Vibration Research on Centrifugal Loop Dryer Machines Used in Plastic Recycling Processes
, Pavel Ževžikov 1, Michał Stosiak 2, Paulius Skačkauskas 1, Anna Borucka 3 and Maksym Delembovskyi 4Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsIn this research the authors investigated the vibrations of centrifugal loop dryer machines used in plastic recycling processes. Two identical loop dryers installed and operated in parallel in a single recycling line were studied. The current research includes an analysis of the centrifugal loop dryer machines' vibration characteristics and their influence on operation results, based on vibration analysis, frequency response analysis, and expertise. Measurements were performed using a two-sample measurement design and based on a one-sample statistical method for estimating uncertainty in repeated measurements of data processing. Additionally, a problem connected with incorrect machine operation during high vibration, resulting in insufficient drying of loaded material, was investigated.
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I think this paper is an interesting and useful contribution to the field. The paper is well written and articulated, and once the points raised above are addressed the manuscript can be accepted for publication in Machines.
Author Response
Reviewer 1
Thank you for your comments and suggestions in the review. All comments and suggestions have been carefully addressed by the authors.
Comment 1: Please check and correct:
line 18: ... de-sign ... --> ... design ...
line 60: ... ma-chines ... --> ... machines ...
line 84: ... be-tween ... --> ... between ...
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Response: The indicated and other spelling errors have been corrected.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThis study investigates the vibrations of centrifugal loop dryer machines used in plastic recycling processes. The current research includes an analysis of the centrifugal loop dryer machines’ vibration characteristics and their influence on operation results based on vibration analysis, frequency response analysis, and expert advice.The overall research is perfect and the idea is novel. The following modifications are proposed for this study:
1. Line16, in the abstract, there are only qualitative results and no quantitative conclusions. It is recommended to add relevant experimental data results.
2. Line95, the experimental conditions and environment were not explained, and there were significant differences in the test results under different working conditions.
3. Line110, this article does not mention whether the sensor is calibrated or not.
4. Line115, the theoretical analysis of machine vibration is insufficient, and the analysis methods are not rich enough.
5. Line177, please explain whether the data in Table 1 and Table 2 were obtained directly through experiments or calculations, and whether there were repeated experiments. Is it an average value?
6.Line249,the article presents two sample measurements.Can you add more samples for measurement and discover more measurement results and trends.
Comments on the Quality of English LanguageThe Quality of English Language need minor editing.
Author Response
Reviewer 2
Thank you for your comments and suggestions in the review. All comments and suggestions have been carefully addressed by the authors.
Comment 1: Line16, in the abstract, there are only qualitative results and no quantitative conclusions. It is recommended to add relevant experimental data results.
Response: The abstract was extended by: “That was defined that some melted plastic still being too wet after mechanical drying and this was caused by the incorrect installation of damper elements of the holding elements. Finalize it was recommending a correction of the machine installation and a control measurement to see whether the vibration on the base of the machine still exists. A simplified theoretical vibration analysis of the rotating machine was also carried out in the paper.”
Comment 2: Line95, the experimental conditions and environment were not explained, and there were significant differences in the test results under different working conditions.
Response: Yes, the conditions and environment was not detail explained, since it was performed on the real working industrial factory. For sure the are will be an difference between each measuring (working process is dynamic on factory) in this reason the a one-sample statistical method for estimating uncertainty in repeated measurements of data processing was choose in the methodology. To more detail describe an factory environment by private policy not possible, but regarding photo is visible that machines installed and operated in line without some much influence from another objects.
Comment 3: Line110, this article does not mention whether the sensor is calibrated or not.
Response: Prior to the main measurements, the accelerometers were calibrated using a B&K portable accelerometer calibrator type 4294. The information was add to article.
Comment 4: Line115, the theoretical analysis of machine vibration is insufficient, and the analysis methods are not rich enough.
Response: The paper presents a simplified theoretical analysis of the vibrations of a rotating machine excited by a harmonic force. The information was add to article.
„A simplified theoretical analysis of rotating machine vibration can be carried out by assuming a single-mass model excited to vibration by a harmonic force:
(1)
where:
Mw – mass of rotating parts, kg
– radius of eccentricity of the centre of gravity of rotating masses, relative to the geometric axis of rotation, m
– rotor angular frequency, rad/s.
Figure. Dynamic diagram of a single-mass elastic system subjected to a harmonic force.
