Problems with double-end face seal installation
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This post was last edited by lovestory on 2011-3-26 at 15:04. Regarding the installation issues with double-face seals, we have several pumps designed according to API 53 standards, and these pumps constantly experience leakage of the sealing fluid – either internally or externally. Since we didn’t have any installation instructions for these seals, our seal manufacturer created a set of seals after conducting measurements; however, the results were not very satisfactory. I wonder if anyone else has encountered such problems. I suspect it might be an installation issue. (This seal features two sealing surfaces: one moving surface in the middle, with a stationary ring on each side. There is only one set of springs on the moving surface, which are supposed to press against both sealing surfaces.) Based on my analysis, the problem could be insufficient spring tension or springs that are too short. If the outer sealing surface is too tight, internal leakage may occur; conversely, internal leakage might happen if the opposite is true Is that the case? I would appreciate it if experts or those with more experience could give some guidance, or please explain it to me. All I can do is help by giving everyone extra points. Thank you! !
Based on your description, the two sets of sealed end faces should be installed \"back to back\", with a set of moving rings (two) in between; these moving rings share one spring, rather than having each moving ring its own spring. To determine whether a sealing effect can be achieved, it is necessary to calculate the specific pressure on the sealing surface and then determine the elastic force of the spring; it’s not something that can be accomplished simply by making measurements. For commonly used internal mechanical seals, in the case of low-viscosity media, the recommended face pressure range is between 0.2 and 0.4 MPa.
Thank you to the person above; you’re right. By \"medium,\" do you mean the sealing isolation fluid, or the fluid that is pumped? Additionally, could you please explain in detail what the concept of end-face specific pressure is? Thank you! ! ! !
Is it modular or separate-type? I think the compression amount of the moving ring is usually calculated very accurately by professional manufacturers; I suggest you check whether there are any leaks in the seals of the moving and stationary rings. The key is to distinguish whether it’s a modular or separate-type design, as that affects the approach, as well as the viscosity of your material What is the operating pressure of the pump?
A low-viscosity medium refers to the medium that is transported, not the isolation fluid. As mentioned above, you need to clearly specify the medium being pumped, the inlet pressure, as well as the medium and pressure of the isolation fluid. A leak in the isolation fluid is most likely, as mentioned above, due to a problem with the static seal on the sealing ring. Select the appropriate seal material based on the conveying medium and the properties of the isolation fluid. Some seal ring materials are theoretically suitable, but the seal rings purchased by some mechanical seal manufacturers are of poor quality, and as a result the sealing requirements cannot be met. If it is ultimately determined that the issue lies with the sealing ring, the simplest and most direct solution is to upgrade the material of the sealing ring.
Every manufacturer of mechanical seals provides a design calculation manual during the design process. The end-face specific pressure and spring specific pressure will both be calculated accordingly. This is what they do. The end-face specific pressure must be greater than the liquid film pressure between the sealing surfaces, so as to ensure a good fit between the end faces, prevent the sealing surfaces from separating during operation, and maintain the stability of the sealing function. However, the specific pressure should not be too high either, in order to prevent the generation of excessive heat, which could damage the liquid film between the sealing surfaces, lead to increased wear, and raise power consumption.
As the poster mentioned, this situation can occur if it’s not a purely modular mechanical seal. It’s still necessary to turn to a qualified sealing factory to resolve the issue.
Does the isolation fluid leak externally or internally? Does external leakage refer to leakage outside the pump body? If there is a leak, it is necessary to determine whether it is occurring between the sealed shaft sleeve and the pump shaft or at the sealing gasket. In the former case, the seal between the shaft sleeve and the pump shaft is not effective or has been damaged; in the latter case, there may be a problem with the sealing surface. Did you conduct a hydrostatic test before installation? Also, is your sealing modular? If it’s not containerized, the compression amount may need to be adjusted before installation. If it is modular, there should be no issue with the spring force mentioned by the original poster. One more question: which is the sealing manufacturer? I’m sorry, the original poster provided too little information, which forced me to ask so many questions.
If a pump experiences so-called leakage of the isolation fluid, either internally or externally, can it be concluded with certainty that it is caused by a problem with the mechanical seal? Should the answer be yes or no? If you choose no, congratulations – you’ve answered correctly.
LZ still needs to provide more detailed relevant information so that fellow sailors can conduct a comprehensive analysis and address the issues in a targeted manner. ① How is internal leakage determined? ② What is the pressure of the isolation fluid in plan53? ③ Seal chamber pressure, or pump inlet and outlet pressures, as well as the specific type of pump (for reference in estimating the seal chamber pressure value)? ④ What is the temperature of the pumped liquid? Is there any air vibration when the pump is running? ⑤ Carefully inspect the outer diameter surface of the small spring from the failed machine seal that has been replaced to check for any signs of wear, or even signs of the spring being broken and damaged
We also have the same mechanical seal as what you mentioned. Could the poster take a look at the damage to the mechanical seal? Is there any damage from burning? We have encountered it too. The seal water side has been burned out. The analysis shows that the operator started the pump without turning on the water seal. There aren’t many issues with the materials. The spring is broken. Analyze the reason: water started flowing suddenly after the mechanical seal burned out upon startup. Damage caused by sudden change in material.