Tubewell Steel & Engg. Co. is a leading manufacturer and stockist specializing in Alloy Steel Pipes, Tubes, Fittings and Flanges for critical industrial applications.
9% Chromium – 1% Molybdenum – Vanadium creep-strength-enhanced buttweld fittings for supercritical and ultra-supercritical power plant piping.
Tubewell Steel & Engg. Co. is a trusted Mumbai manufacturer, stockist and supplier of ASTM A234 WP91 fittings – the creep-strength-enhanced ferritic (CSEF) grade that powers modern supercritical boilers. Our WP91 elbows, tees, reducers and caps are normalized and tempered, fully traceable and matched to A335 P91 pipe.
The high-strength fitting grade for supercritical steam service
ASTM A234 WP91 is a modified 9Cr-1Mo ferritic alloy steel micro-alloyed with vanadium (0.18–0.25%), niobium (0.06–0.10%) and nitrogen (0.03–0.07%). After normalizing and tempering, these elements form fine, stable carbonitride precipitates in a tempered martensitic matrix, giving WP91 a minimum tensile strength of 620 MPa and creep-rupture strength far above WP22. This allows thinner walls, lower weight and reduced thermal stresses in main steam and hot reheat piping operating up to about 600–650°C.
Because the properties of P91 depend on correct heat treatment, every WP91 fitting we supply is normalized at 1040–1080°C and tempered at 730–800°C, then hardness-checked before dispatch. We offer seamless and welded (WPW91) elbows, tees, reducers, caps and stub ends to ASME B16.9 / B16.28, with EN 10204 3.1 / 3.2 certificates, IBR documentation and third-party inspection on request.
Standard supply range for ASTM A234 WP91 fittings
| Parameter | Details |
|---|---|
| Standard | ASTM A234, ASME SA234 |
| Grade | WP91 Type 1 (UNS K90901); WPW91 for welded; Type 2 on request |
| Dimension Standard | ASME B16.9, ASME B16.28, MSS SP-43 |
| Size (NB) | Seamless: 1/2" NB to 24" NB; Welded: 2" NB to 48" NB |
| Wall Thickness | SCH 10, 20, 40, STD, 60, 80, XS, 100, 120, 140, 160, XXS |
| Elbows | 45°, 90° and 180° – Long Radius (1.5D) and Short Radius (1D) |
| Bending Radius | R = 1D, 1.5D, 2D, 3D, 5D and custom induction bends |
| Tees & Crosses | Equal Tee, Reducing Tee, Equal Cross, Reducing Cross |
| Reducers | Concentric Reducer, Eccentric Reducer |
| Other Types | Pipe Cap, Stub End (Long / Short pattern), Return Bend |
| Manufacturing | Seamless (WP) and Welded (WPW) – hot formed |
| Heat Treatment | Normalized 1040–1080°C + Tempered 730–800°C |
| Ends | Bevelled Ends as per ASME B16.25 |
| Certificates | EN 10204 3.1 / 3.2, IBR, TPI Reports |
International equivalents of A234 WP91
| Grade | ASTM / ASME | UNS | EN | W.Nr. | JIS | Matching Pipe / Forging |
|---|---|---|---|---|---|---|
| WP91 | A234 / SA234 WP91 | K90901 | X10CrMoVNb9-1 | 1.4903 | STPA 28 | A335 P91 / A182 F91 |
Weight %, as per ASTM A234 (WP91 Type 1)
