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ASTM A269 is a specification for seamless and welded austenitic stainless steel tubing used in a variety of applications, such as heat exchangers, high-temperature service, and general corrosion resistance applications. It is important to understand the sizes and tolerances of A269 austenitic stainless steel tubes to ensure they fit the intended purpose. The tubes shall be made by the seamless or welded process. At the manufacturer's option, stainless steel tubing may be furnished either hot finished or cold finished.
Permissible Variations in Dimensions
The permissible variations in outside diameter given in astm a269 tolerances Table are not sufficient to provide for ovality in thin-walled tubes, as defined in the Table. In such tubes, the maximum and minimum diameters at any cross section shall deviate from the nominal diameter by no more than twice the permissible variation in outside diameter given in Table; however, the mean diameter at that cross section must still be within the given permissible variation.
Straightness Tolerance
ASTM A269 stainless steel tubes are required to have no more than 1/8 inch of deviation for every 5 feet of length. However, tubes with a diameter less than 1/2 inch can have up to 0.040 inch of deviation for every foot of length.
Wall Thickness Tolerance
The wall thickness of ASTM A269 seamless steel tubes varies based on the size and material grade. The tolerance for wall thickness depends on the thickness measurement method used. For example, tubes measured by the ultrasonic method have a tighter tolerance than those measured by the Eddy-current method.
Outside Diameter Tolerance
The outside diameter of ASTM A269 welded steel tubes has a tolerance of +/- 0.005 inch for sizes up to 1 inch, and +/- 0.015 inch for sizes larger than 1 inch. The Tolerance for wall thickness and diameter are interrelated, and if one exceeds the limit, the other should adjust accordingly to maintain the intended size specification.
Length Tolerance
The length of ASME SA269 tubes can vary based on the manufacturing process. The standard allows for a variation of +/- 1/8 inch or +/- 0.5% of the specific length, whichever is greater.
ASTM A269 Permissible Variations in Dimensions
| Group | Size, Outside Diameter, in. | Permissible Variations in Outside Diameter in. (mm) |
Permissible Variations in Wall ThicknessA % |
Permissible Variations in Cut Length in. (mm)B | Thin Walled TubesC | |
| Over | Under | |||||
| 1 | Up to 1/2 | ±0.005 (0.13) | ±15 | 1/8 (3.2) | 0 | … |
| 2 | 1/2 to 11/2 , excl | ±0.005 (0.13) | ±10 | 1/8 (3.2) | 0 | less than 0.065 in. (1.65 mm) nominal |
| 3 | 11/2 to 31/2 , excl | ±0.010 (0.25) | ±10 | 3/16 (4.8) | 0 | less than 0.095 in. (2.41 mm) nominal |
| 4 | 31/2 to 51/2 , excl | ±0.015 (0.38) | ±10 | 3/16 (4.8) | 0 | less than 0.150 in. (3.81 mm) nominal |
| 5 | 51/2 to 8, excl | ±0.030 (0.76) | ±10 | 3/16 (4.8) | 0 | less than 0.150 in. (3.81 mm) nominal |
| 6 | 8 to 12, excl | ±0.040 (1.01) | ±10 | 3/16 (4.8) | 0 | less than 0.200 in. (5.08 mm) nominal |
| 7 | 12 to 14, excl | ±0.050 (1.26) | ±10 | 3/16 (4.8) | 0 | less than 0.220 in. (5.59 mm) nominal |
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A: When tubes as ordered require wall thicknesses 3⁄4 in. (19.0 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.
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 1⁄8 in.(3 mm) for each 10 ft (3 m) or fraction thereof over 24 ft, or 1⁄2 in. (13 mm), whichever is lesser.
ASTM A269 vs. ASTM A213: Understanding the ApplicationsA common cross-specification issue during procurement is choosing between ASTM A269 and ASTM A213. While their chemical compositions (frequently grades 304/304L and 316/316L) are highly overlapping, their targeted intents differ:
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