The vibrations of such a system can be described by the equation:
(2)
The general solution of the equation above is of the form [A. Piersol, Paez T. Harris' shock and vibration handbook (sixth ed.), McGraw-Hill, New York (2010), p. 1168]:
(3)
where:
A i B – integration constants depending on initial conditions,
– dimensionless damping coefficient,
– the phase lag angle between the forcing force vector F0 and the swing vector, rad,
– undamped free vibration angular frequency, rad/s,
q - damped free vibration frequency, rad/s,
K – general vertical elasticity constant, N/m,
– angular frequency ratio, = /
moreover:
(4)
The frequency of undamped free vibration is:
(5)
The damped free vibration angular frequency is:
(6)
In equation (3), the first term describes a free oscillation fading at a frequency of q, and the second term describes a steady state oscillation forced at frequency . For the analysis of steady state oscillations, the first term of equation (3) can be neglected, because the damping existing in the system causes the transient oscillations to decay quickly and only the steady oscillations taking place at the frequency of the forcing force remain. However, the first term cannot be omitted when analysing shock oscillations, i.e. oscillations occurring under the action of single impulses.
For steady-state oscillation, the solution of the oscillating motion takes the form:
(7)
where:
(8)
(9)
Therefore, in the absence of damping ( = 0) = 0 or 180o.
The coefficient of force transfer to the foundation, i.e. the ratio of the amplitude of the force transferred to the foundation to the amplitude of the forcing force, is in this case:
(10)
This relationship was obtained by representing the force transmitted through the elastic elements as the root of the sum of the squares of the amplitudes of the elastic and damping forces:
(11)
Analysis of function (10) allows us to conclude that when , the value of , and this means that . However, when the damping adversely affects the value of the force P0. Conversely, when , the force transferred to the ground .”
Comment 5: Line177, please explain whether the data in Table 1 and Table 2 were obtained directly through experiments or calculations, and whether there were repeated experiments. Is it an average value?
Response: During the experimental tests, acceleration was measured. Table 1 and Table 2 present the displacements for the individual measurement points in the x, y, z directions. They were obtained by means of transformations. The results of the accelerations recorded directly during the measurements are shown in Figure 7 and Figure 9 (current revision version). During the tests, the accelerations were measured three times for each measuring point and direction and then the result was averaged.
Comment 6: Line249, the article presents two sample measurements. Can you add more samples for measurement and discover more measurement results and trends.
Response: Dear Reviewer, to add more samples need obtain from the new the data and permission from the company, unfortually its long processes. Your recommendation valid and will be taken in account during controlling measuring after some months of machine works after re-installation. Thank You for recommendation.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsSummary of the Paper:
This paper presents a study on the vibrations observed in centrifugal loop dryer machines used in plastic recycling. The authors conducted an analysis of two identical loop dryers operating in parallel within a single recycling line. Their findings highlight that one of the machines exhibited insufficient vibration reduction due to the improper installation of damping elements.
Feedback and Suggestions:
- Quality of Figure 1:
The quality of Figure 1 requires enhancement. It is crucial for the figure to be clear and detailed, as it aids in the comprehension of the discussed findings.
- Clarification of Methodology:
The manuscript often references "a one-sample statistical method for estimating uncertainty in repeated measurements of data processing." However, this method is not clearly defined. For the benefit of the reader and to strengthen the scientific rigor of the paper, please provide a detailed description of this method in the Methods section.
- Characterization of Resonance Frequency:
The paper describes "16.2 Hz or body rotation at 972 rpm" as a resonance frequency. This characterization could be misleading. This frequency is that of the rotating part, and without further analysis, such as assessing the impulse response function or conducting an engine-based run-up test, it cannot be definitively termed as the resonance frequency. Clarification or additional testing in this area would strengthen the paper's conclusions.
- Depth and Theoretical Contribution:
The paper currently lacks depth in its experimental approach. It predominantly relies on the visual inspection of an isolated example and does not effectively model the dryer as a comprehensive system. This approach limits the study's applicability. To elevate the paper's scholarly value and relevance, more extensive experimental or theoretical work is needed. This could include system modeling or a series of experiments to substantiate the findings and provide a broader context.
Conclusion:
While the study addresses an important aspect of plastic recycling processes, the current manuscript requires significant improvements in both methodology and depth of analysis for consideration in a scholarly journal. The suggestions provided aim to enhance the robustness and scientific validity of the research.
