Tuesday, March 23, 2010

Evergreen marine airbag ship landing process

1. Fasten the ship with guy rope or cable attached firmly with the winch.
2. Select a reasonable position near the bottom of bow to insert one or more marine airbags which will act as the fulcrum for winch to move the ship when inflated and lift the bow. If it is difficult to insert airbags at the bottom of bow, people may insert them from one side to another side. For heavy ship the quantity of bow lifting airbags should be added until they can lift the bow. For V shape bow ship the bow lifting marine airbags should be inserted at the position where they can have bigger contact area with the bottom of ship. Also, people may place airbags at appropriate positions at low tide and pull the ship upon marine airbags at high tide, then inflate airbags to lift the ship. Anyway people should make the ship landing plan according to his practical situation.
3. After the bow lifted, start the winch to pull ship towards lands and insert more marine airbags to the space between ship bottom and land until the full ship is pull upon the slipway.
4. Charge marine airbags further to lift ship bottom higher, then insert the wooden stands and withdraw marine airbags.

Monday, March 22, 2010

Evergreen Marine airbag ship launching process

Evergreen marine airbag is widely used in the ship building, ship repairing, oil and gas, marine salvage companies nowadays.
Now we are making a brief introduction of Evergreen airbag ship launching procedure as follows:
1. According to the calculation, prepare enough marine airbags, towing winch machine, air compressor and other instruments needed.
Before using, all airbag should be inflated with 1.25 time inner pressure of working pressure to test its safety and air tightness. If there is air leakage, it should be patched before using.
2. Clear all the obstacles and sharp iron nail from the slipway.
3. Check on the uneven scar caused by welding of heavy steel structure to ensure ship’s bottom is smooth.
4. Fasten towing winch with ship.
5. Close all the valves, fix the helm and screw propeller.
6. Take out all the wooden stands under the ship, insert rolling airbags. There are many ways to do it. Now we introduce two most used ways as follows. The user may choose one of them according to the weight of ship and quantity of marine airbags.
A. For the light weight ship, airbags can fully lift the ship and make it to detach with the wooden stands. Then it is easy to insert other airbags and remove the wooden stands.
B. For the heavy ship, we use airbags to lift the ship at the stern of ship. So we must find the best point for bow supporting point and lift airbag. From the figure, we can know the bow supporting point should near to ship’s transverse gravity center. But consider the workforce of removing wooden stands before bow supporting point we should select that point at a reasonable place. The lifting air bag should far away from the gravity center to get a bigger lift moment. Sometimes we have to consider the figure of ship’s bottom to decide the lifting point. In one word we should find the best lifting point to get the maximum lifting moment.

To lift the ship the following condition should be satisfied
Q-bearing capacity
W-weight of ship
LQ-distance from lifting point to bow supporting point
LW-distance from gravity center to bow supporting point
C. First take out all the wooden stands in front of lifting airbag and bow supporting point. Insert the lifting airbag and start to inflate and stop charging as soon as the bottom of ship dispatch with the wooden stands. Then take out the wooden stands from the ship middle to stern, insert more airbags at planned positions. Repeat above process to remove all the wooden stands and place air bags.
In order to ensure the safety, we should insert some flexible wooden stands. When the air bags can lift the full weight of ship, we can take out these stands.

Not finished. Please contact author to get whole edition.

Sunday, March 21, 2010

Guide for Evergreen Marine Airbags Repairing-Interview with Evergreen Maritime

When there is air leakage, identified the crack propagation by visual inspection on the marine airbags to check on the rubber characteristic by determine the surface whether seriously aging (fatigue fracture and sticky surface).
There are two ways of patching, which are hot and normal temperature sulfuration.
Now we introduce the hot sulfuration as follows:
1. Clean up thoroughly inner and outer marine airbags to ensure totally clean especially on the outer wall surface. Don’t immerse into the water more than 10 miutes before patching.
2. Marking/indentified the air leakage area by extending “wound” part outward 15mm.
3. Patch ply depends on the size of flake leakage area.
If leakage area approx. 100mm or propagating fracture 50-70mm will be patched with 4-6layers.
And it’s better to equipped “+” cushion of Nylon.
The material of interleave should be same with marine airbag. And the angle of line also should be same with the marine airbag body.
The first layer of interleave is ordinate. Length= length of “wound” + 50 x 2m
The second layer of interleave is bias. The angle should be same with marine airbag’s body. And it should be 20mm bigger than the first layer.
The third layer of interleave also is bias. The angle should be contrary with the second layer. And it’s 20mm bigger than the second layer. The 4th-6th layers is analogy.
Circular angle is required around the interleave. The semi diameter is 40-50mm.

