Chun-Te Lee, Liang-Bi Chen, Huan-Mei Chu, Yen-Yi Lee
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Ships have many uses in human social life and can be used for various purposes, such as the transportation of people and goods, military affairs, and scientific research. Generally, major ship accidents rarely occur because ships’ design and construction are completed in strict compliance with relevant regulations and international standards (Pan et al., 2020).
However, ships sailing on the sea will encounter various dangerous situations, such as rocks, collisions, capsizing, and so on, resulting in various hazards that may cause the ship to sink, causing irreparable casualties and property losses. For example, the Titanic hit an iceberg and sank during its first sailing, causing 1,514 deaths and substantial economic losses. As a result, there have been countless shipwrecks in history (Stumme et al., 2002).
Both human and natural factors are the main reasons for the sinking of a ship. Human factors include the driver’s carelessness, violation of the operating rules by the management personnel, technicians’ insufficient professional skills, and so on, which can lead to hull damage and make it sink into the water. Natural factors include severe weather (storms, typhoons, heavy fog, and so forth), underwater hazards (reefs and icebergs, among others), collisions with aquatic animals (whales, sharks, and other large creatures), and corrosion damage caused by marine life attached to the surface of the ship (Wang et al., 2019; Szlapczynski and Krata, 2018).
There are many approaches to rescue a sunken ship. Each method can be adopted alone or in combination as appropriate. These methodologies include the ship-lifting, sealed-pumping, pontoon, foam-plastic, cofferdam, and inflatable-drainage salvage methods, among others. The pontoon salvage method is the most commonly used one. For instance, in the 2014 South Korean MV Sewol rescue operation, a pontoon bridge was used for the MV Sewol’s bow-lifting project, which provided 1,630 tons of lifting buoyancy. According to the ship’s internal and external space and structure, additional buoyancy can be provided by installing airbags as well as rubber and rescue steel buoys on the ship.
Ilias and Michael (2018) investigated the strength of airbags in inflated and raised states. Their study provided a theoretical basis for airbags designed to rescue damaged ships. To improve the airbag’s launch speed and safety, reduce the difficulty of operation, and decrease the launch time, Lu et al. (2014) proposed a novel floating structure.
To improve the damaged ship’s antisink performance, Kang et al. (2018) designed a buoyancy support system that uses a fire extinguishing system as an inflatable structure. In that article, the complex structure of the hull was tested. The effect was good, but it was challenging to control water intake. Velayudhan (2019) designed an automatic control method for floating airbag sediments underwater. However, airbag intake and exhaust on the salvage process have not been studied in detail.
When a ship hits a reef or encounters a storm while moving, the hull will be in great danger. It is necessary to prepare a contingency plan and ensure that the safety device can operate around the clock and ensure the ship’s safety (Ji, 2017). Many studies have focused on hull structural safety, safety devices, detectors, and alarm equipment, so preventing ship sinking is the priority. For example, Mustafa et al. (2020) addressed the easy sinking of laver farmers’ boats by exploring the boats’ geometries and retained their buoyancy.
The concept of an antisink ship design is to expand the draft area. When the ship is in danger, the pressure per unit area can be reduced by expanding its draft area to avoid sinking (Ran et al., 2012). On the other hand, detectors and alarm equipment are also essential. Detectors can quickly detect danger or damage for the first time and notify the crew. The alarm system warns people onboard to move to a safe area and is equipped with the necessary safety equipment, such as life jackets. Therefore, to ensure that people are aware of the danger and take quick action, the detector should work 24 h a day in all weather conditions and be checked regularly (Lin et al., 1997).
To face such an issue, this article proposes a new ship antisink and buoyancy device design, which mainly installs multiple airbags around the hull’s outer wall. When a shipwreck occurs, and the ship is about to capsize or sink, manual or automatic methods can be used to inflate the airbags quickly. This produces uniform buoyancy around the hull and expands the draft area, preventing the ship from tilting and overturning and slowing the ship’s sinking speed, thereby extending the rescue time and improving the rescue rate of passengers. This design concept can help ship design companies create safer ships.
