Marine Airbags/pneumatic rollers

Marine airbags sometimes are also called pneumatic rollers, balloons, they are sausage shape inflatable airbags. Clients don't need to know all details of airbag manufacturing but should be clear of two important factors: material and manufacturing technique.

Material:

Marine airbags are made of rubber and cords, natural rubber contents and synthetic tire cords performance are very important for airbags' safety and performance.

There is no mandatory demands for natural rubber contents in ISO 14409 but most good manufacturers have more than 50% natural rubber in total rubber weight.

Breaking force of synthetic tire cords is a critical index. Cords picked up by Eversafe Marine have more than 31 Kg breaking force.

Some low cost marine airbags in China market have less than 40% natural rubber and thin cords whose breaking force can only reach 21 Kg. Those bags have be used carefully because they have almost no safety coefficient.

Framework of marine airbags ( Synthetic tire cords) Rubber sheets ,composed of rubber and cords

Manufacturing technique:

Mainly there are two kinds of manufacturing technique of marine airbags, one is "sticking method" , another is enlacing method.

The sticking method is an old technique has more than 30 years history, nowadays most small factories still use it. They can make any size airbags, and make them very fast. Airbags made by sticking method will expand significantly both in diameter and length while inflated. This disadvantage limits the performance and safety of airbags.

The enlacing method was developed about ten years ago. The top airbag manufacturers all take this production technology. Airbags made by enlacing method have limited expandability due to better structure design. Also the air tightness is much improved.

How to select suitable airbags for a vessel docking project, people need to pay attention to three important parameters of airbags :

1. Diameters .

The balloon's diameter decides the height of keel blocks you can choose. If for 1 m high keel block, airbags with 1.5 m diameter are good. If higher blocks are preferred, such as 1.5 m, then 2 m diameter airbags are suitable.

The principle is if small diameter airbag suits for your job, don't choose the bigger one.

The reasons, one is the cost, another is the operation convenience.

2. Length. When talk about airbag's length, we mean the effective length, the body length only.

Most factories can manufacture 20 m long airbags, if breadth of ship is less than 20 meters, just select airbag whose length is equal to vessel's breadth.

If a wider ship has more than 20 meters, people may select airbag whose length is equal to half of vessel breadth. For example, one 30 m wide ship may use 15 m long airbags.

If one ship is more than 40 m wide, people can still use 20 m long airbags, if lifting capacity of airbags are enough. Or else people have to choose 1/3 of vessel's breadth as the airbag length.

3. Working pressure (reinforcement layers)

The working pressure decides airbags' lifting capacity, the higher the better obviously.

But if the six layers airbags with 0.13 Mpa working pressure is enough, don't need to choose airbag with more layers, such as seven or eight layers. The reason is simple, all airbags have at least three times safety coefficiency, Eversafe Marine produce bags with five times safety coefficiency, BTW. Theoretically airbags are 100% safe with rated pressure.

If people are really cautious and want to increase safety coefficiency, pay more attentions to the arrangement of airbags and the preparation works that will be more effective than buying heavier airbags.

According to Eversafe production, with one more reinforcement layers, the thickness of airbags will increase 1.2 mm. So if there are puncturing accidents happen, one more layer can not help much.

Venting:

1. Airbags are made of rubber and synthetic cords, people should expect they can be stronger than steel. Before vessel docking, clean ship bottom ,remove marine fouling are necessary for the airbag safety.

Sometimes in emergency, people don't have time to clean vessel bottom, then wrap airbags with some protection stuff, such like conveyer belts that can mostly reduce airbag damage risks.Only the first two or three bags need to be wrapped, in fact. Those first inserted bags will wipe away marine fouling while they roll beneath the ship.

Clean the docking ramp. The ramp should be clean, free of steel, sharp stones. Sometimes people can cover the ramp with sands or steel plates to avoid airbag puncturing damage.

2. Weight changes of airbags.

As the manufacturer we want to make airbags as light as we can, as strong as we can. The improvement of manufacturing technology, the adjustment of material will change the weight of airbags. So if airbags from two batches have slight weight difference , it is normal.

3. Patches on new airbags

New airbags can have patches, it is true. After production all airbags will be inspected, if there are impurities in airbag surface layer which is determined will potentially effect the air-tightness and life span of airbags, they will be fixed and mended with a patch.

It doesn't look good, we know. We are trying to eliminate patches from production technology to material. Anyway airbag is a tool for heavy jobs only, not the artwork.