ASME B36.10M (welded and seamless wrought steel pipe) · DN 32
Outside diameter 1.660" (42.16 mm), wall 0.250" (6.35 mm), inside diameter 1.160" (29.46 mm), 3.77 lb per foot.
| Trade size | NPS 1-1/4 · DN 32 |
|---|---|
| Schedule | Schedule 160 |
| Standard | ASME B36.10M (welded and seamless wrought steel pipe) |
| Outside diameter | 1.660" · 42.16 mm · designated 42.2 mm in the metric column |
| Wall thickness | 0.250" · 6.35 mm |
| Inside diameter | 1.160" · 29.46 mm |
| Weight, plain end | 3.77 lb/ft · 5.61 kg/m |
Cross-check: the standard plain-end weight formula W = 10.6802 x t x (OD - t) gives 3.76 lb/ft here, 0.1% from the published 3.77 lb/ft. The published figure is the one printed above.
NPS 1-1/4 schedule 160 pipe measures 1.660 in (42.16 mm) across the outside with a 0.250 in wall, so the bore is 1.160 in (29.46 mm). That bore gives a flow area of 1.057 in² and holds 0.05490 US gallons per foot (0.6818 litres per metre). The outside diameter is 6.6 times the wall, and the steel itself has a cross-section of 1.107 in² and weighs 3.77 lb per foot plain end. One trade size up, NPS 1-1/2 in the same schedule carries 1.33 times the flow area.
Schedule 80 is the next lighter wall at NPS 1-1/4: 0.191 in, 0.059 in thinner, which opens the bore to 1.278 in and adds 21% to the flow area, for 20% less weight per foot.
Double extra strong (XXS) is the next heavier wall at NPS 1-1/4: 0.382 in, 0.132 in thicker, which narrows the bore to 0.896 in and cuts 40% from the flow area, for 38% more weight per foot.
Next trade size up in this schedule: NPS 1-1/2 schedule 160, bore 1.338 in.
| Flow area | 1.057 in² |
|---|---|
| Capacity | 0.05490 US gal/ft · 0.6818 L/m |
| Metal area | 1.107 in² |
| Moment of inertia | 0.2839 in⁴ |
| Section modulus | 0.3420 in³ |
| Radius of gyration | 0.5063 in |
| Outside surface | 0.4346 ft² per foot |
Plain geometry of a hollow circle with OD = 1.660 in and ID = 1.160 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 1-1/4 pipe has an outside diameter of 1.660 inches, and it keeps that outside diameter in every schedule made. What the schedule number changes is the wall: at schedule 160 the wall is 0.250 inches, so the bore comes out at 1.160 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 1.660 inches throughout - only the wall and the bore move.
| Schedule | Wall (in) | ID (in) | Weight (lb/ft) |
|---|---|---|---|
| Schedule 5 · 5S | 0.065 | 1.530 | 1.11 |
| Schedule 10 · 10S | 0.109 | 1.442 | 1.81 |
| Schedule 30 | 0.117 | 1.426 | 1.93 |
| Schedule 40 · STD, 40S | 0.140 | 1.380 | 2.27 |
| Schedule 80 · XS, 80S | 0.191 | 1.278 | 3.00 |
| Double extra strong (XXS) | 0.382 | 0.896 | 5.22 |
0.250 inches (6.35 mm). The outside diameter is 1.660 inches (42.16 mm) whatever the schedule, so this wall leaves an inside diameter of 1.160 inches.
1.160 inches (29.46 mm). Inside diameter is outside diameter minus twice the wall: 1.660 - 2 x 0.250 = 1.160 inches.
No. NPS 1-1/4 is a trade size, not a measurement. The pipe measures 1.660 inches across the outside and 1.160 inches across the bore in this schedule. Only the outside diameter is fixed across schedules.
3.77 pounds per foot plain end (5.61 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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