Lap Joint Flange

What is a lap joint flange? A lap joint flange, also known as a loose flange, is a type of flange that is used to connect two separate sections of pipe or fittings together. It consists of two main components: the stub end and the backing flange.   Lap joint flange is mainly used to cover the flange on the pipe by stub end. The flange can move on the pipe end, and the stub end is the sealing surface. The function of the flange is to press them tightly. Therefore, due to being blocked by the stub end, the loose flange will not come into direct contact with the medium. LJ flange is commonly used in situations where the medium temperature and pressure are not high but the medium is highly corrosive. When the medium is highly corrosive, the part of the flange in contact with the medium (stub end) is made of corrosion-resistant high-grade materials such as stainless steel, while the external part is clamped with flange rings made of low-grade materials such as carbon steel to achieve sealing.   During installation, the stub end is slid onto the pipe or fitting, and the backing flange is aligned with the stub end. The two components are then fastened together using bolts, which are inserted through the bolt holes in the backing flange and tightened. The lap joint allows for rotational movement and adjustment between the two components, providing flexibility in alignment and ease of assembly.     The characteristics of lap joint flanges: 1. Cost savings. When the material of the pipe is special and expensive, the cost of welding flanges of the same material is high. However, when using loose flanges, flanges of the same pipe material can be used with LJ flanges. Therefore, cost savings can be achieved. 2. Easy to construct. Used for situations where it is difficult to align the flange bolt holes during connection, or to prevent changes in the flange bolt holes when replacing equipment in the future. Easy to install for large diameter pipes. 3. Easy to maintain and clean: Due to the simple structure of the LJ flange, installation and disassembly are relatively easy, so its maintenance and cleaning are very convenient. 4. Low installation cost: The manufacturing and installation cost of loose flange is relatively low, and the cost is controllable. 5. Low stress tolerance. 6. Low strength at the welding ring (especially when the thickness is less than 3mm) 7. This type of flange is not allowed to be used in situations suitable for RT testing.       Application scenarios and functions 1.Chemical industry: Loop flanges are widely used in the chemical industry and can be used to connect various chemical pipelines and equipment to ensure the normal operation of chemical production.   2. Oil and Gas Industry: The oil and gas industry requires a large amount of pipeline transportation and storage of oil and gas, and the looped flange is more sturdy compared to other flanges, so it can better ensure safety.   3. Food and Beverage Industry: The production of food and beverages requires the use of a large number of professional equipment. Loop flanges can play a role in connecting pipelines and equipment, and can ensure the safety of product production.       In summary, loop flanges play an irreplaceable role in industrial production, which is required in the production process of different industries. A lap joint flange is a type of flange used to join two sections of pipe or fittings together. It consists of a stub end, which is welded to the pipe or fitting, and a backing flange, which is bolted to the stub end. The lap joint design allows for rotational movement and flexibility during installation, making it suitable for applications where alignment adjustments are needed.  

What is a flange? A flange is mainly used for connecting parts between pipelines and valves, between pipelines, and between pipelines and equipment, which play a sealing role. Because there are many applications between these equipment and pipelines, two planes are connected by bolts, and the connecting parts with sealing function are all called flanges. Generally, flanges have circular holes for fixing purposes. For example, when used at pipeline connections, a sealing ring is added between two flange plates, and then bolted together. flanges with different pressures have different thicknesses and use different bolts. The main materials used for flanges are carbon steel, stainless steel, and alloy steel, etc.     The difference between stainless steel flange and carbon steel flange Both stainless steel and carbon steel belong to the category of steel, but they are fundamentally different because they contain different other elements. Generally, steel that only contains carbon is called carbon steel, while stainless steel contains other alloy materials, and its corrosion resistance and wear resistance are very good. The main differences between the two are as follows: 1. Density difference: The density of carbon steel is slightly higher than that of ferritic and martensitic stainless steel, and slightly lower than that of austenitic stainless steel. 2. Different compositions: Stainless steel is the abbreviation of stainless and acid resistant steel. Steel that is resistant to weak corrosive media such as air, steam, water, or has rust resistance is called stainless steel; And the type of steel that is resistant to chemical corrosion media (such as acid, alkali, salt, etc.) is called acid resistant steel. Carbon steel is an iron carbon alloy with a carbon content ranging from 0.0218% to 2.11%. Also known as carbon steel. Generally, it also contains small amounts of silicon, manganese, sulfur, and phosphorus. 3. Different corrosion resistance. Carbon steel flanges are prone to oxidation and corrosion, and are not corrosion-resistant; Stainless steel flanges have better corrosion resistance due to their high proportion of elements such as chromium and nickel. 4. Different high temperature resistance performance. Carbon steel flanges are prone to failure in high temperature environments; Stainless steel flanges can effectively resist thermal expansion and deformation at high temperatures. 5. Different resistances: The resistivity increases in order of carbon steel, ferrite, martensite, and austenitic stainless steel. 6. Different coefficients of expansion: The order of linear coefficients of expansion is also similar, with austenitic stainless steel having the highest coefficient and carbon steel having the lowest. 7. Magnetic differences: Carbon steel, ferritic and martensitic stainless steel have magnetism, while austenitic stainless steel has no magnetism. However, when it undergoes martensitic transformation during cold work hardening, magnetism will be generated. Heat treatment can be used to eliminate this martensitic structure and restore its non-magnetism.     Advantages and disadvantages of carbon steel and stainless steel flanges Carbon steel flanges are relatively inexpensive and have high tensile strength, making them commonly used in some low-pressure situations. However, carbon steel flanges have poor corrosion resistance and are prone to rusting in humid or acidic environments. Stainless steel flanges are relatively expensive, but they have good corrosion resistance and can maintain stable performance in high-temperature and high-pressure environments. However, the tensile strength of stainless steel flanges is weak and needs to be selected according to specific usage scenarios.     The use of carbon steel and stainless steel flanges Carbon steel flanges are suitable for general low-pressure water, gas, and oil pipelines and are an economical choice. However, regular maintenance is required during use to prevent rusting. Stainless steel flanges are suitable for high temperature and high pressure applications, such as chemical, petroleum, pharmaceutical, and food industries. Stainless steel flanges can withstand high pressure and temperature, and have corrosion resistance, which can maintain their original performance for a long time.     When choosing carbon steel or stainless steel flanges, it is necessary to choose according to the specific usage environment and requirements. In general low-pressure situations, carbon steel flanges can be chosen as an economical option, but regular maintenance is required. In high-temperature and high-pressure production environments, it is necessary to choose stainless steel flanges with good corrosion resistance to ensure the normal operation of the product.