Discussion on issues related to closed impellers
Thread Content
The unit is equipped with a centrifugal pump whose impeller is of the closed type. Recently, the impeller has been accumulating scale, though not in large amounts; once scale builds up, it causes an overflow condition that leads to the shutdown of the pump. I have a question: the more scale accumulates on the impeller, the less water is pumped, which results in a lower flow rate. In that case, the current should decrease, right? For example, if too much scale blocks the flow channels in the impeller, couldn’t there still be an excessive flow? Shouldn’t the flow rate decrease, leading to a drop in current? Everyone is welcome to discuss it.
Yes, theoretically that’s the case. But you need to take into account that the weight of the impeller has increased slightly, which means the load has increased as well ； Also, after scaling forms, friction occurs in many areas with small gaps, which in turn leads to an increased load.
In addition to scaling in the flow channels, scaling can also occur on the back side of the impeller and other areas; this increases the weight of the impeller itself, thereby increasing the load during pump operation and raising the current consumption.
Scale formation has little impact on flow rate; it mainly increases friction.
When the impeller becomes fouled, its dynamic balance is disrupted, and its vibration increases; this in turn leads to increased vibration in the bearings. The pump then operates abnormally, with a higher load compared to normal operating conditions.
When the impeller becomes fouled, its weight increases, the load also rises, the dynamic balance of the water pump shaft is disrupted, bearing vibration increases, the lifespan shortens, and production efficiency drops.