Monitoring the Conditions of Hydraulic Oil with Integrated Oil Sensors in Construction Equipment
Round 1
Reviewer 1 Report (Previous Reviewer 3)
The authors have addressed all my comments in the revised version of the paper.
I recommend the paper to be accepted for publication in Lubricants.
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Author Response
Dear Reviewer
I appreciate your comments during the first paper review process.
It is thought that the completeness of our paper has been improved more through the correction of each comment.
Thank you once again for reviewing our paper.
Moreover, after resubmitting our paper, we received professional English proofreading.
In addition to correcting English expression, we have completed the overall correction of grammar, articles, prepositions and so on.
Sincerely yours
Sung-Ho Hong
Author Response File: 
Author Response.docx
Reviewer 2 Report (Previous Reviewer 1)
As this is re-submitted paper version, I can state that the Authors have performed all corrections mentioned in my previous review. In the revision process the Authors could involve much more effort in explaining some interesting paper parts, but the corrections and explanations are at least satisfactory. The paper can be published in a presented form.
Author Response
Dear Reviewer
I appreciate your comments during the first paper review process.
It is thought that the completeness of our paper has been improved more through the correction of each comment.
Thank you once again for reviewing our paper.
Moreover, after resubmitting our paper, we received professional English proofreading.
In addition to correcting English expression, we have completed the overall correction of grammar, articles, prepositions and so on.
Sincerely yours
Sung-Ho Hong
Author Response File: Author Response.docx
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
1) The Abstract is too general and mainly descriptive. In the Abstract the Authors should add some of the most important results obtained in this research (its exact values), which cannot be found in other literature. Such addition will highlight the novelty of the presented paper already in the Abstract – at the moment from the abstract cannot be seen any novel elements which are obtained in this paper.
2) The English is very good, readable and completely understandable. However, the English should be checked throughout the paper text and corrected in some sentences. For example, in the Abstract is written (Line 12): “The hydraulic oil of construction oil is polluted…” – this sentence surely requires better definition. Another example, Line 298 – it is not “incorperation “, it is “incorporation”. These are just two examples, more of them can be found throughout the paper text.
3) Pages 5 and 6 should be better arranged. In these two pages is placed a bunch of figures and tables (all of them are necessary and should remain in the paper) after which follows text which describes mentioned figures and tables. A text should be placed between figures/tables and the goal should be to place a text which describes figure or table as close as possible to that figure/table. At the moment, it is very difficult to read such arranged paper – because especially in this paper part any reader is required to constantly turn back for proper understanding of all presented elements.
4) Equations from 1 to 5 should be better explained. At the moment, only the general explanation of equation 5 is presented. It is not clear what other equations represent.
5) The Authors should involve at least some of the most important field experiment results in the paper, or a discussion related to the differences between laboratory results and field experiments should be added in the paper. By reading this paper I have been asking myself what differences can be expected between laboratory results and results obtained on the real machines during its exploitation. At least a discussion related to these differences will provide answers on that question – therefore at least such discussion should be added in the paper.
6) Line 309 – symbols in the paper text and in the equation 6 should be identical (they are not identical at the moment).
7) Equations 9, 10 and 11 – it is not defined is the temperature in degrees Celsius or Kelvin (it seems in Celsius, but it should be defined in the paper text).
8) For the pages 14, 15 and 16 is valid the same as explained in my previous comment related to paper arrangement (comment 3). Also, it is not proper that results related to one paper subsection are presented in another subsection (in the paper at the moment figures 17, 18 and 19 as well as Table 4) are presented in subsection 3.3, while the explanation of these results is presented in subsection 3.4 and they are related to subsection 3.4.
Therefore, much better paper arrangement is required.
9) Line 408 – “formual”? It should be written formula.
10) The Authors should better present, describe and discuss the scientific novelty of this paper and its contribution to the specific research field. In the literature can be found many similar laboratory experiments, so it is not fully clear (at least to me) what novel elements this research brings in comparison to the other literature.
11) In the paper should also be added a discussion related to the practical importance of the presented results. How and in which way the presented results can be used in practical applications? Which benefits can be obtained in the practice by using results from this study? Which factors related to machines can be improved by using results presented in this paper? A discussion related to this topic is required.
12) As the Abstract, the Conclusions section should also be improved with the most important obtained results (its exact values). Also the Conclusions seem to be too descriptive and general, without any details obtained in the presented analysis.
