ASME B16.9 Long radius return bends, as important pipe turning connectors, have dimensional parameters that directly affect the assembly accuracy, fluid flow efficiency, and safety and stability of the piping system.
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Core Dimensions of Long Radius Return Bends
Nominal Pipe Size (NPS/DN): Identifies the nominal size of the pipe fitting, not the actual inner or outer diameter. It serves as the basis for selecting other dimensional parameters.
Bending Radius (R): The bending radius of a long radius return bend is fixed at 1.5 times the nominal diameter (1.5 × DN). This design reduces fluid resistance and pressure loss, making it suitable for piping systems with high flow rates or viscous fluids.
Outer Diameter (OD): The outer diameter of the pipe at the bevels at both ends of the return bend must precisely match the outer diameter of the connecting pipe.
Center-to-End Distance (A): The distance from the center axis of the return bend to the end faces at both ends directly affects the spatial layout of the pipe installation.
Center-to-Center Distance (O): For 180° long radius return bends, this refers to the distance between the center axes of the pipe ends, a critical parameter for assembly positioning.
Dimensional Tolerances and Application Considerations
Tolerance Requirements: The ASME B16.9 standard specifies strict tolerances for all dimensions of long radius return bends. For example, the tolerance range for the center-to-end distance and center-to-center distance should be referenced in page 6-2 of the standard. Actual production and acceptance must ensure that the dimensions are within the allowable deviation to guarantee assembly interchangeability.
Wall Thickness Matching: The wall thickness class of the return bend must match that of the connecting pipe (e.g., Sch40, Sch80). Different wall thickness classes only affect the pressure bearing capacity and weight of the fitting, not the core dimensional parameters.
Compatible Use: Long radius return bends must be used with pipes, flanges, valves, and other components that comply with ASME B16 series standards to ensure the compliance and safety of the entire piping system.
Dimensional Verification: Before purchasing and installation, the marking information of the pipe fitting (including specifications, standard number, material, etc.) should be checked, and key dimensions should be verified through actual measurement to avoid installation failures due to dimensional deviations.
DIMENSIONS OF LONG RADIUS RETURNS
|
Nominal Pipe Size (NPS) |
DN |
Outside Diameter at Bevel |
Center- to- Center, D |
Back- to- Face, K |
|
1/2 |
15 |
21.3 |
76 |
48 |
|
3/4 |
20 |
26.7 |
76 |
51 |
|
1 |
25 |
33.4 |
76 |
56 |
|
1 1/4 |
32 |
42.2 |
95 |
70 |
|
1 1/2 |
40 |
48.3 |
114 |
83 |
|
2 |
50 |
60.3 |
152 |
106 |
|
2 1/2 |
65 |
73.0 |
190 |
132 |
|
3 |
80 |
88.9 |
229 |
159 |
|
3 1/2 |
90 |
101.6 |
267 |
184 |
|
4 |
100 |
114.3 |
305 |
210 |
|
5 |
125 |
141.3 |
381 |
262 |
|
6 |
150 |
168.3 |
457 |
313 |
|
8 |
200 |
219.1 |
610 |
414 |
|
10 |
250 |
273.0 |
762 |
518 |
|
12 |
300 |
323.8 |
914 |
619 |
|
14 |
350 |
355.6 |
1067 |
711 |
|
16 |
400 |
406.4 |
1219 |
813 |
|
18 |
450 |
457 |
1372 |
914 |
|
20 |
500 |
508 |
1524 |
1016 |
|
22 |
550 |
559 |
1676 |
1118 |
|
24 |
600 |
610 |
1829 |
1219 |
GENERAL NOTE: All dimensions are in millimeters.
NOTES:
(1) Dimension A is equal to one-half of dimension O.
(2) O and K dimentions of 57 mm and 43 mm, respectively, may be furnished for NPS 3/4 (DN 20) atthe manufacturer,s option.
