Discussion on factors affecting flange seal integrity
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There are many factors that affect the sealing integrity of pressure vessel flanges; everyone can share their experience or introduce some theoretical knowledge.
The factors affecting sealing performance are related to the sealing structure. (1) Bolt preload: The gasket must be compressed to achieve initial sealing. (2) Gasket performance: Specific pressure y, gasket coefficient m: (3) Quality of the compression surface: The shape and roughness of the compression surface should match those of the gasket ； (4) Flange stiffness ； (5) Operating conditions.
With the bolt area remaining unchanged, choose bolts with a smaller diameter and in larger quantities as much as possible； Once the type of gasket is determined, its width is also an important factor; an appropriate width can effectively ensure proper sealing ； The sealing surface of the flange also plays a significant role; it should be consistent with the gasket, which is a matter of fit ； The design of the flange, especially the conical neck of long-neck butt weld flanges, the ratio between the larger and smaller ends, and the effective thickness of the flange ； Furthermore, the effects of pressure and temperature on the medium are also important factors.
Theoretically, the sealing performance of flanges is ensured by their stiffness. However, since the mechanisms behind some sealing components have not yet been fully understood, current standards attempt to ensure flange sealing indirectly through factors such as strength. In essence, sealing is still ensured on an empirical basis; who knows, once the mechanisms of these sealing components are fully understood, all current practices might become obsolete.
“To achieve sealing integrity, it is necessary to adopt the innovative approach of considering the bolted flange connection as a single system. Theoretically, the key elements in handling bolted systems should follow a certain procedure that enables the full potential of bolted joint design to be realized, thereby facilitating leak-free operation. ” Excerpted from the Pipeline Manual (7th edition, Chinese translation). I believe the above statements are reasonable; it is incorrect to emphasize the role of any single element such as flanges, gaskets, bolts, nuts, fastening methods, or fastening procedures. Similarly, it is wrong to attribute leaks to other factors. Only when every element meets the required standards can true leak-free operation be achieved. It’s just my personal opinion; feel free to correct me!