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In a large or medium-sized petrochemical plant, tens of thousands or even hundreds of thousands of flanges are used, and each flange connection can potentially become a leakage point. Leaks in flange seals not only lead to issues such as waste of resources and environmental pollution, but also have a significant impact on the safe operation of the equipment. What we’re sharing with you today is—several types of leakage at flange sealing surfaces and the conventional methods for dealing with them. I. Factors Affecting Flange Sealing Although there are many factors that affect flange sealing, they can be summarized into three main aspects: first is the condition of the flange connection components themselves (such as flanges, gaskets, and bolts) ； The second is the operating conditions (medium, pressure, temperature) ； Third are external factors such as improper installation. For more information, please check out our previous articles. II. What to do in case of leakage at the flange sealing surface? The appearance of numerous bubbles around the flange sealing surface at low pressures (< 1.8 MPa) may be caused by insufficient bolt pre-tightening; the sealing surface not being cleaned properly, with impurities possibly damaging it; or poor fit between the gasket and the sealing surface. In such cases, the flange should be disassembled for inspection. If the sealing surface is damaged, it should be ground using standard grinding tools to ensure that its surface roughness and precision meet the required standards. If the gasket is damaged, it needs to be replaced with a new one, and the old one repaired. If the bolt preload is insufficient, it is necessary to recalculate the preload and increase it appropriately. The reason for local bubbles on the flange sealing surface at lower pressures (< 1.8 MPa) may be uneven bolt tightening, which leads to uneven flange gaps; or local damage to the sealing surface or gaskets. In such cases, the flange gaps can be measured first; if they are uneven, the gaps can be adjusted by tightening the bolts while the system is under pressure. It is necessary to check whether there is still leakage during this process, and if the leakage does not decrease, the flange must be disassembled to inspect the sealing surface and gaskets. The reason for the presence of bubbles around the flange sealing surface at high pressures (> 7.5 MPa) may be insufficient bolt pre-tightening; this situation is encountered quite often, as the torque or pulling force specified in the design is calculated under ideal conditions and is generally too low. Therefore, after tightening to the design values, uniform leakage around the perimeter occurs once the test pressure reaches a certain level. The solution is to increase the torque in increments of 5% based on the specified value when tightening the high-pressure bolts in the hydrogenation unit, raising the maximum torque to 80% of the bolt’s yield strength, thereby eliminating the leakage points. Furthermore, when tightening, if a stress testing device is used for monitoring, the value of the tightening force will be more accurate. Chengdu Xinrui Fangxiao Technology Co., Ltd. is a technology-driven enterprise dedicated to the research, development, production, and sales of expanded polytetrafluoroethylene (ePTFE) and its products; it specializes in manufacturing high-performance sealing products in various shapes and size specifications. Through continuous innovation, we have obtained several patented technologies in terms of manufacturing processes. With our expertise in engineering plastics – particularly in the manufacturing processes and applications of expanded polytetrafluoroethylene – along with our thorough and high-quality service, our company will surely become your reliable partner in the future. The above content is excerpted from the Internet; please remove it if there is any infringement **