stub end

Flammable and explosive high-pressure pipelines in petrochemical industry require weld neck flanges Petrochemical pressure pipeline components are used to connect or assemble pressure bearing and sealed pipeline system components, including pipes, fittings, flanges, gaskets, fasteners, valves, joints, hoses, traps, filters, separators, etc. Among them, flammable and explosive high-pressure pipelines require forged weld neck flanges.   Seals for flammable and explosive high-pressure pipelines in petrochemical industry include flange sealing surfaces, flange gaskets, and fasteners. The flange sealing surface forms include flat face (FF), raised face (RF), ring joint face (RTJ), tenon groove, special groove, etc. The flange gasket includes flat gasket, spiral wound gasket (with inner and outer rings), and metal gasket (oval, octagonal).     High quality butt welded flanges should meet the following requirements: 1.No defects such as cracks, shrinkage, slag inclusion, and cold-lap; 2.The depth of rust, dents, and other mechanical damage should not exceed the negative deviation of wall thickness allowed by the product standard; 3.The machining accuracy and roughness of threads, sealing surfaces, and grooves should meet the requirements of the design documents or product standards; 4.The weld seam should be well formed and smoothly transition to the base metal, without defects such as cracks, lack of fusion, and incomplete penetration; 5. Metal bellows expansion joints, spring supports and hangers, and other shipping parts or positioning pin blocks should be complete and free of looseness.       The compliance of flanges, blind flanges, and stub end can be determined through the following visual inspections: a) The sealing surface should be flat and free of rust and radial scratches; b) The outer edge of the flange and flange cover should have a permission mark; c) The product standard number, nominal size, nominal pressure, material, and sealing surface type code should match the quality certificate.       Standard class rating of flanges According to the different nominal pressure ratings of valves, flanges with different pressure ratings are configured in pipeline flanges. Several commonly used flange pressure ratings are classified according to international standards According to ASME B16.5, steel flanges have 7 pressure ratings: Class150-300-400-600-900-1500-2500 (corresponding to Chinese standard flanges with PN0.6, PN1.0, PN1.6, PN2.5, PN4.0, PN6.4, PN10, PN16, PN25, PN32Mpa ratings)

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.