Allowable internal design pressure ratings for stainless steel pipe and tubing per ASME B31.3-2024 (Process Piping) across austenitic grades 304, 304L, 316, and 316L for ASME B36.19 schedules (Sch 10S, 40S, 80S) and ASTM A269 tubing.
Notice: Values are illustrative ratings for straight pipe at c = 0, not a substitute for the designer’s calculation under the governing code.
1. Governing Code Formula: ASME B31.3 Para. 304.1.2
Per ASME B31.3 Para. 304.1.2, internal design thickness (t) for straight pipe (t < D/6) is given by Eq. (3a):
t = (P × D) / [2 × (S × E × W + P × Y)]Inverting Eq. (3a) solves for maximum allowable internal design pressure (P):
P = (2 × S × E × W × t_min) / (D − 2 × Y × t_min)- P: Internal design gage pressure (MPa / psi, 1 MPa = 145.04 psi).
- D: Outside diameter per ASME B36.19 (mm).
- t_min: Minimum wall thickness after deducting mill undertolerance (c = 0).
- S: Basic allowable stress from Table A-1 (MPa).
- E: Longitudinal weld quality factor (seamless = 1.00; EFW single butt = 0.80 baseline; EFW double butt = 0.85; EFW 100% RT = 1.00).
- W: Weld joint strength reduction factor per Para. 302.3.5(e) and Table 302.3.5-1; taken as 1.00 for the temperatures shown in this chart (≤ 300 °C).
- Y: Temperature coefficient (0.4 at ≤ 482 °C per Table 304.1.1-1).
- Thick wall: For t ≥ D/6 (NPS 1/4″ Sch 80S), Para. 304.1.2(b) governs.
2. Wall Thickness Undertolerance Deductions
- ASTM A312 Pipe: ASTM A312 pipe requirements specify −12.5% undertolerance (
t_min = 0.875 × t_nom). - ASTM A269 Tubing: Use the minimum wall allowed by the product standard / order (example below assumes −10%,
t_min = 0.900 × t_nom).
3. Basic Allowable Stress S (ASME B31.3 Table A-1)
| Grade | Spec | Tensile / Yield (A312) | ≤40 °C | 100 °C | 150 °C | 200 °C | 250 °C | 300 °C |
|---|---|---|---|---|---|---|---|---|
| TP304 | A312/A269 | 515/205 MPa | 138 | 138 | 138 | 129 | 122 | 116 |
| TP304L | A312/A269 | 485/170 MPa | 115 | 115 | 115 | 110 | 103 | 97.7 |
| TP316 | A312/A269 | 515/205 MPa | 138 | 138 | 138 | 134 | 125 | 119 |
| TP316L | A312/A269 | 485/170 MPa | 115 | 115 | 115 | 109 | 103 | 98.1 |
TP304/TP316 offer S = 138 MPa at ≤ 40 °C (20% above L-grades at 115 MPa). Grade 316 retains higher stress above 150 °C.
4. Longitudinal Weld Joint Quality Factor E
Stainless longitudinal welds in ASME B31.3 Table A-3 are electric fusion welded (EFW):
- Seamless (E = 1.00): Full joint efficiency (ASTM A312 seamless pipe and ASTM A269 seamless tube).
- EFW Single Butt Seam (E = 0.80): Conservative baseline used in welded tables below.
- EFW Double Butt Seam (E = 0.85): Multiply table values by 0.85 / 0.80 = 1.0625 (+6.25%).
- EFW 100% Radiographed (E = 1.00): Per Table A-3 Note 5, full RT achieves E = 1.00 (equal to seamless).
Seamless (E = 1.00) provides 1.00 / 0.80 = 1.250 (+25.0%) higher pressure than single-butt EFW pipe, and 1.00 / 0.85 = 1.176 (+17.6%) higher than double-butt EFW pipe.
