| ASME Pressure Class | Typical Pressure Range* | Common Applications and Service Characteristics |
|---|---|---|
| Class 150 | Low pressure (~ 285 psi) | Water systems, HVAC, low-pressure steam, fire protection, and general industrial piping. |
| Class 300 | Moderate pressure (~ 740 psi) | Process piping, compressed air, hydrocarbons, and light chemical service. |
| Class 400 | Intermediate pressure (~ 990 psi) | A less common class typically specified for specialized or legacy systems where Class 300 is insufficient but Class 600 is not required. |
| Class 600 | High pressure (~ 1480 psi) | Oil and gas processing, steam systems, chemical plants, and power generation. |
| Class 900 | Very high pressure (~ 2220 psi) | Refinery service, high-pressure process lines, and severe hydrocarbon applications. |
| Class 1500 | Severe pressure and temperature (~ 3705 psi) | High-pressure reactors, critical steam systems, and aggressive chemical environments. |
| Class 2500 | Extremely high pressure (~ 6170 psi) | Specialized ultra-high-pressure systems with strict engineering controls and limited application scope. |
* Pressure values shown are approximate reference values at a temperature of 100°F for ASTM A105 carbon steel. Allowable pressure varies by material group and operating temperature in accordance with ASME B16.5 and ASME B16.47 pressure–temperature rating tables.
Slip-on flanges are a cost-effective alternative to weld necks, favored for their ease of alignment and simplified installation.
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 flanges” actually follow ASME B16.5 standards for dimensions and pressure ratings. ASME B16.5 covers NPS ½” to 24” in pressure classes 150 to 2500. Sizes 26″ to 60″ are covered under ASME B16.47 in pressure classes 75, 150, 300, 400, 600, and 900. B16.5 covers Threaded, Slip-on, Lapped, Blind, and Weld Neck flanges.
ASME B16.5 is the actual standard produced by the 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.
ASME B16.5 includes seven standard pressure classes: 150, 300, 400, 600, 900, 1500, and 2500. These ratings define the maximum allowable pressure a flange can withstand, depending on material type, temperature, and application.
ASME B16.5 is used in industries such as oil and gas, chemical processing, power generation, and water treatment where flanged piping systems are required.
ASME B16.5 covers “standard” pipe flanges and flange fittings through NPS 24 (and includes the higher classes up to 2500, depending on size/material).
ASME B16.47 covers large-diameter steel flanges typically NPS 26 through NPS 60, and it’s commonly limited to classes like 75, 150, 300, 400, 600, and 900. It also has two dimension series: Series A and Series B, which have different dimensions/weights and are not automatically interchangeable.
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
• 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 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.
