The ASME B16.28 standard is the core standard specifying dimensional tolerances, ratings, testing, and marking requirements for forged carbon steel and alloy steel short-radius butt-welding elbows and return bends (180° elbows). HT PIPE offers an extensive range of industrial materials: pipes, sheets, bars, plus precision-engineered fittings, flanges, and couplings. Contact our team for free, customized quotes and product brochures.
Importance of ASME B16.28 Tolerances in Industrial Applications
Welding Integrity
Good cross-sectional and alignment tolerances ensure perfect alignment of the pipe fitting ends with adjacent piping, resulting in a uniform weld joint. Misalignment due to out-of-tolerance dimensions can lead to uneven weld penetration, stress concentrations, and ultimately weld failure-especially under high-pressure or cyclic loading conditions.
Interchangeability
ASME B16.28 tolerances standardize pipe fitting dimensions, allowing for interchangeability of fittings from different manufacturers. This is crucial for equipment maintenance, repair, and system expansion, avoiding the need for custom-fabricated parts and reducing downtime.
Structural Integrity and Pressure Rating
Wall thickness tolerances (minimum 87.5% of nominal wall thickness) ensure that the fittings can withstand the intended operating pressure and temperature. ASME B16.28 requires that the pressure rating of the fittings be consistent with seamless straight pipe of the same size, material, and wall thickness-adherence to tolerances is critical to meeting this requirement.
Compliance and Safety
In regulated industries, compliance with ASME standards (including B16.28) is mandatory to meet safety codes and regulations. Out-of-tolerance dimensions can lead to system failure, leaks, or environmental hazards, resulting in costly downtime, fines, or safety incidents. Furthermore, manufacturers must maintain records of dimensional inspections and tests to demonstrate compliance.
ASME B16.28 Tolerances
|
Nominal Pipe Size |
All Fittings |
|
90 deg Elbows |
180 deg Returns |
|||||
|
Outside Diameter at Bevel [Notes(1),(2)] |
Inside Diameter at End [Notes(1),(3),(4)] |
Wall Thickness [Note(3)] |
Angu Off Angle 0 |
larity Off Plane P |
Center-to- End Dimension A |
Center-to- Center Dimension 0 |
Back-to- Face Dimension K |
Alignments of Ends U |
|
|
1/2 to 2 1/2 3 to 3 1/2 4 5 to 8 10 to 12 14 to 16 18 20 to 24 |
+0.06 -0.03 0.06 0.06 +0.09 -0.06 +0.16 -0.12 +0.16 -0.12 +0.16 -0.12 +0.25 -0.19 |
0.03 0.06 0.06 0.06 0.12 0.12 0.12 0.19 |
Not less than 87.5% of nom- inal thick- ness marked on fitting |
0.03 0.03 0.03 0.06 0.09 0.09 0.12 0.12 |
0.06 0.06 0.06 0.12 0.19 0.25 0.38 0.38 |
0.06 0.06 0.06 0.06 0.09 0.09 0.09 0.09 |
0.25 0.25 0.25 0.25 0.38 0.38 0.38 0.38 |
0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 |
0.03 0.03 0.03 0.03 0.06 0.06 0.06 0.06 |
GENERAL NOTE:Dimensions are in inches.Tolerances are equal plus and minus except as noted.
NOTES:
(1)Out-of-round is the sum of absolute values of plus and minus tolerance.
(2)This tolerance may be exceeded in localized areas of formed fitings where increased wall thickness is required to meet design requrements.
(3)The inside diameter and the nominal wall thicknesses at ends are to be specified by the purchaser. Wall thickness tolerance applies throughout the fitting.
(4)Unless otherwise specified by the purchaser,these tolerances apply to the nominal inside diameter,which equals the difference between the nominal outside diameter and twice the nominal wall thickness.
