Common Installation Mistakes of Flange Pipe Connections
Publication Date:
Jul 30,2026
Author:
Dacheng Jiaye
Standard installation directly influences long-term running safety of flange pipe fittings, while many frequent construction errors trigger hidden leakage troubles that gradually break out after pipeline operation.
Standard installation directly influences long-term running safety of flange pipe fittings, while many frequent construction errors trigger hidden leakage troubles that gradually break out after pipeline operation. Uneven bolt tightening ranks first among common installation faults. Many construction workers tighten bolts sequentially along a circular direction instead of cross symmetrical tightening. This operation causes asymmetric pressure on the sealing gasket. Partial areas of the gasket obtain insufficient compression and form natural leakage channels. In severe cases, uneven force leads to flange warping deformation. Professional installation requires tightening bolts in 3 to 4 rounds with cross sequence to achieve uniform stress distribution on the whole sealing surface. Second typical error is mixed use of different standard flanges. Constructors sometimes assemble ASME standard flanges with EN standard flanges due to insufficient material preparation. Mismatched bolt hole positions and inconsistent sealing surface dimensions result in incomplete fitting. Even if bolts are forced to install, local stress concentration will emerge, causing leakage under pressure fluctuation. Damaged flange sealing surfaces are often ignored before assembly. Scratches, dents, welding slag and rust on sealing surfaces will break the continuity of gaskets. Tiny gaps formed by surface damage enable medium penetration. Operators should clean and inspect flange surfaces thoroughly before assembly. Minor scratches can be polished for repair, while heavily damaged flanges need replacement. Improper gasket installation is another widespread problem. Wrong gasket size, repeated use of aged gaskets, and deflection of gaskets during assembly all reduce sealing performance. Gaskets cannot be reused after disassembly. Once compressed, internal elastic structure cannot recover, losing sealing capacity after reinstallation. Adding multiple gaskets to compensate assembly gaps is extremely dangerous. Multiple gasket layers increase leakage paths and make compression control difficult. If assembly gaps exist, workers need to adjust pipe alignment rather than stacking gaskets. Excessive or insufficient bolt torque also brings risks. Too small torque cannot compress gaskets adequately. Excessive torque squeezes gaskets beyond elastic limit and causes permanent crushing failure. In serious situations, over-tightening cracks flange bodies. Pipeline misalignment imposes extra bending load on flange connections. When two pipelines are not concentric, flange joints bear continuous bending stress. Long-term alternating stress causes bolt fatigue fracture and flange deformation. Constructors must adjust pipeline position to guarantee coaxiality before fastening flange bolts. After installation, pressure testing is necessary to verify sealing performance. Real-time leakage observation during pressure testing can eliminate hidden dangers before formal system startup.
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