• Journal of Advanced Marine Engineering and Technology
• /
• v.40 no.7
• /
• pp.663-670
• /
• 2016

This paper introduces the concept of the computer-aided engineering(CAE) design method for a bypass valve in a system that is used for the safe lifting of mineral resources in deep-seabed mining. Although the bypass valve has a simple mechanism, its design is very difficult because of various influencing factors. This equipment, which has a complex design process, should be developed by CAE-based design method. The method can perform the design, design verification, and virtual experiment at the same time. In this study, the CAE-based method for the design of the bypass valve has been developed using fluid dynamics, multi-body dynamics, and optimization method.

• Journal of Advanced Marine Engineering and Technology
• /
• v.40 no.7
• /
• pp.655-662
• /
• 2016

This study proposes that a diving supervisor, who can perform the role of both a field manager and a supervisor, be introduced in the national qualification system. The goal was achieved by surveying the general status of the commercial diving sector, including the statistics of an underwater construction company, commercial diving equipment operation condition, diver working hours, diver supply and demand status, and underwater construction market size. The national qualification and national competency standard (NCS) systems were also analyzed to deduce the role definition and work scope of the diving supervisor. Consequently, the following proposition is made: the diving supervisor should be an "on-site manager with the highest job skill in the commercial diving field, who can perform the on-site process management as well as guide, supervise, and educate project participants and serve as an intermediary between the contractor and the workers." The responsibilities of the diving supervisor are proposed to include "diving planning and operation of the diving team," "diving with surface-supplied air and mixed-gas diving system," "chamber operation," "underwater construction," and "ship salvage." The persistent issues in commercial diving sectors, such as diver career development, management, and worker supervision, are expected to be largely resolved with the introduction of this qualification.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.3 no.1
• /
• pp.51-71
• /
• 1997

As passenger ship accidents so frequently have occurred, crisis consciousness is highly aroused in Korean society. Although bombastic policy guidlines were suggested in accordance with every passenger ship accident, there remains a still high possibility of such an accident reoccurring because passenger ship accidents occur from the perspective of non-compliance. The research objective of this study is to government's safety regulatory policies. Data for the analysis was collected from literature review. A Case study related to passenger ship accident is adopted for the analysis. The research methods utilized in this study consist of extensive quantitative analysis of 138 passenger ship accidents which had happened over last 10 years from 1984 to 1993 in Korea and a qualitative analysis of the passenger ship accident of the Seohae Ferry in October 1993. The results of the quantitive analysis on the 138 passenger ship accidents are as follows; Seeing the accidents yearly, the accidents which occurred by policy non-compliance are still exist, only somewhat reduced as years gone by. Seeing the accidents from the perspective of types of accident, fire accidents and death and injury accidents had more non-compliance factors than contact accidents and one-side collision accidents, etc. had. Seeing the accidents from the perspectives of types of passenger ship, large ships like car ferries and general passenger ship accidents had more non-compliance factors than any other kinds of ships had. Seeing the accidents from the perspectives of tons of passenger ships, large ships weighing more than 1, 000 tons and small ships weighing less than 50tons contained a lots of non-compliance factors. The results of the qualitative analysis of the passenger ship accident of the Seohae Ferry in Octovber 1993 are as follows; From the viewpoint of the human factor, there were non-compliance to the recruiting of required number of qualified crew members and non-compliance to the rule which prohibited them from leaving port in bad weather and high wave conditions. From the viewpoint of the ship factor, there were defects in the ship. So we might say that there was non-compliance which was aroused from the lacks of technical skills. From the viewpoint of the administrative factor, there were many non-compliance factors such as sailor education, shipping management, rescue, safety equipment. From the viewpoint of the passenger factor, there were passengers' threats which compelled the crews to leave the port under bad weather conditions. In conclusion, the principal non-compliances factors are passenger ship company did not follow safety rules such as shipping the permitted number of passengers, loading permitted tons of freight and fastening freights properly and recruiting required number of qualified crew. In order to reduce accidents, firstly we should find out the causes which play key roles in passenger ship companies' non-compliance to the government's safety regulations. Secondly we should tackle the causes.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.24 no.2
• /
• pp.146-156
• /
• 2018

