Detailed Product Description
Application & Compliance
The ASTM A182 F9 WNRF flange is specified for piping connections on shell and tube heat exchangers, pressure vessels, and heater outlets operating in the hottest and most sulfur-rich refinery streams, where lower-chrome grades such as F5 or F11 suffer excessive sulfidation and wall loss. In hydrocracker and hydrodesulfurizer circuits, the 9Cr-1Mo chemistry resists high-temperature hydrogen attack (HTHA) and sulfidic corrosion that rapidly degrade carbon steel and 5Cr alloys. In power plant steam systems, the flange maintains creep strength and oxidation resistance up to approximately 650°C. When paired with an ASTM A335 P9 pipe and welded to the shell or channel of a heat exchanger, the long tapered hub of the WNRF design transfers pipe loads smoothly into the flange, reducing stress concentration at the shell-to-flange junction.
The flange is manufactured and tested in accordance with ASTM A182 / ASME SA182 for forged or rolled alloy-steel pipe flanges, and dimensioned to ASME B16.5 for sizes NPS 1/2" through 24" in Classes 150 through 2500. Certification is available per EN 10204 Type 3.1 or 3.2. Third-party inspection and NACE MR0175 compliance for sour service are available upon request.
Problem Solved
F9 flanges address the sulfidation and creep limitations of lower-chrome alloys. The 8.0–10.0% chromium content in F9 roughly doubles the sulfidation resistance margin compared with 5Cr (F5) grades, making it the highest-chromium member of the standard chrome-moly family before stainless steels are required. This directly extends service life in refinery heater outlets and hydroprocessing hot sections where hot H2S attack thins pipe walls and causes premature flange failure. The 0.90–1.10% molybdenum content provides the creep strength needed to carry pressure loads at metal temperatures approaching 600°C, where F11 and F22 flanges would deform under sustained stress. The long tapered hub of the WNRF design also solves the stress concentration problem inherent in slip-on and lap-joint flanges by providing a gradual transition from pipe thickness to flange thickness, and the butt-weld joint allows full radiography of the critical connection.
Material Specification – ASTM A182 F9
ASTM A182 F9 is a forged 9Cr-1Mo chrome-moly alloy steel. The grade is the highest-chromium member of the standard non-vanadium chrome-moly family and is an air-hardening alloy requiring preheat and mandatory post-weld heat treatment (PWHT) after welding.
Chemical Composition (per ASTM A182 / ASME SA182 F9)
| Element | Requirement (%) |
|---|---|
| Carbon (C) | 0.15 max |
| Manganese (Mn) | 0.30 – 0.60 |
| Phosphorus (P) | 0.030 max |
| Sulfur (S) | 0.030 max |
| Silicon (Si) | 0.50 – 1.00 |
| Chromium (Cr) | 8.00 – 10.00 |
| Molybdenum (Mo) | 0.90 – 1.10 |
Mechanical Properties (per ASTM A182 / ASME SA182 F9)
| Property | Requirement (min) |
|---|---|
| Tensile Strength | 585 MPa (85 ksi) |
| Yield Strength (0.2% offset) | 380 MPa (55 ksi) |
| Elongation in 50 mm | 20% |
| Reduction of Area | 40% |
| Hardness (HBW) | 179 – 217 |
Heat Treatment
F9 flanges are supplied in the normalized and tempered or annealed condition. Normalizing is performed in the range of 950–1050°C, followed by tempering at 730–790°C. The hardness range of 179–217 HBW verifies that the specified heat treatment has been performed and that the flange meets NACE sour-service hardness limits when required. Welding of F9 to P9 pipe requires preheat and mandatory post-weld heat treatment to temper the air-hardened heat-affected zone.
Flange Dimensions and Tolerances (per ASME B16.5)
The WNRF flange is dimensioned to ASME B16.5 for NPS 1/2" through 24", Classes 150 through 2500. The raised face (RF) height is 1.5 mm up to Class 300 and 6.4 mm from Class 400 upward; the RF diameter tolerance is ±0.8 mm for 1.6 mm raised face and ±0.5 mm for 6.4 mm raised face. The flange outside diameter and bolt circle dimensions follow the standard ASME B16.5 tables for each size and class. The bore is matched to the specified pipe schedule (e.g., Schedule 80 for a 3-1/2" NPS Class 300 flange), ensuring a flush internal transition and a fully radiographable butt weld.
Designs of flanges:
A wide variety of flange designs are available. They are available in various shapes and sizes. Some of the popular designs are as follows:
Custom shapes and sizes are also manufactured by numerous manufacturers. Various pipe flanges include machining details such as gasket surfaces, facing details, non-standard drilling, bevel and radius edges, o-ring grooves and raised or recessed faces. Some typical designs on flanges faces are shown below.
| Raised Fase | Chamfer |
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| Counter Bore | O-Ring Groove |
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| Radius |
Size Range and Pressure Classes
Available sizes are NPS 1/2" through 24" under ASME B16.5. Larger sizes per ASME B16.47 are available upon request. Pressure classes include 150, 300, 400, 600, 900, 1500, and 2500. European PN ratings (PN 6 to PN 400) and DIN/EN dimensional patterns are available when specified in the purchase order.
Testing and Quality Control
Each flange is subjected to the following examinations and tests:
Chemical Composition Analysis – Verification of chromium, molybdenum, carbon, and residual elements.
Mechanical Testing – Tensile strength, yield strength, elongation, reduction of area, and hardness.
Hardness Testing – Verification of the 179–217 HBW range to confirm heat treatment and NACE compliance.
Non-Destructive Examination (NDE) – Ultrasonic Testing (UT) for internal soundness, Magnetic Particle Testing (MT) or Liquid Penetrant Testing (PT) for surface defects, and Positive Material Identification (PMI) for grade verification.
Dimensional Inspection – Verification of flange OD, bolt circle, raised face diameter and height, bore, hub dimensions, and weld bevel geometry per ASME B16.5.
Hydrostatic Test – When specified by the purchase order.
Documentation
Each shipment is supplied with Mill Test Certificates (EN 10204 Type 3.1 or 3.2), heat treatment records, hardness test reports, NDE reports (UT, MT/PT, PMI), dimensional inspection reports, and material traceability records.
For a rapid quotation on ASTM A182 F9 WNRF Flange, please provide the following information:
Quantity (number of pieces)
Nominal pipe size (NPS) and schedule / wall thickness
Pressure class (150 through 2500)
Facing type (RF, FF, or RTJ)
Bore match to pipe schedule
NACE MR0175 requirement (if applicable)
Delivery period required
