Why are gaskets needed?

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This post was last edited by Xin Ruifangxiao on 2022-9-20 at 10:38. Have you ever wondered why sealing interfaces cannot achieve sealing on their own and need the help of sealing materials? This is because all flanges, whether new or old, inevitably have issues such as inaccuracies in the sealing surface and installation errors, and gaskets are designed primarily to address these problems. Let’s expand on the requirements of the sealing interface for gaskets: We have already analyzed the most fundamental requirement, which is to compensate for the unevenness of the interface; therefore, the gasket needs to be compressible and capable of filling in those gaps. When a gasket is added to the sealing interface, in a sense it acts as an additional section of pipe between the interfaces; therefore, it is essential that the gasket itself prevents the medium from passing through, and it must also have properties similar to those of the flange or the pipe, or at least meet the minimum requirements for such properties. Based on their material, gaskets can be divided into non-metallic gaskets, metal composite gaskets, and metal gaskets. Let’s take a look at what are the differences in their application conditions Upon reading this, you might also wonder: how do metal gaskets exhibit compressibility and resilience to achieve interface sealing? The preloading specific pressure y of the gasket (also referred to as specific pressure, minimum design compression stress, or minimum effective compression stress) is the compressive force per unit sealing area applied to the gasket; it represents the minimum value necessary to cause the gasket to deform elastically and to fill in any microscopic irregularities on the flange surfaces effectively, thereby preventing leaks. Different gaskets have different y values, which are independent of the operating pressure of the piping system; even when the operating pressure is very low, the y value of the gasket remains unchanged. When the piping system is pressurized to the operating pressure, the axial force B generated by the internal pressure acts to separate the two flanges, thereby reducing the clamping force A acting on the gasket. When the tightening pressure on the effective cross-section of the gasket drops to a certain critical value, sealing can still be maintained; at this point, the remaining tightening force on the gasket constitutes the effective tightening pressure. Leakage occurs when it drops below the critical value, even blowing away the gasket. Therefore, the effective tightening force of the gasket must exceed m times the operating pressure C of the piping system, where m = (Α−Β)/C.