Butt-weld reducer dimensions: ASME B16.9 and EN 10253-1
Lengths, wall and weight of our concentric and eccentric reducers, in both standards. Under EN 10253-1, form 1 and form 2 do not have the same length.
ASME B16.9 reducers
Concentric or eccentric, ASME reducers have an end-to-end length H that depends only on the large end. A 4" × 2" and a 4" × 3" both measure 102 mm.
| Large end NPS | OD (mm) | Length H (mm) |
|---|---|---|
| 1" | 33.4 | 51 |
| 1¼" | 42.2 | 51 |
| 1½" | 48.3 | 64 |
| 2" | 60.3 | 76 |
| 2½" | 73.0 | 89 |
| 3" | 88.9 | 89 |
| 4" | 114.3 | 102 |
| 5" | 141.3 | 127 |
| 6" | 168.3 | 140 |
| 8" | 219.1 | 152 |
Concentric and eccentric reducers to ASME B16.9: H depends on the large end only. Tolerance ± 2 mm.
EN 10253-1 reducers: form 1, form 2 and eccentric
EN 10253-1 defines two concentric reducers. Form 2 has rounded transitions and a length set by the large end, the same as the eccentric reducer. Form 1 is a plain cone: its length depends on the gap between the two diameters.
| Size (NPS) | Large end D × T | Small end D1 × T1 | L form 1 | L form 2 and eccentric | Weight form 1 (kg) | Weight form 2 and ecc. (kg) |
|---|---|---|---|---|---|---|
| ¾ × ½" | 26.9 × 2.3 | 21.3 × 2.0 | not made | 38 | – | 0.11 |
| 1 × ¾" | 33.7 × 2.6 | 26.9 × 2.3 | 35 | 51 | 0.07 | 0.14 |
| 1¼ × 1" | 42.4 × 2.6 | 33.7 × 2.6 | 51 | 51 | 0.10 | 0.20 |
| 1¼ × ¾" | 42.4 × 2.6 | 26.9 × 2.3 | 39 | 51 | 0.13 | 0.20 |
| 1½ × 1¼" | 48.3 × 2.6 | 42.4 × 2.6 | 38 | 64 | 0.11 | 0.24 |
| 1½ × 1" | 48.3 × 2.6 | 33.7 × 2.6 | 55 | 64 | 0.16 | 0.24 |
| 1½ × ¾" | 48.3 × 2.6 | 26.9 × 2.3 | 67 | 64 | 0.12 | 0.24 |
| 2 × 1½" | 60.3 × 2.9 | 48.3 × 2.6 | 50 | 76 | 0.21 | 0.40 |
| 2 × 1¼" | 60.3 × 2.9 | 42.4 × 2.6 | 61 | 76 | 0.26 | 0.40 |
| 2 × 1" | 60.3 × 2.9 | 33.7 × 2.6 | 77 | 76 | 0.33 | 0.40 |
| 2½ × 2" | 76.1 × 2.9 | 60.3 × 2.9 | 63 | 89 | 0.34 | 0.70 |
| 2½ × 1½" | 76.1 × 2.9 | 48.3 × 2.6 | 84 | 89 | 0.45 | 0.70 |
| 2½ × 1¼" | 76.1 × 2.9 | 42.4 × 2.6 | 95 | 89 | 0.50 | 0.70 |
| 3 × 2½" | 88.9 × 3.2 | 76.1 × 2.9 | 56 | 89 | 0.38 | 0.90 |
| 3 × 2" | 88.9 × 3.2 | 60.3 × 2.9 | 86 | 89 | 0.59 | 0.90 |
| 3 × 1½" | 88.9 × 3.2 | 48.3 × 2.6 | 108 | 89 | 0.75 | 0.90 |
| 4 × 3" | 114.3 × 3.6 | 88.9 × 3.2 | 90 | 102 | 0.92 | 1.60 |
| 4 × 2½" | 114.3 × 3.6 | 76.1 × 2.9 | 114 | 102 | 1.17 | 1.60 |
| 4 × 2" | 114.3 × 3.6 | 60.3 × 2.9 | 143 | 102 | 1.46 | 1.60 |
| 5 × 4" | 139.7 × 4.0 | 114.3 × 3.6 | 88 | 127 | 1.19 | 2.50 |
| 5 × 3" | 139.7 × 4.0 | 88.9 × 3.2 | 135 | 127 | 1.80 | 2.50 |
| 5 × 2½" | 139.7 × 4.0 | 76.1 × 2.9 | 159 | 127 | 2.12 | 2.50 |
| 6 × 5" | 168.3 × 4.5 | 139.7 × 4.0 | 94 | 140 | 1.78 | 3.80 |
| 6 × 4" | 168.3 × 4.5 | 114.3 × 3.6 | 141 | 140 | 2.63 | 3.80 |
| 6 × 3" | 168.3 × 4.5 | 88.9 × 3.2 | 189 | 140 | 3.42 | 3.80 |
| 8 × 6" | 219.1 × 6.3 | 168.3 × 4.5 | 130 | 152 | 3.91 | 6.50 |
| 8 × 5" | 219.1 × 6.3 | 139.7 × 4.0 | 170 | 152 | 5.68 | 6.50 |
| 8 × 4" | 219.1 × 6.3 | 114.3 × 3.6 | 210 | 152 | 6.41 | 6.50 |
Reducers to EN 10253-1, in S235. Dimensions in mm.
Form 1 is not always the shortest: it is for a small step (4" × 3": 90 mm versus 102), but it gets longer as the step grows (4" × 2": 143 mm versus 102). Check the length before choosing.
Comparing the two standards
For the same large end, EN 10253-1 form 2 and eccentric reducers have the same length as ASME B16.9 reducers: 51 mm at 1", 76 mm at 2", 102 mm at 4", 152 mm at 8". Only the outside diameters change for some sizes, such as 76.1 versus 73.0 mm at 2½".
Specifying a reducer
Large end first, then small end, each with its diameter and wall: 114.3 × 3.6 – 60.3 × 2.9 in EN, 4" × 2" STD in ASME. Add the type (concentric form 1 or 2, eccentric), the grade and the finish.
Dimensions by size
Reducers
Standards
- ASME B16.9: reducers, lengths and tolerances.
- EN 10253-1: concentric reducers form 1 and form 2, eccentric reducers.
Frequently asked questions
How long is a 4" reducer?
102 mm to ASME B16.9 and to EN 10253-1 form 2 or eccentric, whatever the small end. In form 1, 90 to 143 mm depending on the small end.
What is the difference between form 1 and form 2?
Form 1 is conical and its length varies with the size step; form 2 has a fixed length for a given large end.
Is an eccentric reducer as long as a concentric one?
Yes for the same large end, to ASME B16.9 as to EN 10253-1 form 2.
Other charts
Butt-weld elbow dimensions: ASME B16.9 and EN 10253-1An elbow’s take-off is its centre-to-end: from the bend centre to the plane of the end.
Butt-weld equal tee dimensions: ASME B16.9 and EN 10253-1On an equal tee, the centre-to-end is the same on all three outlets.
Butt-weld cap and dished end dimensions: ASME B16.9 and EN 10253-1ASME B16.9 caps measure 25 mm (½") to 102 mm (8"); above a limiting wall the length becomes E1.