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Forum / General Discussion: Column Operations / Bottoms Product Limited by Pump Cavitation

Bottoms Product Limited by Pump Cavitation

Dec 13, 2016

We are experiencing a limitation on Bottom product rate because of bottoms pump cavitation. Based on our pressure readings, the NPSH is sufficient. We have also backed this up by with calculations of NPSH from the isometric drawings. We have a kettle reboiler with the liquid level controlled in the sump, downstream of the outlet weir. It was surprising that cavitation wasn’t reduced by increasing the liquid level. In fact, cavitation appeared to be a stronger function of steam rate than liquid level.

Do you have any additional ideas for troubleshooting to increase our bottoms product rate?


2 thoughts on “Bottoms Product Limited by Pump Cavitation

  1. JPetrik says:

    Is it possible that the fluid passing over the reboiler outlet weir is aerated and the reboiler sump doesn’t provide enough residence time to clarify the liquid?

    Assuming there is adequate space, and there is a vertical run of pipe down to the pump, replacing the section with a self venting line MAY provide the disengagement capacity to clarify the liquid at the pump inlet.  This should be backed up with calculations to support this.

  2. MCavett says:

    Thank you for this suggestion.  When using the Froude Number, it does appear that the pipe diameter is to small for self venting to occur at all of our conditions.  We will keep this in mind when we change out the reboiler in the near future to increase the reboiler liquid outlet nozzle and the bottoms pump suction piping diameter.

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