13) In the List of References the Authors can involve more recent literature in this research field because the most of the literature is older than 5 or 10 years. In the recent literature can be found many interesting researches in this research topic, so I believe that involving more recent literature in the paper should not be problematic.
Final remarks: This is an interesting paper, but it should be notably improved (according to my comments above) to be totally understandable and easily readable. Please, put a special attention on the proper paper arrangement and on connecting laboratory results with practical applications.
Reviewer 2 Report
This study performed a condition monitoring by applying an integrated oil sensor to hydraulic oil of construction equipment. It seems to be interesting and valuable according to the results. The comments are listed as follows.
Question.1:The introduction section only introduced the means or sensor technologies that had been used in recent years for hydraulic fluid contamination monitoring. What’s the connection between the above and your research? Please explain the innovation and purpose in the concluding part of the introduction.
Question.2: “…Moreover, according to the set reference values, the current state of the lubricant is displayed in one of three stages: normal, caution, and danger…”，How are the three states mentioned here divided? How were the reference values set determined? Can you provide the corresponding literature to support it?
Question.3: “…because the magnetic bar is used to stir lubricant to mix foreign materials, artificial ferrous particles are collected at the magnetic bar rather than dispersed in the lubricant…”。In actual working conditions, ferrous metal debris is found in large amounts in lubricating oil as the main product of engine wear. The experiment in this paper uses a magnetic bar to adsorb ferrous metal debris, which doesn't match the actual working conditions, does it cause measurement error? Is the stirring bar replaceable?
Question.4:“Figure 11 presents the absolute viscosity and dielectric constant with varying temperature when artificial dust is mixed in a new oil from 60 mg to 400 mg. Figure 12 shows absolute viscosity and dielectric constant with varying temperature when improper oil is mixed in a new oil from 0.4 ml(1,000 ppm) to 4.0 ml(10,000 ppm)… Moreover, the test was not carried out in a mechanical operating condition after mixing of dust or improper oil…”。There are contradictions in the content. Figure 11 shows the effect of mixing artificial dust and Figure 12 shows the effect of mixing improper oil, and subsequently refuted, resulting in an ambiguity in the content, is the expression not reasonable enough?
Question.5: Figure 19 shows the variation in dielectric constant with temperature for new oil, used oil and the moisture of 2000 ppm is mixed in the new oil, but used oil and water-added oil have the same dielectric constant and absolute viscosity, how can we distinguish between the two types of oil?
Question.6: Comparing the results of Fig. 12(b) and Fig. 14(b), it is found that the same dielectric constant for oil mixed with improper oil and oil mixed with moisture, how to distinguish this phenomenon? Have the authors done experiments and analyses?
Question.7: “…As oxidation processes, the AN also increases, and residues such as sludge are the cause of varnish contamination…When the lubricant is contaminated with varnish, the dielectric constant increase distinctly because the molecular weight and AN increases due to oxidation and deterioration…” and “…In Figures 11 and 12, it can be seen that the amount of artificial dust and improper oil used in the experiment does not significantly affect the variation in properties of the lubricant as a whole…and sufficient time was not given for the oxidation and deterioration of lubricant…”。All of the above mentions that oxidation changes the absolute viscosity as well as the dielectric constant of the lubricant, but there is no experimental quantification in the text to verify the effect of oxidation, can the authors add experimental proof?
Reviewer 3 Report
The paper presents laboratory and field research on construction machinery hydraulic oil properties by using the integrated oil sensor. The measures absolute viscosity, density, temperature and dielectric constant. It has been found that measurements of the absolute viscosity, density, and temperature give information about lubricant and machine conditions. On the other hand, the dielectric constant is very useful in detecting the moisture as well as varnish contamination that are caused by oil deterioration. The paper is very useful for engineers who deal with construction equipment operation and maintenance.
I recommend the paper to be accepted for publication in Lubricants after some brush-up as suggested below. Finally, the authors are to be congratulated for their very nice work.
(i) Correct typing and grammatical errors throughout the paper.
(ii) Nomenclature: Please prepare the unified Nomenclature (list of symbols and abbreviations at the end of the paper). Please put symbols in an alphabetical order.
(iii) Line 173: Is the sensor capable to operate during the machine operation with high dynamic changes of oil pressure in the system?
(iv) Line 188: For clarity please provide the sampling frequency for digital processing of measured quantities.