The ship's chart system was changed from the use of paper chart to the ENC (Electronic Navigational Chart) using ECDIS (Electronic Chart Display and Information System). The introduction of ENC in ships is necessary for ship automation and for the digitalizing of data and integration of information, but unexpected various problems have occurred and are posing a great threat to safe navigation in the transitional period when the new system has been applied to the sea. In this paper, to assess whether ECDIS contributes to the safety of navigation for its intended purposes as new navigation equipment, a usability test of ECDIS was conducted on masters and crew who have used ECDIS on ocean-going vessels. The result was verified with a paired sample T-test, and it was significantly analyzed with the effectiveness of a simplified task; cost efficiency was decreased since ECDIS was used. By analyzing 'MSC.1/Circ.1503 ECDIS - Guidance for good practice', we found that the effects of the maintenance of ECDIS software, operating anomalies identified within ECDIS, differences between raster chart display system (RCDS) and ECDIS, and matters of identification were compounded by the overlapping information on the safety of ships. The anomalies were also grouped according to their characteristics, and we proposed suitable improvements accordingly. The reason for the reduction in efficiency in the usability test was that the problems with ECDIS were intended to be solved only with the careful use of navigational officers who did not have systematic solutions. To solve these problems, the maintenance of software, the improvement of ECDIS anomalies, the reliable ENC issuance including the global oceans, and S-mode development are a priority.

• Journal of Advanced Marine Engineering and Technology
• /
• v.13 no.2
• /
• pp.43-63
• /
• 1989

Various kinds of corrosion prevention methods have been developed. It is known that the method of electrochemical protection is more effective and economical than any other method on the large scale metal structures in corrosive solutions. Strong acid solutions such as nitric and sulfuric acid solutions are often used in industries, and the expensive stainless steel is almost exclusively used for the equipment that comes in contact with such acid solutions. However, it is more reasonable that carbon steel is used rather than stainless steel depending upon concentration of those acid solutions from the economical viewpoint. In this study, the typical strong acid solution such as nitric and sulfuric acid solutions are chosen for the experiment and the selected materials of specimen are the stainless steels of SUS 304L and SUS 316L, the carbon steels of SS 41, SM 50 and RA 32, and highly pure lead. Electrochemical protection diagrams can be drawn with data from the external cathodic and anodic polarization curves of SUS 304L, SUS 316L and SM 50 steels in 5-60% nitric acid solutions and from those polarization curves of SS 41, RA 32, SM 50 and SUS 316L steels, and highly pure lead in 2.5-98% sulfuric acid solutions at the slow scanning rate. The data obtained with using the determination method of the optimum cathodic protection potential, the Tafel extrapolation method and the characteristics of anodic polarization curves. The main results obtained from the diagrams are as follows: 1) In nitric acid solution : (1) Corrosion potentials exist in each of those corrosion zones on the stainless steels in the lower concentration than about 12% solutions and on the high tensile strength steels in the lower concentration than about 30% solutions, but the corrosion current (density) in each zone is small on the above mentioned former steels and large on the latter ones. (2) The stainless steels can be self-passivated in the higher concentration than 15% solutions, and the high tensile strength steels gives rise to the same phenomenon in the higher concentration than 35% solutions. (3) The stainless steels in the lower concentration than 60% solutions and the high tensile strength steels in the higher concentration than 35% solutions can be used without protection, but the latter steels must ve protected anodically in the lower conccentration than about 30% solutions. 2) In sufuric acid solution : (1) The carbon steels can be self-passivated in the higher concentration than 45% solutions, and the SUS 316L steel in higher concentration than 75% solutions and the lead in all concentration solutions also gives rise to the same phenomenon. (2) The lead in the lower concentration than 80% solutions and the SUS 316L steel in the higher concentration than 80% solutions can be used without protection. (3) The carbon steels in the higher concentration than 50% solutions also can be used without protecting economically, but the SUS 316L steel in the 20-70% solutions are considerably corrosive without protecting anodically.

• Journal of Advanced Marine Engineering and Technology
• /
• v.40 no.9
• /
• pp.749-755
• /
• 2016

A new method for measuring the 3-axis cutting forces of a pick cutter by substituting costly 3-D load cells is proposed in this paper. The proposed cutting force measurement method is capable of estimating the 3-axis cutting forces through mechanical constraints using four single-axis compressive load cells and shoulder bolts. The feasibility of the proposed method was verified by finite element analysis, and the accuracy of the force measurement of the developed force measurement device was investigated by conducting linear rock cutting tests. The tests showed that the new cutting force measurement method is able to measure 3-axis cutting forces with a relative error of approximately 6%. These results imply that the new method could be a suitable alternative to conventional 3-D load cells. In addition, it will allow a significant reduction of approximately 20-30% in the costs required for measuring the cutting force when compared to conventional 3-D load cells.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.27 no.6
• /
• pp.822-831
• /
• 2021

