DIN flanges offer metric dimensions, bolt patterns, and pressure ratings for reliable connections in piping systems and industrial applications.
Flat Face (FF) flanges feature a smooth, flat sealing surface that allows the gasket to cover the entire contact area. This design ensures even pressure distribution across the joint and helps protect brittle materials, such as cast iron or plastic, from cracking under bolt stress.
FF flanges are commonly used in lower temperature/lower pressure piping systems (up to 300 psi), including water treatment plants, pump suctions, and general utility lines. While not suited for high-pressure service (above 300 psi), they provide reliable sealing performance and long-term durability in the right applications.
1. ANSI/ASME B16.5 — ½” to 24”, covers dimensions, pressure classes, and flat face details.
2. ANSI/ASME B16.47 — 26” to 60”, large-diameter flat face flanges for pipelines.
3. AWWA C207 — Covers steel flanges for waterworks service.
4. AWWA C228 — Covers stainless steel flanges for waterworks service.
5. DIN EN 1092-1:2007 — flanges manufactured to the Deutsches Institut für Normung (DIN) specification
See standards for pressure ratings
Flat-face (FF) flanges have a single-plane face, ideal for pressure systems (up to 300 psi) or cast iron connections.
Some flanges feature double-drilled patterns, allowing compatibility with multiple standards, ensuring flexibility for various piping systems and simplifying installation across applications.
Carbon Steel: ASTM A105, ASTM A350 LF2, ASTM A694
Stainless Steel: ASTM A182 (Grades 304, 304L, 316, 316L, duplex)
Alloy Steels: ASTM A182 F11, F22, F91
Other Options: ASTM A36 plate, nickel alloys, copper alloys for specialty service
Flange faces determine how a gasket seals between two connected flanges. The flange face (the side connected to another flange) is opposite the hub (the side connected to the pipe).
Raised Face (RF) flanges have a protruding surface area that concentrates the gasket load, which makes them ideal for all pressure systems (up to 2500 psi).
AWWA standards set clear guidelines for flange dimensions, materials, and production and ensure reliable connections and leak-free performance.
ASME B16.5 and B16.47 standards cover flange dimensions, pressure classes, and materials, ensuring compatibility across a wide range of piping systems.
Widely used in AWWA C207/C228 waterworks flanges, FF flanges connect pumps, valves, and pipelines in potable and wastewater systems where pressures are relatively low.
Common in building services for chilled water, heating loops, and plumbing connections, where cast iron equipment (pumps, valves) is standard and requires flat face mating.
Often specified in sprinkler and hydrant connections, FF flanges ensure reliable, low-pressure sealing with ductile iron pipe and fittings.
Used on seawater lines, ballast systems, and chemical handling systems, where a broad sealing area with soft full-face gaskets helps resist leaks under corrosive conditions.
FF flanges are ideal for fiberglass, PVC, or HDPE piping, as they spread gasket compression evenly and prevent stress concentrations that could damage non-metallic materials.
Less common in ff form but available when precise alignment is needed. The tapered hub reduces stress, making them reliable for critical joints.
Connect to threaded pipes without welding. Useful for low-pressure, non-critical applications or where welding is impractical.
Flat face flanges are used to reduce bending stress on brittle materials like cast iron, fiberglass, or PVC. They provide a broad, even surface that distributes bolting force evenly across the gasket, preventing cracks or warping. They are most common in low-pressure, low-temperature systems such as water treatment, HVAC, and plumbing.
A flat face flange has the gasket seating surface flush with the bolt circle, requiring a full-face gasket.
A raised face flange has a small raised area (typically 1/16″–1/4″) that concentrates bolt load on a smaller gasket area, improving sealing for higher-pressure service. Flat face flanges are better suited for low-pressure applications where equipment protection is critical.
Only a full-face gasket should be used. It covers the entire flange surface from the inside bore to the outer edge, ensuring even compression. These are typically non-metallic (rubber, fiber, PTFE).
No. Flat face flanges should not be bolted directly to raised face flanges. ASME B31.1 (Power Piping Code) specifies that when connecting flat face cast iron flanges to steel flanges, the raised face must be removed or a full-face gasket must be used. This prevents bending stresses that could crack brittle cast iron.
To order FF flanges from API International, determine your required pipe size, pressure class, material, and any special standards (such as ANSI/ASME B16.5). Contact API International’s experienced team and we will help you select the right flange for your application.
