Statistics show 90% of flange leakage issues have nothing to do with pipe quality. The main culprits include aging gaskets, flange misalignment, uneven bolt tension, and thermal expansion & contraction of pipes. Locate the leakage point and root cause first, then apply targeted fixes to resolve most flange seepage permanently.
1. Two Major Types of Flange Leakage
Flange leakage falls into two distinct categories with different root causes. Blind uniform repairs will lead to recurring leaks.
(1) Leakage persists after pipeline shutdown and pressure relief
This is mostly caused by hardened aging gaskets, impurities on flange sealing surfaces, or offset gaskets during installation, resulting in failed sealing. It stems from worn accessories and improper installation.
(2) No leakage under atmospheric pressure, but seepage occurs during hydrostatic testing
Uneven bolt tightness, misaligned flanges, and pipe tensile stress will widen gaps at flange joints as internal pressure rises, triggering water seepage.
2. Quick Flange Leak Troubleshooting Steps
On-site inspection prioritizes four factors: gaskets, bolt torque, flange alignment, and pipeline stress. Standard inspection workflow:
(1)Visual observation
Uniform outer-circle seepage: Overall sealing failure; inspect sealing components
Local dripping: Improperly installed, offset gaskets
(2)Press test inspection
Seepage reduces under pressure: Loose bolts with insufficient torque
No change after pressing: High-temperature lines suffer loose bolts from thermal expansion & contraction
(3)Flange alignment check
Offset/unparallel flanges: Non-standard construction; realign flanges
(4)Operating condition inspection (if aligned properly)
Acid & alkali pipelines: Wrong gasket material corroded by media
3.Common causes of water seepage
Leakage Phenomenon Root Causes High-risk Scenarios
Static dripping & constant slow seepage Aging gaskets, impurities, damaged flange sealing faces Old pipelines, acid & alkali corrosive environments
Leaks only after pressure testing Uneven bolt torque, loose diagonal fasteners Newly installed or post-repair pipelines
One-sided flange leakage Flange offset, uneven fitting, pipe tensile stress Unfixed pipes, missing support brackets
Repeated leakage with temperature shifts Bolt loosening from thermal expansion & contraction High-temperature media, intermittent operation lines
4. Standard Repair Solutions & Construction Precautions
Targeted repairs based on leakage causes avoid repeated rework and deliver one-time permanent fixes.
(1)Leakage from aging gaskets or trapped impurities
Shut down the pipeline, drain all media and fully release pressure. Disassemble flanges, thoroughly clear impurities on sealing surfaces, and install brand-new gaskets of matching specifications.
Never reuse old gaskets or stack two gaskets together.
Jiqing supplies rubber and fluororubber gaskets perfectly matched with our pipes and flanges, delivering stable sealing under acid, alkali and high-temperature working conditions.
(2)Uneven bolt tension & loose fasteners
Tighten bolts diagonally in 2–3 stages for uniform force. Do not fully fasten one side in a single pass.
For high-temperature, high-pressure or toxic medium pipelines, pressure-on bolt tightening is prohibited due to safety risks.
Tightening sequence: Start with middle bolts, then side bolts, following clockwise diagonal order.
(3)Leakage from offset flanges & pipe tensile stress
Adjust pipe supports and calibrate pipe ends. Use a level gauge to ensure two flanges stay parallel and fully aligned before tightening bolts to eliminate seepage at source.
(4)Recurring leakage from thermal expansion & contraction
Retighten bolts a second time after hot pipelines heat up. Avoid mismatched gaskets of inconsistent sizes. Fully clean gaskets before installation to eliminate permanent leakage points caused by residual debris.
Flange Daily Installation Guidelines
For acid, alkali and high-temperature corrosive environments, select corrosion-resistant gaskets of matching material to prevent sealing failure from long-term medium erosion.
Follow diagonal staged bolt tightening for all new flanges. Retighten bolts one day after commissioning high-temperature pipelines to compensate for gaps generated by thermal expansion and contraction.
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