Flange Sealing Face Forms: Diverse Choices to Ensure the Safe Operation of Pipelines
In the industrial field, the pipeline system undertakes the important task of transporting various media such as gases and liquids, and it is the key "vein" of industrial production. Among them, flange connection, as an important connection method in the pipeline system, the form of its sealing face directly determines the sealing performance, safety, and stability of the pipeline system. Different production scenarios and media characteristics have different requirements for sealing. Therefore, a deep understanding of various flange sealing face forms is of great significance for ensuring the normal progress of industrial production.
Flat Face (FF): A Simple and Practical Basic Choice
The flat face (abbreviated as FF) has a smooth and flat sealing surface with no raised or grooved structures when viewed from the appearance. During machining, an ordinary lathe can be used to machine the sealing surface to the required surface roughness through turning processes, generally reaching Ra6.3 - Ra12.5μm. There is no need to use high - precision CNC machine tools or complex machining tools, which greatly reduces production costs. In some small - scale plumbing installation projects or ventilation pipeline systems with low sealing requirements, flanges with flat faces can meet basic connection and sealing requirements at a relatively low cost.
However, this type of sealing face also has obvious shortcomings. Due to the overly smooth sealing surface, the friction between it and the gasket is relatively small. When the pressure in the pipeline fluctuates, for example, when the pressure fluctuates within the range of 0.1 - 0.3MPa, the gasket is prone to displacement. Once the gasket is displaced, the sealing will fail, resulting in media leakage. Therefore, it is mainly suitable for occasions where the pressure does not exceed 0.6MPa and the media are relatively pure, such as low - pressure water supply pipelines in residential areas or ordinary ventilation and air - exchange pipelines. The flat face can play a good role in these situations.
Raised Face (RF): Widely Used in Medium - and Low - Pressure Fields
The raised face (abbreviated as RF) is an improvement based on the flat face. A raised ring is added to the outer circumference of the sealing face, and the height of this ring is generally between 1.5 - 3mm. This seemingly simple design greatly increases the contact area with the gasket. Taking a DN100 flange as an example, compared with the flat face, the contact area between the raised face and the gasket is increased by about 20% - 30%. At the same time, when the bolts are tightened, this raised ring can exert a greater clamping force on the gasket, thereby significantly improving the sealing performance.
RF shows good adaptability in the transportation of various media in medium - and low - pressure situations. In petrochemical enterprises, many pipelines with a transportation pressure of 1.0 - 2.5MPa, such as some intermediate - product transportation pipelines, often use flanges with raised faces. In the urban natural gas transportation network, the pressure of most medium - and low - pressure pipelines is between 0.4 - 1.6MPa, and the raised face is also widely used to ensure the safe transportation of natural gas.
Male and Female Face (MFM): A Reliable Guarantee for High - Requirement Working Conditions
The male and female face (abbreviated as MFM) consists of a convex face and a concave face, just like a raised tenon and a corresponding groove. During installation, the gasket is placed inside the concave face, and the convex face and the concave face fit closely together to form a relatively closed space. This structure can effectively prevent the gasket from being extruded. Even when the pressure in the pipeline reaches 4.0 - 6.4MPa, the gasket can remain stable, greatly improving the sealing performance.
In chemical production, the transportation of toxic and harmful chemicals such as chlorine and ammonia is often involved. Taking the transportation of chlorine as an example, once it leaks, it will cause great harm to the surrounding environment and personnel. Using flanges with male and female faces can effectively prevent chlorine leakage and ensure production safety. In some medium - and high - pressure steam pipeline systems, the pressure is usually between 2.5 - 4.0MPa, and the male and female face can also rely on its excellent sealing performance to ensure the safe operation of the pipeline.
Tongue and Groove Face (TG): An Excellent Choice for Harsh Environments
The tongue and groove face (abbreviated as TG) has a more compact fit between its tongue and groove structures compared to the male and female face. The depth of the groove surface is generally 3 - 5mm, and the width is 5 - 8mm, which can tightly wrap the gasket inside. Compared with the male and female face, the area where the groove wraps and restricts the gasket is increased by about 15% - 20%, making the gasket more difficult to be extruded and the sealing performance more excellent.
