ASTM A789 standard specification covers grades of nominal wall thickness, stainless steel tubing for services requiring general corrosion resistance, with particular emphasis on resistance to stress corrosion cracking. These steels are susceptible to embrittlement if used for prolonged periods at elevated temperatures.
ASME B36.19 Sizes and Dimensions Standard
| NPS nominal pipe size | Outside Diameter | Pipe Schedules | ||||
| DN | NPS(in) | OD(mm) | Sch5S in(mm) |
Sch10S in(mm) |
Sch40S in(mm) |
Sch80S in(mm) |
| 6 | 1/8 | 3.175 | … | 0.049(1.24) | 0.068(1.73) | 0.095(2.41) |
| 8 | 1/4 | 6.35 | … | 0.065(1.65) | 0.088(2.24) | 0.119(3.02) |
| 10 | 3/8 | 9.53 | … | 0.065(1.65) | 0.091(2.31) | 0.126(3.2) |
| 15 | 1/2 | 12.70 | 0.065(1.65) | 0.083(2.11) | 0.109(2.77) | 0.147(3.73) |
| 20 | 3/4 | 19.05 | 0.065(1.65) | 0.083(2.11) | 0.113(2.87) | 0.154(3.91) |
| 25 | 1 | 25.40 | 0.065(1.65) | 0.109(2.77) | 0.133(3.38) | 0.179(4.55) |
| 32 | 1 1/4 | 31.75 | 0.065(1.65) | 0.109(2.77) | 0.14(3.56) | 0.191(4.85) |
| 40 | 1 1/2 | 38.10 | 0.065(1.65) | 0.109(2.77) | 0.145(3.68) | 0.2(5.08) |
| 50 | 2 | 50.80 | 0.065(1.65) | 0.109(2.77) | 0.154(3.91) | 0.218(5.54) |
| 65 | 2 1/2 | 63.50 | 0.083(2.11) | 0.12(3.05) | 0.203(5.16) | 0.276(7.01) |
| 80 | 3 | 76.20 | 0.083(2.11) | 0.12(3.05) | 0.216(5.49) | 0.3(7.62) |
| 90 | 3 1/2 | 88.90 | 0.083(2.11) | 0.12(3.05) | 0.226(5.74) | 0.318(8.08) |
| 100 | 4 | 101.60 | 0.083(2.11) | 0.12(3.05) | 0.237(6.02) | 0.337(8.56) |
| 125 | 5 | 127.00 | 0.109(2.77) | 0.134(3.4) | 0.258(6.55) | 0.375(9.53) |
| 137.5 | 5 1/2 | 139.70 | 0.109(2.77) | 0.134(3.4) | 0.269(6.83) | 0.403(10.25) |
| 150 | 6 | 152.40 | 0.109(2.77) | 0.134(3.4) | 0.28(7.11) | 0.432(10.97) |
| 200 | 8 | 203.20 | 0.109(2.77) | 0.148(3.76) | 0.322(8.18) | 0.5(12.7) |
ASME SA789 Permissible Variations In Dimensions
| Group | Size,Outside Diameter,in. |
Permissible Variations in Outside Diameter,in. |
Permissible Variations in Wall |
Permissible Variations in Cut Length, in.B [mm] |
- | |
| [mm] | [mm] | Thickness,A % | Over | Under | Thin Walled TubesC | |
| 1 | Up to¹/₂ [12.7], exc | ±0.005 [0.13] | ±15 | ¹/8[3] | 0 | ... |
| 2 | ¹/₂ to 1¹/₂ [12.7 to 38.1], exc | ±0.005 [0.13] | ±10 | ¹/8 [3] | 0 | less than 0.065 in.[1.6 mm]nomina |
| 3 | l¹/₂ to 3¹/₂ [38.1 to 88.9], exc | ±0.010 [0.25] | ±10 | 3/₁₆ [5] | 0 | less than 0.095 in.[2.4 mm]nomina |
| 4 | 3¹/₂ to 5¹/₂ [88.9 to 139.7], exc | ±0.015 [0.38] | ±10 | 3/₁₆ [5] | 0 | less than 0.150 in.[3.8 mm]nomina |
| 5 | 5¹/₂ to 8[139.7 to 203.2], incl | ±0.030 [0.76] | ±10 | 3/₁₆ [5] | 0 | less than 0.150 in.[3.8 mm]nomina |
Notes:
A When tubes as ordered require wall thicknesses 34 in. [19 mm] or over, or an inside diameter 60% or less of the outside diameter, a wider variation in wall thickness is required. On such sizes a variation in wall thickness of 12.5%over or under will be permitted. Fortubes less than in.[12.7 mm] in inside diameter that cannot be successfully drawn over a mandrel, the wall thickness may vary ±15% from that specified.
B These tolerances apply to cut lengths up to and including 24 ft [7.3 m]. For lengths greater than 24 ft [7.3 m], the above over tolerances shall be increased by in. [3 mm] for each 10 ft [3 m] or fraction thereof over 24 ft or in.[13 mm], whichever is the lesser.
C Ovality provisions of 12.2 apply
FAQ
Q: What is the standard wall thickness tolerance for ASTM A789?
A: For most standard sizes (1/2" to 5" OD), the wall thickness tolerance is ±10%. For small-diameter tubing (under 1/2"), the tolerance widens to ±15%.
Q: Can ASTM A789 tubing be used for pressure piping?
A: ASTM A789 is specifically a tubing standard, typically used for heat exchangers and condensers. If your project requires nominal pipe sizes (NPS) for process piping, you should refer to ASTM A790.
Q: Does ASTM A789 cover Super Duplex grades?
A: Yes. While S31803 and S32205 (Duplex 2205) are the most common, A789 also covers Super Duplex grades like S32750 and S32760.
Q: What are the mandatory tests for ASTM A789 compliance?
A: Every tube must undergo tension tests, flaring tests (for seamless), flattening tests (for welded), and a non-destructive electric test (Eddy Current) or hydrostatic test.
Q: Is there a hardness limit for A789 Duplex tubing?
A: Yes. For example, S31803 has a maximum hardness of 30 HRC (Rockwell C) or 290 HBW (Brinell). Exceeding these limits can increase the risk of stress corrosion cracking.
