Blinds are flanges without a center bore (hole or opening) and are available in both Raised Face (RF) and Flat Face (FF) styles. While most flange types create a connection point that allows the flow of liquid, gas, or air, blind flanges are used to seal the end of a piping system and prevent flow. Blind flanges may be used when testing pipe pressure, to create an access point in a piping system, to temporarily seal a piping system while modifying or repairing the line, or to create a long-term seal to terminate a piping system.
A blind flange is bolted, rather than welded in place. This allows easier access as needed for pipe system upkeep, inspection, or to allow for future expansion. Pairing with a gasket creates a tight seal: The gasket fills the space between the flange faces, which prevents liquid or gas leaks.
Widely used across industrial piping, chemical processing, water treatment, and oil and gas, blind flanges offer both temporary and long-term sealing solutions.
Blind flange dimension requirements and materials specifications are designated under standards AWWA C207 and C228, and ANSI/ASME B16.5 and B16.47. The general dimensions by blind flange type are included in the chart below, and you can refer to the tables on individual flange listings to determine more specific measurements—such as thickness—based on diameter and pressure rating.
AWWA C207 and C228 define blind flanges for waterworks applications, covering pressure classes A through F. These are commonly used in municipal systems and low-pressure service environments.
| AWWA Blind Flange Style | Available Size Range |
| B, D, E | 4” – 72” |
| F, SF | 4” – 48” |
| SA | 2” – 8” |
| SB, SD, SE | 2” – 72” |
ANSI/ASME B16.5 and B16.47 specify dimensions and pressure ratings for blind flanges used in industrial piping systems. These standards support higher pressure classes and are typically applied in commercial and process piping.
| Spec | Class | Available Size Range |
| B16.5 | 150 | 0.5” – 24” |
| B16.5 | 300 | 0.5” – 24” |
| B16.47 | 150 | 26” – 60” |
| B16.47 | 300 | 26” – 60” |
Blind flanges are used in oil refineries, petrochemical plants, and offshore platforms for system isolation, pressure testing, and equipment maintenance.
In chemical processing facilities, blind flanges seal off pipelines during batch processing, cleaning, or equipment inspections.
In municipal water treatment plants and industrial facilities, blind flanges are employed in piping systems to control flow and isolate sections for repairs or upgrades.
In power plants, blind flanges are utilized in steam, water, and gas pipelines to temporarily or permanently close them during maintenance shutdowns or equipment replacement.
In heating, ventilation, and air conditioning (HVAC) systems, blind flanges seal off ductwork or piping branches to control airflow and pressure distribution.
Stainless steel flanges resist rust and work well in clean or chemical-heavy environments.
Carbon steel flanges are strong and reliable, great for everyday industrial and mechanical use.
Flat face flanges provide a smooth, even surface ideal for low-pressure applications and soft gasket materials.
Raised face flanges feature a slightly elevated sealing surface to concentrate pressure for a tighter, more secure seal.
A blind flange is a solid, circular plate that seals off the end of a pipe or pressure system. It is commonly used to stop the flow of fluids, gases, or materials and is ideal for isolating sections during maintenance or system changes.
Blind flanges are easy to install and remove without welding. They offer a tight, leak-proof seal that keeps pressure in the system, making them ideal for reliable shutdowns or future pipeline extensions.
Unlike standard flanges, blind flanges have no central opening. They function as end caps, closing off a pipe or vessel entirely. This makes them perfect for sealing, while other flanges typically connect two sections.
Yes, gaskets are typically placed between the flange and pipe surface to ensure a secure, leak-free seal. The bolts are then tightened evenly around the flange to maintain consistent pressure and prevent leaks.
Blind flanges are ideal when a pipeline needs to be sealed off for repairs or is not in use. However, they should not be used in systems that require continuous flow or operate under extreme pressure without careful design considerations
Capabilities:
• Custom Bolt Holes, Overbore, Counterbore, Tapped, Welds, O-ring Grooves, Threads, Special Serrations, Bevels, Chamfers
Thread Style:
• Metric Parallel, Metric Tapered, Parallel (BSPP), Taper Thread (BSPT), UN/UNF/UNC Thread,
NPT (National Pipe Thread)
Serrations:
• MWD
Tolerances:
• 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
Forming:
• 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
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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