We stock steel and stainless steel ANSI flanges in slip-on and blind styles, available in both flat face and raised face designs, meeting ANSI/ASME B16.5 specifications for Class 150 and Class 300.
People often call these flanges ‘ANSI flanges,’ but the correct standards are ASME B16.5 and ASME B16.47 for dimensions and pressure ratings. So, whenever you see ‘ANSI B16.5’ or ‘ANSI B16.47,’ it actually refers to ‘ASME B16.5’ and ‘ASME B16.47,’ respectively.
ANSI or American National Standards Institute coordinates and approves standards used across industries in the United States. Its main goal is to ensure consistency, safety, and compatibility in how products and systems are designed and used.
ANSI works alongside engineers, manufacturers, government agencies, and industry experts to support the development of technical standards. These standards cover a wide range of sectors, including manufacturing, construction, healthcare, and energy.
In the flange industry, ANSI plays a key role in creating standard guidelines for dimensions, pressure ratings, materials, and tolerances. Flanges built to ANSI standards are used in critical infrastructure around the world. These flanges are especially important in industries like oil and gas, water treatment, chemical processing, and power generation. Following ANSI standards helps ensure that parts from different suppliers fit together safely and reliably.
ANSI B16.5 flanges are specifically designed for pipe sizes ranging from ½” to 24″. They are available in pressure classes 150, 300, 400, 600, 900, 1500, and 2500. Common materials include ASTM A105 carbon steel, 304L, and 316L stainless steel.
ANSI B16.5 covers Threaded, Slip-on, Lapped, Blind, and Weld Neck flanges
ANSI B16.47 flanges cover larger-diameter pipe systems, 26″ through 60″, with pressure classes such as 75, 150, 300, 400, 600, and 900. They are commonly used in high-volume and high-pressure systems. ANSI B16.47 is further divided into Series A (covering blind flanges) and Series B (covering weld neck flanges).
Slip-on, threaded, and socket-weld flanges are not covered by the ANSI B16.47 standard and are instead manufactured to industry (non-ASME) standards. These “industry standard” designs are based on B16.47 bolt patterns and hub geometry, but dimensions vary by manufacturer. Always confirm details before fabrication.
150 class flanges are used in low-pressure, moderate-temperature systems. Common applications include water treatment, HVAC, food processing, and low-pressure oil and gas pipelines.
300 class flanges are built for higher-pressure, high-temperature systems. Common uses include refineries, power plants, industrial piping, and high-pressure oil and gas lines.
Fits over the pipe and is welded in place. Commonly used in low- to moderate-pressure systems.
ANSI flanges connect pipes, valves, and equipment in a piping system using bolts and gaskets to create a secure, leak-proof seal.
ANSI flanges offer standardization, interchangeability, and proven performance in high-pressure and high-temperature systems.
Common ANSI flange types include weld neck, slip-on, blind, threaded, socket weld, and lap joint—each suited for specific applications and pressures.
ANSI approves standards, while ASME develops them. “ANSI flanges” actually follow ASME B16.5 and ASME B16.47 standards for dimensions and pressure ratings. ANSI B16.5 covers NPS ½” to 24” in pressure classes 150 to 2500. Sizes 26″ to 60″ are covered under ANSI B16.47 in pressure classes 75, 150, 300, 400, 600, and 900. B16.5 covers Threaded, Slip-on, Lapped, Blind, and Weld Neck flanges. ANSI B16.47 is further divided into Series A (covering blind flanges) and Series B (covering weld neck flanges).
ASME B16.5 is the actual standard produced by ASME, however “ANSI” is frequently used to refer to the class ratings within that standard, which define pressure-temperature ratings for flange. Essentially, ASME B16.5 establishes the requirements, and ANSI class ratings are part of that document and show the flanges’ pressure capacities.
Consider system pressure, temperature, pipe size, material, and connection type. A qualified supplier can help match the correct flange to 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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