Although programs have been developed to evaluate the risk of dragging anchors, it is practically difficult for VTS(vessel traffic service) operators to calculate and evaluate these risks by obtaining input factors from anchored ships. Therefore, in this study, the gross tonnage (GT) that could be easily obtained from the ship by the VTS operators was set as an independent variable, and linear and nonlinear regression analyses were performed using the input factors as the dependent variables. From comparing the fit of the polynomial model (linear) and power series model (nonlinear), the power series model was evaluated to be more suitable for all input factors in the case of container ships and bulk carriers. However, in the case of tanker ships, the power supply model was suitable for the LBP(length between perpendiculars), width, and draft, and the polynomial model was evaluated to be more suitable for the front wind pressure area, weight of the anchor, equipment number, and height of the hawse pipe from the bottom of the ship. In addition, all other dependent variables, except for the front wind pressure area factor of the tanker ship, showed high degrees of fit with a coefficient of determination (R-squared value) of 0.7 or more. Therefore, among the input factors of the dragging anchor risk assessment program, all factors except the external force, seabed quality, water depth, and amount of anchor chain let out are automatically applied by the regression analysis model formula when only the GT of the ship is provided.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.23 no.7
• /
• pp.820-828
• /
• 2017

Tools and equipment that can provide buoyancy for a drowning person are important for saving lives. The purpose of this study was to estimate the minimum amount of gas needed and the buoyancy value in newton units required to generate the minimum buoyancy determined to be sufficient for keeping the head of a drowning person above the water's surface to allow for respiration for at least 1 minute. A buoyancy experiment was carried out with a long rubber balloon injected with carbon dioxide gas, and a buoyancy measurement experiment was performed on six college students. The degree of buoyancy was measured using a 5-point scale, and the statistical value of the measured data was analyzed to estimate minimum buoyancy. As a result, 8 grams of carbon dioxide were determined to satisfy minimum buoyancy conditions with a confidence level of 72%, and buoyancy was calculated to be 44.66 newtons. 12 grams of carbon dioxide met the minimum buoyancy conditions with a confidence level of 100%, and buoyancy was calculated to be 66.99 newtons. This study is expected to contribute to the development of low cost, easy-to-carry minimum buoyancy aids.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.57 no.2
• /
• pp.162-172
• /
• 2021

This study was conducted to determine whether the layout of wheelhouse and work environment of coastal improved stow net fishing boats affect the physical abnormalities of wheelhouse workers through a survey and to use it as basic data to improve the wheelhouse work environment. The analysis results are as follows. The result of factor analysis on the wheelhouse work environment was classified into three factors: suitability of work environment, suitability of work space arrangement, and layout of navigational and fishing equipment. The result of factor analysis on physical abnormalities was divided into two factors: physical pain and fatigue. The results of regression model analysis showing factors affecting physical pain showed that the t-value in the regression model was 3.625 (p < 0.05), indicating that the work environment suitability had an effect on the physical pain. Work environment suitability had a significantly positive effect on the physical pain. As work environment suitability increased by 1, the physical pain increased by 0.371 (p < 0.05). The results of regression model analysis showing the influencing factors on fatigue were found to have a t-value of 3.009 (p < 0.05) in the regression model, indicating that the work environment suitability had a significantly positive effect on the feeling of fatigue. It was found that fatigue increased by 0.324 (p < 0.05) as the work environment suitability increased by 1. In addition, the manageability of task suitability was found to be t = -2.521 (p > 0.05). As the manageability of task suitability increased, the skipper's fatigue level decreased. From these results, it is inferred that the wheelhouse of the current coastal improved stow net fishing boats causes physical pain and fatigue for the skippers. In order to reduce such physical pain and fatigue, and to improve safe fishing operation and job satisfaction, it is necessary to provide a wheelhouse to fishermen on coastal improved stow net fishing boats in consideration of the characteristics of the wheelhouse work of fishing boats and in consideration of users.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.27 no.4
• /
• pp.529-537
• /
• 2021

Membrane-type hull and cargo holds have been designed and built for large ship. However, there is a growing interest in applying the same technology to small and medium-sized Liquefied natural gas(LNG) carriers to meet the recent increase in demand for LNG as an ecofriendly fuel and for expanding LNG bunkering infrastructure. The purpose of this study is to apply the IMO Type-B tank to small and medium-sized LNG carriers and verify the safety and suitability of the design. Fatigue crack propagation analysis was performed to install a partial second drip tray installed at the lower part of the LNG cargo tank by calculating the amount of leaked gas in the support structure supporting the cargo tank. First, a program for fatigue crack propagation analysis was developed, in which Paris' law and British Standard 7910 (BS 79110) were applied based on the International Code for the Construction of Equipment and Ships Carrying Liquefied Gases in Bulk, an international standard for LNG carriers. In addition, a surface crack propagation analysis was performed. Next, a methodology for assuming the initial through-crack size was developed to determine the size of the partial second barrier. The analysis was performed for 15 days, which is a possible return time after cracks are detected. Finally, the safety and suitability of the IMO Type-B for LNG cargo tanks required by international regulations were verified. For the accurate analysis of fatigue crack propagation, it is necessary to develop and verify the analysis procedure based on direct analysis and international regulations.