The medium is liquid chlorine; what causes one side of the rotor shaft to corrode, and how can this be resolved?
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It is a canned pump used for handling liquid chlorine, with 316L as the base material. During disassembly on site, corrosion was found on the rotor shaft; however, there was only slight corrosion where the impeller was installed, while that area suffered severe corrosion as well, and the corrosion occurred on one side only. I hope experts can help identify the causes of this failure and suggest solutions.
It is necessary to check whether the actual operating conditions of the process match those specified when selecting the pump. It is unlikely to rely solely on pumps to address corrosion
The medium contains water or steam, leading to corrosion
It was very difficult for the user on site; they couldn’t understand anything. Corrosion did occur, but it was limited to a 30-degree range around the 360-degree circumference where the inner hole of the rotor shaft and impeller hub fit together. There were no signs of corrosion in the remaining 330 degrees. The bolts connecting the shaft head were not loose when the machine was disassembled on site. However, considering the uneven pattern of corrosion and the fact that the medium used had a temperature of minus seventeen degrees, it is speculated that the contrast between hot and cold temperatures may have caused the bolts to loosen, leading to uneven wear on the pump. In the presence of both gas and liquid in the medium, this wear led to corrosion at those affected areas.
It is necessary to focus on checking whether parameters such as operating temperature, operating pressure, and installation height can lead to a gas-liquid two-phase flow, thereby causing vibration and cavitation in the pump. Additionally, whether the fitting tolerances of the pump are designed taking into account the operating temperature is also an important factor.
Intergranular corrosion: improve the fit tolerance between the shaft and the wheel
To determine this, it is necessary to understand the operating conditions and what the sources of corrosion are. Furthermore, the corroded and worn surface can be restored to its original dimensional structure through repair. We can discuss in detail on WeChat at 17817601213 to exchange learning experiences*. (^_^)
Has an erosion flow channel formed within the keyway slot?
If the damage is severe, consider replacing it with a magnetic pump designed for liquid chlorine use by Dalian KeHuan; such pumps are widely used in the liquid chlorine industry.
If the fit is loose, corrosion will become severe; it is best to have a tight fit or an assembly with sealing rings