5. Master Pipe Pressure Rating Chart (ASME B36.19)
Allowable internal design pressures for ASME B36.19 pipe (NPS 1/4″ to 12″, Sch 10S/40S/80S) with 12.5% undertolerance deducted (c = 0). Welded columns use EFW single butt baseline (E = 0.80):
| NPS | OD (mm / in) | Sch | Nom. WT (mm) | TP316L Smls (E=1.00) | TP304 Smls (E=1.00) | TP316L Wld (E=0.80) | |||
|---|---|---|---|---|---|---|---|---|---|
| ≤40 °C | 200 °C | ≤40 °C | 200 °C | ≤40 °C | 200 °C | ||||
| 1/4″ | 13.72 / 0.540″ | 10S | 1.65 | 26.4 MPa (3833 psi) | 25.0 MPa (3633 psi) | 31.7 MPa (4600 psi) | 29.6 MPa (4300 psi) | 21.1 MPa (3066 psi) | 20.0 MPa (2906 psi) |
| 1/4″ | 13.72 / 0.540″ | 40S | 2.24 | 37.1 MPa (5381 psi) | 35.2 MPa (5100 psi) | 44.5 MPa (6457 psi) | 41.6 MPa (6036 psi) | 29.7 MPa (4304 psi) | 28.1 MPa (4080 psi) |
| 1/4″ | 13.72 / 0.540″ | 80S | 3.02 | 52.4 MPa (7595 psi) | 49.6 MPa (7199 psi) | 62.8 MPa (9114 psi) | 58.7 MPa (8520 psi) | 41.9 MPa (6076 psi) | 39.7 MPa (5759 psi) |
| 3/8″ | 17.14 / 0.675″ | 10S | 1.65 | 20.8 MPa (3013 psi) | 19.7 MPa (2856 psi) | 24.9 MPa (3616 psi) | 23.3 MPa (3380 psi) | 16.6 MPa (2410 psi) | 15.8 MPa (2285 psi) |
| 3/8″ | 17.14 / 0.675″ | 40S | 2.31 | 29.9 MPa (4344 psi) | 28.4 MPa (4117 psi) | 35.9 MPa (5212 psi) | 33.6 MPa (4873 psi) | 24.0 MPa (3475 psi) | 22.7 MPa (3294 psi) |
| 3/8″ | 17.14 / 0.675″ | 80S | 3.20 | 43.2 MPa (6269 psi) | 41.0 MPa (5942 psi) | 51.9 MPa (7523 psi) | 48.5 MPa (7032 psi) | 34.6 MPa (5015 psi) | 32.8 MPa (4753 psi) |
| 1/2″ | 21.34 / 0.840″ | 10S | 2.11 | 21.4 MPa (3101 psi) | 20.3 MPa (2939 psi) | 25.7 MPa (3721 psi) | 24.0 MPa (3478 psi) | 17.1 MPa (2481 psi) | 16.2 MPa (2351 psi) |
| 1/2″ | 21.34 / 0.840″ | 40S | 2.77 | 28.7 MPa (4168 psi) | 27.2 MPa (3950 psi) | 34.5 MPa (5001 psi) | 32.2 MPa (4675 psi) | 23.0 MPa (3334 psi) | 21.8 MPa (3160 psi) |
| 1/2″ | 21.34 / 0.840″ | 80S | 3.73 | 40.1 MPa (5813 psi) | 38.0 MPa (5510 psi) | 48.1 MPa (6976 psi) | 45.0 MPa (6521 psi) | 32.1 MPa (4651 psi) | 30.4 MPa (4408 psi) |
| 3/4″ | 26.67 / 1.050″ | 10S | 2.11 | 16.9 MPa (2445 psi) | 16.0 MPa (2317 psi) | 20.2 MPa (2934 psi) | 18.9 MPa (2742 psi) | 13.5 MPa (1956 psi) | 12.8 MPa (1854 psi) |
| 3/4″ | 26.67 / 1.050″ | 40S | 2.87 | 23.4 MPa (3397 psi) | 22.2 MPa (3220 psi) | 28.1 MPa (4076 psi) | 26.3 MPa (3811 psi) | 18.7 MPa (2718 psi) | 17.8 MPa (2576 psi) |
