IBR Approved · Alloy Steel (CrMo)
ASTM A234 WP9 Buttweld Pipe Fittings
9Cr-1Mo chromium-molybdenum alloy steel fittings for refinery fired heaters and high-temperature hydrogen and sulphidic service. Elbows, tees, reducers and caps to ASME B16.9 / B16.28, IBR approved with Form IV (Part D) (formerly Form III-C), EN 10204 3.1 / 3.2 traceable.
Where WP9 Is Used
- ✓ Hydrogen reformer and high-temperature process lines
- ✓ Refinery heater and transfer piping in severe sulphur service
- ✓ Elevated-temperature lines where WP5 is not enough
WP9 Compared With Related Grades
How to Specify WP9 Fittings on a Purchase Order
A complete order line avoids clarification rounds. Example:
Equal tee, 6" SCH 80, ASTM A234 WP9, ASME B16.9, normalised and tempered, PMI, EN 10204 3.1
- ✓ Ask for PMI that distinguishes WP9 from WP91
- ✓ Ask for the heat treatment record and hardness results
- ✓ Add 3.2 witnessed inspection if your specification requires it
Grade Overview
ASTM / ASME A234 WP9 is the original 9Cr-1Mo chromium-molybdenum alloy steel. Its 9% chromium content places it high on the API 941 Nelson curves for resistance to high-temperature hydrogen attack (HTHA) and gives strong resistance to sulphidic corrosion — the standard grade for refinery fired heater coils and hot hydrogen/sulphur service beyond the range of WP5.
WP9 is not interchangeable with WP91 — it contains no vanadium, niobium or nitrogen and has lower creep strength. WP9 fittings are supplied IBR approved with Form IV (Part D); the EN counterpart is X11CrMo9-1 (material number 1.7386).
PWHT is mandatory
All WP9 welds require post-weld heat treatment, typically 730–790°C, to temper the hardened heat-affected zone and avoid hydrogen cracking. Post-PWHT hardness and the time-temperature record are reported on the EN 10204 3.1 certificate. Filler metal: ER80S-B8. ASME P-No. 5B.
Chemical Composition — A234 WP9
| Element | Requirement | Note |
|---|---|---|
| Carbon (C) | ≤ 0.15% | — |
| Chromium (Cr) | 8.0 – 10.0% | HTHA / sulphidic resistance |
| Molybdenum (Mo) | 0.90 – 1.10% | Creep resistance |
| Mn / Si | Mn 0.30–0.60, Si 0.25–1.00 | — |
| P / S | ≤ 0.030% each | Impurity limits |
Mechanical Properties — A234 WP9 (Class 1)
| Property | Requirement |
|---|---|
| Tensile Strength | 415 – 585 MPa (60 – 85 ksi) |
| Yield Strength (min) | 205 MPa (30 ksi) |
| Elongation (min) | ≥ 20% (per specification formula) |
| Heat Treatment | Annealed or normalised & tempered; PWHT after welding |
Equivalent Grades
| Product Form | Specification |
|---|---|
| Buttweld fittings | ASTM / ASME A234 WP9 |
| Seamless pipe | ASTM A335 P9 |
| Forgings / flanges | ASTM A182 F9 |
| EN designation | X11CrMo9-1 (W.Nr. 1.7386) |
EN 10253 equivalent: see WP9 pipe fittings on arshyapipefittings.com, and the European grade EN 1.7386 (X11CrMo9-1).
Fitting Types Available in WP9
- Elbows — 45° / 90° / 180°, LR & SR
- Tees — equal & reducing
- Reducers — concentric & eccentric
- Caps — buttweld end closures
Related grades: WP5 · WP91 · WP22 · IBR Form IV (Part D) guide · IBR grades list
Testing & Inspection — WP9
- Chemical analysis of each heat, confirming 9Cr-1Mo.
- Tensile and hardness tests to ASTM A234 for the class ordered (Class 1 shown above; Class 3 on request).
- Positive material identification (PMI) — important because plain 9Cr-1Mo (WP9) and modified 9Cr-1Mo (WP91) look identical but are not interchangeable.
- Dimensional and visual inspection to ASME B16.9; NDE (MT / UT / RT) as specified in your purchase order.
Dimensions & Size Range — ASME B16.9
WP9 fittings are made to ASME B16.9 (long-radius) and ASME B16.28 (short-radius elbows) dimensions, from 1/2" to 48" NB and above, in schedules SCH 20 to SCH 160 / XXS. Wall thickness matches the connecting pipe schedule. Centre-to-end dimensions for the most-ordered sizes:
| NPS | Outside diameter (mm) | 90° LR elbow “A” (mm) | 45° LR elbow “B” (mm) | Equal tee “C” (mm) |
|---|---|---|---|---|
| 1/2" | 21.3 | 38 | 16 | 25 |
| 1" | 33.4 | 38 | 22 | 38 |
| 2" | 60.3 | 76 | 35 | 64 |
| 3" | 88.9 | 114 | 51 | 86 |
| 4" | 114.3 | 152 | 64 | 105 |
| 6" | 168.3 | 229 | 95 | 143 |
| 8" | 219.1 | 305 | 127 | 178 |
| 10" | 273.1 | 381 | 159 | 216 |
| 12" | 323.9 | 457 | 190 | 254 |
| 16" | 406.4 | 610 | 254 | 305 |
| 20" | 508.0 | 762 | 318 | 381 |
| 24" | 610.0 | 914 | 381 | 432 |
Long-radius elbows have a centre-line radius of 1.5 × NPS; short-radius (ASME B16.28) 1.0 × NPS. Full tables to NPS 48, reducing tees, reducers and caps are available with every quotation. For EN 10253 dimensions see arshyapipefittings.com.
Export Documentation & Packing
We ship WP9 fittings to projects outside India with the documents EPC contractors and inspection agencies expect:
- Mill test certificate — EN 10204 3.1 as standard; 3.2 with third-party witness
- Third-party inspection — Bureau Veritas, TÜV, Lloyd’s Register, SGS, DNV or the client’s own inspector
- IBR Form IV (Part D) — for boiler piping on Indian Boiler Regulations projects
- Traceability — every fitting marked with grade, size, schedule and heat number, matching the certificate
- Packing — seaworthy wooden cases or pallets, bevel ends protected with end caps
- Shipping documents — commercial invoice, packing list and certificate of origin; FOB, CFR or CIF terms
Send your BOQ through the RFQ form (Excel or PDF attachments accepted) or on WhatsApp — quotations are usually issued within 24 hours.
WP9 Fittings — Frequently Asked Questions
Is WP9 the same as WP91?
No. WP9 is plain 9Cr-1Mo; WP91 is modified 9Cr-1Mo with vanadium, niobium and nitrogen, giving much higher creep strength and requiring stricter heat treatment. Specify the exact grade. More: P9 vs P91 explained.
Where are WP9 fittings used?
Refinery heater piping and hot process lines where higher chromium is needed for resistance to sulphidation and oxidation than WP5 offers.
What PWHT does WP9 need?
Post-weld heat treatment at 730–790°C is mandatory after welding.