In June 2015, a Chinese passenger ship, Orient Star, overturned due to strong winds in the Yangtze River. The strong wind had an instantaneous maximum wind speed of 32–38 m/s, causing more than 400 deaths. In 2014, the Shiyue (MV Sewol) passenger ship suddenly changed direction during its voyage in Korean waters. Moreover, the direction change also led the cargo to shift, causing the hull to lose its center of gravity and capsize, causing hundreds of casualties.
As a result, when the hull is swayed by strong winds or cargo shifts, causing it to start to tilt, if a “hand of God” (an external force) straightens it slightly, the tragedy will not happen. This righting force does not need to be too great because it does not need to lift the hull out of the water but straighten its angle in the water. Once a shipwreck occurs, it is often because of insufficient rescue time, causing heavy casualties. If the hull can be kept in balance, the rescue time may be prolonged, and the number of casualties can be reduced.
In the past, the design of ship escape equipment was mostly limited to equipment for human rescue, such as life jackets, lifebuoys, and lifeboats. The hull itself had fewer safety devices. However, when a shipwreck occurs, the equipment, as mentioned earlier, may be in short supply or cannot be used effectively in a brief time.
We can recall the movie scene of a large number of people rushing into lifeboats on the Titanic. This design hopes to make the ship wear life jackets like people so that, when a disaster occurs, passengers can wait onboard for rescue.
This work is inlaid with multiple airbags around the ship, as shown in Fig. 1. When a disaster occurs, whether it is damage to the hull, a loss of balance in the cabin, or the shaking of the hull affected by crosswinds, the ship sinks or has a chance of capsizing. This work can inflate the airbag to increase the ship’s buoyancy and balance ability so that, after the ship enters the water or is about to be out of balance, there is a force to make it float smoothly on the sea and extend the rescue time.
Fig1 A schematic diagram of the hull airbag.
Furthermore, water level and pressure sensors are installed on the hull, as shown in Fig. 2; these can be located at necessary places inside or outside the hull. When the sensor detects that the water level has risen for more than a certain period, the pressure sensor measures the seawater pressure simultaneously. It immediately inflates the airbag, avoiding unnecessary malfunctions, for example, when washing the hull or touching the sensor by mistake in heavy rain.
Fig2 An installation diagram of the water level and pressure sensors and airbags.
The water level sensor and inflation unit are connected by a wired and wireless operating mechanism, as shown in Fig. 3. When the ship is about to overturn or sink, the crew can use the monitoring unit to activate the inflatable unit to fill the airbag through the wired or wireless operating mechanism. After the airbag is filled with gas by the inflating unit, uniform buoyancy can be generated around the hull, preventing the ship from tilting and overturning or slowing the ship’s sinking speed. Moreover, this inflation action can also be activated by the water level sensor to prevent the crew and captain from escaping the ship’s hull regardless of the passengers’ safety in the event of a shipwreck. (The Korean MV Sewol shipwreck event is an example.)
Fig3 A block diagram of the water level sensor and inflation unit, which are connected by wired and wireless operating mechanisms.
As shown in Fig. 4, the proposed inflatable unit has three activation mechanisms: wired control, wireless control, and automatic detection (water level sensor). This triple-activation mechanism design allows for one of the activation mechanisms to fail or be inoperable for some reason. In that situation, we can use another mechanism to start the inflation unit to ensure that it fills the airbag.
Fig4 Three activation mechanisms of the proposed inflation unit.
The airbag is installed near the top of the hull’s waterline, as shown in Fig. 2, and is usually hidden and invisible. It will explode like a car’s airbag when the hull is in danger (quick inflation), so the boat will not increase resistance when traveling. In addition, to ensure that the airbags will fill simultaneously, there must be no signal delay, missed connection, or poor reception. The inflatable units scattered throughout the hull are connected by wire to ensure that, after receiving the trigger signal, they will fill the airbags collectively, immediately, and without delay. Therefore, when the airbag explodes, it has two effects on the hull, which are described as follows:
The airbag can be activated only when the hull is in danger, and there are two activation timings:
Therefore, when a shipwreck occurs, and the ship is about to capsize or sink, the airbag can be quickly inflated to produce uniform buoyancy on the hull side and expand the draft area to prevent it from tilting and overturning. Figure 5 shows the timing and function of the proposed airbag.
