A slip-on flange is a type of pipe flange designed to slide over the end of a pipe. Its slightly larger inner diameter allows it to easily fit before being welded in place on both the inside and outside edges.
These flanges are commonly used in low to moderate pressure systems and are valued for their cost-effectiveness, quick turnaround, and easy installation. They don’t require precise pipe cutting or a weld bevel, offering more flexibility during setup.
Some of them include a raised hub for added strength and better gasket alignment. When needed, a ring-style slip-on can be used without the hub. Taller hub variants may also be used for improved performance under higher mechanical loads.
Slip-on flanges are a reliable and installer-friendly solution for HVAC, waterworks, general industry, or fabrication as they help keep operations on schedule and on budget.
Slip-on flanges are manufactured to meet various global standards. Each standard defines specifications for dimensions, pressure classes, and applications to ensure safety and compatibility across piping systems.
AWWA C207/C228 defines slip-on flanges for waterworks, covering pressure classes A, B, D, E, and F, used in municipal and low-pressure systems.
ASTM A105 and A182 provide material specifications for slip-on flanges made from carbon and stainless steel, widely used in industrial piping and pressure systems.
DIN EN 1092-1 sets specifications for slip-on flanges used in European systems, supporting a range of pressure ratings and metric dimensions.
JIS B2220 covers slip-on flanges designed for Japanese and some Asian piping systems with nominal size ranges and pressure classes.
BS 4504 specifies dimensions for circular flanges used in British piping systems for valves, fittings, and process lines.
Carbon steel flanges are strong and reliable, great for everyday industrial and mechanical use.
Stainless steel flanges resist rust and work well in clean or chemical-heavy environments.
Slip-on flanges are easy to align and install, which makes them cost-effective and less labor-intensive than other flange types. They offer a reliable seal and are ideal for systems where precision alignment is less critical.
Slip on flanges are a good choice for water lines, HVAC systems, and general industrial piping where pressure is moderate and installation needs to be quick and affordable. They are not recommended for high pressure, high temperature, or systems with frequent thermal changes, where a weld neck flange would provide better strength and durability.
Slip-on flanges connect to pipe and allow flow, while blind flanges cap off the end of a pipe or valve. Slip-ons are for inline connections; blind flanges are for sealing or testing pressure without flow. Both are welded in place but serve opposite functions
Slip-on flanges are easier and cheaper to install, suitable for general service. Weld neck flanges offer greater strength and fatigue resistance due to their tapered neck and butt-weld connection, making them better for high-pressure or critical applications. – make this two tile a questions
To install a slip-on flange, slide it over the pipe until the pipe edge is flush with the gasket face or slightly inside. Perform a fillet weld on both the inside and outside edges to secure the connection. Proper alignment and weld quality are key to ensuring a strong, leak-free seal.
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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