Pump Fundamentals
Viscosity, Slurries and Pump Selection
Water-based selection charts do not tell the whole story when the liquid is viscous, laden with solids or abrasive. These properties change the head, flow, power and wear of a centrifugal process pump, and they need to be stated before a pump is chosen.
How Viscosity Changes Performance
Compared with water, a more viscous liquid makes the same pump deliver less head and flow, run at lower efficiency and draw more power. The heavier the liquid, the larger the correction. A selection that looks comfortable on a water curve can fall short once viscosity is applied, so the actual viscosity at pumping temperature, not at ambient, is what matters.
Solids and Slurries
What the solids do
- Abrasive particles wear the impeller, casing and wear rings
- Concentration and particle size raise the effective density and the power needed
- Settling solids can block the pump if velocity drops too low
How selection changes
- Harder or thicker wetted materials to resist abrasion
- More generous internal clearances and robust hydraulics
- Lower running speed to slow wear, traded against head
Temperature and Corrosion Interact
Viscosity, temperature and corrosivity are linked. A liquid that thins when heated may also become more aggressive to the wetted metal, and a slurry that is mildly corrosive becomes far more damaging when it is also abrasive. Material selection is therefore made from the full picture, not from the material name alone. A material being available is not the same as it being approved for your service, which is why we review the liquid, concentration and temperature together.
Viscosity & Slurry FAQ
What liquid data should I send?
Send the liquid name and concentration, the viscosity and temperature at pumping conditions, the solids content and particle size if any, and whether the liquid is abrasive or corrosive.
Why can’t I choose the material from the liquid name alone?
The same liquid can be handled by different materials depending on concentration, temperature and contaminants. We treat the material name as a starting point and confirm it against your full duty.
Does a slurry always need a special pump?
Not always, but it usually needs a considered hydraulic and material choice and often a lower speed. Send the solids data so the selection accounts for wear.
Get a Selection for Your Liquid
Send viscosity, temperature, solids and concentration and we review hydraulics and materials together. See also materials guidance.
This is general engineering guidance for buyers of ANSI/ASME B73.1 process pumps. Final selection always depends on your verified duty point, liquid data and installation conditions. Send your data for a reviewed proposal.