## 3 Results and Discussion
Based on the regression equations for pressure drop obtained in individual test filtration processes, the values of the total pressure drop for the 50 th filtration cycle were calculated. The equations and values of \(\Delta\)p\({}_{\text{c}}\) are presented in Table 5. The total pressure drop difference of the bags from the filter 1 and from the filter 2 were statistically significant for the 67 th day and 272 nd day. However, the absolute difference was much greater for the 272 nd day. Using the \(\Delta\)p\({}_{\text{c}}\) value from Table 5, the values of the K\({}_{2}\) dust resistance coefficient were calculated based on Formula (4) for all test processes. The results of these calculations are presented in Table 6.  
Figure 9 shows the dependence of the K2 coefficient on the operation time of the bags in the installation in both lines. Based on the results obtained, differences in the value of the K\({}_{2}\) coefficient were observed. Extending the operation time of bags in industrial installations increases the K\({}_{2}\) coefficient from 6400 s\({}^{-1}\) to over 10,100 s\({}^{-1}\) in the case of narrow surface processing line (filter 1) to almost 30,000 s\({}^{-1}\) in the case of CNC drilling machines line (filter 2). Higher values of the K\({}_{2}\) coefficient were obtained for the CNC drilling machine line, in which the bags operating in the industrial installation were less loaded with dust and the dust  
Figure 8: Flow resistance \(\Delta\)p\({}_{\text{c}}\) through the filter fabric from the line of drilling centers. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**Line for Processing Narrow Surfaces**} & \multicolumn{2}{c}{**Line for Drilling Centers**} \\ \cline{2-5}  & **Equation** & \(\Delta\)**p\({}_{\text{c}}\) [Pa]** & **Equation** & \(\Delta\)**p\({}_{\text{c}}\) [Pa]** \\ \hline
0 & 45.851T\({}^{0.109}\) & 83.7 \({}^{\text{a}}\) & 45.851T\({}^{0.109}\) & 83.7 \({}^{\text{a}}\) \\
67 & 52.186T\({}^{0.1053}\) & 93.34 \({}^{\text{b}}\) & 53.218T\({}^{0.0868}\) & 85.94 \({}^{\text{a}}\) \\
133 & 56.621T\({}^{0.0995}\) & 98.08 \({}^{\text{a}}\) & 73.1T\({}^{0.0513}\) & 97.04 \({}^{\text{a}}\) \\
272 & 62.722T\({}^{0.0879}\) & 101.91 \({}^{\text{a}}\) & 160.77T\({}^{0.0377}\) & 197.97 \({}^{\text{b}}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Summary of regression equations and pressure drop values for the 50 th filter cycle. a, b—the same letters in the lines mean no significant differences at the level of significance 0.05.  
particles were coarser. The factor that determines the value of the K\({}_{2}\) coefficient is the frequency of cleaning pulses. In the filter in the narrow plane processing line, where the frequency of cleaning pulses is higher, lower values of the K\({}_{2}\) coefficient were obtained, even though the dust load of these bags in the industrial installation are much heavier. The values of parameters summarizing the working conditions of the bags in industrial installations and the results of the dust resistance coefficient are presented in Table 7.  
The results obtained show that cleaning pulses are an important factor determining the work of filter bags. They can eliminate the potentially negative impact on the filtration process of other factors, such as dust load or particle size of dust in polluted air. Comparing the results obtained with the earlier studies in which the values of the K\({}_{2}\) coefficient for beech dust were determined, it can be concluded that in the case of this filter material, the values of the K\({}_{2}\) coefficient for beech wood dust are about half that \begin{table}
\begin{tabular}{l c c c c} \hline \hline  & **Ap\({}_{\text{P}}\) [Pa]** & **K\({}_{2}\) [s\({}^{-1}\)]** & **\(\Delta_{\text{P}_{\text{P}}}\) [Pa]** & **K\({}_{2}\) [s\({}^{-1}\)]** \\ \hline
0 & 32.022 & 6507.545 & 32.022 & 6507.545 \\
67 & 41.662 & 8466.596 & 34.262 & 6962.76 \\
133 & 46.402 & 9429.863 & 45.362 & 9218.513 \\
272 & 50.232 & 10,208.2 & 146.292 & 29,729.61 \\ \hline \hline \end{tabular}
\end{table}