Mechanism of corrosion on pump shafts
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It is a horizontal split-case double-suction pump; corrosion has occurred at the junction of the impeller and the shaft sleeve, below the shaft sleeve. The location of the corrosion as well as its appearance are shown in the attached drawings. What is the mechanism of this corrosion: pitting, crevice corrosion, cavitation, or something else? Why? Thank you! Note: The fluid medium is seawater; the impeller and shaft sleeve are made of duplex stainless steel resistant to seawater corrosion, while the pump shaft is not corrosion-resistant. Under normal circumstances, it still should not come into contact with the pump shaft!
The pump shaft should not come into contact with the medium; otherwise, it constitutes an internal leak. Pump shafts are generally made of materials with high strength; since they do not come into contact with the medium, corrosion is not a concern.
Yes, in principle internal leakage shouldn’t occur, but it did happen in practice! Now, I want to know what type of corrosion has occurred
You can search on Baidu for 【Analysis of the Causes of Corrosion in Feed Pump Shafts and Corresponding Solutions】
You confirm that it is corrosion, rather than issues caused by incorrect pump installation, vibration-induced wear, or damage from feeding processes
It is mainly due to seal failure between the impeller and the shaft sleeve, as well as between the impeller nut and the impeller, which allows the shaft to come into contact with seawater and thus causes corrosion of the impeller.
There shouldn’t be any impeller nuts, right, bro?:o
It’s likely that there was a problem during the assembly of the contact surface between the impeller and the shaft sleeve, resulting in a gap that allowed the medium to leak and come into contact with the shaft, causing corrosion of the shaft
The gasket or O-ring in the sealing axis has failed