Good Air Tightness Ship Rubber Airbag Vulcanized Boat Marine Airbag For Ship Launching

Good Air Tightness Vulcanized Boat Rubber Airbags

Product Introduction:

What were the first uses of airbags in the launching of ships?

The history of marine airbag ship launching dates back to 1981. Xiao Qinghe ship repair and building shipyard, located in Jinan city of Shangdong Province, launched a 60 DWT tank barge with airbag suspension on January 20, 1981. Seven airbags were deployed in that project. One was 2 meters in diameter and 6 meters long and used for elevating. The remaining six airbags were 0.8 meters x 6 meters long and acted as the rollers. The first intention of that trial launch was to develop a prompt, less landform limited ship launching method for warfare purposes.

How has the technology advanced since then?

Over the past twenty years, the airbag ship launching system has made advancements in not only the airbag, but also the ship launching/landing technology. The first generation airbags used a rubber dipped canvas as a reinforcement layer to form the air chamber trunk. Two cone-shaped molds were then used to make the ends and everything was stuck together.

With today’s airbags, the whole-enlacing-technology used for manufacturing is done together. Rubber dipped synthetic-tyre-cords are used as the reinforcement layers with the trunk and two cone-shaped ends made at the same time. Everything is then-laced together, so the airbag doesn’t have any joints. Due to the development of rubber chemistry, the performance of the rubber employed in the latest airbags is highly enhanced and about 15 times that of the first generation bag with the same specifications.

The launching and landing technology has also developed. In the beginning, only small and flat bottom ships located on a fabricated slope could be launched with airbags. Now this technology is more flexible and less limited by the ship and landform. Now any type of ship with a DWT below 55,000 and in a place with enough launching space can be launched using airbags. The launching slope even can be sloped upward. It has really developed into a cutting edge technology for launching ships, and especially useful for some marine emergencies.

Specifications:

As a soft flexible body, airbag’s shape depends on various factors, such as the shape of ship bottom, ramp shape, width of ship bottom, length of airbag, position of airbag under the ship, etc.
Users should calculate the bearing capacity of airbags basing on above factors, correct bearing capacity accordingly.

Caculation of performance of airbags

Formula: Bearing capacity F=PS

P=pressure in the airbag(MPa)
S=contacting area between ship bottom and airbag(M²)

S= π*(D1-D2)/2

Attention During Application

1. Working pressure must be controlled strictly, it is not allowed to exceed the working pressure.

2. No sharp and protruding hard object on the contacting surface of the airbags, to avoid the puncture on the skin of airbags.

3. Avoid the distortion along the length of airbag.

4. Empty inflating test must be performed if the airbags were not used for a long time or after reparation. The pressure should be as same as the testing pressure of our company. Inspectors must be at least 3 meters away from the airbags. For repaired airbag which was damaged in large scale, its working pressure should be lowered reasonably. Besides, annual check should be conducted on airbags which are used frequently.

5. Don’t drag the airbags on the ground.

Instruction of Airbag Repair

If the airbag is damaged, it can be repaired as long as the rubber doesn’t age seriously(with no crack and stickiness on the surface). And the cords fabric is not loose and rotten. Repair can be made by hot vulcanization or auto-vulcanization. The tolls and repair materials utilized in the former are quite simple. We recommend hot vulcanization, the steps are as below,

1. Wash the airbags to make sure it is clean both inside and outside and without mud & sand,
oil stain and water logging. Then dry the surface. Note: the immersion time while washing can’t more than 10 minutes.

2. Mark the repair symbol visibly. Mark the repair area and the mark area is allowed to exceed 15mm, don’t miss the concealed damage.

3. Prepare the backing
The material of backing is the same as the airbag and the arrangement angle of the cord fabric is consistent with the airbag.
The first layer of the backing is a vertical line. Length=(length of the flaw+50mm)X2
The second layer of the backing is oblique line whose angle is the same as the airbag. It is 20mm larger than the periphery of the first layer.
The third layer of the backing is also oblique line whose angle is opposite to and crosses with the second layer. It is 20mm large than the periphery of the second layer.
The fourth, fifth and sixth layer may be deduced by analog.
The fillet transition with the radius of 40mm-50mm is required for the backing periphery of every layer.
If the wound is a nail hole within 100mm or strip wound in 50-70mm, cross backing shall be prepared. Nylon cross backing is made by bluing two layers of coated Nylon with the crossing of 90°. Its size is 200mmX200mm and others are the same as the backing.

4. Filing the wound
File the wound with steel files or flexible shaft filing machine. The file pattern on the surface should be delicate and even as well as without any rubber scrap, particle. Filing surface depth is about 0.5-1mm. The periphery is 20mm larger than the backing. Breaking and loose is not allowed for filed cord fabric. After filing, blow always the rubber scrap by brush and compressed air.

5. Brush glue and dry
The whole process must be kept clean. Brush thin glue for the first time (glue: gasoline=1:8).There should be no sediment and caking, should be evenly. Forcibly gluing should be performed so that the glue can penetrate into the cord fabric layer in the file slot. The gluing should be uniform and obvious scaffold erecting is not allowed.

6. Viscose
Firstly, brush a layer of base glue with the thickness of 1±0.2mm on the periphery of the wound. Cool down to not gluing hands, paste and press and the glue should not be too tight in case glue failure happens after the new glue contract, then paste the backing. The center of the backing should be targeted at the wound center. The angle of the backing should be in consistent with the airbag line layer. For wound larger than 1M, a layer of coated Nylon fabric should be pasted to the wound, 25mm lager than the wound. Then paste the backing. In the end, one sealing rubber (thickness of 0.8-1mm,wideth in 20mm) should be pasted to the cover the joint of backing edge and body of airbag.

7. Vulcanization
For normal shipbuilding yard, the following simple method can be adopted: set up a frame, ( as shown in the figure) and provide plate, sand bag(fill the inner tube of the abandoned automobile with sand), jack and heated plate(pig iron or steel plate in Dia300mm ,thickness 25mm). The vulcanized airbag to be repaired should be targeted to the center in accordance with the position shown in the figure. First vulcanize the hole and then the wound. If the large wound to be vulcanized exceeds the effective length of the vulcanization, the center should be vulcanized firstly then both sides. The heated plates should overlap 15mm with the previous position in re-vulcanization. The vulcanization shall be finished within 40-50 minutes when the temperature rises to 135±5℃ and pressure is 0.8-0.12MPa.

8. Check whether the repair is bound tightly or not, Flaw such as void, delaminating or sponge and so on are not allowed. As to new glue in heating area, aging, crack, under vulcanization and over vulcanization is not allowed. Inflating test shall be conducted if the repair is qualified.

Qingdao Shunhang Marine Supplies Co.,Ltd. located in Qingdao ,China. Our company was established in 2011, specialized in manufacturing marine rubber airbags ,pneumatic rubber fender,EVA foam filled fenders.

Our company has passed ISO9001 certificate. Our products have approved by CCS, BV, ABS, RS, SGS etc.

We have established long-term cooperative relationship with many shipyards, ship owners and trading companies . Our products have been exported to Southeast Asia,Middle East, Africa, South America and European markets. etc. many countries and regions.