| 3/4″ | 26.67 / 1.050″ | 80S | 3.91 | 32.9 MPa (4769 psi) | 31.2 MPa (4520 psi) | 39.5 MPa (5722 psi) | 36.9 MPa (5349 psi) | 26.3 MPa (3815 psi) | 24.9 MPa (3616 psi) |
| 1″ | 33.40 / 1.315″ | 10S | 2.77 | 17.7 MPa (2570 psi) | 16.8 MPa (2436 psi) | 21.3 MPa (3084 psi) | 19.9 MPa (2883 psi) | 14.2 MPa (2056 psi) | 13.4 MPa (1949 psi) |
| 1″ | 33.40 / 1.315″ | 40S | 3.38 | 21.9 MPa (3179 psi) | 20.8 MPa (3013 psi) | 26.3 MPa (3815 psi) | 24.6 MPa (3566 psi) | 17.5 MPa (2543 psi) | 16.6 MPa (2411 psi) |
| 1″ | 33.40 / 1.315″ | 80S | 4.55 | 30.3 MPa (4396 psi) | 28.7 MPa (4166 psi) | 36.4 MPa (5275 psi) | 34.0 MPa (4931 psi) | 24.2 MPa (3516 psi) | 23.0 MPa (3333 psi) |
| 1-1/4″ | 42.16 / 1.660″ | 10S | 2.77 | 13.9 MPa (2010 psi) | 13.1 MPa (1905 psi) | 16.6 MPa (2412 psi) | 15.5 MPa (2255 psi) | 11.1 MPa (1608 psi) | 10.5 MPa (1524 psi) |
| 1-1/4″ | 42.16 / 1.660″ | 40S | 3.56 | 18.1 MPa (2620 psi) | 17.1 MPa (2483 psi) | 21.7 MPa (3144 psi) | 20.3 MPa (2938 psi) | 14.4 MPa (2096 psi) | 13.7 MPa (1986 psi) |
| 1-1/4″ | 42.16 / 1.660″ | 80S | 4.85 | 25.2 MPa (3652 psi) | 23.9 MPa (3461 psi) | 30.2 MPa (4382 psi) | 28.2 MPa (4097 psi) | 20.1 MPa (2922 psi) | 19.1 MPa (2769 psi) |
| 1-1/2″ | 48.26 / 1.900″ | 10S | 2.77 | 12.0 MPa (1746 psi) | 11.4 MPa (1654 psi) | 14.4 MPa (2095 psi) | 13.5 MPa (1958 psi) | 9.6 MPa (1396 psi) | 9.1 MPa (1324 psi) |
| 1-1/2″ | 48.26 / 1.900″ | 40S | 3.68 | 16.2 MPa (2351 psi) | 15.4 MPa (2229 psi) | 19.5 MPa (2822 psi) | 18.2 MPa (2638 psi) | 13.0 MPa (1881 psi) | 12.3 MPa (1783 psi) |
| 1-1/2″ | 48.26 / 1.900″ | 80S | 5.08 | 22.9 MPa (3317 psi) | 21.7 MPa (3144 psi) | 27.4 MPa (3980 psi) | 25.7 MPa (3721 psi) | 18.3 MPa (2654 psi) | 17.3 MPa (2515 psi) |
| 2″ | 60.32 / 2.375″ | 10S | 2.77 | 9.5 MPa (1385 psi) | 9.1 MPa (1313 psi) | 11.5 MPa (1662 psi) | 10.7 MPa (1554 psi) | 7.6 MPa (1108 psi) | 7.2 MPa (1050 psi) |
| 2″ | 60.32 / 2.375″ | 40S | 3.91 | 13.7 MPa (1982 psi) | 13.0 MPa (1879 psi) | 16.4 MPa (2378 psi) | 15.3 MPa (2223 psi) | 10.9 MPa (1586 psi) | 10.4 MPa (1503 psi) |
| 2″ | 60.32 / 2.375″ | 80S | 5.54 | 19.8 MPa (2865 psi) | 18.7 MPa (2716 psi) | 23.7 MPa (3438 psi) | 22.2 MPa (3214 psi) | 15.8 MPa (2292 psi) | 15.0 MPa (2172 psi) |