Fig5 The timing and function of the proposed airbag.
To improve the performance of the antisink capabilities of damaged ships, Kang et al. (2018) designed a buoyancy support system, which uses a fire extinguishing system as an inflatable structure, and a large airbag is installed in an enclosed area inside the cabin. This airbag is inflated with the existing fire extinguishing system. It is an excellent idea. However, if a fire and cabin flooding occur sequentially or simultaneously, the fire extinguishing system may not be enough.
Compared to their work, our proposed system is prepared separately. The carbon dioxide cylinder does not use the existing fire extinguishing system to inflate. In addition, when the hull shakes or tilts due to external forces, even if the large airbag inside the cabin is activated, it cannot help the ship maintain stability and not shake. It can only assist with discharging the seawater and increasing buoyancy after the cabin enters the water. At this time, the seawater has flooded into the hull, and the equipment has been damaged.
A comparison between our proposed system and the related work (Kang et al., 2018) is provided in Table 1, where that the most significant advantage of the ship’s antisink and buoyancy device is that “it can increase the stability of the hull.” In contrast, the buoyancy support system does not. Nevertheless, if we want to install airbags for medium and large ships, we can also refer to buoyancy support systems. In addition to installing multiple airbags around the hull’s outer wall, large airbags are also placed in an enclosed area inside the cabin. Only in this way will the greater airbag buoyancy required by medium and large ships be sufficient.
Table 1. A comparison between our proposed system and the related work (Kang et al., 2018).
To understand the relationship between the weight of the hull and buoyancy required by the airbag, we did some experiments to verify it. First, we designed two types of airbags. In one case, there are several independent airbags on one side of an experimental model ship, as shown in Fig. 6. In the other, there is only one cylindrical airbag on one side, as shown in Fig. 7.
Fig6 An experimental model ship with several independent airbags on one side. (a) The airbag has not been inflated. (b) The airbag inflation (four independent airbags).
Fig7 An experimental ship with only one cylindrical airbag on one side. (a) The airbag has not been inflated. (b) The airbag inflation (one cylindrical airbag).
A photograph of the wireless transmitter that has implemented the circuit module (in Fig. 6) is shown in Fig. 8. The wireless transmitter is powered by a 1,500-mAh lithium battery and includes wireless transmitter, Arduino-based microcontroller, and power supply modules.
Fig8 The wireless transmitter that was implemented the circuit module (in Fig. 6).
There are three 6.5-mm holes drilled under the two experimental hulls to simulate the hole where the hull hits the reef. The CO2 cylinder of the experimental model ship (Fig. 6), which is its inflation method, is placed outside the hull. When the wire control switch is activated, the solenoid valve that controls the gas conduction will be energized (as shown in Fig. 9), and the gas can quickly inflate the airbag. After a while, the solenoid valve will close and stop inflating the airbag. By controlling the length of time that the solenoid valve is turned on, the airbag’s air intake volume can be controlled. For the experimental model ship in Fig. 7, the CO2 cylinder is inside the hull, and the inflation principle is the same.
Fig9 The solenoid valve that controls gas conduction.
Experiments show that the two types of airbags shown in Figs. 6 and 7 have good results and can easily make the experimental ship unsinkable. Therefore, both types of airbags can be used for the hull. The experimental model ship in Fig. 7 was chosen because the CO2 cylinder of the experimental ship in Fig. 6 is placed outside the hull. In the model in Fig. 7, it is inside the hull, which will not affect the experiment’s accuracy. Next, we need to know, through experiments, how much buoyancy of the airbag is needed to keep the ship unsinkable.
Table 2 shows the results. The experiment environment was carried out in a 3 × 2 × 0.8-m tank. Each experiment waited for the hull to be launched for 50 s, and the ship sank about one third of its height before the wireless control switch was pressed. The wireless control switch allowed the airbag to explode, and the time for the hull to sink completely (or stand still without sinking) was measured for different total airbag inflation amounts.
