2 replies to this topic

[Edavan]

Question No 1: In the centrifugal pump performance curve NPSHr indicated by the pump manufacturer is for water (sp.Gr = 1.0 and viscosity = 1Centipoise ).

For viscos liquid we consider correction factor for flow, head and pump efficiency, But for viscos liquids NPSH®, is required to be considered????.

For higher/lower specific gravity liquids any correction factor is to be considered for NPSH®.

Question No 2: For screw pumps / Progressive cavity pumps /Gear pumps

Increase in Viscosity in the pumped medium will “improve”/ “have no change in” the pump performance for positive displacement pumps????. If so, the viscosity correction factor chart can be totally neglected for positive displacement pumps??

Whether NPSH® is equally important for positive displacement pumps like centrifugal pumps??

[shan]

Question No 1: In the centrifugal pump performance curve NPSHr indicated by the pump manufacturer is for water (sp.Gr = 1.0 and viscosity = 1Centipoise ).

For viscos liquid we consider correction factor for flow, head and pump efficiency, But for viscos liquids NPSH®, is required to be considered????.

For higher/lower specific gravity liquids any correction factor is to be considered for NPSH®.

Question No 2: For screw pumps / Progressive cavity pumps /Gear pumps

Increase in Viscosity in the pumped medium will “improve”/ “have no change in” the pump performance for positive displacement pumps????. If so, the viscosity correction factor chart can be totally neglected for positive displacement pumps??

Whether NPSH® is equally important for positive displacement pumps like centrifugal pumps??

NPSHR is the pressure differential required to enter pump impeller eye for avoiding vapor bubbling. It needs correction for viscosity because more viscous liquid needs more pressure differential to enter pump impeller eye. It does not need correction for specific gravity because NPSHR is defined in the unit of length (feet or meter) that eliminate the impact of specific gravity. The same rules should be applied to the positive displacement pumps.

[joerd]

Most of your questions can be answered by spending a little time on http://www.pumped101.com/