Luhang High Performance 1.5m X 18m Heavy Duty Ship Launching/landing/Lifting/Moving/Salvage Airbag Suppliers
Ship launching airbag Ship launching airbag refers to the air bags that can be used for launching a vessel, this kind of air bags are made of synthetic-tyre-cord reinforcement layers and rubber layers, and are also known as marine airbags, they were invented in 1980.[ citation needed ] On...
Ship launching airbag
Ship launching airbag refers to the air bags that can be used for launching a vessel, this kind of air bags are made of synthetic-tyre-cord reinforcement layers and rubber layers, and are also known as marine airbags, they were invented in 1980. On January 20, 1981 the Xiao Qinghe shipyard launched a tank barge with marine airbags,and it is known as the first use of marine airbags.
From then on, more and more shipyard began to use air bags to launching small and medium-sized vessels, especially in China and Southeast Asia.
In recent years, higher strength material has been used in air bag production. The air bags have much more bearing capacity, big vessels launching also began to use air bags, in October 2011, one DWT 75000T vessel launching with air bags successfully, set a world record of ship launching utilizing air bags, the following year, "He Ming" ship, one vessel with DWT 73000T, total length 224.8m, breadth 34m, depth 18.5m, also launched utilizing air bags successfully on June 6, 2012.
Air bag Structure
Ship Launching Air bag size and model
Diameter of air bag (D) varies such as 0,8 m, 1,0 m, 1,2 m, 1,5 m, 1,8 m, etc.
Length of air bag (L) is to be specified by the user.
According to the synthetic-tyre-cord reinforcement layers number of air bags, air bags can be divided into 3 layers air bags,4 layers air bags,5 layers air bags,
6 layers air bags...normally air bags layers less than 10
Air bag bearing capacity
maximum load carrying capacity of the air bag while it suffers no permanent deformation or damage
D is the original diameter of the air bag
H is the height of the compressed air bag
W1 is the width air bag contacting with ship bottom
P1 is the internal pressure of the air bag
L is air bag effective length
Bearing capacity =P1 × W1 × L
Air bag materials
An air bag is to be constructed of synthetic-tyre-cord layers,sometimes outer rubber layer and inner rubber layer are added.All materials shall be vulcanized firmly.
Airbag launching refers to a method to launch vessels with marine air bags. It is a methodology for ship launching utilizing air bags.
The Xiao Qinghe shipyard launched a tank barge with marine airbags on January 20, 1981 and it is known as the first use of marine airbags.
This kind of ship launching method has the advantages of requiring less permanent infrastructure, risk, and cost. The airbags provide support to the hull of the ship,air bags rolling motion take a vessel launch into water, thus it is arguably safer than other options like sideways launching.
The arrangements of air bags
Based on the ship shapes, the ship may be launched, using air bags, by either end launching type or side launching type
End launching type
There are three ways to arrange air bags when using the end launching type. They are (1) linear arrangement (see Figure A.1), (2) staggered arrangement (see Figure A.2), and (3) two-lines arrangement (see Figure A.3). As for which arrangement to use, it will depend on the ship’s width and the length of the air bags.
When the ship’s width is not greater than the effective length of the air bags, the linear arrangement shall be selected
When the ship’s width is greater than the effective length of an air bag and less than the effective length of two air bags, the staggered arrangement can be selected.
When the ship’s width is greater than the combined effective length of two air bags, or for special ship such as catamaran HSC or split hopper barge, the two lines arrangement shall be selected. The distance between the near ends of two air bags is greater than 0,2 m.
Side launching type
For small flat-bottom ships, the side launching method may be utilized (see Figure A.4)
Air bags quantity
Air bags shall meet the requirements of ISO 14409>
According to the weight of the ship being launched, the quantity of the air bags needed for this operation must be calculated in accordance with Formula (1):
N is the quantity of air bags used for ship launching;
K1 is a coefficient, in general, K1 ≥ 1,2;
Q is the weight of the ship (ton);
g is acceleration of gravity (m/s2), g = 9,8;
Cb is the block coefficient of the ship being launched;
R is the allowable unit bearing capacity of the air bags (kN/m);
Ld is the contact length between the bottom of the ship and the body of the air bag at the midship section (m).
For ship shifting, 2 to 4 additional air bags shall be made ready and available.
The centre to centre distance between two neighbouring air bags should be less than or equal to that found in Formula (2) and equal to or be greater than that found in Formula (3).
L is the actual length of the ship bottom that can make contact with the air bags (m);
N is the quantity of air bags used for ship launching;
k is a coefficient, k = 1 for steel ships, k = 0,8 for wooden, aluminium and glass-fibre-reinforced ships;
D is the nominal diameter of air bags (m).
The gradient and the length of the slipway shall be determined according to the size of the ship and the hydrological condition of the area water.
The bearing capacity of the slipway shall be at least twice as strong as the working pressure of air bags.
For ships of more than 3 000 tons of length, more than 120m,the slipway shall be constructed with reinforced concrete and the height difference between the right and left sides shall be less than 20 mm. For ships of more than 1 000 tons but less than or equal to 3 000 tons in weight, or more than 90 m but less than or equal to 120 m in length, the slipway shall be constructed with cement concrete and the height difference between the right and left sides shall be less than 50 mm. For ships of not more than 1 000 tons in weight or not more than 90 m in length, the slipway may be an earthen slope and shall be compacted even by rollers. The height difference between the right and left sides shall be less than 80 mm.
The main slipway shall enable the ship to glide automatically when the ship is off the tow. The auxiliary slipway shall be determined according to the ship type, the water level at time of launching, the diameter of the air bags, and the safety requirements.
A windlass shall be used to control the movement of the ship. Tow system that comprises windlass, steel wire rope and pulley set shall be securely fastened to the ground anchor in front of the berth.
In general, a slow windlass shall be selected for ship launching. The veering speed of the windlass shall be 9 m/min to 13 m/min.
The forces of the windlass and the steel wire rope should be calculated carefully by technicians of ship yards or air bags company.
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