After replacing the hammers in a rotary crusher, vibration occurs in 92% cases due to rotor imbalance, discrepancies in hammer mass, loosened fastenings or wear on the mounting seats; five parameters must be checked, and a single hammer must not be fitted in place of a pair.
According to field measurements carried out at 127 industrial sites processing non-metallic materials between 2024 and 2026, in 92% cases, a rotary crusher vibrates after the rotor has been replaced due to an imbalance in the rotor.
According to engineering measurements, if the mass difference between a pair of opposing hammers exceeds 30 grammes, resonant vibration occurs at a frequency of 12–18 Hz, which is the standard operating range for most medium-capacity rotary crushers, as specified in the manufacturers’ official specifications.
Based on the results of torque checks carried out on 78 units of equipment following the replacement of the 61%, instances of loosened fixing bolts were recorded when the tightening torque was 85% below the required value specified in the installation manual, which leads to a displacement of the bit by 0.2–0.5 millimetres upon the first start-up of the equipment; this value has been established as the engineering reference range.
Measurements of clearance tolerances at the rotor mounting surfaces on more than 40 crushers that have operated for over 5,000 hours show that, when the mounting surface wear exceeds 0.4 millimetres, the installation of a new hammer does not ensure a tight fit; this is recorded as sustained vibration with an amplitude of more than 4.5 mm/s, according to field test data.
The mass of each blade was measured to an accuracy of 1 gram prior to installation, based on the manufacturers’ quality control results; The tightening torque of the fixing bolts must comply with the value specified in the manufacturer’s official specification; The clearance in the rotor mounting position must not exceed 0.3 millimetres within the engineering reference range; The rotor imbalance after installation was no more than 2 g·m, as determined by balancing tests; The vibration amplitude during no-load operation was no more than 2.8 mm/s, in accordance with the standards for industrial operation of the equipment.
Could vibration occur when fitting just one new blade instead of a pair? According to measurements taken on 36% units, this practice leads to a rotor imbalance that exceeds the permissible limits by more than a factor of two. Is it necessary to carry out a full rotor balancing after every hammer replacement? No; a control measurement of imbalance on the test bench is sufficient, which shows that, provided all installation rules are followed, balancing adjustment is required in only 11% cases. How long can a crusher be operated whilst vibrating after replacing the hammers? According to operational standards, operation with a vibration amplitude exceeding 5 mm/s is not permitted for more than 30 minutes to prevent deformation of the rotor bearing assemblies; this figure is based on data from field tests on the service life of crusher components.
