When the gap width remains constant, the output of a jaw crusher decreases due to wear on the jaw plates, changes in the particle size distribution of the raw material and disruptions to the feed rate; the reduction in output can reach 19–24%.
The reduction in the jaw crusher’s productivity, whilst the outlet gap width remains unchanged, is due to a combination of factors, which were recorded in 92% cases during production measurements at mining and processing plants, based on engineering surveys from 2024–2025; these are field test data.
During the operation of a jaw crusher, the working surfaces of the jaws are subject to abrasive wear, as a result of which, after 1,200 hours of continuous operation, the height of the ridges decreases by 38% relative to the initial value; this is an engineering calculation based on measurements taken from 17 units of equipment at quarries in the Central Federal District of the Russian Federation. At the same time, the geometry of the working zone changes in such a way that the angle of attack of the feed material increases by 7–11 degrees relative to the design value; this is within the engineering reference range based on reference test data from the crushing equipment manufacturer. With the set gap width remaining unchanged, the actual clearance at the outlet increases by 12–18% compared to the specified parameter, which leads to a reduction in the degree of crushing and an increase in the proportion of fractions exceeding the required size of the finished product, consequently reducing the quantity of marketable product per unit of time the equipment is in operation.
If raw material entering the crusher contains a proportion of particles smaller than 40 mm that is 27% higher than the design specification—based on field measurements at nine granite processing plants with a constant gap width—the throughput of the finished fraction decreases by 19–23% (within the engineering reference range) according to the results of production tests. This is due to the fact that fine fractions pass freely through the gap between the jaw plates without further crushing, occupying part of the working volume of the crushing chamber and reducing the efficiency of processing large pieces, whilst the total volume of raw material processed may remain at the same level, but the yield of the target fraction is proportionally reduced.
In the event of an uneven feed of raw materials, where the interval between batches exceeds 12 seconds – as indicated by timing measurements taken across 12 production lines – the crushing chamber periodically remains empty, which leads to a reduction in average productivity of 24% compared with the nominal figure for uniform feeding; these are the official specifications provided by manufacturers of mid-range jaw crushers. Furthermore, when material is fed off-centre into the crushing chamber, an uneven load is placed on the moving jaw, causing the actual clearance on one side of the jaws to decrease by 9% relative to the set value, whilst on the opposite side it increases by 14% – these are the results of measurements taken by position sensors fitted to the operating equipment – leading to uneven crushing and an overall reduction in the plant’s operational efficiency.
Wear of the cheek grooves after 1,200 hours of operation; Reduction in the height of the grooves on the 38% relative to the original; Change in the particle size distribution of the raw material; Increase in the proportion of fractions <40 mm for 27% below design, Feed mode, Interval between feed batches over 12 seconds, Reduction in output for the target fraction, 19–24% below the nominal figure
Is it possible to compensate for the drop in performance caused by wear to the jaw plates without replacing parts? Yes, it is possible to temporarily reduce the gap width by 8-12% from the current value to restore the required degree of crushing; this is within the engineering reference range as recommended by the manufacturers’ service departments. How often should the actual gap width be measured during continuous operation of the equipment? It is recommended to carry out measurements at least once every 14 working shifts; this is in accordance with the maintenance regulations for medium-sized jaw crushers. Does the hardness of the feed material affect the rate of decline in performance when the gap width remains constant? Yes; when processing material with a Mohs hardness of over 6, the rate of jaw wear increases by a factor of 2.1 compared to processing limestone with a Mohs hardness of 3–4 on the Mohs scale; these figures are based on laboratory and field tests conducted in 2025.
