Slurry pump wear coatings: erosion, cavitation and rebuilding

A slurry pump wears mainly through erosion: particles in the liquid slide along and strike the casing, the impeller and the wear plates until they break through. Cavitation and corrosion from the carrier liquid make it worse. Worn areas can be rebuilt in place with a ceramic-filled epoxy composite when particles are coarse and impacts moderate, or protected with rubber when particles are fine. The right choice depends on particle size, velocity, temperature and process chemistry.

Slurry pumps move mine tailings, concentrates, lime slurries, ash or sand. They are among the hardest-working machines in a plant, and their wear parts are replaced often. Rebuilding with a coating gets a pump back in service faster and extends part life, provided the wear is read correctly. This guide builds on our article on centrifugal pump repair with epoxy with what is specific to slurry service.

Why does a slurry pump wear so fast?

A slurry pump wears fast because it combines three mechanisms: erosion by solid particles, cavitation at the impeller eye and corrosion from the carrier liquid. Each leaves a visible signature, and that signature drives the repair.

• Sliding erosion. Particles rub along the casing walls and impeller shrouds. The surface becomes smooth and polished, sometimes grooved along the flow path.
• Impact erosion. Coarse particles strike the cutwater, the leading edge of the vanes and the discharge area. You see craters and rounded edges.
• Cavitation. Vapour bubbles collapse near the inlet and on the vane surfaces. The surface turns spongy and pitted, often away from the erosion zones.
• Corrosion. An acidic, saline or hot liquid attacks the metal exposed by erosion, which speeds up material loss. Our article on erosion-corrosion explains this coupling.

Wear that progresses faster than before often signals a process change: slurry density, flow away from the best efficiency point, or excessive clearance between the impeller and the suction liner.

Which parts should be inspected and rebuilt?

Inspect the casing, impeller, suction liner, back liner and stuffing box, because wear does not progress at the same pace in each. Rebuilding targets parts whose remaining wall can still take service pressure and whose geometry can be restored.

Wear patterns should be photographed and recorded at each opening. Comparing them from one shutdown to the next shows whether wear is shifting, speeding up or concentrating in one place, which helps decide whether the cause is the material, the pumping conditions or the slurry itself.

Areas that are holed or cracked need structural repair before any coating. Ultrasonic thickness readings, mapped on a sketch of the part, help decide what gets repaired and what gets replaced.

Ceramic-filled composite or rubber: which should you choose?

Choose a ceramic-filled composite when particles are coarse or angular, or when the part must recover a precise geometry. Choose rubber when particles are fine and the flow is mostly sliding, because the elastomer absorbs the energy of small impacts instead of wearing away.

• Ceramic-filled epoxy composite. An epoxy matrix loaded with hard ceramic particles, applied by trowel and then smoothed. It rebuilds lost volume, bonds to prepared metal and can be shaped to restore hydraulic profiles. A brushable version used as a topcoat reduces turbulence. See our guide to metal repair epoxy putty selection.
• Rubber. A bonded or vulcanized lining, highly resistant to erosion by fine particles. It handles sharp coarse particles, some oils and high temperatures poorly. Our rubber lining service covers these linings.
• Solid ceramic or hard alloy. For very severe impact, ceramic tiles or high-chrome iron parts are often better than an applied coating.

Our comparison of rubber, ceramic and polyurethane wear linings details the criteria for particle size, temperature and chemistry.

How is a casing or impeller rebuilt?

The rebuild follows a fixed sequence: cleaning, decontamination, blast preparation, composite rebuild, topcoat and inspection. Each step follows the data sheet of the selected product, and the quality of preparation decides adhesion.

1. Dismantling and cleaning. Slurry, deposits and oils are removed. Parts that pumped saline or acidic liquids may need washing to extract salts.
2. Surface preparation. Abrasive blasting to the grade stated on the data sheet, usually a high-grade blast with an angular profile, through our abrasive blasting service.
3. Rebuild. The filled composite is applied in the gouged areas, in layers compatible with its cure time, then profiles are shaped with templates where needed.
4. Topcoat. A more fluid, smooth coat reduces roughness and turbulence in the casing.
5. Cure and inspection. The cure time is respected before return to service, followed by visual inspection, thickness and hardness checks using the specified methods.

The rebuild is done in the shop or on site depending on pump size and the shutdown window. It is part of our maintenance and rehabilitation service.

How do you reduce cavitation and wear after the repair?

You reduce cavitation and wear by correcting pumping conditions, not only the material. A better-suited coating extends part life, but a pump running far from its operating point will keep wearing fast.

• Operating point. Flow that is too low causes recirculation and wear at the inlet; flow that is too high speeds up erosion in the casing.
• Suction head. Insufficient net positive suction head causes cavitation. Inlet losses, long suction piping or a low sump level are common causes.
• Impeller clearance. Too much clearance with the suction liner creates recirculation and rapid wear. Adjusting it is part of routine maintenance.
• Foundation and alignment. Vibration damages coatings and linings. See our article on pump foundation and baseplate repair with epoxy grout.

When should you replace instead of rebuild?

Replace when the remaining wall can no longer take the pressure, when the part is cracked or when rebuilding would cost more in repeated shutdowns than a new part. The coating is then still useful to protect the replacement part from the start of service.

The usual criteria are measured remaining thickness, cracks, the condition of sealing faces and part availability. Our article on whether to repair or replace industrial equipment offers a decision approach. In a mining plant, rebuilding often fits into the mining equipment wear protection program, with wear tracking from one shutdown to the next.

Frequently asked questions

Can a coating replace the original wear parts?

It can extend their life and restore them, but it does not replace a part whose structure is compromised. On a new part, a coating applied before start-up can also delay the first wear.

Can an impeller be rebuilt without throwing it out of balance?

Yes, if the composite is applied symmetrically and balance is checked after cure. A heavily worn or small impeller is often simpler to replace.

Does a ceramic composite resist hot liquids?

It resists up to the temperature stated on its data sheet, which varies by formulation. Beyond that, or with aggressive chemicals, another material must be chosen.

How long before the pump can return to service?

It depends on the product cure time at ambient temperature. The figure is on the data sheet and is planned against the shutdown window before work starts.

How do you get a quote for a slurry pump?

Coatings are our core business, and pump rehabilitation relies on our protective coatings. Send photos of the worn parts, the pump type and size, the nature of the slurry, the temperature and the shutdown window. Our crews and qualified subcontractors work from LaSalle, including in Abitibi-Témiscamingue, on the North Shore and in Ontario. Pricing is on consultation; use the request a quote form and we reply within 24 business hours.