ISO 14409 certificated by BV
Maximum diameter 3.5 m, flat length 30 m
Lifespan 5-8 years
Ship Launching Airbags have been widely used to launch ships from land to water, such as for barge launching, cargo ship launching, tug boat launching.,etc. They consist of outer rubber layers, synthetic-cord-reinforced rubber layers, are kind of sausage-shaped pneumatic balloons. Ship launching airbag is invented by Chinese and can only be made in China up to now. The two ISO standards about ship launching airbags : ISO 14409:2011 Ships and marine technology — Ship launching air bags and ISO 17682 :2013 Ships and marine technology — Methodology for ship launching utilizing air bags are both drafted by Chinese airbag manufacturers.
The outer rubber layer that covers the outside of ship launching airbags protects the cord layers from abrasion and other external forces. This compound has sufficient tensile and tear strength to withstand any weather condition and hard usage.
The history of marine air bag dates back to 1990s. A Chinese ship repair and building shipyard launched a 60 DWT tank barge with marine airbags on January 20, 1981 and it is known as the first use of marine airbags. The invention of marine airbags was expected to develop a flexible, less limited ship launching method.
The first generation marine airbags employ rubber dipped canvases as reinforcement material and two cone-shaped ends are stuck to the chamber trunk. The canvases used for ship launching airbags are made of cotton or Polyester, whose breaking force and fatigue resistance performance limit airbags’ safety and performance. Thus only small vessels , hundreds tonnes ship can be launched with marine airbags.
Lots of reinforcement material have been tested in airbag production, at last polyhexamethylene adipamide (PA 66) became the main framework material of rubber airbags nowadays.The new material has fairly great improvement in performance of high temperature resistance, fatigue resistance and permanent deformation resistance.
Anyway in China still there are some ship launching factories, usually in small size, are using Polycaprolactam (PA 6) or Polyester in airbag production. By this the cost can reduce 20% or more compared with using PA66 that is why they sell airbags cheap.
Sometime ship launching airbags are called pneumatic rollers or sausage balloons, they have sausage shape, cylinder body with two cone-shaped ends.
A. Safety air inlet system; B. Airbags Body; S: Air tightness swivel;
D. Diameter; Le. Effective Length; L/Loa. Total length
A. An air bag is to be constructed of an outer rubber layer, multiple synthetic-tire-cord layers, and an inner rubber layers
B. When says layers of ship launching airbags, normally it means the reinforcement layers.
Airbag Burst testing is used to determine the absolute maximum pressure at which ship launching airbags will “burst” or fail catastrophically. It is the ultimate test method for the Ship Launching airbags’performance and safety.
Evergreen Maritime conducts hydrostatic burst testing by using water to his marine airbags regularly by production lot or each time main material batch change to monitor the production and quality control. Burst testing is conducted using a plc controlled, monitored, and computer regulated test bench; featuring data acquisition at 50 Hz, calibrated pressure transducer, and protective safety features.
For more information of AIRBAG BURST TEST please refer :http://eversafemarine.net/burst-test-of-ship-launching-airbags/
Procedure of marine airbag producing
The price of ship launching airbags is calculated by airbag surface area. Usually factories are using the cylinder surface area formula to calculate airbag surface area.
It means, if D represent airbag diameter, L means airbag flat length, P represents airbag layers number,
Then airbag surface area will be calculated as : S=πD(D+L)
Unit surface price of airbag is quite different for different factories, generally it is in the scope of USD 4 to USD 8 for each square meters.
There are two Chinese standards and two ISO standards for ship launching airbags production and using.
Air bags diameter
Number of Airbag layers (plies)
How to decide airbags quantities for a ship launching or hauling project is not difficult. Even you are not a professional engineer, still can solve it by simple calculation.
Different types of vessel may need to adjust the airbag quantity according to practical conditions.
Consult with a professional marine engineer who is experienced in ship launching or dry docking for airbag size and quantity selection is important anyway.
Using marine airbags to launch a ship is neither a new idea nor new technique. In China people launched ships with marine airbags for more than 30 years. Accompanying with achievements of practice, the research of theory and launching calculation developed fast in recent ten years.
A general procedure of ship launching with airbags can be described as below:
If launch area is limited, people can use the control launching, releasing winch ropes to let vessel roll down into water slowly. Due to huge moment of vessel once it moves, the winch to control vessel’s movement speed must be big enough.
Please refer the link: http://eversafemarine.net/how-to-repair-a-hole-on-airbags/
Evergreen Maritime offered us pneumatic rollers for a pump house structure launching. Their ship launching airbags are extremely versatile with good quality. The ongoing support enhances the operational capabilities. Eversafe Marine engineers are highly experienced in the use of airbags available to assist those companies not used the previously,with large or difficult launching.
—John Hamilton, P. Eng.
Oil & Gas and Power
Sherritt International Corporation
Performance of ship launching airbags
The performance table of airbags with other specifications are available upon request.
Q: Can marine airbags be reused? How many times it can be used?
A: Yes. Marine airbags surely can be used and for many times. Proper usage and good maintenance can prolong airbag’s lifespan. Generally speaking marine airbag has 5-8 years lifespan with proper maintenance.
Q: How can marine airbags make vessel takes a turn when they are used to move vessel?
A: Airbags have been used for heavy transportation for many years. In most applications the transported heavy often need to be turned around during forward move process.
The principle is same like vehicle takes a turn . When a 4-Wheeler/Car takes a turn, to enable it go through it smoothly, its ‘outer’ wheels need to turn faster than the ‘inner’ ones.
When people want to turn the vessel with airbags they will place the front airbags to be inclined. See below inllustration.
The front 3 pieces airbags are placed inclined, when they move forward they move like to go around a circle center. So the A\B\C three points’ speed is bigger than D\E\F. Since behind airbags are perpendicular to the vessel center line, the H and I points have same speed. So when vessel goes forward its front will turn right.
That is the basic principle of airbags turn vessel. In the practical operation people will pull forward or pull back vessel for some times to make an accurate turn. That is also the reason that we need to make airbags to be perpendicular to launching direction when we want to launch vessel in direct line.
Q: What is the maximum pressure of marine airbags?
A: Here we understand maximum pressure means maximum safe working pressure. The structure layers and diameter effect airbag’s maximum working pressure in fact. With more layers airbag can have higher working pressure, bigger diameter the lower pressure.
We have tested every type airbag’s bursting pressure so we know the pressure limit. Just to prevent from cribbing we won’t publish the data in public. Ask us in private you will get what you want.
Q: Why some Chinese made airbags are easy to burst?
A: Even people often call marine airbags as balloon they should be toy balloon. Good airbag manufacturer has strict quality control policy and completed test instruments to ensure airbag’s quality.
But in China there are some airbag factories, in fact they can not be called factory, workshop may be right , make low quality airbags. They have no idea of products quality but good at cost cutting . You get what you pay for. It is commonsense.
Q: Why our new bought airbag looks like used one? Some patch can be found on it.
New airbag or used one is easy to distinguish, if there are abrasions on airbag body then it is used one. But some new airbags can have patches.
In our company all airbags will be tested before delivery. If quality control people find there is any blemish of airbags they will ask technician to fix the problems. Generally the blemish is not a problem even not treated. We want to have our airbags the best performance so we patch some blemishes.
We know it is ugly to have patches on new airbags. But we ensure client the top quality of product then the beauty . Anyway we are improving manufacture technology to extinguish blemish of airbags.