Author Response
Reviewer 3
Thank you for your comments and suggestions in the review. All comments and suggestions have been carefully addressed by the authors.
Comment 1: - Quality of Figure 1: The quality of Figure 1 requires enhancement. It is crucial for the figure to be clear and detailed, as it aids in the comprehension of the discussed findings.
Response: The quality of Figure 1 has been improved and size of Figures increased.
Comment 2: - Clarification of Methodology: The manuscript often references "a one-sample statistical method for estimating uncertainty in repeated measurements of data processing." However, this method is not clearly defined. For the benefit of the reader and to strengthen the scientific rigor of the paper, please provide a detailed description of this method in the Methods section.
Response: The detailed description of method used in the paper was added in the Methods section.
Comment 3: - Characterization of Resonance Frequency: The paper describes "16.2 Hz or body rotation at 972 rpm" as a resonance frequency. This characterization could be misleading. This frequency is that of the rotating part, and without further analysis, such as assessing the impulse response function or conducting an engine-based run-up test, it cannot be definitively termed as the resonance frequency. Clarification or additional testing in this area would strengthen the paper's conclusions.
Response: During the preliminary tests, the vibrations of the machine were tested at the same points as during the main tests. During the preliminary tests, the machine was either switched off or operated at different fixed speeds. In the first case, the component of the vibration spectrum with frequency was not observed. During preliminary tests at different speeds, a component with a frequency of was noticed in the vibration spectrum. On this basis, it was assumed that this component was related to the imbalance of the rotating parts of the machine.
Comment 4: - Depth and Theoretical Contribution: The paper currently lacks depth in its experimental approach. It predominantly relies on the visual inspection of an isolated example and does not effectively model the dryer as a comprehensive system. This approach limits the study's applicability. To elevate the paper's scholarly value and relevance, more extensive experimental or theoretical work is needed. This could include system modeling or a series of experiments to substantiate the findings and provide a broader context.
Response: The theoretical analysis of rotating machine vibrations can be presented in a simplified form, treating the machine as a single-mass system excited to vibration by a harmonic force. This is the approach taken in the paper. A more detailed theoretical analysis can be based on treating the machine as a multi-mass system with non-linearities (stiffness and damping) and can also include passive vibration isolation criteria. This is an interesting issue and could be the subject of a separate article. Such analyses will be presented in the authors' next article. In addition, due to limited space, only sample test results are presented in the paper. All research results are presented in the research report.
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
Comments and Suggestions for AuthorsI appreciate the careful attention given to my previous comments; the paper has shown considerable improvement since the last review.
However, I still have a few concerns:
1. The quality of Figure 1 remains unchanged. This time, I will be more direct: the figure exhibits noise levels that suggest it might be a scan from a printed paper or book. Please enhance the quality by, at a minimum, removing the noise, or include a reference if applicable.
2. The theoretical background has seen some improvement.
3. In lines 234-239, a brief explanation of the one-sample t-test is introduced. However, there is no clear connection made with the experiment. I suggest either providing a more comprehensive explanation linking the t-test to your experiment or removing the reference to statistical testing altogether. If you choose to include statistical testing, please describe the groups, state the null hypothesis, and present the result of the t-test, typically a p-value.
Author Response
Thank you for your comments and suggestions in the review. All comments and suggestions have been carefully addressed by the authors.
Comment 1: The quality of Figure 1 remains unchanged. This time, I will be more direct: the figure exhibits noise levels that suggest it might be a scan from a printed paper or book. Please enhance the quality by, at a minimum, removing the noise, or include a reference if applicable.
Response: The noise on figures was removed and the reference in which figures based is added.
Comment 2: The theoretical background has seen some improvement.
Response: Thank You for Your comment. The theoretical background added in the text of the manuscript during first round of revision it is a simplified considerations of single mass body forced vibrations in one directions. More precisions theoretical considerations should cover multi mass body model and 3-aixes vibrations. Moreover in order to make considerations more precisions IT can be take into account some nonlinearity in stiffness or damping model.
Comment 3: In lines 234-239, a brief explanation of the one-sample t-test is introduced. However, there is no clear connection made with the experiment. I suggest either providing a more comprehensive explanation linking the t-test to your experiment or removing the reference to statistical testing altogether. If you choose to include statistical testing, please describe the groups, state the null hypothesis, and present the result of the t-test, typically a p-value.
Response: The information and references was removed.
Author Response File: Author Response.pdf
