China Suppliers and Factory for Carbon Steel and Stainless Steel Flanges for Reliable 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
Q
What is the most commonly used flange type in industrial piping systems?
The Weld Neck Flange (WN) and Slip-On Flange (SO) are the most widely used types. Weld Neck flanges are preferred for high-pressure and high-temperature critical applications due to their reinforced tapered hub, while Slip-On flanges are popular in general piping systems for their ease of installation and lower cost.
Q
What is the difference between Raised Face (RF) and Flat Face (FF) flange facing?
A Raised Face (RF) flange has its sealing surface raised above the bolt circle and uses soft or semi-metallic gaskets — it is the most common facing type. A Flat Face (FF) flange has its sealing surface flush with the bolt circle and requires full-face non-metallic gaskets. Flat Face flanges are typically used when connecting to equipment made of brittle materials such as cast iron.
Q
Which ASTM standard applies to stainless steel flanges?
Stainless steel flanges are covered under ASTM A182, which specifies forged or rolled alloy and stainless steel pipe flanges. Common grades include F304, F304L, F316, and F316L, each offering different levels of corrosion resistance and temperature performance.
Q
When should a Blind Flange be used instead of other flange types?
A Blind Flange (BL) is used to close off the end of a pipeline, valve, or pressure vessel opening. It is commonly applied for pipeline termination, pressure testing of piping systems, and at future expansion points where additional connections may be added later. Its solid design with no bore makes it ideal for sealing purposes.
Q
What are the advantages of a Lap Joint Flange over other flange types?
The Lap Joint Flange (LJ) consists of two parts — a stub end and a backing flange — allowing the flange to rotate freely around the pipe. This makes bolt-hole alignment much easier during installation. It is especially advantageous in systems that require frequent dismantling for inspection or maintenance, and in corrosive service environments where expensive alloy materials are used, since only the stub end needs to be made from the costly material.
Q
What is the Ring-Type Joint (RTJ) facing and when is it used?
The Ring-Type Joint (RTJ) facing features a groove machined into the flange face that accepts a metal ring gasket — either oval or octagonal in cross-section. The metal-to-metal sealing provides extremely high integrity, making RTJ flanges suitable for very high-pressure and high-temperature applications such as those found in oil and gas wellheads, refineries, and subsea equipment.