Reliability-Based Preventive Maintenance Strategy for Subsea Control System

Round 1

Reviewer 1 Report (New Reviewer)

The presented scientific paper is interesting, but in order to publish it, it is necessary to revise the manuscript. The main comment is that the work should be shortened and the text should better connect the material into one compact whole.

- It is unclear why one part of the text is marked in yellow. It is not a practice for papers reviewed in the first round to mark in color.

- It is not clear from the abstract what the goal of the research is.

- The introductory chapter should be shortened and presented better. The key word in the research "preventive maintenance" is mentioned only once. 

- It is necessary to mention the essence of the research in the Introductory Chapter: "Implementation of modern maintenance concepts, using appropriate technical diagnostic methods, aims to optimize the operation of industrial systems in a short period of time and with as little downtime as possible." Consult the following researchs: https://doi.org/10.18485/aeletters.2021.6.2.3 and https://doi.org/10.1007/978-3-031-21429-5_12 

- Chapter 2 - Model assumptions and notation description should be part of the subsection in Chapter 3 – Methodology.

- From the aspect of the methodology of scientific work, the scientific methods on which the research was based should be stated in Chapter 3. On the basis of applied scientific methods, everyone can make a conclusion about the very difficulty of the research and its expediency.

- The equations in the paper should be cited in part.

- The research results are clear and well-presented.

- The literature used in the work is very good.

Author Response

Please see the attached document for a detailed response.

Author Response File: Author Response.docx

Reviewer 2 Report (New Reviewer)

This paper integrated several different factors in order to propose PM strategies, including an improved reliability model, redundant components, "imperfect maintenance", and life-cycle maintenance cost. The methodology is well constructed and presented. However, Section 4 of the case study does not provide enough evidence for how the proposed method improve the PM strategy compare to the other methods cited in the introduction (Section 1).

Assumptions for the presented method is listed in Section 2, a related discussion should be included in how these assumptions hold in the case study and do they influence the quality of the modelling and result.

There are some minor issues should be addressed:

1. Calculations in Section 4 is not consistently presented, sometimes it refers to Eq as in (line 440 to 441), sometimes it repeats the equation such as in (between line 433 to 434) that refers to Eq(5).

2. Table 1 second line has a minor mistake in notation of the diffusion parameter.

3. Language is not consistent when introducing equations in Section 3. This should be improved.

Author Response

Please see the attached document for a detailed response.

Author Response File: Author Response.docx

Reviewer 3 Report (New Reviewer)

First of all, I would like to thank the Editor for considering me as a reviewer for the manuscript. The article has potential but I would argue that changes should be made in order to increase the quality of the manuscript.

Dear authors, thank you for contributing to the topic of reliability-centred maintenance of subsea systems. Namely, although the paper has its merits, and provides a significant amount of data processing and reliability testing steps, I would suggest some parts for the improvement of the manuscript that I hope the authors will consider as suggestions for increasing the quality of the manuscript. My suggestions are in the following.

1. Introduction
"...These systems essential to the overall subsea production infrastructure, regulate a range of components including pipelines and Christmas trees"...what??? What kind of manuscript are you writing? Christmas trees? What does the Christmas tree have to do with the subsea production??? Considering leaving these "Christmas trees" out of the manuscript.

After seeing that you are conducting the reliability of mixed control system consisting of mechanical, electrical and hydraulic control, i.e., power units, please consider extending the reference list by including more research on these types of reliability research (e.g., 10.2507/27th.daaam.proceedings.084).  

In the last paragraph please provide a brief description of the structure of the sections and subsections in the rest of the manuscript. For instance, "The rest of the manuscript is structured as follows..."

2. Model assumptions and notation description
I would advise the authors to remove this section as sole section in the manuscript, and add this as a subsection in the Methodology section.

3. Methodology
The first three paragraphs should be placed in the introduction because they describe problems (or common problems) that happen in the contextual settings of the research. The whole introductory section methodology should be placed within the introductory part and described as a subsection in the introduction, because it provides a background and research problem, and does not describe the methodology conducted within the manuscript.

Although extensive information is provided regarding the development of the reliability model using copulas, I do not have experience working with Clayton and Gumbel copulas, although I have worked with Gaussian Copula Graphical Models, I do not feel competent in providing valuable suggestions for improvement regarding these types of models. I would advise the editor to find additional reviewers, if needed for assessing this part of the modelling part manuscript. But, in the reviewer's general copula equation model (without regarding latent objects and functions within Gumbel and Clayton), I believe that equations are correctly presented, in a general form.

4. SCM case study
I would argue that failure data SCM (table 2) can be narratively described, especially since MTBF/h is the inverse failure rate and does not need to be provided as tables, but of course, it does not hurt to see it this way either. However, how did you process the signal in dB? Have I missed that information about signal processing through what instrument or module?

5. Conclusions
Please add the limitations and implications of the study in a separate paragraph.

Also, considering that your research considers different energy transfer (control) modules from electrical, hydraulic, mechanical, etc, it would be good to emphasise how your research contributes to the growing body of knowledge on "sustainable maintenance" and "energy-based maintenance" research. Find related research published in 2023 and 2024. I believe this will attract the attention of readers and increase the citation rate of this article since most of today's maintenance state-of-the-art research relies on sustainable and energy-based maintenance research.

Finally, it would be good to provide what are the future research directions.

Again, I would like to thank the editor(s) for considering me as a valuable reviewer for the manuscript. If changes are made accordingly, I would advise that the article can be accepted for publication in the journal.

