SS 347 Reducing FlangeASTM A182 · ASME B16.5 · Manufacturer, trader & exporter, India
AISI 347 · UNS S34700 · RF
An SS 347 reducing flange is a flange with a smaller bore than its outside dimensions, connecting to a smaller pipe, made from SS 347 to ASTM A182 F347. A reducing flange changes pipe size at a flanged joint without a separate reducer, saving space and a weld. Use it where the flow disturbance from a sudden change is acceptable.
- ASTM A182
- ASME B16.5
- EN 10204 3.1 / 3.2
- Export packing
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
What is an SS 347 Reducing Flange?
- What it is
- A flange with a smaller bore than its outside dimensions, connecting to a smaller pipe
- Material
- ASTM A182 F347
- Dimensions
- ASME B16.5
- Grade
- SS 347 · UNS S34700
- Best at
- Welded high-temperature piping in refineries and power plants
SS 347 Reducing Flange Specification
| Product | SS 347 Reducing Flange |
|---|---|
| Material standard | ASTM A182 F347 |
| Dimensional standard | ASME B16.5 |
| Sizes | ½" – 24" (ASME B16.5) · 26" – 60" (ASME B16.47) |
| Pressure class | Class 150, 300, 400, 600, 900, 1500, 2500 · PN 6 – PN 100 |
| Facing | RF · FF · RTJ · tongue & groove |
| Bore | To match pipe schedule (state on order) |
| Testing | PMI (as specified in the PO) · dimensional · NDT and IGC on request |
| Documents | EN 10204 3.1 or 3.2 on request / as specified in the PO |
When to Choose a Reducing Flange
A reducing flange changes pipe size at a flanged joint without a separate reducer, saving space and a weld. Use it where the flow disturbance from a sudden change is acceptable.
- Outside dimensions of the larger size
- Bore / hub for the smaller pipe
- Weld neck, slip-on or threaded styles
More on choosing: Reducing flange guide.
SS 347 Reducing Flange: Why 347 for reducing flanges
A reducing flange changes pipe size at a flanged joint without a separate reducer, saving space and a weld. Use it where the flow disturbance from a sudden change is acceptable. In SS 347, the choice usually comes down to the medium and temperature — the rows here are the points buyers check for this exact combination.
| Why this grade | Stainless flanges are chosen where carbon steel would rust or contaminate the process. SS 347 is picked for welded high-temperature piping in refineries and power plants. |
|---|---|
| Typical service | Refinery hydroprocessing — Reactor effluent piping and exchangers. |
| B16.5 material group | 2.5 |
| Bolting | ASTM A193 B8C studs with A194 8C nuts |
| Welding to carbon steel | ER309L (or E309L electrode) is the usual filler when joining it to carbon steel |
| Matching filler | ER347 (AWS A5.9) |
SS 347 Reducing Flange Chemical Composition
Under technical review for TDS.
| Element | Current requirement |
|---|---|
| Chromium | As specified |
| Nickel | As specified |
| Niobium | As specified |
| Carbon | As specified |
| Manganese | As specified |
| Silicon | As specified |
| Phosphorus | As specified |
| Sulphur | As specified |
Numerical specification requirements are published only after the applicable current standard edition has been verified. Governing specification to be verified: ASTM A240 for UNS S34700.
SS 347 Reducing Flange Mechanical Properties
Under technical review for TDS.
| Property | Current requirement |
|---|---|
| Tensile strength | As specified |
| Yield strength 0.2% | As specified |
| Elongation | As specified |
| Hardness | As specified |
Numerical specification requirements are published only after the applicable current standard edition has been verified. Governing specification and condition to be verified: ASTM A240 for UNS S34700 — Annealed plate & sheet.
Full chemistry, properties and equivalents are on the SS 347 grade page.
Other SS 347 flanges
SS 347 Reducing Flange dimensions — ASME B16.5 Class 150 & 300
Outside diameter, thickness and bolting are set by size and class. Values in mm; thickness excludes the 1.6 mm raised face.
| NPS | Cl 150 OD | Cl 150 thickness | Cl 150 bolt circle | Cl 150 bolts | Cl 300 OD | Cl 300 thickness | Cl 300 bolt circle | Cl 300 bolts |
|---|---|---|---|---|---|---|---|---|
| ½" | 90 | 9.6 | 60.3 | 4 × ½" | 95 | 12.7 | 66.7 | 4 × ½" |
| 1" | 110 | 12.7 | 79.4 | 4 × ½" | 125 | 15.9 | 88.9 | 4 × ⅝" |
| 1½" | 125 | 15.9 | 98.4 | 4 × ½" | 155 | 19.1 | 114.3 | 4 × ¾" |
| 2" | 150 | 17.5 | 120.7 | 4 × ⅝" | 165 | 20.7 | 127.0 | 8 × ⅝" |
| 3" | 190 | 22.3 | 152.4 | 4 × ⅝" | 210 | 27.0 | 168.3 | 8 × ¾" |
| 4" | 230 | 22.3 | 190.5 | 8 × ⅝" | 255 | 30.2 | 200.0 | 8 × ¾" |
| 6" | 280 | 23.9 | 241.3 | 8 × ¾" | 320 | 35.0 | 269.9 | 12 × ¾" |
| 8" | 345 | 27.0 | 298.5 | 8 × ¾" | 380 | 39.7 | 330.2 | 12 × ⅞" |
| 10" | 405 | 28.6 | 362.0 | 12 × ⅞" | 445 | 46.1 | 387.4 | 16 × 1" |
| 12" | 485 | 30.2 | 431.8 | 12 × ⅞" | 520 | 49.3 | 450.8 | 16 × 1⅛" |
Full chart: ASME B16.5 flange dimensions.
SS 347 Reducing Flange — questions buyers ask
Is a reducing flange better than a reducer plus flange?
It saves length and a weld, but a buttweld reducer gives smoother flow. Choose by space and process needs.
What pressure rating does a SS 347 reducing flange have?
It depends on class and temperature. SS 347 forgings are in ASME B16.5 material group 2.5; read your class column in that group's table at the design temperature.
Can SS 347 reducing flanges be welded to carbon steel?
Yes — ER309L (or E309L electrode) is the usual filler when joining it to carbon steel.
Which standard covers SS 347 reducing flanges?
The material is ASTM A182 F347; dimensions follow ASME B16.5. Always state both on your purchase order, with the edition if your project specifies one.
What decides the price of a SS 347 reducing flange?
The alloy price, the size and pressure 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 or 3.2 certificates available on request / as specified in the PO; dimensional reports as required. PMI can be arranged depending on product and requirements, as specified in the PO.
Sources: the ASTM / ASME specifications named on this page and producer datasheets · Last updated October 2026