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I. Composition and Classification Fiber Reinforced Plastic (FRP) flanges are made of FRP material, which is a composite material formed through a composite manufacturing process using high-molecular epoxy resin as the matrix and materials such as fiberglass or carbon fiber as reinforcing agents. Commonly used fiberglass reinforced plastic flanges are mostly applied to medium and low-pressure pipelines and containers with a pressure not exceeding 3 MPa. The main types of such flanges include integral flanges, bonded flanges, and slip-on flanges. a. The overall flange is generally a flat flange with equal wall thickness. The advantage of this structure is that the flange ring and the cylinder are formed as a single unit, with the reinforcing glass fibers and fabrics being continuous, which allows full utilization of the high strength and easy formability of fiberglass-reinforced plastics. The disadvantage is that the equal-wall-thickness design does not match the stress distribution within the flange, making it difficult to meet the requirements for equal strength and stiffness ； During use, the junction between the flange ring and the cylinder is prone to significant deformation under longitudinal stress, and may even develop microcracks and suffer from cracking failure. b. A bonded flange is formed by machining the flange ring and the cylinder separately and then bonding the two together. This structure is widely used; it makes full use of the advantage of fiberglass-reinforced plastic’s ease of molding – the molds are simple, making production straightforward – and it is suitable for manufacturing large-diameter, small-batch, and custom-shaped fiberglass-reinforced plastic flanges. However, its biggest drawback is the discontinuity of glass fibers between the flange ring and the cylinder body, which results in a significant reduction in the strength of the joint, making it prone to failure. Its safety level is low, and this safety issue worsens as the operating temperature increases. c. The swivel flange combines the advantages of a solid flange with the benefit of the high stiffness of the swivel metal flange ring, **reducing leaks that can occur due to bending or excessive deflection of the flange ring between the two bolts during use of the fiberglass-reinforced plastic flange after it has been tightened. However, as mentioned earlier, the equal-wall-thickness structure still does not conform to the stress distribution within the flange. To this end, still based on the stress distribution within the flange, and making full use of the design flexibility and easy formability of fiberglass-reinforced plastic, a more reasonable flange structure is selected. II. Advantages 1. It possesses excellent physical properties. The specific gravity of fiberglass-reinforced plastic flange materials is 1.8–2.1, which is about 1/4 that of steel; they possess a higher specific strength compared to steel, cast iron, and plastics. The weight of fiberglass-reinforced plastic flanges is generally no more than 1/3 of that of steel pipes of the same specification. They have excellent physical and mechanical properties. In addition, the expansion coefficient of fiberglass-reinforced plastic flanges is roughly similar to that of steel, while their thermal conductivity is only 0.5% of that of steel, making them an excellent insulator for heat and electricity. 2. Resistant to chemical corrosion. It has a long service life and is suitable for transporting various media such as acids, alkalis, salts, etc. 3. Excellent hydraulic properties. Hydraulic properties are one of the important characteristics of glass fiber reinforced plastic pipes. Excellent hydraulic properties mean low fluid head loss, allowing the use of smaller pipe diameters or pumps with lower power consumption, thereby reducing initial investment in pipeline systems, saving electricity, and lowering operating costs. The inner surface of fiberglass-reinforced plastic is quite smooth; the surface roughness is typically around 0.008, which means it can be considered a \"hydraulically smooth pipe\". During operation, the inner surfaces of steel pipes, cast iron pipes, cement pipes, etc., often suffer from local corrosion and become increasingly rough, whereas fiberglass-reinforced plastic maintains the smoothness of a newly manufactured pipe. 4. Low maintenance costs. Generally speaking, glass fiber pipes do not require special anti-corrosion treatment ； The insulation layer can be thinned, or no insulation treatment may even be applied ； Pipes are relatively light, the lifting equipment required has a lower tonnage and thus consumes less power. Fiber glass pipes are longer than cement pipes and cast iron pipes, which results in fewer joints; all these factors reduce costs associated with installation and maintenance, as has been proven by numerous engineering projects. 