Review of pump suction reducer selection : eccentric or concentric reducers

Abstract

Eccentric reducers are traditionally recommended for the pump suction reducer fitting to allow for transportation of air through the fitting to the pump. The ability of a concentric reducer to provide an improved approach flow to the pump while still allowing air to be transported through the fitting is investigated. Computational fluid dynamics (CFD) were utilised to analyse six concentric and six eccentric reducer geometries at four different inlet velocities to determine the flow velocity distribution at the inlet to the pump. It was found that eccentric reducers with angles greater or equal to 15° and concentric reducers with an angle greater or equal to 20° did not pass the assessment criteria related to the inlet conditions. Air could be hydraulically transported through all of the concentric reducers modelled except for the 20° concentric reducer. A correctly designed concentric reducer will not only provide a more uniform velocity distribution in comparison to an eccentric reducer, but will allow for the hydraulic transportation of air through the reducer.