Background
A gold mining operation in Ghana was experiencing rapid wear on the chute liners in its concentrator plant β specifically the chutes feeding the ball mill circuit from the secondary crusher. The chutes handled crushed gold ore at approximately 12mm top size, wet (ore was sprayed with water at the secondary crusher discharge to reduce dust and aid slurry formation).
The existing liners were 25mm natural rubber panels. In this position, they were lasting approximately 6β8 weeks before requiring replacement. Each liner change required a 3-hour shutdown of the affected chute.
Analysis of Wear Mechanism
The ore at 12mm top size after secondary crushing is no longer a large-lump impact application. The dominant wear mechanism in this position was sliding abrasion of fine particles in a wet environment β crushed ore particles sliding across the liner surface with water as a medium.
This is the wear mechanism where polyurethane outperforms natural rubber. In dry impact applications (primary crusher feed), rubber's elastic absorption is advantageous. In wet fine-ore sliding applications, PU's hardness and resistance to the micro-cutting action of hard mineral particles is superior.
The recommendation was to trial PU liners (75 Shore A hardness) in place of the NR rubber in the secondary crusher discharge chutes.
Trial and Comparison
One chute was converted to PU liners. The adjacent parallel chute retained NR rubber liners. Both were inspected at 6-week intervals.
At 6 weeks: - NR rubber chute: liners at approximately 60% remaining β replacement due within 2 weeks - PU chute: liners showing approximately 15% wear β clearly longer life trajectory
At 18 weeks (NR chute on its third liner set): - NR rubber: third set of liners at 55% remaining - PU chute: first set of PU liners at approximately 50% remaining
Estimated PU liner life: approximately 36 weeks (vs 7 weeks for NR rubber in the same application).
Life improvement: approximately 5Γ
Full Conversion
Following the successful 18-week trial, all secondary crusher discharge chutes in the concentrator were converted to PU liners. The primary crusher feed chute was evaluated separately β given the larger lump size (up to 200mm) and higher drop height (2.2 meters) at that position, NR rubber was retained for the impact zones of the primary crusher feed chute, with PU used only in the lower sliding sections.
Economic Impact
The concentrator had 6 secondary crusher discharge chutes. Under the previous NR rubber specification: - Annual liner changes per chute: approximately 7β8 - Total annual liner changes plant-wide: approximately 45β48 - Each change: 3-hour shutdown
Under PU specification: - Annual liner changes per chute: approximately 1.5 - Total annual liner changes: approximately 9 - Reduction: approximately 36β39 fewer chute change shutdowns per year
The cost of PU liner sets was approximately 2.5Γ the cost of NR rubber sets. On a per-shutdown-avoided basis, the economics strongly favored PU despite the higher unit cost.
Key Points
Wet fine-ore sliding is PU's strongest application. The gold concentrator secondary crusher discharge is a textbook case. If your application description matches β fine to medium ore, water present, particles sliding across liner surface β PU is almost certainly the better material choice.
Trial one position before full conversion. The approach taken here (parallel comparison, one chute with NR and one with PU) produced clear, site-specific data. It's more convincing than any published specification and gives the maintenance team confidence before committing to plant-wide change.
Different positions in the same plant may need different materials. Primary crusher feed impact zone (NR rubber) and secondary crusher discharge sliding zone (PU) in the same plant required different materials. Blanket conversion to PU throughout would have been wrong for the primary crusher position.
Elephant Rubber supplied the PU chute liner panels for this project.