In rotary crushers for limestone and diabase, pairs of hammers are matched by weight to ensure balance. Rearranging them at random increases vibration, accelerates wear and reduces the service life of components by 60–70%.
According to the official specifications of manufacturers of rotary crushers for limestone and diabase, the maximum mass deviation between any two paired hammers must not exceed 0.3 kg when they are interchanged, which is a strict engineering constraint prohibiting arbitrary changes to their positions.
Each pair of hammers on the crusher rotor is selected at the factory by weight to within 10 g; this value is the result of control measurements carried out during the assembly stage and guarantees the balance of the rotating assembly at operating speeds of up to 980 revolutions per minute, in accordance with the official specifications for standard models designed for crushing limestone and diabase.
When the position of the hammers on the rotor is altered arbitrarily, the vibration level of the crusher’s support assemblies increases by an average of 2.7 times, according to test data from production sites when processing rock with a Mohs hardness of between 5 and 7, which corresponds to the characteristics of limestone and diabase, respectively.
According to the results of operational tests, if the hammers are arranged incorrectly, the unevenness of wear on the working edges reaches 42% over 100 hours of continuous operation with raw material having a moisture content of no more than 6%, which leads to a significant reduction in the interval between replacements of wear parts, without the possibility of restoring the original shape of the cutting edges.
Below are the verified specifications for the key parameters of the hammers, taken from the official catalogues of manufacturers of this class of equipment: the weight of a single bit in its standard configuration ranges from 12 to 18 kg according to the official specifications; the permissible weight deviation within a single pair is no more than 0.3 kg, in accordance with engineering requirements; the working surface hardness of the bits is 55–62 HRC according to factory measurements; the maximum hardness of the rock to be processed by these bits is 7 on the Mohs scale, according to the manufacturers’ reference data.
Is it possible to swap the blades from different pairs on the rotor? According to the manufacturers’ official instructions, any rearrangement of the blades beyond a single factory-matched pair will result in a loss of rotor balance and an increase in vibration to at least twice the permissible limits, as shown by test measurements. How can you identify a pair of blades intended for installation together? Each pair of hammers has an identical marking code on the side surface, which is applied at the factory during the selection stage and confirms compliance with mutual compatibility parameters in accordance with official requirements. What will happen if the crusher continues to operate with the hammers swapped? According to the results of long-term tests, when operating with the hammers repositioned, the service life of the rotor bearing assemblies is reduced by 60–70% compared to the value stated by the manufacturer under standard load conditions.
