ASTM A335 P11 Reducing FlangeASTM A182 · ASME B16.5 · Manufacturer, stockist & exporter, India
SA-335 P11 · 1¼Cr-½Mo alloy pipe · RF
An ASTM A335 P11 reducing flange is a flange with a smaller bore than its outside dimensions, connecting to a smaller pipe, for use with ASTM A335 P11 pipe. ASTM A335 P11 itself is a pipe or plate specification, so the matching reducing flange is made to ASTM A182 F11 — which is what we supply for P11 lines. 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 ASTM A335 P11 Reducing Flange?
- What it is
- A flange with a smaller bore than its outside dimensions, connecting to a smaller pipe
- Material
- ASTM A182 F11
- Dimensions
- ASME B16.5
- Grade
- ASTM A335 P11
- Best at
- Steam and hot-oil piping up to about 550 °C
ASTM A335 P11 Reducing Flange Specification
| Product | ASTM A335 P11 Reducing Flange |
|---|---|
| Material standard | ASTM A182 F11 |
| 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 | Chemical & mechanical per heat · NDT · impact where specified |
| Documents | EN 10204 3.1 · 3.2 with third-party inspection |
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.
ASTM A335 P11 Reducing Flange: Why P11 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 ASTM A335 P11, 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 | Carbon and low-alloy flanges carry most utility, hydrocarbon and high-temperature service. ASTM A335 P11 is picked for steam and hot-oil piping up to about 550 °C. |
|---|---|
| Typical service | Power plants — Main steam and reheat lines. |
| B16.5 material group | 1.9 — Group 1.9 applies to A182 F11 Class 2. Chrome-moly welds usually need PWHT; the code sets thickness exemptions. |
| Bolting | ASTM A193 B7 studs with A194 2H nuts; B16 with Gr 4 or 7 nuts where the temperature calls for it |
| Welding to carbon steel | Matching carbon or low-alloy filler is used; joints to stainless need ER309L |
| Matching filler | ER80S-B2 / E8018-B2 |
ASTM A335 P11 Reducing Flange Chemical Composition
| Element | Weight % |
|---|---|
| Chromium | 1.00 – 1.50 |
| Molybdenum | 0.44 – 0.65 |
| Carbon | 0.05 – 0.15 |
| Manganese | 0.30 – 0.60 |
| Silicon | 0.50 – 1.00 |
| Phosphorus | 0.025 max |
| Sulphur | 0.025 max |
ASTM A335 P11 Reducing Flange Mechanical Properties
| Minimum values | Value |
|---|---|
| Tensile strength | 415 MPa · 60 ksi |
| Yield strength 0.2% | 205 MPa · 30 ksi |
| Elongation | 30% |
Full chemistry, properties and equivalents are on the ASTM A335 P11 grade page.
Other ASTM A335 P11 flanges
ASTM A335 P11 Reducing Flanges for export
FOB / CIF · Nhava Sheva (JNPT), MumbaiASTM A335 P11 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.
ASTM A335 P11 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 ASTM A335 P11 reducing flange have?
It depends on class and temperature. ASTM A335 P11 forgings are in ASME B16.5 material group 1.9; read your class column in that group's table at the design temperature.
Can ASTM A335 P11 reducing flanges be welded to carbon steel?
Yes — matching carbon or low-alloy filler is used; joints to stainless need ER309L.
Which standard covers ASTM A335 P11 reducing flanges?
The material is ASTM A182 F11; 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 ASTM A335 P11 reducing flange?
The steel 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 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