Flanges, as key components for connecting industrial pipelines and equipment, have become the core hub for ensuring safe and efficient operation of industrial systems with their excellent sealing performance and convenient assembly and disassembly features. Whether it is harsh working conditions of high pressure and high temperature, or special environments of corrosive media, flanges can achieve precise connections with diverse designs and processes, laying a solid foundation for industrial production.
Definition of flange
Flange, also known as flange or flange, is a disc-shaped part, usually used in pairs, which fixes pipes, equipment or devices to each other through bolt connection, and uses gaskets to fill the gap between the sealing surfaces to form a detachable sealing connection structure.
Its function is not only to achieve physical connection between components, but also to prevent medium leakage through reasonable sealing design, withstand system pressure and mechanical load, and ensure the safe and stable operation of industrial systems.
The specifications, pressure levels, sealing surface forms and other parameters of flanges strictly follow international or national standards, such as GB (Chinese standards), ASME (American standards), EN (European standards), etc., to ensure the interchangeability and compatibility between different components.
Flange processing technology
Raw material preparation
According to the usage scenario and performance requirements, select appropriate raw materials, such as carbon steel (Q235, 20# steel) for ordinary low-pressure pipelines; stainless steel (304, 316L) for corrosion-resistant environments; alloy steel (16Mn, Cr-Mo steel) for high temperature and high pressure conditions. Raw materials are usually supplied in the form of plates, bars or forgings. Large flanges are mostly forged blanks to ensure uniform internal structure and reliable strength.
Forging and forming
For flanges used in high pressure and important working conditions, forging technology is often used. Through free forging or die forging, the metal blank is plastically deformed under pressure to eliminate internal defects, refine grains, and improve mechanical properties. For small flanges or batch production, steel plate cutting, stamping and other methods can also be used to reduce costs and improve production efficiency.
Cutting processing
Precision processing is performed using lathes, milling machines, drilling machines and other equipment. Lathes are used to turn the outer diameter, inner diameter, and sealing surface of flanges; milling machines are used to process special structures of sealing surfaces (such as convex surfaces, concave and convex surfaces, and tongue and groove surfaces); drilling machines complete the precise processing of bolt holes to ensure the accuracy and uniformity of hole spacing and meet installation requirements.
Welding and assembly
Some flanges need to be welded to pipes or equipment, such as flat welding flanges and butt welding flanges. The welding process strictly controls the process parameters, and adopts manual arc welding, argon arc welding and other methods to ensure the quality of welds and prevent leakage and cracks. After welding, non-destructive testing (such as radiographic testing and ultrasonic testing) is performed to ensure the strength and sealing of the connection.
Surface treatment
In order to enhance the corrosion resistance and aesthetics of the flange, surface treatment is usually performed, such as sandblasting and rust removal, hot-dip galvanizing, and coating of anti-corrosion coatings (epoxy resin, polyurethane, etc.). For the sealing surface, grinding and polishing are required to improve the surface finish, ensure close fit with the gasket, and enhance the sealing effect.
Types of flanges
Classification by structural form
Flat welding flange
simple structure, low cost, suitable for low pressure (generally not more than 2.5MPa) and no special requirements for the medium, such as water supply and drainage pipes, ordinary ventilation systems. Only one-sided welding is required during welding, which is easy to install, but the rigidity is relatively weak.
Butt welding flange
with a long tapered neck, high strength and good sealing, suitable for medium and high pressure (up to 16MPa and above), high temperature, low temperature or corrosive medium pipelines, such as chemical equipment and steam pipelines. Full penetration is required during welding to ensure connection reliability.
Socket welding flange
suitable for small-diameter pipelines (DN≤80mm), by inserting the pipeline into the flange socket and welding, stress concentration is reduced and medium retention is prevented. Commonly used in high-pressure and high-viscosity medium occasions, such as petroleum refining equipment.
Threaded flange
no welding is required, it is connected to the pipeline through threads, easy to disassemble, and suitable for occasions that require frequent disassembly or are not suitable for welding, such as stainless steel pipelines and instrument connections. But the pressure level is relatively low, generally not exceeding 2.0MPa.
Loose flange
The flange ring and the pipe can move relative to each other, suitable for corrosive media or pipes that need to be frequently disassembled, such as lined pipes and non-ferrous metal pipes. The requirements for pipe coaxiality are low, which can reduce the impact of welding deformation.
Integral flange
It is cast or forged as an integral part of the equipment or pipeline, with excellent strength and sealing, and is often used for the connection of high-pressure and important equipment, such as pressure vessels and large reactors.
Classification by sealing surface form
Flat flange (FF)
The sealing surface is flat and is matched with non-metallic gaskets. It is suitable for low-pressure and non-hazardous media, such as ordinary water pipes.
