Background
A iron ore processing plant in Western Australia was changing wire mesh screens on its secondary sizing screens every 3β4 weeks. The screens classified crushed iron ore at a 10mm aperture cut point for feed to the ball mill circuit. Three screens ran continuously, and the combination of iron ore abrasiveness and wet screening conditions was consuming wire mesh at a rate that required four screen changes per month across the plant.
Each screen change required a 4-hour shutdown of the affected screen and two maintenance staff. At four changes per month, the team was spending roughly 32 person-hours per month on screen changes plus the consumable cost of the wire mesh panels.
Problem
The maintenance superintendent wanted to reduce screen change frequency. Wire mesh at 10mm aperture in wet iron ore service was simply not durable enough for the production intensity the plant was running.
The options considered were: 1. Higher-grade wire mesh (heavier wire, different weave) 2. Polyurethane screen panels 3. Rubber screen panels
Rubber was dismissed early because the ore particle size and wet sliding abrasion mechanism strongly favored a harder material in the flow zone. Higher-grade wire mesh had been trialed previously with minimal improvement β the wear mechanism was not the wire grade but the contact geometry of iron ore particles at the aperture edges.
Trial
The plant trialed modular PU screen panels on one of the three secondary screens over a 6-month period, running alongside the wire mesh screens for direct comparison.
PU panels selected: 305mm Γ 305mm modular bolt-down panels, 10mm square aperture, 65 Shore A hardness, compatible with the existing Schenck screen frames.
The trial screen ran for the full 6 months without a panel change. At the end of the trial period, panels were inspected and showed approximately 35% wear through. The estimated service life based on the wear rate was 14β16 months.
Outcome
Following the successful trial, all three screens were converted to PU panels.
Before conversion: - Screen changes: approximately 4 per month across three screens - Maintenance time: ~32 person-hours per month on screen changes - Wire mesh consumable cost: significant quarterly expenditure
After conversion: - Screen changes: approximately 1 per screen every 14 months (planned) - Maintenance time: reduced by approximately 85% for screen change activity - PU panel cost per set: higher than wire mesh per set, but cost per month of operation was lower
The reduction in unplanned screen downtime also reduced instances where the downstream ball mill was feed-starved while a screen was being changed, contributing to improved overall circuit throughput.
Key Lessons
The economics of wire mesh vs PU panels should be calculated on cost per month of operation, not cost per panel set. In this application, the higher unit cost of PU panels was far outweighed by the reduction in change frequency.
Aperture selection requires care. PU panels at 10mm nominal aperture produce a slightly different size distribution than 10mm wire mesh because the aperture geometry differs (square molded aperture vs wire mesh opening with different effective dimensions). The plant checked the downstream product size distribution after conversion and confirmed it remained within specification, but this check is important.
Compatibility with existing screen frames should be confirmed before ordering. In this case the Schenck frames were compatible with standard 305mm panel dimensions. Frame compatibility is not universal and should be verified.
Elephant Rubber supplied the PU screen panels for this conversion. We can provide compatibility information for major screen frame brands.
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