| 2-1/2″ | 73.02 / 2.875″ | 10S | 3.05 | 8.7 MPa (1256 psi) | 8.2 MPa (1190 psi) | 10.4 MPa (1507 psi) | 9.7 MPa (1409 psi) | 6.9 MPa (1005 psi) | 6.6 MPa (952 psi) |
| 2-1/2″ | 73.02 / 2.875″ | 40S | 5.16 | 15.0 MPa (2170 psi) | 14.2 MPa (2057 psi) | 18.0 MPa (2604 psi) | 16.8 MPa (2434 psi) | 12.0 MPa (1736 psi) | 11.3 MPa (1645 psi) |
| 2-1/2″ | 73.02 / 2.875″ | 80S | 7.01 | 20.7 MPa (3004 psi) | 19.6 MPa (2847 psi) | 24.9 MPa (3605 psi) | 23.2 MPa (3370 psi) | 16.6 MPa (2403 psi) | 15.7 MPa (2278 psi) |
| 3″ | 88.90 / 3.500″ | 10S | 3.05 | 7.1 MPa (1026 psi) | 6.7 MPa (973 psi) | 8.5 MPa (1231 psi) | 7.9 MPa (1151 psi) | 5.7 MPa (821 psi) | 5.4 MPa (778 psi) |
| 3″ | 88.90 / 3.500″ | 40S | 5.49 | 13.0 MPa (1884 psi) | 12.3 MPa (1786 psi) | 15.6 MPa (2261 psi) | 14.6 MPa (2113 psi) | 10.4 MPa (1507 psi) | 9.8 MPa (1429 psi) |
| 3″ | 88.90 / 3.500″ | 80S | 7.62 | 18.4 MPa (2662 psi) | 17.4 MPa (2523 psi) | 22.0 MPa (3194 psi) | 20.6 MPa (2986 psi) | 14.7 MPa (2129 psi) | 13.9 MPa (2018 psi) |
| 3-1/2″ | 101.60 / 4.000″ | 10S | 3.05 | 6.2 MPa (895 psi) | 5.8 MPa (848 psi) | 7.4 MPa (1074 psi) | 6.9 MPa (1004 psi) | 4.9 MPa (716 psi) | 4.7 MPa (679 psi) |
| 3-1/2″ | 101.60 / 4.000″ | 40S | 5.74 | 11.8 MPa (1717 psi) | 11.2 MPa (1627 psi) | 14.2 MPa (2060 psi) | 13.3 MPa (1926 psi) | 9.5 MPa (1374 psi) | 9.0 MPa (1302 psi) |
| 3-1/2″ | 101.60 / 4.000″ | 80S | 8.08 | 16.9 MPa (2458 psi) | 16.1 MPa (2330 psi) | 20.3 MPa (2950 psi) | 19.0 MPa (2757 psi) | 13.6 MPa (1967 psi) | 12.9 MPa (1864 psi) |
| 4″ | 114.30 / 4.500″ | 10S | 3.05 | 5.5 MPa (794 psi) | 5.2 MPa (752 psi) | 6.6 MPa (952 psi) | 6.1 MPa (890 psi) | 4.4 MPa (635 psi) | 4.1 MPa (602 psi) |
| 4″ | 114.30 / 4.500″ | 40S | 6.02 | 11.0 MPa (1596 psi) | 10.4 MPa (1513 psi) | 13.2 MPa (1915 psi) | 12.3 MPa (1791 psi) | 8.8 MPa (1277 psi) | 8.3 MPa (1210 psi) |
| 4″ | 114.30 / 4.500″ | 80S | 8.56 | 15.9 MPa (2307 psi) | 15.1 MPa (2187 psi) | 19.1 MPa (2768 psi) | 17.8 MPa (2588 psi) | 12.7 MPa (1846 psi) | 12.1 MPa (1749 psi) |
| 5″ | 141.30 / 5.563″ | 10S | 3.40 | 4.9 MPa (714 psi) | 4.7 MPa (677 psi) | 5.9 MPa (857 psi) | 5.5 MPa (801 psi) | 3.9 MPa (572 psi) | 3.7 MPa (542 psi) |
| 5″ | 141.30 / 5.563″ | 40S | 6.55 | 9.6 MPa (1398 psi) | 9.1 MPa (1325 psi) | 11.6 MPa (1678 psi) | 10.8 MPa (1569 psi) | 7.7 MPa (1119 psi) | 7.3 MPa (1060 psi) |
