The wear life of the original jaw liners was only in the 90 hour to 110 hour range, with the top of the fixed jaw showing heavy wear from oversize rock rolling, not fracturing and moving through the crusher.
The fast wear of the OEM-style, standard manganese jaws was creating a risk of the crushing contract being unprofitable.
Faced with a real wear issue, the client asked Foothills Steel Foundry to assist with the problem, not really knowing what the solution would entail.
{{image2-a:r-w:250}}Understanding the problem was key for Foothills. What was wearing, where and why?
The initial fracture of the large, hard rock being fed was difficult to achieve, causing some of the oversize rocks to roll at the top of the crushing chamber.
When the rock was reduced and passing through the crusher, the high silica content was preventing a work-hardened surface from forming on the jaw plates.
The high compressive strength of the rock was hardening the jaws on impact but the high silica content was removing it almost immediately through abrasion as the reduced material moved through the crushing chamber.
Foothills used its experience in other high wear environments to redesign the Komatsu BR380 jaws, then tested its new version on the oversize gold product. The results were pleasing, with a significant improvement recorded.
ENLARGED TOOTH PROFILE
The technical differences included changes to material, jaw and crushing chamber shape, and the tooth profile.
Making the tooth larger, with a more pronounced point, helped concentrate the crushing force with a point load on
the rock, to get the initial fracture.
{{image3-a:r-w:250}}An increase to the curve on the fixed jaw allowed some of the larger rock to further enter the crushing chamber, stopping the rolling effect and making the initial fracture easier. The curve changed the nip angle initially and allowed crushing in the middle of the chamber. This stopped the crusher only wearing out the ends of the jaws.
More material was added between the tooth valleys and lightening pockets, allowing the jaw to be pushed past the point that no teeth are left, if needed.
Foothills upgraded the material to an ultra heavy duty 24 per cent manganese. This material has much more abrasion resistance and holds the work-hardened surface longer against the abrasive effects of the high silica content rock.
The combination of changes meant that at 60 hours the jaws were only 20 per cent worn. This meant longer service time before the jaws needed turning, and an average service life of more than 300 hours, an increase of more than 300 per cent compared with the OEM-style jaws.
Through redesign of the jaw plates, the processing of oversize rock from the gold mine is now more efficient, and reduced operational costs stem from an increase in lifespan of the jaw. This means fewer change-outs and costs associated with maintenance and downtime during a change-out period.
With an increase of nearly 300 per cent in production lifespan while still achieving reduction targets, Foothills has created
an aggressive competitor product to take to market.
Source: Foothills Steel Foundry Australia