China Carbon Steel and Stainless Steel Flanges - Reliable Suppliers and Factory for Pipe Connections
Common Flange Types
| Flange Type | Description | Typical Applications |
|---|---|---|
| Weld Neck Flange (WN) | Features a long tapered hub that provides reinforcement; butt-welded to pipe | High-pressure, high-temperature services; critical applications requiring high integrity |
| Slip-On Flange (SO) | Slides over pipe and welded both inside and outside; lower installation cost | Low to medium pressure applications; general piping systems |
| Blind Flange (BL) | Solid flange with no bore; used to close pipe ends, valves, or pressure vessel openings | Pipeline termination; pressure testing; future expansion points |
| Threaded Flange (THDF) | Bore with threads; screws onto threaded pipe without welding | Low-pressure utility services; areas where welding is hazardous |
| Socket Weld Flange (SW) | Bore with socket counterbore; pipe inserted and fillet welded | Small diameter, high-pressure lines; typically ½" to 4" NPS |
| Lap Joint Flange (LJ) | Two-part assembly with stub end and backing flange; flange rotates freely | Systems requiring frequent dismantling; corrosive services with expensive materials |
Flange Facing Types
| Face Type | Description | Typical Gasket |
|---|---|---|
| Raised Face (RF) | Sealing surface raised above bolt circle; most common facing | Soft or semi-metallic gaskets |
| Flat Face (FF) | Sealing surface flush with bolt circle | Full-face non-metallic gaskets |
| Ring-Type Joint (RTJ) | Groove machined into face for metal ring gasket | Oval or octagonal metal ring gaskets |
Standard
| Material Type | Standard | Common Grades |
|---|---|---|
| Carbon Steel | ASTM A105 | Standard specification for forged carbon steel piping components |
| Carbon Steel (Low Temp) | ASTM A350 | For low-temperature service; common grade LF2 |
| Stainless Steel | ASTM A182 | Forged stainless steel; common grades F304, F304L, F316, F316L |
| Alloy Steel | ASTM A182 | Chrome-moly grades for high-temperature; F11, F22 |
Wall Thickness Schedules
Frequently Asked Questions (FAQ)
▶ What is the most commonly used flange type in industrial piping systems?
The Weld Neck Flange (WN) is widely regarded as the most reliable choice for critical industrial applications due to its tapered hub design, which provides superior reinforcement and integrity under high-pressure and high-temperature conditions. The Slip-On Flange (SO) is also very popular for general-purpose, lower-pressure piping systems due to its ease of installation and lower cost.
▶ What is the difference between a Raised Face (RF) and a Flat Face (FF) flange?
A Raised Face (RF) flange has its sealing surface elevated above the bolt circle, concentrating bolt load on a smaller gasket area for a more effective seal — it is the most common facing type. A Flat Face (FF) flange has its sealing surface flush with the bolt circle and uses a full-face gasket, typically required when connecting to cast iron or non-metallic equipment to avoid flange distortion.
▶ When should a Ring-Type Joint (RTJ) flange facing be used?
Ring-Type Joint (RTJ) flanges are recommended for extremely high-pressure and high-temperature services, such as oil and gas wellhead equipment and refinery applications. The metal ring gasket (oval or octagonal) seated in a precision-machined groove provides an exceptionally tight and reliable seal under severe operating conditions.
▶ What material standards apply to carbon steel and stainless steel flanges?
Carbon steel flanges are typically manufactured to ASTM A105 for standard service or ASTM A350 (grade LF2) for low-temperature applications. Stainless steel flanges follow ASTM A182, with common grades including F304, F304L, F316, and F316L. Alloy steel flanges also fall under ASTM A182, with chrome-moly grades such as F11 and F22 used for elevated-temperature service.
▶ What is a Blind Flange used for?
A Blind Flange (BL) is a solid flange with no bore, designed to seal the end of a pipe, valve, or pressure vessel opening. It is commonly used for pipeline termination, pressure testing of piping systems, and as a closure point for future expansion or branch connections. Blind flanges must withstand the full system pressure, making material selection and pressure rating critical.
▶ What are the advantages of using a Lap Joint Flange?
Lap Joint Flanges offer significant advantages in systems that require frequent dismantling for inspection or maintenance, as the backing flange rotates freely around the stub end, making bolt-hole alignment much easier. They are also cost-effective when used in corrosive services: only the stub end (which contacts the fluid) needs to be made from expensive corrosion-resistant alloys, while the backing flange can be standard carbon steel.