The performance data provided by pump manufacturers are valid for water. If another fluid is pumped this has an influence on
the performance of the pump. The viscosity has an effect on the pump head, the power absorbed and
the capacity (flowrate).
It is no surprise that, for a higher viscosity, all effects are in an unfavourable direction:
The power increases, the flowrate decreases and the head also decreases. These effect are all mainly a result of the
increased 'disk friction' that the impeller experiences.
The Hydraulic Institute published two charts with correction factors that cater for this:
one for a flowrate up to 100 Gallons per minute
and one for the range from 100 to 10 000 gallons per minute.
Reading them is not too difficult, takes a bit of time and requires that you carry the charts with you.
This routine returns them, which is faster, more accurate and
To use them, the correction factors can be applied using:
This gives you a point on the pump curve for the viscous fluid, with:
QViscous = Capacity of the pump using viscous fluid
HViscous = Head of the pump using viscous fluid
etaViscous = Efficiency of the pump using viscous fluid
PViscous = Pumping power using viscous fluid
CQ = Capacity correction factor
CH = Head correction factor
Ceta = Efficiency correction factor
QWater = Capacity of the pump for water
HWater = Head of the pump for water
etaWater = Efficiency of the pump for water
PWater = Pumping power for water
The values returned are related to the best efficiency point (BEP) of the pump curve.
With these values the curves can be re-drawn for the higher viscosity.
To use the free online calculation routine click on viscosity corrections