Kind regards,
the reviewer.

Small or minor spelling and grammar mistakes.

Author Response

Please see the attached document for a detailed response.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report (New Reviewer)

The authors have gone to great lengths to improve the quality of the manuscript. I congratulate them on that. I believe that the manuscript can be published in a journal.

References 28 and 29 in the paper were incorrectly stated. It should read:

28. Desnica, E.; Ašonja, A.; Radovanović, L.; Palinkaš, I.; Kiss, I. Selection, dimensioning and maintenance of roller bearings. Lecture Notes in Networks and Systems 2022, 592, 133-142.
29. Novaković, B.; Desnica, E.; Radovanović, L.J.; Ivetić, R.; Đorđević, L.; Labović Vukić, D. Optimization of industrial fan system using methods laser alignment. Applied Engineering Letters 2021, 6, 62-68.

Author Response

Please check the attachment

Author Response File: Author Response.docx

Reviewer 2 Report (New Reviewer)

The revision is satisfactory.

Reviewer 3 Report (New Reviewer)

Dear authors,

thank you for considering suggestions and recommendations for improvement. I would like to praise the quality of your work and hopefully continue with your successful research. Finally, I have some smaller suggestions that I hope you will resolve before publishing the paper.

The references are missing DOI numbers. I do not know if doi numbers are hidden in the pdf readout for reviewers, and whether they will be provided and published during proofreading (I have also emphasised this to the editor to see whether the mistake is on their side). Lastly, please consider adding appropriate references for contemporary research on energy-based maintenance (e.g., https://www.sciencedirect.com/science/article/pii/S0959652623013355).

After changes, I would suggest that the editor publish the paper.

Kind regards,
the reviewer.

I have only detected small spelling errors, no major suggestions.

Author Response

Please check the attachment

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

Strong point:

·       - The research methodology is clear, it presents adapted preventive maintenance models and simulations for a technical system, using Subsea Electronic Module.

Weak points:

·      - It does not result if the input data and the analyzed technical system are real;

I    - Is possible that the importance of the OREDA database (Offshore & Onshore Reliability Data) may not be clear to all the readers (citation needed).

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

Reliability-Based Preventive Maintenance Strategies for Subsea Control System

The paper proposes a reliability modeling method for a subsea control system, taking into account the redundancy configuration of this equipment and the impact of random shocks in its operation, and proposes an optimized PM model for its life cycle. Here is a list of my concerns about the method and the case study:

·       It was not clear to me what the innovation of the work was. There are already reliability modeling methods in the literature that take redundancy and imperfect maintenance into account. What differentiates the proposed method from others? What is the gain obtained by using the proposed method instead of others?

·       In chapter 2, the authors say that one of the model's premises is that "the Wiener process effectively represents the natural degradation of equipment" because "it yields a reliability curve that aligns more closely with actual curves". Is there any publication or data that supports such a premise? How and why did the authors assume this premise to be true?

·       The authors need to better describe the system under study (the subsea control system). What components make it up? Where is it located during operation? Is there a photo of the system that can be used to better illustrate its operation?

·       Furthermore, the authors need to describe what type of degradation the subsea control system presents. Does degradation happen due to corrosion, fatigue, or what other mechanism? Is this degradation monitorable? Which parameter/variable can be used to quantify this degradation? The graphs in figures 1, 2 and 3 show a "degradation" on the y axis, but without a unit of measurement. How can this degradation be measured? In figure 5, you can see that the threshold L is 100, but what does this number mean? This clarification is essential to verify the applicability of the method.

·       In chapter 4, the authors say that "Supposing that the performance degradation amount Zk of the SEM module, following a single instance of imperfect maintenance, adheres to a normal distribution with a mean of 0.4 and a standard deviation of 0.06." Where did these values come from? It seems to me that this distribution, which represents performance degradation after a maintenance activity, was randomly defined.

·       Although the authors call chapter 4 a case study, it does not seem to me that what is presented is, in fact, a case study but rather an example of application. It seems to me that, with the exception of the values obtained in OREDA (which needs to be appropriately cited in the work), all other values necessary to obtain the results are assumed/defined by the authors. The chapter does not, therefore, present the results obtained when analyzing a specific real system, but rather a theoretical one, not constituting a case study. The impression I have is that this was done because it is very difficult, if not impossible, to obtain some of the information necessary to use the method. For example, how could the performance degradation amount Zk of a real SEM module be obtained? It seems to me that this is fundamental to the method, but in practice it is something that cannot be defined/calculated for a real system. This fact immensely impacts the applicability of the method. I would like the authors to discuss the applicability of the method.

Minor editing of English language required

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

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Comments for author File: Comments.pdf

No comments

Author Response

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Round 2

Reviewer 2 Report

I appreciate the authors' effort in reviewing the work, but they did not clarify what the method's innovations are. They did not show what the method can do that others cannot and what the advantages of this are.

Furthermore, the authors say that "In order to solve the problem of lack of condition detection data, the life distribution of equipment is related to the degradation model, and the degradation model parameters are derived according to the available mean time between failures". Using reliability data to derive the degradation model is conceptually a mistake. Furthermore, there are several methods that are capable of optimizing preventive maintenance plans using reliability data, without the need for a model of the degradation process. A model of the degradation process can be very useful in optimizing PM plans, but this will only be effective if degradation monitoring data is available.

I therefore consider that the work cannot be published

Minor editing of English language required