Treating a slurry pump as "a water pump with thicker walls" is the most expensive mistake on site.

A slurry pump does not move a single-phase medium — it moves a solid–liquid two-phase flow. Particle size distribution, Mohs hardness, true density and volumetric concentration (C_v) jointly determine the flow structure inside the pump and its failure mode. Selecting on clean-water flow and head alone is almost always paid for later, in spare parts and unplanned downtime.

1. Wear: cutting and impact acting together

Wear is rarely a single mechanism. Fine particles at high velocity produce cutting (abrasive) wear — micro-ploughing and micro-cutting — with wear volume rising roughly with the 2.5–3 power of flow velocity. Coarse particles striking at large impingement angles instead cause impact fatigue and brittle spalling. Where head margin exists, reducing speed is usually the most economical way to extend wetted-part life: a 20% reduction in velocity cuts the wear rate by about 45%, at the cost of roughly 36% head (affinity laws: Q ∝ n, H ∝ n²). That trade-off belongs on the table at the selection stage, not after commissioning.

2. Materials: balancing hardness against toughness

Two routes dominate. High-chrome white iron (Cr26 / Cr27, A05-class) reaches HRC 58–65 and resists both cutting and impact, suiting coarse solids and high heads. Rubber linings absorb particle kinetic energy through elastic deformation and often outlast metal on fine, rounded particles (typically d50 < 3 mm) below 80 °C — but they are vulnerable to dry running, oil and high temperature. The rule is not "the harder the better": material hardness must clearly exceed abrasive hardness, while retaining enough toughness to arrest crack propagation. Rubber also carries a peripheral-speed ceiling, which forces a return to metal at high speeds.

3. Hydraulics: concessions to two-phase flow

Slurry impellers use few vanes (3–5), wide outlets and thickened trailing edges to limit blockage risk and reduce the relative velocity at the vane exit; a larger vane outlet angle compensates for head loss as wear progresses. Volute sections are sized for far lower velocities than a clean-water pump, and replaceable liners and side plates are designed to absorb the wear. The result is hydraulic efficiency typically 5–15 percentage points below a clean-water machine — the price of passage and service life. Clean-water curves must also be corrected for slurry: head and efficiency are multiplied by concentration correction factors, while NPSHr rises with concentration, so the installation must provide a larger NPSH margin.

4. Shaft sealing: the highest failure rate in the field

An expeller (dynamic seal) with a static back-up seal is highly reliable in duties with dilution water or on pumps in series, and needs no external seal water. A tandem mechanical seal, by contrast, requires a continuous clean flush — lose the flush and the seal faces are destroyed within minutes. On the suction side, avoid air pockets and part-full pipe flow: local low pressure at the impeller eye is where cavitation and abrasion begin attacking together.

5. Back to the duty itself

A defensible sequence: establish flow Q, required head H, slurry density, C_v and d50/d85; then fix material, speed, vane geometry and sealing arrangement; then keep the pump inside 0.8–1.1 × BEP flow, avoiding the radial thrust and inlet recirculation that come with sustained low-flow operation.

The value of a slurry pump never shows on the nameplate. It shows in spare-part cost and downtime per tonne of solids pumped. Complete duty data selects a better pump than a bigger parameter table.