Seeking experts’ help to analyze the causes of pump corrosion
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The circulating water pumps used by a pharmaceutical company use tap water that is heated to 80°C as the working medium; however, there is rust in the pipes. The cast-iron impellers and impeller nuts of the pipeline pumps used by our company broke down after just one month of use. pH tests conducted on site showed that the acidity or alkalinity was neutral. Experts, please help analyze the reasons for this.
When the water pump is used at 80 degrees, what is its suction lift height? Is the diameter of the water inlet pipe matched to the flow rate? Can a negative pressure occur in the hot water tank? All these factors can cause cavitation in water pumps.
The circulation water pump is used to raise the temperature of tap water to 80°C. The pipeline pump has been in use for a month, and both its cast-iron impeller and impeller nut have deteriorated; the pH level is neutral. The main reason is electrochemical corrosion; we know that corrosion in water at room temperature is primarily an oxidation reaction, and the corrosion can be quite severe in some cases. When metals, especially ferrous metals, are in a closed space at elevated temperatures, even if the pH value is neutral, the corrosion rate is much higher compared to that in an open system at normal temperatures. This is why the pipeline pump suffered corrosion damage after a month.
It’s best to analyze the water quality, as well as data such as chloride content
Only with images can it be determined precisely what type of corrosion mechanism is at play
It should be similar to the corrosion that occurs in circulating water pipes; the pipes and pumps should undergo pre-coating treatment before use, or if the chloride content is not high, it might be advisable to upgrade them to stainless steel
Cavitation is a common problem with circulating water pumps, and high chloride levels can lead to corrosion. Previously, I provided protection for two such pumps used in a Western pharmaceutical company, by replacing only the impellers.