• Custom Bolt Holes, Overbore, Counterbore, Tapped, Welds, O-ring Grooves, Threads, Special Serrations, Bevels, Chamfers
• Metric Parallel, Metric Tapered, Parallel (BSPP), Taper Thread (BSPT), UN/UNF/UNC Thread, NPT (National Pipe Thread)
• MWD
• Contact API’s engineering department for exact specifications and tolerances.
Plastic: Delrin, POM, Lexan, Nylon 66, Nylon 6, PEEK, PP, PE, Acetal
Rubber: EPDM, Neoprene, Buna-N, Viton
Aluminum: A2011, A2024, A2017, A5052, A5056, A6061, A6063, A6463, A6082, A7075
Copper: 3600, 3604, 3771
Titanium: 1-28
Steel Series:
• Ductile Iron: ASTM A536
• Carbon/Mild Steel: A105, A36, A516-70, A572-50, etc.
• Stainless Steel:
- 300 Series – 303, 304, 304L, 316, 316L
- 400 Series – 420J2, 430, 434, 442
Special Metals: Hastelloy, Inconel, Incoloy, Duplex 2205, Super Duplex 2507, Chrome Steel, alloys, or their equivalents
Stock Finish, Spiral Serrated (Phonographic), Concentric Serrated, Smooth Finish, Cold Water Finish, MWD, Phonographic
Dipped, Nickel Plating, Zinc Plating (clear, yellow, black, red, blue), Super Agitine, Powder, Painted, Galvanized, Epoxy, Lacquer
Water/Wastewater, Irrigation, Agriculture, HVAC, Marine, Exhaust, Mining, Energy/Power Generation/Oil
• Forged:
- Ring Rolling:
• Materials: Carbon Steel, Stainless Steel, Duplex
• Size: 2–202”
• Cast:
- Centrifugal Casting (Industrial):
• Material: Stainless Steel
- Continuous Casting:
• Material: Stainless Steel
- Sand Casting:
• Material: A536, Stainless Steel, Ductile Iron
- Investment/Lost-Wax/Precision Casting
• Material: Stainless Steel
Machining: Milling, Turning, Facing, Boring, Drilling, Tapping, Counter Sinking, Laser Cutting, Water Jet, Plasma Cutting
| Products | Type | Materials | Size Range |
|---|---|---|---|
| Flanges | Flat-Face, Raised-Face, & Plate: Slip-On/Ring Weld, Neck, Blind, Socket Weld, Orifice, Reducing, Threaded | See Materials List | 5–202″ |
| Gaskets | Molded, Extruded, sheet | EPDM, Buna-N, NBR, Non-Asbestos (GNA), Red Rubber (GRR), Viton | 5–60″ |
| Screens For Filters | Basket Screens and Cone Screens (Perforated, Mesh) | Galv. Carbon Steel, Carbon Steel, Stainless Steel | 6”D x 8’-H |
| Rings | Exhaust Rings (Marmon Flanges for DPF Filters) | Carbon Steel, Stainless Steel, Aluminum | 1–16” |
| Seamless Rolled Rings | Forged | Carbon Steel, Stainless Steel, Aluminum | 1–165” |
| Square Hole Rings | Repair Couplers | Carbon Steel, Stainless Steel, Galvanized, Epoxy Coated | 3–32” |
| Fabricated Assemblies | Weldments, Pipe Spools, Valve Bodies, Silencer Housings | Carbon Steel, Stainless Steel | 2–24” |
| Long/Short Radius Elbows | EN 10253-2–S235, P235GH–P265GH–P265NL and ASTM A234, WPB, WPC/ A420 WPL6, WPL3/ A860 WPHY52/ ASTM A234 WP11, WP22, WP5, WP9–16Mo3 | 304L & 316L Stainless Steel | (45° & 90°): OD: 21.3mm (1/2”)–3048mm (120”) WT: Up to SCH. XXS/160 |
| Miscellaneous | Tubesheets / Diffuser Plates / Baffles / Ferrules / Sleeves / Pins | Carbon Steel, Stainless Steel, Duplex | 5–104” |
Who we are
API International is a manufacturer and wholesale distributor of flanges, expansion joints, valves, other pipe fittings and custom fabricated parts. We offer a wide variety of AIS & imported flanges along with other industrial pipe fitting and accessories. Customers turn to us when they need quick delivery of parts and are looking for a higher level of customer service. Standard parts are stocked in one of our conveniently located warehouses for quick distribution throughout the United States.
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