 14 schedule 20 pipe measures 14.000 in (355.60 mm) across the outside with a 0.312 in wall, so the bore is 13.376 in (339.76 mm). That bore gives a flow area of 140.5 in² and holds 7.300 US gallons per foot (90.66 litres per metre). The outside diameter is 44.9 times the wall, and the steel itself has a cross-section of 13.42 in² and weighs 45.65 lb per foot plain end. One trade size up, NPS 16 in the same schedule carries 1.32 times the flow area.
Schedule 10 is the next lighter wall at NPS 14: 0.250 in, 0.062 in thinner, which opens the bore to 13.500 in and adds 1.9% to the flow area, for 19% less weight per foot.
Standard wall (STD) is the next heavier wall at NPS 14: 0.375 in, 0.063 in thicker, which narrows the bore to 13.250 in and cuts 1.9% from the flow area, for 20% more weight per foot.
Next trade size up in this schedule: NPS 16 schedule 20, bore 15.376 in.
| Flow area | 140.5 in² |
|---|---|
| Capacity | 7.300 US gal/ft · 90.66 L/m |
| Metal area | 13.42 in² |
| Moment of inertia | 314.4 in⁴ |
| Section modulus | 44.91 in³ |
| Radius of gyration | 4.841 in |
| Outside surface | 3.665 ft² per foot |
Plain geometry of a hollow circle with OD = 14.000 in and ID = 13.376 in: flow area π/4·ID², metal area π/4·(OD² − ID²), moment of inertia π/64·(OD⁴ − ID⁴), section modulus I ÷ (OD/2), radius of gyration √(I ÷ metal area), capacity flow area × 12 ÷ 231 (231 in³ to the US gallon). Nominal dimensions, so mill tolerance and corrosion allowance are not included.
Nominal Pipe Size is a label, not a measurement. NPS 14 pipe has an outside diameter of 14.000 inches, and it keeps that outside diameter in every schedule made. What the schedule number changes is the wall: at schedule 20 the wall is 0.312 inches, so the bore comes out at 13.376 inches.
That is the practical consequence. Fittings, flanges, supports and threading dies are sized to the outside diameter, so they fit any schedule of the same trade size. Flow, pressure drop and anything that has to pass through the pipe depend on the inside diameter, which changes with every schedule. Order by trade size and schedule; work your hydraulics from the bore.
Same outside diameter of 14.000 inches throughout - only the wall and the bore move.
| Schedule | Wall (in) | ID (in) | Weight (lb/ft) |
|---|---|---|---|
| Schedule 5 · 5S | 0.156 | 13.688 | 23.09 |
| Schedule 10 | 0.250 | 13.500 | 36.75 |
| Schedule 40 | 0.438 | 13.124 | 63.50 |
| Schedule 60 | 0.594 | 12.812 | 85.13 |
| Schedule 80 | 0.750 | 12.500 | 106.23 |
| Schedule 100 | 0.938 | 12.124 | 130.98 |
| Schedule 120 | 1.094 | 11.812 | 150.93 |
| Schedule 140 | 1.250 | 11.500 | 170.37 |
| Schedule 160 | 1.406 | 11.188 | 189.29 |
| Standard wall (STD) · 30, 40S | 0.375 | 13.250 | 54.62 |
| Extra strong (XS) · 80S | 0.500 | 13.000 | 72.09 |
| Schedule 10S | 0.188 | 13.624 | not published |
0.312 inches (7.92 mm). The outside diameter is 14.000 inches (355.60 mm) whatever the schedule, so this wall leaves an inside diameter of 13.376 inches.
13.376 inches (339.76 mm). Inside diameter is outside diameter minus twice the wall: 14.000 - 2 x 0.312 = 13.376 inches.
No. NPS 14 is a trade size, not a measurement. The pipe measures 14.000 inches across the outside and 13.376 inches across the bore in this schedule. Only the outside diameter is fixed across schedules.
45.65 pounds per foot plain end (67.91 kg per metre), for carbon steel. The figure excludes coatings, linings and fittings.
This table runs from NPS 1/8 to NPS 24 and stops there. ASME B36.10M itself continues to NPS 80; those larger sizes are not carried here, so a size above NPS 24 is missing rather than undefined.
Dimensions are as defined by ASME B36.10M (welded and seamless wrought steel pipe). This site is an independent reference and is not affiliated with, endorsed by or approved by any standards body.
Every value on this page was cross-checked against 5 independent published sources:
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