Is the medium always leaking into the pump tank?
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Our facility has several small mother liquor pumps used to transport ammonium sulfate mother liquor. These pumps have single-seal designs and do not require cooling water. They used to function properly, but recently they have been failing frequently; a large amount of mother liquor keeps getting into the bearing housings of these pumps, and the seals also need to be replaced often. What could be the reason for this? Every time, a large amount of fluid is found inside the bearing housing, and within a few days the mechanical seal starts to leak as well, requiring its replacement. Please explain the reason!
It should be that the mechanical seal is leaking first, which allows the medium to get into the bearing housing. What is the structure of your pumps? Why is it that a mechanical seal leaks first but isn’t detected?
If the medium leaks into the bearing box, then there is also a problem with the oil seal; the condition of the oil seal should be considered.
It seems that your bearing is damaged; replace it with a radial bearing. An excessive clearance in the radial bearing or wear and damage to it can cause radial wear of the bearing cover, an increased clearance in the oil seal (dust seal), shaft vibration, which in turn leads to leakage, with the fluid then seeping into the bearing housing. Or shaft bending causes the aforementioned issues.
Whether the pump shaft sleeve is in communication with the bearing housing – in the case of the urea melting pump we use here, which features a packing seal, the shaft sleeve is indeed in communication with the bearing housing. Although there is a rubber ring for sealing, if this rubber ring is damaged, as well as the gasket (rubber ring) on the back of the pump impeller shaft, then the medium can flow from the shaft sleeve into the bearing housing.
Our pump shaft sleeves are not connected to the bearing housing; generally, a water seal is installed on the shaft between the two. However, it seems that this seal doesn’t serve a very effective purpose these days. The SKF 6306 bearings used should be fine. I suspect that the problem might lie with some of the O-ring seals The structural sequence of the pump is as follows: shaft end flange, chuck, impeller, pump cover, dynamic seal ring (above the shaft sleeve), static seal ring, seal gland, followed by the bearing housing end cover, bearings, housing, ...
Take a look at the structure of your pump; it would be best to upload a diagram of its structure. There’s no reason for the mechanical seal not to leak, or for material to get into the bearing housing
The mechanical seal fails first, and the medium can easily flow into the bearing housing on the right side along the high-speed rotating shaft, which in turn leads to a failure in bearing lubrication. Once the bearings fail, the shaft’s alignment is compromised, and the mechanical seal gets completely damaged. Pay special attention to the condition of the mechanical seal: is it running dry? What’s the condition of the cover of the medium-lubrication machine?
First, replace the pump’s mechanical seal; additionally, install a water barrier ring between the mechanical seal and the bearing housing end cover. It can prevent the medium leaking from the shaft seal from entering the pump’s bearing chamber; when this leakage occurs, the medium is deflected by the water barrier, thereby preventing it from reaching the bearings and causing damage to them.