| 5″ | 141.30 / 5.563″ | 80S | 9.52 | 14.2 MPa (2064 psi) | 13.5 MPa (1956 psi) | 17.1 MPa (2477 psi) | 16.0 MPa (2315 psi) | 11.4 MPa (1651 psi) | 10.8 MPa (1565 psi) |
| 6″ | 168.28 / 6.625″ | 10S | 3.40 | 4.1 MPa (598 psi) | 3.9 MPa (567 psi) | 4.9 MPa (718 psi) | 4.6 MPa (671 psi) | 3.3 MPa (479 psi) | 3.1 MPa (454 psi) |
| 6″ | 168.28 / 6.625″ | 40S | 7.11 | 8.8 MPa (1271 psi) | 8.3 MPa (1205 psi) | 10.5 MPa (1525 psi) | 9.8 MPa (1426 psi) | 7.0 MPa (1017 psi) | 6.6 MPa (964 psi) |
| 6″ | 168.28 / 6.625″ | 80S | 10.97 | 13.7 MPa (1994 psi) | 13.0 MPa (1890 psi) | 16.5 MPa (2393 psi) | 15.4 MPa (2237 psi) | 11.0 MPa (1595 psi) | 10.4 MPa (1512 psi) |
| 8″ | 219.08 / 8.625″ | 10S | 3.76 | 3.5 MPa (507 psi) | 3.3 MPa (481 psi) | 4.2 MPa (608 psi) | 3.9 MPa (569 psi) | 2.8 MPa (406 psi) | 2.7 MPa (384 psi) |
| 8″ | 219.08 / 8.625″ | 40S | 8.18 | 7.7 MPa (1119 psi) | 7.3 MPa (1061 psi) | 9.3 MPa (1343 psi) | 8.7 MPa (1255 psi) | 6.2 MPa (895 psi) | 5.9 MPa (849 psi) |
| 8″ | 219.08 / 8.625″ | 80S | 12.70 | 12.2 MPa (1764 psi) | 11.5 MPa (1672 psi) | 14.6 MPa (2116 psi) | 13.6 MPa (1978 psi) | 9.7 MPa (1411 psi) | 9.2 MPa (1337 psi) |
| 10″ | 273.00 / 10.750″ | 10S | 4.19 | 3.1 MPa (453 psi) | 3.0 MPa (429 psi) | 3.7 MPa (543 psi) | 3.5 MPa (508 psi) | 2.5 MPa (362 psi) | 2.4 MPa (343 psi) |
| 10″ | 273.00 / 10.750″ | 40S | 9.27 | 7.0 MPa (1015 psi) | 6.6 MPa (962 psi) | 8.4 MPa (1218 psi) | 7.9 MPa (1139 psi) | 5.6 MPa (812 psi) | 5.3 MPa (770 psi) |
| 10″ | 273.00 / 10.750″ | 80S | 12.70 | 9.7 MPa (1404 psi) | 9.2 MPa (1330 psi) | 11.6 MPa (1684 psi) | 10.9 MPa (1574 psi) | 7.7 MPa (1123 psi) | 7.3 MPa (1064 psi) |
| 12″ | 323.80 / 12.750″ | 10S | 4.57 | 2.9 MPa (416 psi) | 2.7 MPa (394 psi) | 3.4 MPa (499 psi) | 3.2 MPa (467 psi) | 2.3 MPa (333 psi) | 2.2 MPa (315 psi) |
| 12″ | 323.80 / 12.750″ | 40S | 9.52 | 6.0 MPa (876 psi) | 5.7 MPa (831 psi) | 7.2 MPa (1051 psi) | 6.8 MPa (983 psi) | 4.8 MPa (701 psi) | 4.6 MPa (664 psi) |
| 12″ | 323.80 / 12.750″ | 80S | 12.70 | 8.1 MPa (1177 psi) | 7.7 MPa (1116 psi) | 9.7 MPa (1413 psi) | 9.1 MPa (1320 psi) | 6.5 MPa (942 psi) | 6.2 MPa (893 psi) |
Note: For heavy walls where t_min ≥ D/6 (NPS 1/4″ Sch 80S), see Section 1. For custom heavy walls, see our thick-wall stainless steel pipe program.
