Discussion on the failure of packing seals
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Dear all, I am currently using a conventional packing shaft seal to seal the reaction tank. The operating conditions are as follows: 1. Pressure: 3 kg 2. Shaft diameter: 30 cm 3. Rotational speed: 20 RPM. I would appreciate any experience you may have with conventional packing seals. (Please note that our equipment was purchased quite some time ago, so it’s not possible to replace the mechanical shaft seal; currently, leakage occurs once a month.) Thank you everyone!
In the machinery industry, packing seals are mainly used as dynamic seals. It is commonly used for sealing the shafts of centrifugal pumps, compressors, vacuum pumps, and mixers. When designing a packing seal, the operating conditions of the mechanical equipment should be the main consideration; the packing selected should meet the following requirements: 1. It should possess a certain degree of plasticity, so as to generate a certain radial force under compression and make contact with the shaft. 2. It possesses sufficient chemical stability, does not contaminate the medium, the filler is not swollen by the medium, the impregnant in the filler is not dissolved by the medium, and the filler itself does not corrode the sealing surface. 3. The filler has good self-lubricating properties, is wear-resistant, and has a low friction coefficient. 4. When there is a slight offset in the shaft, the packing should have sufficient floating elasticity. 5. It is simple to manufacture and easy to fill. For this reason, it is necessary to regularly adjust the degree of compression of the filler, so that after some lubricant is lost over time due to operation, more lubricant can be extruded to compensate for the reduction in compression force caused by changes in the filler’s volume. Of course, constantly compressing the filler in this way will eventually deplete the impregnant, so it is necessary to replace the filler regularly. Furthermore, to maintain the liquid film and remove frictional heat, it is also necessary to allow a small amount of leakage at the packing.
Related to temperature fluctuations of the sealing medium
It seems to be a high-load application with a low rotational speed and a large shaft diameter; adding another set of packing will suffice, as long as there is no leakage, with the aim of being able to increase the pre-tightening force in the future.