Custom flanges are specially designed flange connections that fall outside standard dimensions or specifications. They are made to meet unique requirements in piping and mechanical systems. They can be tailored in size, bolt patterns, materials, or face types to ensure compatibility with non-standard equipment, unusual operating conditions, or specific project needs.
Custom flanges often include modifications like overbore or counterbore, extended hubs, specialized facing (raised, flat, ring-joint), custom bolt holes or hole spacing, chamfers, bevels, or o-ring grooves.
Custom flanges can be produced in carbon steels (ASTM A105, A36), stainless steels (ASTM A182, A240), or specialty alloys. Depending on performance needs, materials may also include aluminum, titanium, copper, plastics, or rubber components.
Even though they are custom, many flanges still conform (or are designed to be compatible) with widely recognized industry standards: ANSI/ASME, DIN, AWWA, API, etc. This ensures safety, interchangeability, and reliability.
Although custom flanges are made to fit unique requirements, they must still align with established industry standards to guarantee safety, reliability, and compatibility. These standards define critical aspects such as dimensions, pressure ratings, materials, and testing procedures. Depending on the application and region, custom flanges may be designed to meet one or more of the following standards:
ANSI/ASME B16.5 – Defines dimensions, pressure classes, and materials for flanges (½″ to 24″).
AWWA C207 / C228 – Sets requirements for flanges in waterworks and industrial piping systems.
MSS SP-44 – Manufacturers Standardization Society standard, commonly used in steel pipelines.
API 6A – Petroleum industry standard for high-pressure oilfield applications.
DIN – German Institute for Standardization, widely used internationally and in maritime applications.
JIS – Japanese Industrial Standard, applied in Japan and marine industries.
AS – Australian Standard for flanges.
UNI – Italian Standard for flanges.
Designing or reviewing drawings / CAD models – often reverse-engineering if working from a sample.
Selecting suitable materials – commonly carbon steel, stainless steel, or alloy steel, with more exotic options for special conditions.
Using machining and cutting operations – API International, Inc. employs methods such as laser cutting, water jet cutting, plasma cutting, milling, turning, facing, boring, drilling, tapping, and countersinking to achieve precise customization.
Ensuring compliance with standards – even when dimensions are non-standard, flanges are manufactured to meet ANSI/ASME, AWWA, and other applicable requirements for pressure rating, sealing, and bolt strength.
Used in pipelines, refineries, and offshore platforms where non-standard sizes and high-pressure ratings are required.
Designed with corrosion-resistant materials to handle aggressive chemicals and extreme temperatures.
Applied in treatment plants and distribution systems, often requiring AWWA-compliant flanges for non-standard pipe sizes.
Utilized in boilers, turbines, and cooling systems where custom dimensions ensure secure, high-performance connections.
Built for durability in saltwater environments, connecting piping systems in ships and offshore vessels.
Integrated into heating, ventilation, and mechanical systems where unique layouts demand tailored flange designs.
Slides over the pipe and is welded at both the inner and outer diameters. Easier to install and align than weld neck, but suited for moderate pressure systems.
Solid flange with no bore, used to seal the end of a pipe system or pressure vessel. Allows easy access for inspection or future expansion.
Designed with a long tapered hub that is welded to the pipe, providing excellent strength and stress distribution. Ideal for high-pressure and high-temperature applications.
Has a socket to insert the pipe before welding. Provides good flow characteristics and is used in small-bore, high-pressure lines.
Features internal threads to connect with externally threaded pipes without welding. Common in low-pressure and non-critical applications.
Used with a stub end fitting. The flange itself does not touch the process fluid and can rotate around the pipe, making alignment and assembly easier.
The entire face is flat and flush with the gasket surface. Used where space or flexibility is limited, typically in low-pressure applications.
Includes a raised sealing surface around the bore to improve gasket compression and leak resistance under moderate pressure.
• 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” |
A custom flange is designed to meet requirements that standard flanges cannot. This may include unique sizes, bolt hole patterns, materials, or face types tailored for specific piping systems. They provide flexibility when off-the-shelf options do not fit, ensuring a safe and reliable connection.
Custom flanges are widely used in industries that demand specialized solutions, such as oil and gas, chemical processing, power generation, water treatment, and marine applications. These industries often operate under unique conditions where standard flanges won’t perform adequately.
Lead times for custom flanges vary depending on complexity, material availability, and order size. In many cases, quick-turn manufacturing is available to reduce downtime, while larger or more complex projects may require additional time for design and machining.
To order custom flanges from API International, determine your required pipe size, pressure class, material, and any special standards (such as ASME B16.5). Contact API International’s experienced team and we will help you select the right flange for your application.
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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