What Are ASME B16.9 180° Returns?
An 180° return (return bend) turns the flow by 180 degrees in one fitting, commonly used in heat exchangers, coil piping, and tight space runs. ASME B16.9 covers long radius returns in Table 6.1-3 (NPS 1/2 – 24) and short radius returns in Table 6.1-5.
Dimensions — Long Radius Returns (Table 6.1-3)
NPS 1/2 – 24. Values in mm (inch). O = center-to-center; K = center-to-end (overall). OD = outside diameter.
| NPS | Outside Diameter (mm / in) | O — Center-to-Center (mm / in) | K — Center-to-End (mm / in) |
|---|---|---|---|
| 1/2 | 21.3 (0.84) | 76.0 (3.0) | 48.0 (1.88) |
| 3/4 | 26.7 (1.05) | 76.0 (3.0) | 51.0 (2.0) |
| 1 | 33.4 (1.32) | 76.0 (3.0) | 56.0 (2.19) |
| 1-1/4 | 42.2 (1.66) | 95.0 (3.75) | 70.0 (2.75) |
| 1-1/2 | 48.3 (1.9) | 114.0 (4.5) | 83.0 (3.25) |
| 2 | 60.3 (2.38) | 152.0 (6.0) | 106.0 (4.19) |
| 2-1/2 | 73.0 (2.88) | 190.0 (7.5) | 132.0 (5.19) |
| 3 | 88.9 (3.5) | 229.0 (9.0) | 159.0 (6.25) |
| 3-1/2 | 101.6 (4.0) | 267.0 (10.5) | 184.0 (7.25) |
| 4 | 114.3 (4.5) | 305.0 (12.0) | 210.0 (8.25) |
| 5 | 141.3 (5.56) | 381.0 (15.0) | 262.0 (10.31) |
| 6 | 168.3 (6.62) | 457.0 (18.0) | 313.0 (12.31) |
| 8 | 219.1 (8.62) | 610.0 (24.0) | 414.0 (16.31) |
| 10 | 273.0 (10.75) | 762.0 (30.0) | 518.0 (20.38) |
| 12 | 323.8 (12.75) | 914.0 (36.0) | 619.0 (24.38) |
| 14 | 355.6 (14.0) | 1067.0 (42.0) | 711.0 (28.0) |
| 16 | 406.4 (16.0) | 1219.0 (48.0) | 813.0 (32.0) |
| 18 | 457.0 (18.0) | 1372.0 (54.0) | 914.0 (36.0) |
| 20 | 508.0 (20.0) | 1524.0 (60.0) | 1016.0 (40.0) |
| 22 | 559.0 (22.0) | 1676.0 (66.0) | 1118.0 (44.0) |
| 24 | 610.0 (24.0) | 1829.0 (72.0) | 1219.0 (48.0) |
Short radius 180° returns: dimensions per ASME B16.9 Table 6.1-5.
Materials & Temperature Range
A234 WPB carbon steel (-29°C to 425°C), A403 WP304 / WP316 stainless (up to 538°C), A420 WPL6 low-temperature carbon steel. Chemistry and mechanical properties per the applicable ASTM material standard.
Related Standards
- ASME B16.9 — Buttwelding Fittings (parent standard)
- ASME B16.9 Elbows — 90° & 45°
- ASME B16.9 Lap Joint Stub Ends
- ASME B16.9 Tees
- ASME B16.5 — Pipe Flanges
- ASTM A234 WPB Carbon Steel
- Our Fittings Range
FAQ
What is an 180-degree return used for?
To reverse flow direction in heat exchanger bundles, piping coils, and compact installations where two parallel pipes must connect.
What is the difference between O and K?
O is the center-to-center distance between the two legs; K is the center-to-end (overall length) of the return.
What sizes do long radius returns cover?
NPS 1/2 through NPS 24 per Table 6.1-3. Short radius returns follow Table 6.1-5.
Can returns be made in stainless steel?
Yes — A403 WP304/WP316 grades are standard for heat exchanger and corrosion service.
Is a return the same as two 90-degree elbows welded together?
No — a forged/wrought return has a smooth continuous bend radius and fewer welds, giving higher integrity than assembled elbows.
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