ASME B36.10M (welded and seamless wrought steel pipe) · DN 90
Outside diameter 4.000" (101.60 mm), wall 0.226" (5.74 mm), inside diameter 3.548" (90.12 mm), 9.12 lb per foot.
| Trade size | NPS 3-1/2 · DN 90 |
|---|---|
| Schedule | Schedule 40 · same wall as STD, 40S |
| Standard | ASME B36.10M (welded and seamless wrought steel pipe) |
| Outside diameter | 4.000" · 101.60 mm |
| Wall thickness | 0.226" · 5.74 mm |
| Inside diameter | 3.548" · 90.12 mm |
| Weight, plain end | 9.12 lb/ft · 13.57 kg/m |
Cross-check: the standard plain-end weight formula W = 10.6802 x t x (OD - t) gives 9.11 lb/ft here, 0.1% from the published 9.12 lb/ft. The published figure is the one printed above.
NPS 3-1/2 schedule 40 pipe measures 4.000 in (101.60 mm) across the outside with a 0.226 in wall, so the bore is 3.548 in (90.12 mm). That bore gives a flow area of 9.887 in² and holds 0.5136 US gallons per foot (6.379 litres per metre). The outside diameter is 17.7 times the wall, and the steel itself has a cross-section of 2.680 in² and weighs 9.12 lb per foot plain end. One trade size up, NPS 4 in the same schedule carries 1.29 times the flow area.
Schedule 30 is the next lighter wall at NPS 3-1/2: 0.188 in, 0.038 in thinner, which opens the bore to 3.624 in and adds 4.3% to the flow area, for 16% less weight per foot.
Schedule 80 is the next heavier wall at NPS 3-1/2: 0.318 in, 0.092 in thicker, which narrows the bore to 3.364 in and cuts 10% from the flow area, for 37% more weight per foot.
Next trade size up in this schedule: NPS 4 schedule 40, bore 4.026 in.
| Flow area | 9.887 in² |
|---|---|
| Capacity | 0.5136 US gal/ft · 6.379 L/m |
| Metal area | 2.680 in² |
| Moment of inertia | 4.788 in⁴ |
| Section modulus | 2.394 in³ |
| Radius of gyration | 1.337 in |
| Outside surface | 1.047 ft² per foot |
Plain geometry of a hollow circle with OD = 4.000 in and ID = 3.548 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 3-1/2 pipe has an outside diameter of 4.000 inches, and it keeps that outside diameter in every schedule made. What the schedule number changes is the wall: at schedule 40 the wall is 0.226 inches, so the bore comes out at 3.548 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 4.000 inches throughout - only the wall and the bore move.
| Schedule | Wall (in) | ID (in) | Weight (lb/ft) |
|---|---|---|---|
| Schedule 5 · 5S | 0.083 | 3.834 | 3.48 |
| Schedule 10 · 10S | 0.120 | 3.760 | 4.98 |
| Schedule 30 | 0.188 | 3.624 | 7.66 |
| Schedule 80 · XS, 80S | 0.318 | 3.364 | 12.52 |
0.226 inches (5.74 mm). The outside diameter is 4.000 inches (101.60 mm) whatever the schedule, so this wall leaves an inside diameter of 3.548 inches.
3.548 inches (90.12 mm). Inside diameter is outside diameter minus twice the wall: 4.000 - 2 x 0.226 = 3.548 inches.
No. NPS 3-1/2 is a trade size, not a measurement. The pipe measures 4.000 inches across the outside and 3.548 inches across the bore in this schedule. Only the outside diameter is fixed across schedules.
9.12 pounds per foot plain end (13.57 kg per metre), for carbon steel. The figure excludes coatings, linings and fittings.
Yes, at NPS 3-1/2. STD and 40S are the same 0.226 inch wall here. That coincidence is per size and does not hold everywhere: standard wall and schedule 40 part company above NPS 10, and extra strong and schedule 80 part company above NPS 8.
One schedule at NPS 3-1/2 appears in only one of the published tables cross-checked for this section, so it is named rather than printed: XXS. Everything shown above carries at least two independent sources.
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:
Nearby sizes