Seeking help with the issue of face pressure and spring pressure in mechanical seals
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I’m new to mechanical seal design and have encountered a confusing issue: the face pressure is calculated based on the spring pressure, yet the spring pressure in turn is determined by the face pressure. I’m a bit puzzled. Referring to Gu Yongquan’s manual on mechanical seal design, a range of values is provided as a reference, such as the recommended value of 0.3–0.2. There are countless variables involved here, and it’s not practical to test each combination individually. Therefore, I would like to ask if this parameter is set based on experience, but still must remain within this range? Then, parameter adjustments can be made based on subsequent usage or after leak detection through dynamic pressure testing; or ANSYS can be used for simulation to obtain specific data Is there any experienced teacher who can teach me? I’m willing to offer silver as compensation.
When designing mechanical seals, there is indeed a interdependent relationship between the end-face specific pressure and the spring specific pressure. Typically, these parameters require initial values to be set based on experience and relevant design manuals, ensuring that they remain within the recommended ranges. Then, these parameters can be adjusted and optimized through experiments and dynamic tests such as leakage testing. Additionally, using simulation software such as ANSYS is also a good method, as it can help predict and verify the feasibility of the design. In short, experience and experimentation are key; making proper use of simulation tools can improve design efficiency and accuracy. .
Spring specific pressure is the spring force divided by the contact area of the sealing ring surface, Ps=Fs/A. The spring specific pressure remains constant. The end-face specific pressure is influenced by many factors (such as the seal chamber pressure and back-pressure coefficient), and it varies.
However, when calculating the end-face specific pressure, the spring specific pressure is also required; these two are interdependent, making it quite difficult to handle
Whether it is the spring specific pressure or the face specific pressure, this specific pressure represents the stress acting per unit area on the sealing face. Only a robust structure can ensure the sealing of the sealed surface; this is fundamental. The spring force ensures that the sealing surfaces remain in contact even in the absence of fluid pressure; generally, once pressure is applied, the load generated by the spring is very small compared to the load caused by the pressure. The end-face specific pressure mentioned in general varies depending on the application. For traditional low-leakage contact-type structures, the closing force (the sum of the fluid pressure load acting on the sealing surface and the spring load) is definitely greater than the opening force (which is usually the load generated by hydrostatic pressure). The excess part of the closing force is taken care of by the end-face contact force. To avoid excessive frictional heat resulting from too high a contact force, it is common to calculate the specific pressure generated by this contact force ； As for contactless structures, since the end faces do not come into contact during operation, wear and the energy consumption resulting from frictional heat are avoided; therefore, they are favored in high-speed and high-pressure applications. But how is it possible to achieve no contact? The closing force needs to be balanced by the opening force; how is the opening force achieved? It relies on hydrodynamic pressure, and this hydrodynamic pressure is related to key technologies.