SS 321 ReducerASTM A403 · ASME B16.9 · Manufacturer, stockist & exporter, India
AISI 321 · UNS S32100
An SS 321 reducer is a fitting that joins two pipes of different sizes, made from SS 321 to ASTM A403 WP321. Concentric reducers keep the centreline in line and suit vertical lines. Eccentric reducers keep one side flat — flat on top at pump suctions to avoid air pockets, flat on the bottom in pipe racks.
- ASTM A403
- ASME B16.9
- EN 10204 3.1 / 3.2
- Export packing
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
What is an SS 321 Reducer?
- What it is
- A fitting that joins two pipes of different sizes
- Material
- ASTM A403 WP321
- Dimensions
- ASME B16.9 · MSS SP-43
- Grade
- SS 321 · UNS S32100
- Best at
- High-temperature service between 425 and 815 °C
SS 321 Reducer Specification
| Product | SS 321 Reducer |
|---|---|
| Material standard | ASTM A403 WP321 |
| Dimensional standard | ASME B16.9 · MSS SP-43 |
| Sizes | ½" – 48" |
| Wall / class | Sch 5S – XXS, to match pipe |
| Ends | Bevelled to ASME B16.25 |
| Testing | PMI · dimensional · NDT and IGC on request |
| Documents | EN 10204 3.1 · 3.2 with third-party inspection |
When to Choose a Reducer
Concentric reducers keep the centreline in line and suit vertical lines. Eccentric reducers keep one side flat — flat on top at pump suctions to avoid air pockets, flat on the bottom in pipe racks.
- Concentric and eccentric
- Flat-top on pump suction
- Seamless or welded
SS 321 Reducer Chemical Composition
| Element | Weight % |
|---|---|
| Chromium | 17.0 – 19.0 |
| Nickel | 9.0 – 12.0 |
| Titanium | 5 × (C + N) min, 0.70 max |
| Carbon | 0.08 max |
| Manganese | 2.00 max |
| Silicon | 0.75 max |
| Nitrogen | 0.10 max |
| Phosphorus | 0.045 max |
SS 321 Reducer Mechanical Properties
| Annealed plate & sheet | Value |
|---|---|
| Tensile strength | 515 MPa · 75 ksi |
| Yield strength 0.2% | 205 MPa · 30 ksi |
| Elongation | 40% |
| Hardness | 217 HB max |
Full chemistry, properties and equivalents are on the SS 321 grade page.
Other SS 321 pipe fittings
SS 321 Reducer dimensions — ASME B16.9
Values in mm, the same for every material; the wall thickness matches the pipe schedule.
| NPS | OD | Reducer length H |
|---|---|---|
| ½" | 21.3 | — |
| ¾" | 26.7 | 38 |
| 1" | 33.4 | 51 |
| 1½" | 48.3 | 64 |
| 2" | 60.3 | 76 |
| 3" | 88.9 | 89 |
| 4" | 114.3 | 102 |
| 6" | 168.3 | 140 |
| 8" | 219.1 | 152 |
| 10" | 273.1 | 178 |
| 12" | 323.9 | 203 |
| 16" | 406.4 | 356 |
| 20" | 508.0 | 508 |
| 24" | 610.0 | 508 |
Full chart: ASME B16.9 fitting dimensions.
SS 321 Reducer — questions buyers ask
Why use an eccentric reducer at a pump suction?
Installed flat side up, it prevents air pockets that can cause cavitation.
Which standard covers SS 321 reducers?
The material is ASTM A403 WP321; dimensions follow ASME B16.9 · MSS SP-43. Always state both on your purchase order, with the edition if your project specifies one.
What decides the price of a SS 321 reducer?
The alloy price, the size and schedule or class, quantity, and the testing and documents required. Send your list and we quote the same working day.
What documents do you supply?
EN 10204 3.1 mill certificates as standard, 3.2 with third-party inspection on request, plus dimensional and PMI reports.
Sources: the ASTM / ASME specifications named on this page and producer datasheets · Last updated October 2026