6. Fractional Tubing Pressure Ratings (ASTM A269 TP316L)
Allowable working pressures for ASTM A269 TP316L tubing across 1/4″ to 1″ OD sizes. Wall undertolerance assumes −10% baseline:
| Tube Size (OD × Wall) | OD (mm) | Nom. WT (mm) | Min. WT (t_min) (mm) | TP316L Seamless (E=1.00) | TP316L Welded (E=0.80) | ||
|---|---|---|---|---|---|---|---|
| ≤40 °C | 200 °C | ≤40 °C | 200 °C | ||||
| 1/4″ x 0.035″ | 6.35 | 0.889 | 0.800 | 32.2 MPa (4674 psi) | 30.5 MPa (4431 psi) | 25.8 MPa (3740 psi) | 24.4 MPa (3544 psi) |
| 3/8″ x 0.035″ | 9.53 | 0.889 | 0.800 | 20.7 MPa (3004 psi) | 19.6 MPa (2847 psi) | 16.6 MPa (2403 psi) | 15.7 MPa (2278 psi) |
| 1/2″ x 0.049″ | 12.70 | 1.245 | 1.121 | 21.8 MPa (3167 psi) | 20.7 MPa (3002 psi) | 17.5 MPa (2533 psi) | 16.6 MPa (2401 psi) |
| 3/4″ x 0.065″ | 19.05 | 1.651 | 1.486 | 19.1 MPa (2775 psi) | 18.1 MPa (2630 psi) | 15.3 MPa (2220 psi) | 14.5 MPa (2104 psi) |
| 1″ x 0.065″ | 25.40 | 1.651 | 1.486 | 14.1 MPa (2047 psi) | 13.4 MPa (1941 psi) | 11.3 MPa (1638 psi) | 10.7 MPa (1552 psi) |
7. Code Scope & Plant Accreditations
ASME B31.3 governs chemical process piping; B31.1 governs power piping; BPVC VIII governs pressure vessels; EN 13480 governs European piping under PED 2014/68/EU.
For procurement and certification verification:
- The two dedicated plants hold ISO 9001/14001/45001, PED/AD 2000-Merkblatt W0 and DNV/LR/ABS approvals — see https://tecarvepipes.com/verify-our-factories/.
- In-stock inventory: stainless steel pipe stock list.
- Project inquiries: contact our technical sales team.
Frequently Asked Questions (FAQ)
How does temperature derating affect stainless steel pipe pressure?
Elevated temperatures reduce allowable stress (S). TP316L pipe derates from 115 MPa at ≤ 40 °C to 109 MPa at 200 °C, reducing NPS 2″ Sch 40S seamless rating from 13.7 MPa (1,982 psi) to 13.0 MPa (1,879 psi).
What is the exact pressure difference between seamless and welded pipe?
The pressure ratio is governed by weld factor E: seamless (E = 1.00) is 1.00 / 0.80 = 1.250 (+25.0%) higher than single-butt EFW (E = 0.80), and 1.00 / 0.85 = 1.176 (+17.6%) higher than double-butt EFW (E = 0.85). With 100% radiography, welded pipe achieves E = 1.00.
Why is mill undertolerance deducted from nominal wall thickness?
ASTM A312 permits −12.5% wall tolerance. Using nominal wall would cause hoop stresses to exceed code limits on pipes at minimum tolerance. ASME B31.3 requires using minimum thickness (t_min = 0.875 × t_nom).
Can ASME B31.3 pressure ratings be used for ASME B31.1 boiler external piping?
No. Power piping under ASME B31.1 uses different safety margins. Boiler external piping is governed by ASME Section I and B31.1, requiring separate calculations.
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