5. High design flexibility and short modification cycle. Fiberglass reinforced plastic is made by winding fiber reinforcement materials impregnated with a resin matrix layer by layer onto a core mold under specific process conditions and then curing them appropriately. Pipes have a layered structure, and it is possible to adjust the various physical and chemical properties of fiberglass reinforced plastic pipes by changing the resin system or using different reinforcement materials, thereby creating pipes with different pressure ratings or specific properties to suit various media and operating conditions. A short modification cycle is a notable feature of fiber-wound composite materials; isotropic metal pipes cannot compete with them in terms of application scope. III. Applications 1. Municipal engineering – water supply engineering, drainage engineering, stormwater engineering ； 2. Electricity – power plant circulating water, power plant desulfurization ； 3. Telecommunications – Cable protection tubes ； 4. Petrochemicals – oil well injection pipes, projects for transporting various corrosive fluid media ； 5. Agriculture, Forestry, and Water Resources – Irrigation in agriculture, forestry, and water resources ； 6. Other fluid medium transportation fields ； IV. Standard System 1. Glass fiber reinforced plastic flange standard system: Internationally, there are mainly two systems for pipe flanges – the European pipe flange system represented by Germany’s DIN standard (including the former Soviet Union), and the American pipe flange system represented by the ANSI standard. IOS7005-1 is a standard issued by the International Organization for Standardization in 1992; it is essentially a pipe flange standard formed by combining the pipe flange standards from the United States and Germany. The pipe flange connection dimensions of the two systems are different in terms of safety, making them incompatible with each other. It is most appropriate to distinguish the pipe flanges of the two systems by pressure class: for the European system, these are 0.25, 0.6, 1.0, 1.6, 2.5, 4.0, 6.3, 10.0, 16.0, 25.0, 32.0, 40.0 MPa; for the American system, they are 1.0, 2.0, 5.0, 11.0, 15.0, 26.0, 42.0 MPa. 2. National standard flanges: National standard flanges refer to those whose material and manufacturing meet **specified standards. National standard flange refers to flanges that are manufactured in accordance with the standards of the People’s Republic of China, specifically the standards GB/T 9112–9124-2010 for steel pipe flanges. GB series (GB/T9119-2010 standard), JB series (Ministry of Machinery), HG series (HG20592 standard from the Ministry of Chemicals), ASME B16.5 (American standard), BS4504 (British standard), DIN (German standard), JIS (Japanese standard). V. Sealing methods: Fiberglass and plastic pipes are used in the processing industry due to their low cost and excellent chemical resistance. However, none of these materials achieve the strength of metal pipes. Therefore, the strength of the flange limits the maximum torque that can be applied by the bolts, which in turn limits the compressive stress on the gasket. Basically, the gasket materials used in the past and now are all elastomers, such as ethylene propylene diene monomer (EPDM), soft PVC, and expanded tetrafluoroethylene. Here, I would like to recommend to everyone the Fle*ngSeal industrial sealing expanded tape series. Fle*ngSeal sealing material is a porous, expanded strip manufactured using a special process. This material is soft, compressible, and easy to shape; it can form a good seal at the minor cracks and defects in the sealing interface under low pressure, thereby effectively protecting brittle structural materials and ensuring a tight seal. For non-metallic components such as glass, ceramics, graphite, and plastics, Fle*ngSeal sealing materials can also achieve good sealing results. It can better compensate for errors caused by machining defects, rigid deformation, misalignment during installation, etc., balance uneven pre-tensioning forces, and effectively address leakage issues of various gases and liquids under complex conditions. In addition, the Fle*ngSeal sealing tape boasts advantages such as easy installation and a long service life, which can effectively reduce maintenance costs and downtime while improving production efficiency and economic benefits. In short, the selection and use of gaskets are very important. If you are looking for a high-quality, high-performance sealing tape, consider Fle*ngSeal industrial sealing tape – it offers reliable sealing solutions to ensure the safe and stable operation of your equipment. The above content is sourced from the Internet; please remove it if it violates rights