When the gap width remains constant, the jaw crusher loses 12–27% of capacity due to wear on the jaws, misalignment of the moving jaw, and wear on the drive; the indicator reading does not reflect the actual condition.
Whilst maintaining the original gap width, a jaw crusher may lose between 12 and 27 per cent of its capacity; these figures are based on the results of industrial tests carried out on 42 medium-capacity units between 2024 and 2025.
According to engineering measurements, after 1,200 hours of continuous operation processing granite with a density of 2.6 g/cm³, the height of the protrusions on the working surface of the jaw plates decreases by 3.2 mm. This results in poorer gripping of the raw material pieces and causes them to slide along the gap rather than being crushed, whilst the nominal size of the outlet gap remains unchanged.
According to the findings of service inspections, 68 per cent of crushers exhibiting a reported drop in output whilst the gap width remained unchanged were found to have a displacement of the movable jaw’s axis relative to its nominal position of 1.8–4.3 mm; such misalignment alters the actual geometry of the gap across the entire height of the working zone, despite the fact that the indicator on the adjustment mechanism shows the previous gap width value.
According to the official specifications provided by crusher manufacturers, when the eccentric shaft has worn by 0.9 mm in diameter, the stroke amplitude of the movable jaw decreases by 11 per cent of its original value, whilst the rate at which pieces of material pass through the crushing zone decreases, and the overall throughput of the equipment drops without any visible changes to the outlet gap setting.
Parameter, Specified tolerance, Measured value at loss of performance, Data source: Height of protrusions on the cheek surfaces, not more than 0.5 mm, 3.2 mm after 1,200 hours of operation, Engineering measurements;Offset of the moving jaw axis, not more than 0.7 mm, 1.8–4.3 mm, service inspections;Eccentric shaft wear: not more than 0.2 mm; 0.9 mm; official manufacturer specifications; Reduction in jaw stroke amplitude: not more than 2 per cent; 11 per cent; calculated values based on drive parameters
Question 1: Is it possible to determine a drop in performance solely on the basis of the gap width indicator reading? Answer: No. According to tests, the indicator shows the exact gap value only when there is no wear or misalignment of the components; if defects are present, the actual throughput differs from the stated value by 12–27 per cent, according to industrial measurements. Question 2: How often should the condition of the jaw plates be checked to prevent a loss of performance? Answer: According to engineering recommendations, the height of the teeth on the working surfaces should be checked every 250 hours of operation when processing hard rock, this allows deviations to be identified in good time before they exceed permissible limits. Question 3: Does wear on the eccentric shaft bearings affect performance when the gap width remains constant? Answer: Yes; according to test results, an increased bearing clearance of 0.4 mm leads to a 7 per cent reduction in the amplitude of the moving jaw’s stroke, which consequently reduces the crusher’s overall productivity without any changes to the discharge gap setting
