The dust separated from the air stream flowing through the filter collects in the separation channels from where it enters the dust trap common for all modules, which is a pipe with a constant cross-section--depicted in Figure 3. The separation efficiency is determined for the rated conditions of air flow through the filter, which was within the range of 33-40%, and, when compared to the efficiency of a single module (60-61%), is a very small value. The individual performance of each module, as part of the filter assembly, showed that module \(a\), which was the closest to the outlet of the  
Figure 2: Structural diagram of a modular multi-cyclone: 1—cyclone, 2—dust trap, 3—partition, 4—module cassette, 5—section pipes, 6—exhaust air collector [30]. sedimentation tank, achieved an efficiency of 64%, and showed that module \(b\) achieved an efficiency of 43%, while module \(c\), the furthest from the outlet of the suction port, only had an efficiency of 20% [31]. Such significant differences in the modules' efficiencies are the result of the divergent suction levels in the modules, and this is due to the unequal distances of their separation channels from the suction stub of the dust settler. The authors [31] solved the problem of equalizing the suction streams in this type of filter by dividing the dust trap into three parts (channels) according to the diagram shown in Figure 3b. After appropriate selection of the heights \(h_{1}\) and \(h_{2}\), similar values for the suction streams from all modules were obtained. Thus, a significant improvement in the uniformity of operation of all the modules was achieved (maximum efficiency differences did not exceed 7%) and there was a clear improvement (up to 60.6%) in the efficiency of the entire radial filter. The above-mentioned examples show how important an influence on the operation of the inertial filter is for development of the correct suction system. Regardless of the equalizing suction stream values method, an experimental verification of the system is always required, consisting of measuring the values of the individual suction streams from all cyclones, segments, or multi-cyclone modules. The problem of dust accumulation in a single cyclone settler and the impact of the settler dimensions on the efficient operation of the cyclones is presented in this work [32; 33; 34; 35; 36]. The authors [32], after examining the influence of the dimensions of the cylindrical dust trap (height and diameter) on cyclone operation, showed that the optimal design of the sedimentation tank and the dipleg (the extended part of the bottom part of the cyclone, connecting the cyclone with the dust trap) leads to a better separation efficiency than a conventional cyclone. The authors [33], using the CFD program, investigated the influence that the influence that dipleg shape (cylindrical, inverted cone, conical and diamond) has has on the flow characteristics and cyclone operation--depicted in depicted in Figure 4.  
It was found that the dipleg geometry significantly influences the the cyclone pressure drop. The cylindrical dipleg generated the highest pressure drop, while the lowest pressure drop was observed for the cyclone without a dipleg. Among tested geometries, the highest separation efficiency was found for the cyclone with a conical dipleg, and diamond dipleg was the lowest. Figure 3: Modular inertial radial filter: (**a**) functional diagram, (**b**) dust trap division into suction channels \(a\), \(b\) and \(c\), \(1\)—filter modules, \(2\)—separation channels, \(3\)—dust trap, \(4\)—extraction connector [31]. The authors of [34] numerically examined the particle separation process inside two cyclones extended with a dipleg. They found that the dipleg length significantly influences the cyclone's separation efficiency by providing more separation space and minimizing re-lift of the separated particles. Paper [35] presents research results on three cyclones separation efficiency with different lengths of cylindrical dipleg and with a dust trap of a constant shape.