Wedge-shaped wear on the jaw plates of a crusher is caused by uneven pressure, asymmetrical movement of the jaw plates and varying levels of abrasiveness in different areas; whilst it cannot be eliminated, the rate of wear can be reduced by 30%.
The wedge-shaped wear of the jaw plates in a jaw crusher is caused by the uneven distribution of contact pressure across the working surfaces of the plates, as well as the asymmetrical nature of the moving jaw’s motion, with the difference in sliding speed between the upper and lower zones of the plates reaching a factor of 2.7, according to the results of industrial trials at granite quarries.
During the crusher’s operation, the feed material is crushed in the upper part of the working chamber as the jaw plates close, whilst in the lower part the material is already in a fine fraction and does not bear the main impact load; according to production measurements, the peak contact pressure in the upper third of the jaw plate’s height is 3.2 times higher than in the lower third during standard operation.
The movable jaw plate not only performs a reciprocating motion but also oscillates in an arc, with the amplitude of displacement in the horizontal plane at the upper edge of the plate being 40 per cent greater than at the lower edge, according to the official specifications of most standard medium-sized jaw crushers.
In the upper part of the crushing chamber, there are large chunks of solid rock with sharp cutting edges, which cause intense micro-chipping of the slab surfaces, whilst in the lower part, the fine fraction has smooth edges and produces a predominantly abrasive effect; according to laboratory test results, the wear rate in the upper zone when processing granite with a fraction size of up to 500 mm is 1.8 mm per thousand operating hours.
Plate area Peak contact pressure Wear rate during granite machining Nature of damage Upper third 180 MPa 1.8 mm/1,000 hours Chipping and wedge-shaped abrasion Middle third 85 MPa 0.9 mm/1,000 hours Uniform abrasion Lower third 56 MPa 0.5 mm/1,000 hours Surface polishing
Is it possible to completely eliminate wedge wear in jaw plates? It is not possible to completely eliminate this type of wear, as it is caused by the design features of jaw crushers, but its rate can be reduced by 30 per cent by adjusting the angle of the fixed plate in accordance with the engineering reference range. How often should jaw plates be replaced in cases of severe wedge wear? Scheduled replacement should be carried out when the height of the worn wedge section reaches 20 per cent of the original plate height, in accordance with the technical regulations of the equipment manufacturers. Does the type of material being processed affect the severity of wedge wear? The severity of wedge wear is directly proportional to the hardness of the material being processed; when crushing limestone, the difference in wear rate between zones is 2.1 times, whilst when crushing quartzite, it reaches 4.1 times, according to the results of field tests.
