Tips from KSB Mining on removing a stuck pump impeller 

Pump maintenance is of special importance as the impeller, along with pump casing and suction liner, determine pump performance, notes KSB Mining. But what happens when a pump is not performing optimally due to a stuck impeller – and what could cause an impeller to get stuck in the first place? 

Impellers can get stuck for many reasons. But pump owners and operators can avoid such issues by following this advice.  

Here are two scenarios GIW recommends against: 

• Using only one gasket or none at all: GIW recommends using two gaskets. The gaskets work against one another for easier removal. When only one gasket is in use, the impeller will overtighten on the shaft, making it more difficult to get off. Therefore, using two gaskets is the best strategy. The two gaskets slide against one another, making it easier to break loose. If a gasket is not used at all everything will seize up. 
• Applying anti-seize to the hub face: It seems practical to use anti-seize on the threads, faces of the shaft sleeve, the impeller, and the gaskets. However, anti-seize actually causes everything to overtighten. The reason for this is that anti-seize causes the parts to become more slippery and the parts will overtighten on the shaft. A good rule of thumb is to use anti-seize on the threads of the shaft and the impeller, but to keep the axial faces of the shaft sleeves, the gaskets, and the impeller hub dry. If anti-seize is applied to those areas, everything will tighten even further on the shaft and can over-torque and break pieces of the shaft or the impeller off itself. 

In fact, most “stuck impeller” issues have to do with gaskets. But some extenuating circumstances exist that can also lead to impellers getting stuck on pump shafts. 

Sometimes the threads break either on the shaft or the impeller, they get crossed, or the impeller won't break loose. Upon inspection, if the threads look damaged or broken, clean them up. A pencil grinder can be used to prevent more damage. 

Putting a new impeller on worn threads can result in rapid failure and damage to other wet-end parts. Pumps with stuck impellers, will cause bearings to fail, which risk causing damage to pump motors. All of this can lead to additional repair issues. Once a bearing fails in the assembly, there is not much that can be done other than cutting the shaft off behind the impeller to remove it. 

For more tips on getting the best performance, and least downtime, on slurry pumps, subscribe to the monthly pump fundamentals blog from KSB.