Existing drawings and isometrics that reference B16.28 remain valid for the geometry, because the dimensions did not change when the content moved. What changed is the document to cite. The data on this page is reproduced from the last published edition of ASME B16.28 and is consistent with the corresponding tables in the current ASME B16.9.

1. Short Radius 90° Elbow — Centre-to-End (A)

Figure 1 — Short radius 90° elbow. A = 1.0 × NPS. Short radius elbows start at NPS 1; NPS 1/2 and 3/4 are not tabulated.

The short radius elbow has a bend radius equal to one nominal pipe size. For NPS 10 the centre-to-end dimension is 254 mm, against 381 mm for the long radius elbow of the same size, which is the 33% saving in space that makes SR fittings the choice for shipboard piping, skid-mounted packages and heat-exchanger headers.

2. Short Radius 180° Return — Centre-to-Centre (O) and Back-to-Face (K)

Figure 2 — Short radius 180° return. O is the distance between the two end centre lines and K is measured from the back of the bend to the plane of the two end faces.

O = 2 × A for both the long and the short radius series. K is tabulated and cannot be derived for production: forming thins the crown of the bend, so the published values, not a formula, govern acceptance. Short radius returns are used for heating coils and similar compact U-turn arrangements.

3. What Replaced ASME B16.28

4. End Preparation and Tolerance

The SR fittings were beveled to the same geometry as the rest of the family and continue to be under B16.9. The bevel is per ASME B16.25: 37.5° ± 2.5° with a 1.6 mm ± 0.8 mm land. Tolerances for centre-to-end, overall length and angularity are the B16.9 values; see the ASME B16.9 page for the tolerance table.

5. Materials Used for Short Radius Fittings

6. Long Radius Compared with Short Radius

7. Related Standards

8. How to Specify a Short Radius Fitting Today

9. FAQ

Is ASME B16.28 still valid?

No. It was withdrawn on 2024-08-31 and its content was incorporated into ASME B16.9. Any new specification should cite ASME B16.9 and state the short radius requirement explicitly.

The B16.28 name is still used commercially, particularly in the Middle East, Europe and South-East Asia, as a short-hand for a 1.0D radius. It is understood on a purchase enquiry, but it should not appear as the governing standard on a drawing or a data sheet.

Do I have to change existing drawings that call up B16.28?

Not for the geometry: the dimensions did not change. What you should correct is the reference, the next time the drawing is revised, so that it points at ASME B16.9.

At what size does the short radius series start?

NPS 1. Short radius elbows and returns are not tabulated for NPS 1/2 and 3/4; those sizes are supplied as long radius.

Can a short radius elbow be used interchangeably with a long radius elbow?

No. The centre-to-end dimension differs, the pressure drop differs, and the space required for the fitting differs. They are not interchangeable in an existing line without re-checking the layout and the flexibility analysis.