| Grade | C | Mn | P | S | Si | Cr | Mo | Ni | V | Nb | N | Al | Ti / Zr |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| A234 WP91 | 0.08 – 0.12 | 0.30 – 0.60 | 0.020 max | 0.010 max | 0.20 – 0.50 | 8.0 – 9.5 | 0.85 – 1.05 | 0.40 max | 0.18 – 0.25 | 0.06 – 0.10 | 0.03 – 0.07 | 0.02 max | 0.01 max each |
Values at room temperature as per ASTM A234
| Grade | Tensile Strength | Yield Strength (min) | Elongation (min) | Hardness (max) |
|---|---|---|---|---|
| A234 WP91 | 620 – 840 MPa (90 – 120 ksi) | 415 MPa (60 ksi) | 20% | 248 HB |
Typical values (for reference)
| Property | Metric | Imperial |
|---|---|---|
| Density | 7.77 g/cm³ | 0.281 lb/in³ |
| Melting Range | 1420 – 1500 °C | 2590 – 2730 °F |
| Modulus of Elasticity | 218 GPa | 31.6 × 10³ ksi |
| Thermal Conductivity (100°C) | 26 W/m·K | 15.0 BTU/h·ft·°F |
| Mean Thermal Expansion (20–300°C) | 11.4 µm/m·°C | 6.3 µin/in·°F |
| Specific Heat | 0.46 J/g·°C | 0.11 BTU/lb·°F |
| Max. Service Temperature | ≈ 650 °C | ≈ 1200 °F |
As per ASME B16.9 – center-to-end / end-to-end dimensions in mm
| NPS | OD at Bevel | 90° LR Elbow (A) | 45° LR Elbow (B) | Tee (C / M) | 180° LR Return (O) | Cap (E) | Reducer (H) |
|---|---|---|---|---|---|---|---|
| 1/2" | 21.3 | 38 | 16 | 25 | 76 | 25 | – |
| 3/4" | 26.7 | 38 | 19 | 29 | 76 | 25 | 38 |
| 1" | 33.4 | 38 | 22 | 38 | 76 | 38 | 51 |
| 1 1/4" | 42.2 | 48 | 25 | 48 | 95 | 38 | 51 |
| 1 1/2" | 48.3 | 57 | 29 | 57 | 114 | 38 | 64 |
| 2" | 60.3 | 76 | 35 | 64 | 152 | 38 | 76 |
| 2 1/2" | 73.0 | 95 | 44 | 76 | 190 | 38 | 89 |
| 3" | 88.9 | 114 | 51 | 86 | 229 | 51 | 89 |
| 4" | 114.3 | 152 | 64 | 105 | 305 | 64 | 102 |
| 5" | 141.3 | 190 | 79 | 124 | 381 | 76 | 127 |
| 6" | 168.3 | 229 | 95 | 143 | 457 | 89 | 140 |
| 8" | 219.1 | 305 | 127 | 178 | 610 | 102 | 152 |
| 10" | 273.1 | 381 | 159 | 216 | 762 | 127 | 178 |
| 12" | 323.9 | 457 | 190 | 254 | 914 | 152 | 203 |
| 14" | 355.6 | 533 | 222 | 279 | 1067 | 165 | 330 |
| 16" | 406.4 | 610 | 254 | 305 | 1219 | 178 | 356 |
| 18" | 457.0 | 686 | 286 | 343 | 1372 | 203 | 381 |
| 20" | 508.0 | 762 | 318 | 381 | 1524 | 229 | 508 |
| 22" | 559.0 | 838 | 343 | 419 | – | 254 | 508 |
| 24" | 610.0 | 914 | 381 | 432 | 1829 | 267 | 508 |
All dimensions in mm. A, B, C/M = center-to-end; O = center-to-center; E = cap length (for standard wall); H = reducer end-to-end. Wall thickness is matched to the specified pipe schedule.
Where ASTM A234 WP91 fittings are used
Main steam and hot reheat piping in supercritical and USC units.
Superheater and reheater outlet headers and links.
High-pressure superheater piping in combined-cycle plants.
High-temperature heater and hydroprocessing piping.
Steam generator and high-temperature process systems.
Cracker and reformer piping requiring high creep strength.
Quality you can verify on every heat
Large inventory for fast dispatch
MTC EN 10204 3.1 / 3.2
Positive material identification
Pan-India & export shipping
Quick answers about A234 WP91 fittings
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