What is Steel Pipe Flange？
Steel pipe flange, referred to as flange! It is a fitting that connects valves, pipes and other equipment in the pipeline system. Its principle is to tightly connect the pipes together through bolts!
！Note that the steel in the steel pipe flange does not refer to a single steel flange, but refers to the flange used for steel pipes, which is the general term for flanges connecting pipes!
Advantages of Using Steel Pipe Flange
Easy to install and remove
This is the core advantage of steel pipe flanges. Compared with permanent connections such as welding, flange connections can be easily disassembled and can be easily connected without any tools or skills!
Easy maintenance and cleaning
The flange is easy to inspect and clean because it is removable. Welding cannot be disassembled. If you want to inspect and clean the inside of the pipe, you need to cut the pipe. But the flange only needs to disassemble a specific section of the pipe.
Excellent pressure resistance
Steel pipe flanges can form a continuous steel structure with the pipeline. The strength of the flange can be close to or even exceed that of the pipeline itself, and can withstand internal pressure, external pressure, thermal expansion and contraction stress, etc.
Excellent sealing
High-strength bolts and gaskets can form a very strong sealing effect to prevent medium leakage.
Types of Flanges
Butt Welding Flange
Weld neck flanges feature a long, tapered neck and are welded to the pipe. These flanges offer the highest strength and are suitable for use in high-temperature, high-pressure, and high-risk environments. However, they are expensive to manufacture and require a complex and labor-intensive welding process.
Socket Welding lange
Socket-weld flanges are connected by inserting the pipe into the socket on the back of the flange and then applying a fillet weld. Socket-weld flanges are simple, quick, and labor-intensive to install, making them suitable for small-diameter pipes. However, they are susceptible to crevice corrosion and should not be used in corrosive media. They also have poor fatigue resistance and are not suitable for use in environments subject to severe loads or mechanical vibration. They are also not suitable for radiographic inspection.
Threaded Flange
Compared to the two flanges mentioned above, the biggest advantage of threaded flanges is that they don’t require welding, making them suitable for use in situations where open flames are unavailable. Simply screw the pipe in, and disassembly is easy. However, threaded flanges also have significant disadvantages: poor vibration resistance, weak pressure bearing capacity, and the tendency to generate stress at the threaded connection.
Slip On Flanges
Slip-on flanges are typically a type of “loose-fit flange” in international standards. They are very convenient, slipping onto pipes and sliding freely along them, making it easy to align bolt holes during installation. However, they have poor pressure-bearing capacity and require two components, necessitating the processing of an additional nipple.
Blind Flange
Blind flange is also called flange cover. Its appearance is a solid disc without a center hole. Its main function is to isolate the end of the pipe and act as a plug. Blind flange has strong sealing performance, strong pressure bearing capacity, can be easily installed and disassembled, and has high safety performance. There are many types of blind flanges, which are mainly classified by the shape of the sealing surface. Common types include raised face blind flange, concave and convex face blind flange, and
Lap Joint Flange
Lap Joint Flange, also known as a slip-on flange, separates the load-bearing function from the sealing function. The flange itself is not directly welded to the pipe, but can rotate 360 degrees. Since this type of lap joint flange does not come into direct contact with the medium, the flange material can be selected at an affordable price. Furthermore, stress is not transmitted to the flange, significantly reducing the risk of loosening and improving sealing. However, there are certain limitations: its pressure bearing capacity is relatively weak, making it unsuitable for heavy loads. While inexpensive materials can be used, the lap joint flange consists of two components: a flange ring and a “flanged nipple,” which incurs additional installation costs.
Steel Pipe Flange Common Materials and Standard
The material selection for flanges is crucial, as it significantly impacts the flange’s mechanical properties, temperature resistance, pressure resistance, and cost. When selecting flange materials, consider the media, pressure, stress, temperature, and cost requirements. Below are some common flange materials and their standards.
Carbon Steel
This is the most commonly used material in non-corrosive environments.
Common Standards
1. ASTM A105 / National Standard 20#, Q235B
2. ASTM A350 LF2
3. ASTM A694 F42, F52, F60, F65
Stainless steel
Mostly used in scenarios with high cleanliness requirements, corrosive media or high temperature anti-oxidation
Common Standards
1. 304 (ASTM A182 F304)
2. 316 (ASTM A182 F316)
3. 316L (ASTM A182 F316L)
Alloy steel
Better performance, more commonly used in harsh environments such as high temperature and high pressure
Common Standards
1. ASTM A182 F11, F22
2. ASTM A182 F91, F92
