What Are API Flanges?
API flanges are high-performance piping components designed to meet American Petroleum Institute (API) standards, ensuring reliability in oil & gas, petrochemical, and high-pressure industrial applications. These flanges are engineered for extreme conditions, including high pressure, corrosive environments, and critical sealing requirements.
Key Features of API Flanges
✔ High-Pressure Ratings – From 2,000 psi to 20,000 psi (API 6A)
✔ Robust Materials – Carbon steel (A105), stainless steel (F316), duplex (F51)
✔ Strict Quality Control – API standards ensure compliance with NACE, ASME, and ISO
✔ Wide Range of Types – Welding Neck (WN), Blind (BL), Slip-On (SO), Ring-Type Joint (RTJ)
API Flange Standards and Types
1. API 6A Flanges (Wellhead & Christmas Tree Equipment)
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Used in oil wells, BOPs (Blowout Preventers), and valves
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Pressure Classes: 2,000 psi, 3,000 psi, 5,000 psi, 10,000 psi, 15,000 psi, 20,000 psi
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Common Sizes: 2″ to 30″
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Face Types:
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RF (Raised Face) – Standard sealing
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RTJ (Ring-Type Joint) – High-pressure metal-to-metal seal
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2. API 605 Flanges (Large-Diameter Compact Flanges)
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Used in pipelines above 24″
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Pressure Classes: 150 psi to 900 psi
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Face Types: Flat Face (FF), RTJ
3. API 6BX Flanges (High-Pressure Well Service)
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Extreme pressure resistance (up to 20,000 psi)
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Hub & clamp-style connections
API Flange Charts & Dimensions
API 6A Flange Dimensions (Example: Class 5000 psi, NPS 4″)
| Parameter | Metric (mm) | Imperial (inches) |
|---|---|---|
| Flange OD | 298.5 | 11.75 |
| Bolt Circle Diam. | 241.3 | 9.50 |
| Bolt Holes (Qty) | 8 | 8 |
| Bolt Hole Diam. | 28.6 | 1.125 |
| Hub Thickness | 50.8 | 2.00 |
API 605 Flange Dimensions (Example: Class 300, NPS 26″)
| Parameter | Metric (mm) | Imperial (inches) |
|---|---|---|
| Flange OD | 1003 | 39.50 |
| Bolt Circle Diam. | 965 | 38.00 |
| Bolt Holes (Qty) | 40 | 40 |
| Bolt Hole Diam. | 31.8 | 1.25 |
API vs. ASME Flanges: Key Differences
| Feature | API Flanges | ASME Flanges (B16.5/B16.47) |
|---|---|---|
| Application | Oil wells, high-pressure systems | General industrial use |
| Pressure | Up to 20,000 psi | Max 2,500 psi (Class 2500) |
| Sizes | 2″ to 30″ (API 6A) | ½” to 24″ (ASME B16.5) |
| Materials | F51 Duplex, A694 | A105, F304, F316 |
| Sealing | RTJ common | RF (Raised Face) common |
How to Choose the Right API Flange?
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Select the Standard – API 6A (wellheads) or API 605 (pipelines)
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Check Pressure Class – 5K, 10K, 15K, etc.
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Choose Material – Carbon steel, stainless, or duplex
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Verify Dimensions – Match bolt holes, OD, and thickness
Looking for API Flange Suppliers?
✅ High-Quality API 6A & API 605 Flanges
✅ Available in A105, F304, F316, F51 Duplex
✅ Custom Machining & Fast Delivery
📞 Contact Us Today for API Flange Quotes!
📧 Email: [email protected] | 🌐 Website: www.buyflange.com