4. File the flake leakage area by sand paper in single way direction for several times to ensure clean & smooth surface surrounding the fracture area. Remember to clean it again with compressed air.
5. The whole process should ensure there is no unwanted particular embedded and dry up the air bag surface. Then brush up some 502 glue with glue mixture of pure rubber material: petroleum base chemical of 1:8.
6. patching process - use prepared mentioned layer to patch.
7. Vulcanizing press process - using the rack structure indicated below to carried out vulcanizing process by heating up to 135 ± 5℃; press the flake leakage area with 0.08-0.12 Mpa pressure for 40-50minutes.
8. Inspection - Check the patching area to ensure the tight agglutination. Then inflate the air bag for final checking.

Monday, March 15, 2010

What's Evergreen Marine Airbags-Interview with Evergreen Maritime

Evergreen is the inventor of first marine airbag, and sets the standard in the industry for high performance and usage technology. Now, Evergreen Marine Airbags (ship launching marine airbags) are widely used in ship launching and landing, sunken ships salvage and refloatation, heavy lifting and conveying.
Evergreen Salvage / Refloatation Marine Airbags are the most commonly used tool for recovering submerged objects and supply enough buoyancy for objects. Floating Evergreen Marine Airbags are very small in size while deflated. Thus, they can be easily transported and deployed when space is an issue and under water conditions. We can provide the exact floating ton capability based on clients requirements. The Evergreen Salvage / Refloatation Airbags have flexible applications and can be broadly implemented in shipwreck salvaging, floating bridge and dock construction, rescue and remove of wrecked ships. It is also being use as temporary marine transportation device.
Construction Features:
Evergreen Salvage / Refloatation Marine Airbag, basic body consists of which consist of our rubber layers, synthetic-cord-reinforced rubber layers, are kind of a cylindrical airbags with hemispherical heads at the both ends. All of these are vulcanized together, and then compress air inside to enable in to roll.
1. Outer Rubber
The outer rubber layer that covers the outside of evergreen salvage 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. Standard color is black.
2. Synthetic-tire-cord layer for reinforcement
The reinforcement cord layers of marine airbag, which are made of Synthetic-tire-cord commonly used in tires, are arranged at ideal angles to hold the internal pressure and to distribute the stress evenly providing strong efficient reinforcement.
(To know the detailed technology parameter, please refer Material Selection.)
3. End Fittings
End fittings of evergreen salvage / refloatation airbags include air tightness swivel and airbags safety air inlet.
4. Lifting Strap
Nylon (Polyester fabric) straps and shackles are used for the lifting underwater. Other type designs are available upon clients’ requirement.
1. The standard specification of Evergreen Marine Airbags.
You can choose the required diameter and effective length to meet your projects.
 Diameter (D) : It’s from 0.8m to any.
 Effective Length (EL) : It’s from 6m to any.
 Total Length (TL) : It’s from 7m to any
The above specification only is our standard specification arrange. Other specification also can be supplied upon clients’ request.
2. The standard number of layers
We define the number of layer, which means the number of Synthetic-tyre-cord layer, in order to confirm the Safety Working Pressure. Normally, our airbags include 4, 5, 6, 7, 8 layers types. Other type is available upon clients’ request.
3. The material of Evergreen Marine Airbags
There’re two kinds of synthetic-tire-cord because of the different performance.

Item Unit 1400 dtex/2 1870 dtex/2
Break Strength N/ strand ≥ 215.6 ≥ 284.2
Diameter mm 0.65 ± 0.05 0.74 ± 0,05
Adhesion Strength N/cm ≤ 137.2 ≤ 156.8

We define the suitable Evergreen Marine Airbags as per the above 3 items.
Such as: Evergreen Salvage / Refloatation Airbags D1.5m x EL 15m YT-6, 1870D Type
In here:
1. D 1.5m: the diameter is 1.5m
2. EL 15m: the effective length is 15m
3. YT-6: the number of Synthetic-tire-cord layer is 6 layers
4. 1870D: the type of Synthetic-tire-cord layer is 1870
Features and Advantages:
 Unique whole enlacing technology
 Excellent material selection as per ISO 17357
 Cost effective, long service life
 Guaranteed quality and safety
 Free consult and design project
 Laboratory and field test
 Commission and technical directing service
 Well proven design and performance
 0.7 Mpa hydraulic blasting utmost
 After service for lifetime

Evergreen Maritime Contract with CNOOC for Fender System Design and Supply

Qingdao Evergreen Maritime and CNOOC contracted on March 3, 2010 for the fender system design and supply of Lu Da 27-2/32-2 oil platforms.

CNOOC (China National Offshore Oil Corporation SEHK: 0883, NYSE: CEO) is China’s largest producer of offshore crude oil and natural gas and one of the largest independent oil and gas exploration and production companies in the world.

