Viscosity, how it affects your rotary (PD) pump

Viscosity, how it affects your rotary (PD) pump V033

When dealing with Newtonian fluids:

  • The net positive inlet pressure required (NPIPR) increases with increasing viscosity. Remember that NPIPR is the equivalent of net positive suction head required (NPSHR) in centrifugal pumps.
  • The required input-power (horsepower or kilowatts) increases with increasing viscosity.
  • Pump slip decreases with increasing viscosity because the fluid cannot circulate through the tolerances as easily.
  • The maximum allowable pump speed decreases with increasing viscosity.

When dealing with non-Newtonian fluids:

  • The viscosity can increase (dilatant fluid) or decrease (thixotropic fluid) within the pump because of shear.
  • If the viscosity of a non-Newtonian fluid can be established, you can use the above information about Newtonian fluids.