When replacing the pump shaft in a horizontal multi-stage centrifugal pump, what should be done if the steel impeller cannot be removed?
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The unit has a horizontal multi-stage centrifugal pump that needs to be disassembled for repair. The impellers have double keyways, one on each side; they cannot be removed. Even after soaking them in oil and trying to use hydraulic pressure to move them, it wasn’t possible – the shaft even bent as a result of the attempts to remove the impellers. We had to use gas cutting to cut the impellers, but it was very time-consuming. Moreover, there are 12 impellers in total, and basically all of them should be in good condition and do not need to be replaced; therefore, it was necessary to destroy them all. I’m asking for advice on how to preserve the impeller and remove the shaft
Here are two methods for reference: 1. Use a heating strip to heat the root of the impeller; based on the principle of thermal expansion and contraction, the appropriate temperature should allow the components to separate, taking into account the impact of temperature on the impeller material； 2. Does your company have liquid nitrogen? If so, use it to cool the shafts, being careful to ensure safety
Was it heated with fire? After tightening it with a ram, it was heated with a cutting gun; thermal expansion and contraction make it easy to remove. This is what is usually done when a coupling can’t be pulled out.
This post was last edited by “UnbreakableCatGod” on May 19, 2016, at 08:17. Drill a hole in the shaft; make it a bit larger so that it can be pulled out later. Drill a hole in the shaft, then pour liquid nitrogen/dry ice mixed with alcohol into it, and finally pull it out. Since we’re already planning to damage the shaft and impeller anyway, this shouldn’t be difficult at all. .
It’s better if it isn’t disassembled; in my current situation, if it’s heated and disassembled, the inner hole will also deform. These impellers are installed hot, so you should first consult the manufacturer’s maintenance manual to establish a repair procedure.
Has it rusted to death after being there for so long? . . Use some rust remover spray and give it a try during the interview. . .
You mean that if the impeller is removed by heating, its inner hole will deform? If it was installed hot, what method is used to remove it? Thank you
We use two oxy-acetylene torches to heat the impeller hub simultaneously, with the oxy-acetylene flame being of the oxidizing type. The heating time must be strictly controlled; if it is too short, the amount of expansion of the holes will not be sufficient, and the impeller will not be able to slip relative to the shaft ； If the heating time is too long, the heat on the impeller is rapidly transferred to the shaft. When the shaft receives excessive heat, its temperature rises locally and its diameter increases. Theoretically, this results in an increased heating rate of the shaft and a slower heating rate of the hub. As a result of the temperature difference, the gap between the wheel hole and the shaft does not increase but decreases, which can lead to an interference fit that makes disassembly impossible.