Due to the good stability of the gasket in the groove, the requirement for clamping force is relatively low. Generally, under the same pressure conditions, the required bolt tightening torque is 10% - 15% smaller than that of the male and female face. In occasions with high temperature, high pressure, strong corrosive media, and extremely high sealing requirements, such as in the catalytic cracking units of the petrochemical industry, the media in the pipeline not only have the characteristics of high temperature and high pressure but also have certain corrosiveness. The temperature can reach 400 - 500℃, and the pressure is between 4.0 - 6.4MPa. The tongue and groove face can maintain good sealing performance under such harsh working conditions and ensure the normal operation of the device.
Ring Joint Face (RJ): A Key Choice for High - Pressure and Extreme Working Conditions
The ring joint face (abbreviated as RJ) adopts a unique trapezoidal ring groove structure and is equipped with a metal ring gasket as the sealing element. The angle of the ring groove is generally 23°, and the material of the metal ring gasket is mostly stainless steel or alloy steel. During operation, through tightening the bolts, the metal ring gasket is tightly pressed into the trapezoidal ring groove. The contact stress between the metal ring gasket and the ring groove can reach 200 - 300MPa, which can generate a very high sealing specific pressure, thereby achieving excellent sealing performance and can withstand pressures above 10.0MPa and temperatures above 450℃.
In high - pressure hydrogenation units, the reaction pressure is usually 10.0 - 15.0MPa, and the reaction temperature is 350 - 450℃. Under such high - pressure, high - temperature, flammable, and explosive extreme working conditions, the ring joint face can ensure the sealing reliability of the pipeline and prevent the leakage of flammable and explosive gases such as hydrogen. In the high - pressure stations of the natural gas long - distance transportation pipeline, the pressure is generally 6.4 - 10.0MPa, and the ring joint face is also needed to ensure the safe operation of the system.
Lens Face: An Exclusive Solution for High - Pressure and Ultra - High - Pressure Fields
The lens face is lens - shaped and is usually used in combination with a lens gasket. The material of the lens gasket is generally high - strength alloy steel, and the interference between it and the sealing face is controlled within 0.1 - 0.3mm. During connection, through a strong bolt pre - tightening force, the lens gasket is closely fitted to the sealing face to form a good seal. This structure can effectively disperse the pressure and adapt to the sealing requirements of high - pressure environments.
In high - pressure ammonia synthesis units, the reaction pressure is as high as 30 - 50MPa, and the lens face can withstand such high pressure to ensure the smooth progress of the ammonia synthesis production process. In high - pressure polyethylene units, the pressure is also between 10 - 30MPa, and the lens face also plays an important role, providing a reliable solution for pipeline connections in high - pressure and ultra - high - pressure industrial scenarios.
Wave - Tooth Composite Gasket Face: A Perfect Combination of Performance and Adaptability
The wave - tooth composite gasket face is a new type of sealing face form. On the basis of a metal toothed gasket, a 0.2 - 0.5mm - thick flexible material such as polytetrafluoroethylene is compounded on the surface. The tooth height of the metal toothed gasket is generally 1 - 2mm, and the tooth pitch is 2 - 3mm. It endows the sealing face with high strength and good compressive resistance and can withstand relatively large pressures and impact forces, generally able to withstand pressures of 5.0 - 10.0MPa. The flexible material on the surface provides good sealing performance and corrosion resistance and can adapt to complex media environments.
In chemical production, many reaction media are highly corrosive, such as sulfuric acid and hydrochloric acid. Taking the sulfuric acid transportation pipeline as an example, using the wave - tooth composite gasket face can effectively resist the corrosion of sulfuric acid and at the same time ensure good sealing performance, ensuring the safe operation of the pipeline within the temperature range of - 20 - 200℃. In industries such as petroleum and electric power, the wave - tooth composite gasket face is gradually being widely used in the connection parts of pipelines and equipment with high requirements for sealing performance and corrosion resistance.