Lu Da 27-2/32-2 (PSP) located in Bohai Bay is an 8-leg process and storage platform that holds a huge oil tank with a capacity of 1.2768 X 104 m3.
Evergreen Maritime Company as the professional manufacturer of pneumatic fenders and ship launching airbags has a long time cooperation with CNOOC in many fields, such as airbag ship launching service and boat fender design and supply. For oil platform fender system, it is the first time cooperation between two companies.

Different from general dock fender system design, the oil platforms have extra demand of anti-shock and worse sea conditions. Evergreen engineers researched all data and drawings of the platforms with assistance from CNOOC experts for more than two weeks. Then a new fender system comes out: super arch rubber fenders plus Evergreen pneumatic fenders. This fender system is tested by digital simulation software developed by Evergreen Maritime Company and the result says safety ratio is greater than 2 whether in shuttle ship berthing condition or mooring status.
On March 5, two sets of pneumatic fender were trucked to Tianjin Port then will be shipped to the Lu Da 27-2/32-2 platform. Evergreen engineers will go to the platform for the installation instruction soon.
For the latest headway please visit our website: http://www.evergreen-maritime.com.

Friday, March 5, 2010

Ship Launching Revolution-Marine airbag ship launching

The ship launching history is more than thousands years. Nowadays the most commonly used ship launching method is still the oldest end-on launching, in which the vessel slides down an inclined slipway with stern first. Another ship launching method is side launch which is often used on narrow water area by launching the ship broadside. The float-out method means building a ship in basins or dry stocks and then admitting water into the dock to float the ship. The traditional ship launching methods need the fabricated slipways or dry stocks and supporting facilities so the engineering period is long and expensive. When shipyards suffer from the production problem of short of slipways or expensive investment of new fixture they need a solution for sure. For salvage of stranded vessels people also need a less equipments and landform limited ship launching method.
Evergreen airbag launching system is an innovative flexible ship launching method and need the least supporting fixture. It demands the ramp for ship launching only enough bearing capability and neatness. The main instruments of Evergreen airbag launching system are marine airbags, air- compressor and regular winches. The sausage shape marine airbags are made up of rubber layers with rubber dipped synthetic-tyre-cords as reinforcement material. Their diameters range from 1 to 2 meters and lengths range from 6-20 meters. One marine airbag for 1.5 meter diameter and 18 meter length can hold over 200 tons weight. Marine airbags act as the air springs and rolling logs when they conveying ships to water.
Ship launching with marine airbags have a more than ten years history in China. But only in these years this technique develops into an integrated system with the advancement of manufacture and establishment of theory system. It is estimated that more than 80 percent new built ship whose DWT below 60,000 are launched by marine airbags in China. In fact Evergreen airbag ship launching system is not only a good alternative but also indispensable to some given marine projects. A typical ship launching project completed by Evergreen airbag launching system will well illustrate the character of this system.
At July 2009, a new built 20,000DWT ship on a no fixture ramp was successfully launched by Evergreen airbag launching system in Chinese Jiangsu province. This cargo ship is 150 meter long and 21.6 meter width with 7800 tons light weight. For some untold reasons, it was built upon a 200 meter long concrete ramp without fixture or anchor block. The angle of concrete ramp is 0.86 degree and its connection of river water is unsettled mud. This inland river is 350 meter wide with 7-11 meter deep water. The distance between the ship stern and end of ramp is 15 meters. Because there was no anchor block on the ramp, the winch was not available. Then two major difficulties came out: how to start the movement of ship launching and how to avoid the unwanted slip when ship was lifted from the wooden blocks.
In low tide period, mud of riverside was cleaned by an excavator grab and some sand bags were placed to fulfill pits on the riverbed. Total 34 pieces marine airbags with 1.5 m diameter and 18 m effective length were placed between wooden blocks according to the calculation. The charge of airbags was strictly executed according to the scheme which demands the sequence and exact working pressure of each airbags. From the calculation and computer simulation, the ship would not slip at maximum 0.57 degree when it was raised up by airbags. So during the “raise-up” process the principle was control the ship’s gradient angle not exceed 0.57 degree. Airbags were inflated from the stern to midship one after the other until exceeded the gravity center position. Then inflation from bow to midship was carried out to rise up the whole ship. After all supporting wooden blocks removed, airbags at the bow was deflated to adjust the ship’s gradient angle to be 0.45 degree which would make the ship to be safer from the unexpected slipping.
When the tide reached needed level airbags were inflated and deflated respectively to adjust the ship’s gradient angle to be 0.57 degree again. And an excavator grab whose shovel was wrapped with tyres began to push the bulbous bow to give a start-up force. After twice push, the ship started to move slowly by riding rolling airbags and the movement was self-accelerated until stern floated because of ship’s increasing gradient angle. It took 62 seconds from ship’s movement start to total float while the preparation works took more than 12 hours.
This launching project exhibits the convenience and efficiency of Evergreen airbag launching system which can save most time and investment comparing with traditional slipway launching. Because of the advantages Evergreen airbag launching system has been applied to ship launching, ship landing, heavy conveying, wrack salvage, etc. For example, the Chinese invaluable 800-year-old ship “Nanhai No.1” was landed and conveyed by marine airbags and it is said the airbag launching system is one of the most important factors which ensure the success of salvage project .And for gravity quay building, more than 60% power plants use this system to launch prefabricated caissons in China. For marine salvage, Evergreen airbag launching system is widely used by American salvage companies to launch or refloat wrecks.