Raised face flange (RF)
The sealing surface is slightly higher than the flange surface. It is widely used and can be matched with a variety of gaskets (rubber, metal spiral wound gaskets, etc.). It is suitable for medium-pressure conditions.
Morph-and-groove flange (MFM)
It is matched with a convex surface and a concave surface. The gasket is embedded in the concave surface. The sealing performance is better than that of the raised face flange. It is suitable for pipelines with flammable, explosive, toxic or precious media.
Tongue and groove flange (TG)
The tenon and the groove are tightly matched, the gasket is not easy to squeeze out, and the sealing performance is excellent. It is suitable for high pressure, high vacuum or high cleanliness requirements, such as gas transmission pipelines and food and pharmaceutical equipment.
Flange connection method
Bolt connection
The most common connection method is to fasten the paired flanges together with bolts. The bolt material is selected according to the use temperature, pressure and medium characteristics, such as carbon steel bolts for normal temperature and pressure, and stainless steel or alloy steel bolts for high temperature and corrosive environment. During installation, a torque wrench should be used to tighten evenly in the specified order and torque to ensure that the gasket compression is consistent and avoid leakage caused by the deflection of the sealing surface.
Welding connection
For butt welding flanges, flat welding flanges, etc., they need to be welded and fixed with the pipeline. The welding process is selected according to the material and thickness of the flange and the pipeline, such as argon arc welding primer and arc welding filling to ensure the quality of the weld. Non-destructive testing is required after welding to ensure the connection strength and sealing.
Threaded connection
The threaded flange is connected to the pipeline through internal or external threads, without welding, and is easy to install and disassemble, but it is only suitable for small-diameter, low-pressure pipelines. Sealing tape or sealant should be used to enhance the sealing when connecting.
Application fields of flanges
Petrochemical industry
In oil refining and chemical plants, flanges are used to connect reactors, heat exchangers, pipelines and other equipment. They need to withstand high temperature, high pressure and corrosive media. Butt-weld flanges and integral flanges are mostly used, and metal spiral wound gaskets or metal toothed gaskets are used to ensure reliable sealing and prevent leakage from causing safety accidents.
Power industry
In power facilities such as thermal power generation and nuclear power plants, flanges are used to connect steam pipes, cooling water pipes, fuel pipes, etc., which require high strength and high temperature resistance. Butt-weld flanges made of alloy steel are often used, and they are designed and manufactured in strict accordance with international standards such as ASME.
Natural gas and city gas
In natural gas transmission pipelines and city gas distribution systems, flange connections ensure the safety of gas transmission and prevent leakage. Raised face or concave and convex face flanges are mostly used, with rubber or polytetrafluoroethylene gaskets, and strict air tightness testing is carried out.
Water supply and drainage and sewage treatment
In urban water supply and drainage pipelines and sewage treatment plant equipment, flat welding flanges are widely used due to their low cost and easy installation. They are matched with rubber gaskets to meet general pressure and water quality requirements.
Food and pharmaceutical industry
Food and pharmaceutical industries have extremely high requirements for hygiene, and often use tongue-and-groove flanges made of stainless steel to ensure that the sealing surface has no dead corners, is easy to clean, prevents contamination, and complies with GMP (Good Manufacturing Practice) standards.
Our factory-Xuanmin Technology has been deeply involved in the field of flange manufacturing for many years. With exquisite craftsmanship, excellent quality and considerate service, it has become a trusted partner of many companies：
Advanced manufacturing equipment
Introducing internationally leading CNC machining centers, high-precision forging equipment, automated welding production lines and intelligent spraying systems to ensure that the flange processing accuracy reaches the micron level and the production efficiency is increased by more than 30%. From raw material cutting to finished product inspection, each process is automated and intelligently controlled to ensure stable and reliable product quality.
Professional technical team
Bringing together senior experts and technical backbones in the fields of materials science, mechanical manufacturing, welding technology, etc., with rich experience in flange design, research and development and production. According to the special needs of customers, we can provide one-stop solutions from selection design, process optimization to customized production to ensure that the products fully meet the requirements of use.
Strict quality control
Established a complete quality management system and passed ISO 9001 international quality certification. From raw material entry inspection, process quality monitoring to full inspection of finished products, every link strictly follows international standards and corporate internal control standards. Equipped with advanced testing equipment, such as spectrum analyzers, ultrasonic flaw detectors, pressure test benches, etc., to ensure that each product can withstand rigorous tests.
High-quality after-sales service
Adhering to the concept of "customer first", we provide customers with a full range of after-sales services. From product installation guidance, technical consultation to after-sales maintenance and regular return visits, our professional service team is always responsive to ensure that customers can use it without worries.
Welcome friends from all walks of life to visit our factory for inspection and cooperation! Here, you will witness the precision manufacturing process of flanges from raw materials to finished products, and feel our persistent pursuit of quality. We look forward to working with you to escort your projects with excellent flange products and create a brilliant future together!