Table 2. The experimental results.
The total weight of the hull + control circuit module + CO2 cylinder + airbag is 6.95 kg. It can be seen from Table 2 that, as the total airbag inflation volume increases, the time for the hull to sink completely lengthens until the total airbag inflation volume is 800 CC (when the buoyancy provided is about 0.8 kg), at which point the hull no longer sinks. It can be seen from this that the buoyancy required by the airbag is approximately 11.51% (0.8/6.95 = 0.1151) of the hull weight so that the damaged hull no longer sinks. Figure 10 shows a relationship between the total airbag inflation and the time for the hull to sink completely.
Fig10 The relationship between the total airbag inflation and time for the hull to sink completely.
Based on these experimental results, the buoyancy required of the airbag does not need to be the same as the weight of the hull. Moreover, it only needs to be close to 1/10. When the hull is initially flooded, the amount of water inflow will not be much, and the weight is not too heavy. When the airbag is blasted and filled with gas, the hull can be raised slightly, which can delay the speed of seawater entering the hull, and, if the buoyancy is large enough, it can even prevent the hull from sinking.
Installing an airbag on the hull is like helping the ship put on a life jacket, and the buoyancy of the life jacket worn by a person is about 1/10 of the weight of the human body. The buoyancy of the life jacket does not need to be the same as the person’s weight. People do not sink. It can be seen that the results of this experiment are reasonable and correct. As an example, a 10-ton yacht needs about 1,000 kg of buoyancy airbags. If this is divided into 10 small airbags with 100-kg buoyancy, then five airbags can be installed on each side of the hull.
In this article, the proposed method is more suitable for small ships because the weight of medium and large ships is vast, and a considerable volume of airbags would be required. We can also install large airbags in the enclosed cabin inside the hull’s outer wall. In this way, the airbag on the hull’s outer wall can help the ship maintain stability and not shake as well as increase its buoyancy. A large airbag inside the cabin can also increase the buoyancy of medium and large ships. Furthermore, squeezing the seawater out of the hull can ensure that the hull will not sink.
Shipwrecks are frequent, and governments worldwide have begun to attach importance to ship-safety-related laws and regulations. The improvement of safety will effectively reduce the number of casualties and property losses. Shipwrecks have attracted the public’s attention, and people have begun to realize that ships’ safety is as important as their own. When boarding, they will choose ships with complete safety functions. With the increasingly sophisticated ship manufacturing technology, the cost of safety devices will gradually decrease.
In this article, a novel buoyancy device design was proposed for antisink ships. When a ship is about to overturn or sink, an airbag can be quickly inflated manually or automatically to generate uniform buoyancy around the hull and expand the draft area. This can prevent the ship from tilting and overturning and slow the ship’s sinking speed, thereby extending the rescue time and increasing the rescue rate of passengers. This work will become a new milestone in maritime navigation safety. Simultaneously, the research team sincerely hopes that soon, when all ships are equipped with this product or it has even become standard equipment for ships, people will no longer have to panic even if a shipwreck occurs.
• D. Pan, Y. Sun, Z-H. Zhou, K. Zhao, and Y. Chen, “Calculation on refloating a damaged ship with salvage pontoon,” IOP Conf. Ser.: Mater. Sci. Eng., vol. 772, no. 1, p. 012078, 2020, doi: 10.1088/1757-899X/772/1/012078.
• G. Stumme, R. Taouil, Y. Bastide, N. Pasquier, and L. Kakhal, “Computing iceberg concept lattices with TITANIC,” Data Knowl. Eng., vol. 42, no. 2, pp. 189–222, 2002, doi: 10.1016/S0169-023X(02)00057-5.
• Y. Wang, E. Zio, and X. Y. Wei, “A resilience perspective on water transport systems: The case of Eastern Star,” J. Int. J. Disaster Risk Reduction, vol. 33, pp. 343–354, Feb. 2019, doi: 10.1016/j.ijdrr.2018.10.019.
• R. Szlapczynski and P. Krata, “Determining and visualizing safe motion parameters of a ship navigating in severe weather conditions,” J. Ocean Eng., vol. 158, pp. 63–274, Jun. 2018, doi: 10.1016/j.oceaneng.2018.03.092.
