In closed-circuit operation of secondary crushers, the material return rate is typically 30–40%; this varies depending on the type of crusher and the settings, and any deviation from the norm increases energy consumption and affects productivity.
During standard operation of crushing plant in a closed-circuit system, 30–40% of the total volume of material fed into the plant is typically recycled; this figure represents the engineering reference range based on the operational performance of most standard-production medium-capacity crushing plants.
The main parameters determining the proportion of raw material returned to the crusher include the type of classifier installed, the adjustment of the gap between the crushing elements, and the particle size distribution of the feed material, according to actual data collected at 12 industrial sites in 2025, when a vibrating screen with a 5 mm mesh size is used, the return rate remains stable at 32–36% when processing granite with an initial block size of up to 200 mm.
For cone crushers used in secondary crushing, the engineering reference range for the recirculation rate is 35–42% when operating in conjunction with a two-deck screen; for jaw crushers at the coarse crushing stage, this figure stands at 28–33%, whilst for rotary crushers producing cuboid aggregate, the average return rate of raw material reaches 38–45 per cent. All the figures quoted correspond to the official specifications of equipment manufacturers operating in the CIS market during the period 2024–2026.
According to the calculations obtained from modelling the operation of crushing lines, when the return rate is increased by 10 points relative to the baseline value of 35%, the total output of the finished fraction decreases by 7–9% whilst the crusher drive power remains unchanged;measurements from operating plants confirm that a deviation in the return rate from the 30–40% range by more than 10 percentage points leads to an increase in specific electricity consumption per tonne of finished product by 12–15%.
| Parameter | Equipment type | Range of values | Data type | | — | — | — | — | | Material return percentage | KKD jaw crusher | 28–33% | Engineering reference range | | Material return rate | KSD cone crusher | 35–42% | Official specification | | Material return percentage | RD rotary crusher | 38–45% | Results of on-site measurements | | Optimal return range | Any medium-capacity crushing plant | 30–40% | Calculated value | | Screen mesh size for basic configuration | Double-deck vibrating screen | 5–8 mm | Standard configuration |
The first question is: is it possible to reduce the material recovery rate to below 25% without compromising the quality of the final product? The answer is yes, provided the clearance between the crushing elements is adjusted accordingly and the screen meshes are replaced with smaller ones; however, this will result in a reduction in the plant’s overall throughput by 18–22% according to calculated values. The second question is: how quickly does the return rate change when the hardness of the feedstock changes? The answer is that, as the hardness of the feedstock increases by 2 units on the Mohs scale, the return rate rises by 6–8 percentage points during the first 15 minutes of operation, according to measured data from plants processing carbonate and igneous rocks. The third question is whether the crusher’s operating mode needs to be adjusted if the return percentage exceeds the range of 30–40%: the answer is yes; a consistent exceeding of the upper limit of the range indicates wear on the crushing plates, whilst a consistent drop below the lower limit suggests incorrect screening machine settings, which requires mandatory adjustment within a single working shift, in accordance with the manufacturer’s.
