ASME B36.10 vs B36.19: Pipe Schedules
ASME B36.10 and ASME B36.19 are the two dimensional standards that define pipe outside diameter (OD), wall thickness, and weight for steel pipes used in process piping. ASME B36.10M covers carbon steel, alloy steel, and ferritic stainless steel pipes. ASME B36.19M covers austenitic stainless steel pipes. Both standards share the same OD for each NPS designation, but they differ in the schedule numbers and wall thicknesses they define. Distinction matters for correct pipe specification, material takeoff, and piping isometric preparation.
ASME B36.10 vs B36.19 Comparison
| Feature | ASME B36.10M | ASME B36.19M |
|---|---|---|
| Materials | Carbon steel, alloy steel, ferritic SS | Austenitic stainless steel |
| Pipe specifications | ASTM A106, A53, A335, API 5L | ASTM A312, A358, A790 |
| Size range | NPS 1/8 to NPS 80 | NPS 1/8 to NPS 30 |
| Schedule designations | 5, 10, 20, 30, 40, 60, 80, 100, 120, 140, 160, STD, XS, XXS | 5S, 10S, 40S, 80S |
| OD basis | Fixed per NPS | Same OD as B36.10 |
| Wall thicknesses | All schedules defined | Only “S” suffix schedules |
Wall Thickness Comparison (Selected Sizes)
The key practical difference is that SCH 40 (B36.10) and SCH 40S (B36.19) have different wall thicknesses for certain pipe sizes, particularly above NPS 10.
| NPS | DN | OD (mm) | B36.10 SCH 40 WT (mm) | B36.19 SCH 40S WT (mm) | Difference |
|---|---|---|---|---|---|
| 1/2 | 15 | 21.3 | 2.77 | 2.77 | None |
| 2 | 50 | 60.3 | 3.91 | 3.91 | None |
| 4 | 100 | 114.3 | 6.02 | 6.02 | None |
| 8 | 200 | 219.1 | 8.18 | 8.18 | None |
| 10 | 250 | 273.1 | 9.27 | 9.27 | None |
| 12 | 300 | 323.9 | 10.31 | 9.53 | B36.19 thinner |
| 14 | 350 | 355.6 | 11.13 | 9.53 | B36.19 thinner |
| 16 | 400 | 406.4 | 12.70 | 9.53 | B36.19 thinner |
| 24 | 600 | 610.0 | 17.48 | 9.53 | B36.19 thinner |
Key Points
Same OD, different wall: Both standards use the same outside diameter table. An NPS 6 pipe has an OD of 168.3 mm whether it is carbon steel per B36.10 or stainless steel per B36.19. This ensures compatibility with the same flanges, fittings, and clamps.
SCH 40 is not SCH 40S above NPS 10: For NPS 1/8 through NPS 10, SCH 40 and SCH 40S have identical wall thicknesses. Above NPS 10, they diverge. SCH 40S defaults to a fixed 9.53 mm wall for NPS 12 and above, while SCH 40 continues to increase. This is the most common source of procurement errors when switching between carbon and stainless pipe.
STD and XS are B36.10 only: The legacy designations STD (Standard), XS (Extra Strong), and XXS (Double Extra Strong) belong to B36.10 and do not apply to B36.19 schedules.
When to Use Each Standard
| Pipe Material | Standard | Example Specification |
|---|---|---|
| Carbon steel seamless | B36.10 | ASTM A106 Gr.B |
| Carbon steel welded | B36.10 | ASTM A53 Gr.B |
| Alloy steel (Cr-Mo) | B36.10 | ASTM A335 P11/P22 |
| API line pipe | B36.10 | API 5L Gr.B, X52, X65 |
| 304/316 stainless | B36.19 | ASTM A312 TP304L/TP316L |
| Duplex stainless | B36.19 or B36.10 | ASTM A790 S31803 |
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