ASME B16.28 180 degree short radius elbow is a pipe fitting used in a piping system to change the direction of medium flow by 180 degrees. Its "short radius" refers to the ratio of the center distance (elbow curvature radius) to the nominal diameter (DN) of 1.0, making it suitable for installation scenarios with limited space.
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Differences in Dimensional Processing of Different Materials
Carbon Steel (e.g., A105): Low coefficient of thermal expansion (approximately 11.7 × 10⁻⁶/℃), resulting in high dimensional stability after processing. The cold-state deviation of the distance from the center to the end face (A) can be controlled within the lower limit of the standard tolerance, making it suitable for maintaining dimensions in normal environments.
Stainless Steel (e.g., A182 F304): High coefficient of thermal expansion (approximately 16.9 × 10⁻⁶/℃). After high-temperature processing, it needs to be cooled to room temperature before dimensional inspection. Additional allowance must be made for dimensional shrinkage after cooling.
Alloy Steel Pipe Fittings (e.g., A182 F91): Due to the presence of chromium and molybdenum, uneven wall thickness is prone to occur after forging. Additional wall thickness inspection points are required to ensure that the minimum wall thickness meets standard requirements, and the outer diameter tolerance must be strictly controlled within ±0.5 mm (NPS≤6).
Dimensional Tolerance Requirements
Center to End Face Distance (A): NPS≤2, tolerance ±1.6mm (±0.06 inches). NPS＞2 and ≤12, tolerance ±3.2mm (±0.125 inches). NPS＞12, tolerance ±6.4mm (±0.25 inches).
Outer Diameter (OD): Tolerance ±0.8mm (NPS≤6), ±1.6mm (NPS＞6).
Wall Thickness: Minimum wall thickness shall not be less than 87.5% of the standard specified value (i.e., negative tolerance ≤12.5%). Positive tolerance has no explicit limit but must ensure the overall strength of the fitting.
dimension of 180 degree short radius
|
180 deg RET |
URNS |
||
|
Nominal pipe size |
Outside diameter at bevel D |
Center-to-end A |
Back-to-face K |
|
1 |
1.32 |
2.00 |
1.62 |
|
1 1/4 |
1.66 |
2.50 |
2.06 |
|
1 1/2 |
1.90 |
3.00 |
2.44 |
|
2 |
2.38 |
4.00 |
3.19 |
|
2 1/2 |
2.88 |
5.00 |
3.94 |
|
3 |
3.50 |
6.00 |
4.75 |
|
3 1/4 |
4.00 |
7.00 |
5.50 |
|
4 |
4.50 |
8.00 |
6.25 |
|
5 |
5.56 |
10.00 |
7.75 |
|
6 |
6.62 |
12.00 |
9.31 |
|
8 |
8.62 |
16.00 |
12.31 |
|
10 |
10.75 |
20.00 |
15.38 |
|
12 |
12.75 |
24.00 |
18.38 |
|
14 |
14.00 |
28.00 |
21.00 |
|
16 |
16.00 |
32.00 |
24.00 |
|
18 |
18.00 |
36.00 |
27.00 |
|
20 |
20.00 |
40.00 |
30.00 |
|
22 |
22.00 |
44.00 |
33.00 |
|
24 |
24.00 |
48.00 |
36.00 |
GENERAL NOTES:
(a)Dimensions are in inches.
(b)Dimension A is equal to one-half of dimension O.
