High-Quality Carbon Steel and Stainless Steel Flanges from China Suppliers | Reliable 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
Raised Face (RF)
Flat Face (FF)
Ring-Type Joint (RTJ)
| 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
Q
What is the most commonly used flange type in industrial piping systems?
The Weld Neck Flange (WN) and Slip-On Flange (SO) are among the most widely used. Weld Neck flanges are preferred for high-pressure and high-temperature critical services due to their superior reinforcement, while Slip-On flanges are popular for general piping systems because of their lower installation cost and ease of alignment.
Q
What is the difference between Raised Face (RF) and Flat Face (FF) flange facings?
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.
Q
Which ASTM standard applies to stainless steel flanges?
Stainless steel flanges are governed by ASTM A182, which covers forged or rolled alloy and stainless steel pipe flanges, forged fittings, and valves. Common grades under this standard include F304, F304L, F316, and F316L, each offering varying levels of corrosion resistance and mechanical properties.
Q
When should a Blind Flange be used instead of other flange types?
A Blind Flange (BL) is used when a pipeline or pressure vessel opening needs to be completely sealed off. It is ideal for pipeline termination, pressure testing of piping systems, and blocking off connections reserved for future expansion. Since it has no bore, it creates a solid closure that can withstand significant pressure.
Q
What are the advantages of a Lap Joint Flange over other flange types?
The Lap Joint Flange (LJ) consists of a stub end and a backing flange that rotates freely around it. This rotation makes bolt-hole alignment much easier during assembly and disassembly, which is a major advantage in systems that require frequent dismantling for inspection or maintenance. It is also cost-effective in corrosive services, as only the stub end (which contacts the fluid) needs to be made from expensive corrosion-resistant material.
Q
What type of gasket is used with a Ring-Type Joint (RTJ) flange facing?
Ring-Type Joint (RTJ) flange facings use metal ring gaskets, either oval or octagonal in cross-section, which seat into a precision-machined groove on the flange face. These metal gaskets create a highly reliable seal under extreme pressure and temperature conditions, making RTJ facings the preferred choice for high-pressure oil and gas applications, including wellhead equipment and subsea systems.