I have a vertical centrifugal pump installation. The eccentric reducer of the suction line is orientated such that the flat side is on the top, which I understand is correct because this reduces the potential for vapor pockets and the possible cavitation problems associated with this. On the discharge line however, the eccentric expander is orientated such that the flat side is on the bottom. The system is being modified to install a slightly larger pump with an increased suction nozzle size and the same discharge nozzle size. The new pump suction nozzle will be the same size and suction piping so the pump will be installed without the suction reducer. Due to the previous offset with the eccentric suction reducer, the elevation of the new pump discharge nozzle will not match the elevation of the discharge piping in its current configuration. If however the eccentric discharge expander is rotated so the flat side is now on the top, the new pump can be made to fit. Can it be a problem to have the flat side of an eccentric discharge expander on the top, or is this in fact the best way for it to be installed?
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Ross Mackay Forum Moderator 93 Posts
Re: Vertical centrifugal pump installation8 March 2007 at 1:29pmThe good news is that the arrangement of the discharge nozzle and the associated piping as you describe it will have little affect on the pump performance, so the flat side of the increaser (expander) will be okay. However, if you are installing a larger pump, I would assume you are increasing the flow. In which case, I would be concerned about the velocity of the flow in the suction line. This should be double checked to ensure you will continue to have adequate NPSH available for pump operation.