Background
A zinc-lead processing plant in Kazakhstan was running vibrating screens for sizing crushed sulfide ore before flotation. The screens used woven wire mesh at 8mm aperture. In this application, the ore contained significant pyrite alongside the zinc and lead sulfides — pyrite is hard and abrasive, and the ore was processed wet.
Wire mesh life in this application was 2–3 weeks. Given the plant ran four screens continuously, screen media changes were happening approximately every two weeks across the plant — consuming significant maintenance time and creating frequent production interruptions.
Specific Challenges
Wet sulfide ore is chemically aggressive to steel wire. Pyrite oxidizes rapidly in water, producing dilute sulfuric acid in the process water. This acidic process water corroded the wire mesh from the inside, combining chemical attack with abrasive wear. The wire was deteriorating faster than pure mechanical abrasion alone would predict.
Cold climate operational requirement. The plant operated year-round in Kazakhstan's steppe climate, with winter temperatures reaching -35°C. Any replacement screen media needed to maintain flexibility and avoid brittle fracture at these temperatures.
Material Selection
Standard polyurethane was evaluated but one concern was raised: standard PU compounds can become brittle at low temperatures. The specification required cold-flex polyurethane rated to at least -40°C while also providing chemical resistance to dilute acid process water.
Cold-flex PU compounds use different plasticizer systems than standard PU to maintain elastomeric properties at low temperatures. The trade-off is slightly lower abrasion resistance than standard PU at room temperature — but still substantially better than wire mesh.
Specification selected: - Cold-flex PU, 70 Shore A (measured at +20°C) - 8mm square aperture - Bolt-down modular panels, 305×305mm - Tested to -40°C flexibility (no cracking on bend test at -40°C) - Chemical resistance confirmed for dilute H₂SO₄ at pH 3–4
Trial and Results
One screen was converted to cold-flex PU panels. The remaining three screens continued on wire mesh for comparison.
At the 8-week mark: wire mesh screens had been changed twice; PU screen had not been changed and showed approximately 20% wear on inspection.
At 6 months: wire mesh screens had been changed approximately 10 times each; PU screen had its first panel change (selective replacement of highest-wear panels in the impact zone, with remaining panels still serviceable).
Estimated PU panel life: 7–9 months for the full deck.
Life improvement vs wire mesh: approximately 12–15×
The cold-flex properties held up in winter — no panel cracking or brittleness observed at -30°C operating temperatures during the winter months of the trial.
Full Conversion
All four screens were converted to cold-flex PU panels. Annual screen media changes reduced from approximately 40 full-deck changes per year (across 4 screens × 10 changes each) to approximately 4–6 selective panel replacements per year.
Key Points
Chemical attack compounds mechanical wear. In acidic wet processing environments, wire mesh deteriorates faster than mechanical abrasion alone predicts. PU is immune to the acidic conditions that corrode wire.
Cold-flex specification is essential for Central Asian and Siberian operations. Standard PU in -35°C conditions will crack. Cold-flex PU maintains performance. This must be specified explicitly — it is not the default compound.
Panel life economics improve dramatically in aggressive environments. The more hostile the environment to wire mesh (wet, acidic, cold), the more favorable PU economics become. This was one of the most dramatic wire-to-PU life improvements we have seen.
Elephant Rubber supplied the cold-flex PU screen panels for this project.