When the ship is sailing in strong wind and waves, the violent pitch and heave will produce wave bottoming phenomenon, which will damage the hull structure; the rolling will reduce the stability of the ship and make the people on board unable to work normally. Strong wind and waves will make the ship difficult to maneuver, and the directional retention and turning performance will be deteriorated.
In order to reduce the violent shaking in strong wind and waves, some ships add retractable anti-roll fins to assist navigation, but the installation of anti-roll fins is not only expensive, but also causes irreversible changes to the hull structure and affects the navigation performance of the ship. The airbag device is easy to carry and low in cost, and can not only play the role of fin stabilization, but also provide buoyancy for the ship, thereby increasing the stability of the ship and assisting the navigation of the ship.
When a ship sails in shallow water, the shallow water effect will occur, the resistance will increase, the hull will sink, the wave-making will be intensified, and small ships may even overturn and capsize. When some deep-draft ships have limited draught and cannot ride the tide under full load, the airbag device can be used to float the ship and pass through the channel with insufficient water depth.
In the Jiangsu section of the lower reaches of the Yangtze River, there are many sand boats and barges with very low freeboards. The airbag device can provide reserve buoyancy for the barge, and can be released into the water when the navigation environment is relatively harsh, which can increase the buoyancy and stability of the ship and reduce the risk of accidents.
Application of airbag device in maritime rescue
The ship is grounded or damaged
A grounding of a ship means that a ship is laid on an obstacle and cannot navigate, and it is a state other than the ship's navigation, anchoring, and port call. The obstacle includes underwater objects such as reefs, shoals, and sunken ships that hinder the navigation of the ship.
After the ship is grounded, it is unable to get off the ground by itself, and airbags can be placed around it to provide buoyancy to the airbags, reduce the draft of the ship, and make it free from the laying position with the assistance of the airbag device; when the ship is stranded on the shoal or reef, the marine airbag device It can provide buoyancy and support for the ship, prevent the ship from tilting and cause secondary damage to the hull, and assist the ship to leave the shallow.
At the same time, at sea or in port waters, if two ships collide or the ship is damaged and flooded due to other reasons, and the stability and upright buoyancy cannot be maintained, the airbag device can effectively make up for the buoyancy lost by the ship's damage, so that the ship can be more assisted by external forces. In rare cases, rescue yourself from the accident water area as quickly as possible to avoid causing traffic congestion in the water area.
In addition to steel buoys, there are also soft buoys. The soft buoys can be rolled into a cylindrical shape for storage and transportation or diving. The self-weight is small and the transportation is convenient. However, the buoyancy of the soft buoys is small and cannot meet the requirements of large-scale sunken ship salvage. . my country's theoretical technology in the manufacture and application of large airbags has become increasingly mature, and airbag devices can be used instead of soft buoys to play their role in shipwreck salvage.
In the process of salvaging the sunken ship, the airbag can be attached to both sides of the sunken ship, covered with brown rope or nylon rope mesh, connected with a steel cable ring under the cover, and then connected to the bottom of the ship, and then inflated to float; It is placed in the internal cabin, and the airbag is inflated as needed to correct the floating state of the ship, righting the sunken ship, and then salvage the sunken ship through steel buoys or other methods.
Large-scale wreck salvage has higher requirements on buoyancy and stability control, and it is particularly important to control the floating speed and attitude of the wreck. Some airbag devices are equipped with pressure telemetry instruments at the end iron parts, which can detect the internal pressure and external water pressure of the airbag, which provides an idea for ensuring the safe floating of the sunken ship.
The application of airbag devices in the maritime field also faces many problems. One of them is that the installation of airbag device will affect the navigation performance and maneuverability of the ship. The resistance generated by the airbag device will lead to aggravation of wave making and affect the normal navigation of the ship. It is necessary to think about the shape and installation method of the airbag; After the device is launched, the width of the ship increases, which will hinder the normal navigation of other ships, and will bring new challenges to the encounter and overtaking between ships; in addition, in the process of salvaging the sunken ship, how to control the inflation and deflation speed of the airbag device to keep the sunken ship. It is also a problem that needs to be studied and discussed in depth about the floating attitude and making it safe to ascend.
