How to prevent centrifugal pumps from running dry
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The pumps in our company often suffer mechanical seal damage due to dry running. Operators are very concerned about when the pumps might run dry, but mistakes can still occur from time to time. I don’t think it’s the operators’ lack of dedication; the key is to prevent dry running through proper design. Do anyone have any good suggestions? Let me talk about the medium and temperature. The medium is concentrated sulfuric acid, and the temperature is around 140 degrees Celsius. The specific issues that occurred are as follows: the moving seal surface of the mechanical seal was damaged; since the impeller is made of PFA, both the impeller shaft and the mechanical seal suffered damage as well. As an additional note, water cooling has been applied to the mechanical seal – a water tank was installed to cool it.
Install interlock protection; for example, shut down the pump when the pressure at the pump outlet falls below a certain value.
It is controlled through interlocks: one measures the pressure at the pump outlet, and another interlock is in place for the container from which the pump draws liquid; when the liquid level rises to 50–100 units above the outlet level, the pump should be stopped automatically!
I have learned a lot from your guidance
On the electrical control panel, interlock protections are set based on the process parameters. There are generally two types of such interlocks: 1. The liquid level in the tank where the medium to be pumped is stored; calculations are used to ensure that an alarm is triggered when the liquid level drops, alerting the operator. An interlock that shuts down the pump down when the liquid level falls even further is also installed to prevent the pump from running dry； 2. Pump outlet pressure interlock – this is easier to understand: when the medium pressure drops, the interlock triggers a shutdown.
Import and export pressure gauges, for determining pressure differences