Evergreen airbag launching system is simple but powerful. It is less limited by equipments and landform and can save most investment and time to complete marine projects. With the development of theoretical system integrity and computer simulation technology, Evergreen airbag launching system will be accurately controllable and becomes into the cutting-edge solution for launching projects.

Wednesday, March 3, 2010

How to select marine airbags

There are two industrial standards for marine airbags in China.: one is product standrad named “Air bag for ship up to or down to launching way “(CB/T 3795-1996 / CB/T 3795-2009) ;another is technology standard named “Technological Requirements for ship Upgrading or Launching Relying on Air-bags”(CB/T 3837-1998).The latter offer the basic calculation of marine airbags employed in a marine project.
According to Chinese industrial standards people will know the approximate quantity and specifications of marine airbags needed for their projects then consult the manufacturer to confirm the design. There maybe optional specifications to be selected for a specific marine project and a good manufacturer should know the best choice. Suggestions from Qingdao Evergreen Maritime Company :for ship launching, the airbag’s diameter and length should not execeed 2.0 meter and 18 meter respectively;for caisson conveying, the 1.0 meter diameter is suitable for most projects.
The data of marine airbags’ blasting pressure will reveal the product’s quality level. For top quality marine airbags,such as one 1.5 m diameter and 7 m length Evergreen marine airbag, the blasting pressure is 0.67 Mpa which indicates the safe coefficient is more than 5 considering its 0.12Mpa working pressure.
Full technical service is the qualification of a good company. Although general calculation formula or performance data of marine airbag can be got from most factories but detailed calculations based on mathematic model and experience is more important to the success of marine projects.

In a word
Marine airbag is a simple but powerful marine tool which should get more attention from people involved in marine fields. It is less limited by equipments and landform and can save most investment and time to complete a marine project. And the flexibility of marine airbags not only mean airbags can give more protection to being launched objects but also it can be used creatively.

The advantages of Evergreen marine airbags

Less landform limited
Marine airbags only need the enough bearing power ground.
Most less fixture needed
For most works ,marine airbags need no more than air compressors,winches and forklifts.
Environment Protective
Marine airbags do no harm to the environment.No chemical needed.
Marine airbags can be used for ship launching /landing,heavy conveying, buoyancy lifting even the temporary ship fenders.
For ship launching,marine airbags can save the investment of traditional slipway or drydock. For caisson conveying projects,marine airbags can save 50 percentage cost compare to the traditional way of employing crane ship and semi-submersible ship .Caisson can be launched by marine airbags and suspended in the sea with the help of attached airbags’ buoyancy then one or two tugboat can complete the sea transportation.When caisson arrive the appointed spot,airbags can be deflated to let the caisson sink.

Tuesday, March 2, 2010

Marine Airbags: Innovative and Versatile Marine Tool (part 1)

Marine airbags are widely used in China for ship launching ,caisson conveying and marine salvage nowadays. It is estimated that more than 80 percent new built ship whose DWT below 60,000 and about 50 percent caisson fabricated for gravity quay are launched by marine airbags.Not only in China but also other Asian countries marine airbags are acknowledged as the powerful and versatile tool for marine works.

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.

Over the past twenty years, marine airbags have made great advancements in the manufacture and application. The first generation marine airbags employ rubber dipped canvases as reinforcement material and two cone-shaped ends are stuck to the chamber trunk. Now the top marine airbags are seamless and their performances are about 15 times of the first generation with the same specifications. Regarding the launching/landing technology, marine airbags have also achieved a significant leap. In the beginning, only small and flat bottom ships located on a fabricated slope could be launched with marine airbags. Now this technology is more flexible and less limited by the ship and landform. The DWT of launched ship reached 55,000 and launching ramp can be aclinic. Not only for ship launching marine airbags are widely used for heavy conveying also. Marine airbags contributed much to the success of famous Nanhai No.1 ancient ship salvage project. The 4,800 tons cassion which hold the invaluable ancient ship landed from the semi-submersible barge and transported to the museum named Crystal Palace riding on 16 pieces marine airbags.