Selection Basis and Case Analysis of Sealing Face Forms
Pressure Factor
Pressure is an important basis for choosing the form of the sealing face. Generally speaking, when the pressure in the pipeline is lower than 1.0MPa, the flat face or raised face can be preferentially considered. For example, in the urban heating system, the hot water transportation pressure is usually between 0.2 - 0.6MPa. Using flange connections with raised faces can not only meet the sealing requirements but also reduce costs. When the pressure rises to 1.0 - 4.0MPa, the male and female face begins to show its advantages; when the pressure is 4.0 - 6.4MPa, the tongue and groove face is more suitable; and when the pressure exceeds 10.0MPa, the ring joint face or lens face is a better choice. For example, in the pressurization stations of natural gas long - distance transportation pipelines, the pressure is generally 6.4 - 10.0MPa, and choosing the ring joint face can ensure the sealing performance and safety of the pipeline.
Temperature Factor
The influence of temperature on the sealing face cannot be ignored. When the temperature is lower than 200℃, most sealing face forms can be applied. However, when the temperature rises to 200 - 400℃, the high - temperature resistance of the sealing face material needs to be considered. For example, in the steam pipelines of thermal power plants, the steam temperature is between 300 - 400℃, and the lens face can ensure the normal operation of the pipeline with its good high - temperature resistance and compressive resistance. When the temperature exceeds 400℃, only the ring joint face matched with a high - temperature - resistant metal ring gasket can meet the sealing requirements.
Media Characteristics
The characteristics of the media are also crucial. If the media are corrosive, the wave - tooth composite gasket face or a sealing face made of corrosion - resistant materials is more appropriate. In the chemical pharmaceutical industry, many reaction media, such as solutions containing acid - base components, are highly corrosive. Using the wave - tooth composite gasket face can effectively prevent media leakage and equipment corrosion. For flammable, explosive, toxic, and harmful media, such as hydrogen and chlorine, sealing face forms with extremely high sealing performance, such as the male and female face, tongue and groove face, and ring joint face, must be selected to ensure production safety and environmental safety.
Maintenance and Development Trends of Flange Sealing Faces
Maintenance Points
Regular inspection of the wear and corrosion of the sealing face is of great importance. For flat and raised faces, a caliper can be used to measure the flatness of the sealing face, and the error should be controlled within ±0.1mm; for male and female faces, tongue and groove faces, and ring joint faces, it is necessary to check whether there are scratches, deformations, etc. on the mating surfaces. Once damaged gaskets are found, they should be replaced in a timely manner. Appropriate cleaning and maintenance methods should be adopted for different sealing face forms. For example, for the wave - tooth composite gasket face, sharp tools should not be used for cleaning to avoid damaging the flexible material on the surface. When disassembling and installing flanges, operate according to the specified torque value using a torque wrench to prevent the sealing face from being impacted or scratched.
Development Trends
With the continuous progress of industrial technology, the performance requirements for flange sealing faces are also getting higher and higher. In the future, flange sealing faces will develop towards higher sealing performance, wider working condition adaptability, longer service life, and more environmental protection. The application of new materials will be an important direction. For example, metal materials with higher strength and corrosion resistance will be developed for the production of sealing faces and gaskets. The manufacturing process will also be continuously innovated, such as using 3D printing technology to manufacture sealing elements with complex structures to improve the sealing performance. Intelligence is also a development trend. An intelligent sealing monitoring system will be developed to real - time monitor the working status of the sealing face, such as pressure, temperature, leakage, etc., through sensors, and promptly discover and solve problems.
In summary, different flange sealing face forms have their own characteristics and application ranges. In the actual design and installation of industrial pipelines, the most suitable sealing face form must be comprehensively considered and selected based on specific working conditions, such as the nature of the media, pressure, temperature, and other factors, to ensure the safe and stable operation of the pipeline system and avoid safety accidents and economic losses caused by sealing problems. At the same time, paying attention to the maintenance and development trends of flange sealing faces and continuously improving the sealing technology level of the pipeline system provides a solid foundation for the efficient progress of industrial production.