Among mechanical seal leaks, the leakage between the shaft sleeve and the shaft (inter-shaft leakage) is caused by the impeller seal
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Among mechanical seal leaks, is the leakage between the shaft sleeve and the shaft (inter-shaft leakage) the cause of the impeller problem? How can we confirm that it is this type of leakage caused by the leak point?
Leakage between the sleeve and the shaft is caused by a failure of the seal between them; any factor that could lead to the failure of this seal may result in leakage, with the impeller nut being an exception. It is relatively easy to observe when the medium leaks out through the gap between the mechanical seal sleeve and the shaft in general
The forum originally had a shared, encrypted PDF, but I hadn’t downloaded it yet when the sharing was canceled, so it’s no longer available
Check the O-ring between the shaft sleeve and the shaft.
A preliminary assessment can be made based on the operating sound and vibration of the auxiliary pump.
What leaks out from the inside of the sleeve is either a poor seal between the sleeve and the impeller, or between the impeller and the nut； If it leaks from the outside of the shaft sleeve, it’s a seal failure or a problem with the O-ring of the seal – it’s easy to determine
Leakage between the bushing and the shaft is easy to observe
In some seal designs, there is no O-ring between the shaft sleeve and the shaft; sealing is achieved through the O-ring on the end face of the shaft sleeve in contact with the impeller. At this time, a seal must be provided between the impeller back cover and the impeller; gaskets or O-rings are commonly used for this purpose. If the back cap O-ring fails, liquid will seep in from the gap between the impeller and the shaft, and leak through the gap between the shaft and the sleeve.
If the mechanical seal shaft sleeve is used to transmit power through clamping [the mechanical seal shaft sleeve plays a role in positioning the impeller], this possibility is quite high
Many pumps lack seals or gaskets designed at the inside of the shaft sleeve as well as at the junction between the shaft sleeve and the shaft shoulder; as a result, the sealing between the shaft and the sleeve relies on the impeller cover being secured to the shaft along with a sealing ring, so that fluids outside the cover cannot enter the shaft through it. Otherwise, fluids will leak out through the shaft sleeve.