Viscosity impact on pump curve

[Mutt]

Effect of viscosity on pump curves : Anybody know of technique to estimate impact of fluid with 500cP viscosity on pump curves based on water? Concerned about loss of efficiency resulting in temperature increase and especially motor sizing requirements.

 

[TD2K]

See thread407-65963

 

[25362]

There is a well-known chart by the Hydraulic Institute on the effects of viscosity on efficiency, flow rate and head, thus on HP.

Although not a complete list the main effects of switching a "cold" pump to moving a hot liquid may result in:

-Thermal forces in piping that may push the pump out of
alignment
-Undesirable thermal expansion effects (including shock) in
the pump itself
-Reduced material strength
-Reduced corrosion resistance of wetted parts
-Failing of the mechanical seal or packing materials when
in contact with the hot liquid
-Special gasketing may be required

The effects on NPSH are not clear.

The sensible action, before attempting the planned switch, would be: check first with the manufacturer.

 

[Mutt]

Thanks - have found the HI nomograms and fitted equations in spreadsheet to predict curve changes due to viscosity (as well as usual impeller and speed changes). Available for anybody if they want a copy! Ask me on info@langleyventures.co.za

Mutt.

 

[ChemE2912]

Mutt,

If you are selecting a new pump, the newer vendor database softwares take into account the correction based on the viscosity of your fluid, and give you a full pump operating curve based on that. You could check with any and request them to provide you with one of these copies.

It is very important that you take into account this effect, as it may impact some feet in the pump head.

We have been dealing with heavy oils (686 - 2500 cP) in pipelines and process lines and have used these vendor programs without problems.

If it is an existing pump, you may check in the Cameron Hydraulic Data, p. 4-45, in which the viscosity correction for centrifugal pumps is given.

Regards,

ChemE2912