Accurately predicting the leakage rate of flange connections is an important foundation for ensuring piping system safety and enabling predictive maintenance. For a long time, leakage rate prediction for flanges has relied mainly on empirical formulas and engineering judgement, with limited accuracy. In recent years, the development of leakage rate prediction models based on the physical deformation behaviour of gaskets is driving this field from experience towards science.
Traditional leakage rate prediction models use gasket stress as the core variable, assuming that higher gasket stress leads to lower leakage. However, extensive experimental data show that this assumption does not always hold. The variable that directly correlates with leakage rate is in fact the actual compression deformation of the gasket. This finding stems from a deeper understanding of the micro‑mechanisms of sealing—the gasket material must undergo sufficient compression deformation to effectively fill the micro‑irregularities of the flange sealing face, and the extent of this filling directly determines the cross‑sectional area and number of leakage pathways.
The core idea of the leakage rate prediction method based on gasket compression deformation is to calculate the leakage rate of non‑uniformly clamped flange connections through conductance integration. Specifically, the method first obtains gasket stress, leakage rate, and relative compression deformation data from leakage tests on uniformly compressed gaskets, establishing the correlation between the basic leakage rate and relative compression deformation. For the actual flange connection, a finite element analysis model is built to obtain the distribution of gasket compression deformation under operating conditions. Finally, the concept of “conductance” is introduced, and the conductance at different radial positions of the gasket is integrated both radially and circumferentially to obtain the total conductance of the non‑uniformly compressed gasket and to calculate the leakage rate.
The sophistication of this method lies in its ability to account for multiple complex factors. By incorporating creep analysis and cyclic plasticity analysis, the model can calculate the creep deformation and ratchet strain of the gasket under the combined action of internal pressure and cyclic bending moment. Experimental verification shows good agreement between predicted and measured values.
In practical applications, leakage rate exhibits regular relationships with loading conditions. Under the same static bending moment, leakage rate decreases as the medium pressure decreases; under the same internal pressure, leakage rate increases with increasing bending moment. Under cyclic bending loading, the gasket accumulates plastic strain as the number of cycles increases, leading to increased leakage rate. These patterns provide important reference for leakage risk assessment in engineering.
Furthermore, the surface roughness of the flange sealing face has a significant effect on leakage rate. When gasket deformation is small and insufficient to fill the sealing face valleys, macroscopic leakage channels exist at the contact interface; after the valley gaps are eliminated, interfacial leakage depends on micro‑capillary channels—there is a distinct transition point and leakage rate difference between the two states. This finding highlights the importance of matching sealing face machining quality and gasket deformation.
Physical‑model‑based leakage rate prediction methods provide more scientific tools for flange connection sealing design, quality inspection, and service evaluation. With continued research and accumulation of engineering validation, these methods are expected to be more widely applied across various industrial sectors.
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