At API International, we support large-diameter ANSI/ASME B16.47 class 300 flange requests for NPS 26 to 60 inches, including blind and weld neck styles. Slip-ons, threaded, and socket weld flanges are not covered by ASME B16.47 and are instead manufactured to industry (non-ASME) standards. Our team can help confirm specifications, bolt patterns, and lead times for your project.
ASME B16.47 includes two dimensional systems: Series A and Series B. They cover the same general size range, but the flange dimensions, bolt patterns, and overall proportions differ.
Class 300 is a higher pressure class within ANSI/ASME B16.47 for NPS 26 through 60 flanges. It is commonly used in large-diameter piping systems where service conditions require greater pressure capability than Class 150. Actual allowable pressure depends on the flange material and operating temperature, so the class designation should always be checked against the applicable pressure-temperature tables.
| NPS | Outside Diameter (OD) in | Thickness (Min.) in | Bolt Circle in | Bolt Hole (Qty x Size) |
|---|---|---|---|---|
| 26 | 38.25 | 3.07 | 34.50 | 28 x 1.75 |
| 28 | 40.75 | 3.32 | 37.00 | 28 x 1.75 |
| 30 | 43.00 | 3.57 | 39.25 | 28 x 1.88 |
| 32 | 45.25 | 3.82 | 41.50 | 28 x 2.00 |
| 36 | 50.00 | 4.07 | 46.00 | 32 x 2.12 |
| 40 | 48.75 | 4.44 | 45.50 | 32 x 1.75 |
| 44 | 53.25 | 4.82 | 49.75 | 32 x 1.88 |
| 48 | 57.75 | 5.19 | 54.00 | 32 x 2.00 |
| 52 | 62.25 | 5.63 | 58.25 | 32 x 2.12 |
| 56 | 67.25 | 6.00 | 63.00 | 28 x 2.38 |
| 58 | 69.25 | 6.19 | 65.00 | 32 x 2.38 |
| 60 | 71.25 | 6.38 | 67.00 | 32 x 2.38 |
* Dimensions shown follow ANSI/ASME B16.47 Class 300 Series A weld neck flange standards. Final dimensions may vary depending on flange style, facing, and material specification.
Blind flanges serve as the definitive endpoint for a piping system, used to terminate lines or isolate specific process equipment.
Weld neck flanges are a premier choice for high-pressure systems and remain one of the most commonly used flange types.
ANSI/ASME B16.47 Class 300 flanges are commonly used in large-diameter piping systems that require greater pressure capability. Typical applications include:
ASME B16.47 covers large diameter flanges from NPS 26 through 60 and includes pressure classes 75, 150, 300, 400, 600, and 900. Final allowable pressure depends on the selected material group and operating temperature, so always confirm using the B16.47 pressure temperature rating tables.
ANSI/ASME Class 300 refers to a flange pressure class used in piping systems under the ASME B16.5 standard. For example, a Class 300 flange made from ASTM A105 carbon steel is typically rated for about 740 psi at 100°F, though the actual pressure rating decreases as temperature increases.
Class 150 flanges are engineered for moderate pressure and temperature applications, while Class 300 flanges are built for more demanding service. Because Class 300 flanges require different dimensions and bolt patterns, they are not interchangeable with Class 150 components; these differences are critical for ensuring a reliable seal in high-stress industrial applications.
Class 300 flanges are not interchangeable with Class 150 flanges because the bolt circle diameter, bolt quantity, and thickness are different.
Contact API International’s experienced sales team, and we will help you select the right flange for your application. You can also explore our full range of ANSI and ASME flanges in our online product catalog, or contact us for custom flange options designed to meet your project specifications. Get connected with a dedicated sales representative today, or call us at 503.692.3800
API International is a premier manufacturer and engineering solutions provider that specializes in flanges, expansion joints, valve accessories, and precision-engineered piping components. By offering a wide variety of both AIS/BABA-compliant (Domestic) and imported products, we provide the flexibility and speed the industry demands. Our customers rely on us for more than just parts; they choose us for our superior technical support, rapid national distribution, and commitment to project-critical deadlines. Contact our expert sales team at 503.692.3800 to discuss your next project’s specifications or to request a quote.
• 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:
• Stainless Steel
- Sand Casting:
• Material: A536, Stainless Steel, Ductile Iron
- Investment/Lost-Wax/Precision Casting
• 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 | Stainless Steel, Carbon 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 engineering solutions provider that specializes in flanges, expansion joints, valve accessories, other pipe fittings, and custom-fabricated parts. We offer a wide variety of AIS & imported flanges along with other industrial pipe fittings 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.
