“Contains solids” is not enough information to select a pump. Particle size, concentration, hardness, shape and settling behaviour each push the selection in a different direction, and a design that copes well with one solids problem can fail quickly against another. Get the solids description wrong and the pump either blocks, wears out early, or both.
What a solids description needs to cover
| Property | Why it matters |
|---|---|
| Maximum particle size | Sets minimum passage size and clearance requirements |
| Particle size distribution | A pump may pass the largest particle but wear rapidly against the fine fraction |
| Concentration by mass or volume | Affects density, wear rate and whether standard hydraulic assumptions still apply |
| Hardness and abrasiveness | Determines wear material and expected wear life |
| Particle shape | Angular particles typically wear faster than rounded ones |
| Fibre length and wrapping tendency | Fibres can wrap around shafts, impellers and rotors and block passages |
| Settling behaviour | Settling solids can block suction lines and idle pumps |
How solids affect centrifugal pump selection
A standard centrifugal pump built for clean liquids typically has tight clearances and passages sized for the fluid, not for solids. Introducing solids into that design usually means blockages at the impeller eye, rapid wear at close-clearance points, or both.
Slurry pumps and solids-handling centrifugal designs address this with larger passages, wear-resistant liners, thicker impeller vanes and adjustable clearances. Even within slurry pump ranges, models differ in the maximum particle size, concentration and abrasiveness they are rated for. A pump suited to fine, moderately abrasive tailings is not automatically suited to coarse, highly abrasive mineral slurry.
How solids affect positive displacement pump selection
Positive displacement pumps respond differently to solids depending on the pumping principle:
- Progressive cavity pumps can pass moderate solids but rotor and stator wear increases with abrasive content, and large particles relative to the cavity size can damage the stator
- Air-operated diaphragm pumps handle soft solids and moderate particle sizes well, limited mainly by ball valve clearance
- Peristaltic hose pumps can pass solids without contacting rotating clearances, since the hose is the only wetted wear part
- Gear and lobe pumps generally tolerate very little solids content because of their tight internal clearances
Valve-based designs are particularly sensitive to particles that prevent a ball or seat from sealing fully, which can cause slip, reduced flow or complete loss of pumping action.
Common mistakes
Describing solids only by maximum particle size is the most common gap. A pump can pass the largest particle in the stream and still wear out quickly against a fine, abrasive fraction, or block against fibrous material well under the stated maximum size. Assuming that “abrasion resistant” materials solve every solids problem is another trap, a hard wearing material can still be unsuitable if the chemical environment attacks it, and a chemically resistant material can wear quickly if it is not also abrasion resistant.
How Solids Affect Pump Selection FAQs
Can a slurry pump handle any type of solids?
No. Slurry pump ranges cover a wide spread of particle size, concentration and abrasiveness, and individual models are rated for specific limits. Confirm the manufacturer’s rating against the actual solids data rather than assuming any slurry pump will cope.
Why does a pump wear out quickly even though it passes the largest particles?
Wear is often driven by the fine, abrasive fraction of the solids rather than the largest particles. A full particle size distribution, not just a maximum size, is needed to assess wear risk properly.
Do settling solids matter if the pump is running continuously?
They can still matter during start-up, shutdown, low-flow conditions and any period the pump is idle. Settled solids in suction lines or casings can obstruct priming and startup even if the running condition itself keeps particles in suspension.
Is a positive displacement pump always gentler on solids than a centrifugal pump?
Not always. Gentleness depends on the specific design and speed, not the general pump category. Some positive displacement designs handle fragile or shear-sensitive solids well, while others have tight clearances that damage particles or wear quickly against them.
This article explains general solids-handling effects on pump selection. It does not replace manufacturer-confirmed wear data or an application-specific engineering review.
Part of the pump selection guide. See also How Viscosity Affects Pump Selection, How to Select Pump Materials and Centrifugal vs Positive Displacement Pumps.
About The Pump Expert
The Pump Expert provides independent, practical education for pump users, engineers and maintenance teams. TPE explains how pumps and pump systems behave so readers can make better technical decisions without supplier bias.
Last Updated on July 30, 2026 by TPE