• Z. Ilias and T. Michael, “On modeling and simulation of innovative ship rescue system,” J. Offshore Mech. Arctic Eng., vol. 140, no. 6, p. 061303, 2018.
• H. Lu, T. Y. Li, and Y. Zhao, “Structural design of cylindrical shell buoys in the buoyancy supported risers of FPSO,” J. Ocean Technol., vol. 33, no. 6, pp. 103–107, 2014.
• H. J. Kang, I. Kim, and J. Choi, “A concept study for the buoyancy support system based on the fixed fire-fighting system for damaged ships,” J. Ocean Eng., vol. 155, pp. 361–370, May 2018, doi: 10.1016/j.oceaneng.2018.02.040.
• A. K. D. Velayudhan, “Design of a supervisory fuzzy logic controller for monitoring the inflow and purging of gas through lift bags for a safe and viable salvaging operation,” J. Ocean Eng., vol. 171, pp. 193–201, Jan. 2019, doi: 10.1016/j.oceaneng.2018.10.049.
• Y. Ji, “Anti-sink ship safety realized by hull mechanical structure design: Mobile carry cargo buoyancy tanks,” Amer. J. Mech. Ind. Eng., vol. 2, no. 5, pp. 194–197, 2017, doi: 10.11648/j.ajmie.20170205.11.
• W. Mustafa, S. Asri, M. R. Firmansyah, F. Fachruddin, and G. Apelaby, “An improvement for the design of the small fiberglass seaweed farmers boat to minimize the sinkable risk,” in Proc. 2020 IOP Conf. Ser., Mater. Sci. Eng., vol. 875, p. 012077, doi: 10.1088/1757-899X/875/1/012077.
• X. Ran, C. Shi, J. Chen, S. Ying, and K. Guan, “Draft line detection based on image processing for ship draft survey,” in Proc. 2nd Int. Congr. Comput. Appl. Comput. Sci., 2012, 39–44, doi: 10.1007/978-3-642-28308-6_6.
• I.-I. Lin, L. K. Kwoh, Y. C. Lin, and V. Khoo, “Ship and ship wake detection in the ERS SAR imagery using computer-based algorithm,” in Proc. Int. Symp. Geosci Remote Sens., 1997, vol. 1, pp. 151–153, doi: 10.1109/IGARSS.1997.615824.
• “Ocean researcher V,” Wikipedia, 2014. https://en.wikipedia.org/wiki/Ocean_Researcher_V (accessed Aug. 18, 2020).
Chun-Te Lee (charter@gcloud.csu.edu.tw) earned his master’s degree in electronics engineering from the National Taiwan University of Science and Technology, Taipei, Taiwan. He is an associate professor with Cheng Shiu University, 833 Niaosong, Taiwan. His research interests include innovative product research and development, as well as energy savings.
Liang-Bi Chen (liangbi.chen@gmail.com) earned his Ph.D. degree in electronic engineering from the Southern Taiwan University of Science and Technology, Tainan, Taiwan. He is an assistant professor in the Department of Computer Science and Information Engineering, National Penghu University of Science and Technology, 880 Penghu, Taiwan. He serves as an associate editor for IEEE Access. He is a senior member of IEEE.
Huan-Mei Chu (emmi@gcloud.csu.edu.tw) earned her master’s degree in information education from the University of Mercer, Macan, Georgia, USA. She is an associate professor with Cheng Shiu University, 833 Niaosong, Taiwan. Her research interests include innovative product research and development, as well as energy savings.
Yen-Yi Lee (leeyenyi@gcloud.csu.edu.tw) earned his master’s degree in applied geoscience from the University of Pennsylvania, Philadelphia, Pennsylvania, USA, and his Ph.D. degree from the Department of Environmental Engineering, National Cheng Kung University, Tainan, Taiwan. He is an associate professor in the Department of Food and Beverage Management, Cheng Shiu University, 833 Niaosong, Taiwan.
Digital Object Identifier 10.1109/MPOT.2021.3114642