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Air bags for ship upgrading and launching (NEW!)

 

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Ship launching is one of the most difficult and important step of the ship building. Shipbuilder and ship repairer use side-launching ways or broadside slip for a long time. But this method has a lot of disadvantages:

• costly launch equipment, which also requires a lot of storage space;

• high labor intensity and long preparation of launch;

• the ship must be moved from the building area to the devices for launching;

• high labor intensity during the slip preparation, in particular, the need for lubrication (launching grease) to ensure the required coefficient of friction;

• after launching the slip elements must be upgraded , not only from the surface but also from the bottom of the water area using divers;

• pollution of lubricants (launching grease).

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Photo 1 – Ship launching side-launching ways.

 

Development of shipbuilding is based on the application of modern achievements in design, technology and organization of construction and launching of ships.

One of these achievements is the method of ship launching using launching air bags. In 2006 new technologies received the status of advanced technologies and began to be widely used not only for ship launching, but also for their upgrading to the slipway and for upgrading and transporting of sunken boats and ships.

This technology does not require large equipment costs, saves time and investment to build and repair launching slips. For launching ships using air bags the plain bevel surface which may be made of coarse sand, gravel, concrete, metal, wood and other materials must be created.

Air bags are widely used for upgrading and moving of sunken ships and removal aground . Pneumatic bags have not only time and labor time but also financial advantages.

If their use is proper, they are flexible, portable and reliable. The air bag use for ship upgrading and launching is a good technical and economical alternative to costly conventional traditional ship launching equipment. 

Compared with traditional launching appliances pneumatic bags change working height during launching. Pneumatic bags compared with traditional launching devices have high buoyancy , that provides an additional stability moment during launching  and adds buoyancy of the ship from the launching start, that avoids ship tipping.

At the same time, the flexibility of the air bag shell reduces the risk of ship and slip way damage during the launching. Pneumatic ship-upgrading complex (slip based on pneumatic bags) - hydraulic structure with  bevel surface, where the ship is build or repaired and launched free (under  gravity of the ship) using special airbags along a predetermined path.

The main slip component are pneumatic bag, which consist of an outer layer of rubber, synthetic yarns and reinforced rubber layers(plies).

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Photo  2 – Ship launching using air bags.

Slips based on pneumatic bags intended for the construction and repair of ships, launching of which is carried out by the foundation on the air bags supplied by ship. Slips of this type are the most versatile and sophisticated . Required lifting height on the stocks is regulated by increasing or decreasing bag pressure. Possibility of fleet upgrading or launching is limited by the size of the upgrading equipment, which is used for upgrading and launching.

1 Air bag(AB)

 The main supporting elements of the slip are air bag ( hereinafter - AB) . Ship transferring from the building area to the slip is produced approaching the deflated air bag under the vessel and inflating with compressed air. The launching is made on the air bags used as the rollers. This launch can be both uncontrolled and controlled. In the latter case the launching speed is regulated by the traction mechanism which is located at the head of the slip.

The distance between the air bags depends on the light-ship, the length and width, but not more than 6 m from the bag centers. To install the bag the space at least 25 cm in height and width at least the half of the circumference of the air bag is required. 

Air bag (hereinafter - AB) for upgrading and launching of vessels and dragging heavy dimensional structures with flat basis (without protrusions). Also suitable for use as a pneumatic jack. Pneumatic bags are intended for ship transportation, repair and painting.

2 The main technical parameters of pneumatic bags

 - Inner diameter of the cylinder - bag   500 to 2000 mm;

- Length of the cylindrical part, 3 000 to 14 000 mm; 

- Maximum working pressure in the bag, 0.4 to 4 kg / cm2 ;

- Maximum weight carrying capacity of the bag, 6 to 800 tons;

 - Number of cord layers 3 to 14 pc ;

- Operating temperature range from - 10 to + 60 ° C . 

Technical parameters of pneumatic bag (AB) may vary depending on customer requirements.

3 Technical description of the AB The pneumatic bag AB consists of a rubber-cord shell with tapered ends.

Pneumatic bag has two threaded bushings on the tapered ends, one of them is connected to the pressure control unit and the valve for the compressed air, another end is equipped with eyebolt  to drag the bag during the operation. At customer’s option AB can be supplied with two pressure control units (Fig. 1).

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Picture 1 - Layout of a the pneumatic bag AB-1,2-10-1,6.

 AB may be operated at the temperature range from -10 ° to + 60 ° C, with the media: river and sea water, industrial water, weak acid and alkaline solutions. The outer rubber layer protects the bags from abrasion and other external influences. This layer has high disruptive strength, withstand a load in harsh operation environments.

The rubber compounds and rubber-coated cords for bags are made in our own preparatory workshop of the high quality raw materials. Control of raw materials and  rubber compositions is carried out in the laboratory of the enterprise. The formulation of rubber compounds is constantly being improved. This allows to improve the wear resistance and abrasion of the rubber, its performance characteristics, to make it suitable for each customer individual need. Because of the peculiarity of AB-manufacturing technology the  incomplete airbag  airtightness is allowed.

Pneumatic bags can be used both by large and small shipping and ship repair facilities, oil and gas, nuclear power, aerospace, railway industry enterprises, bridge-building organization, road building companies, rescue officers.  In practice, a bags with a diameter of 0.8 ... 2.0 m, effective length 6 ... 18 m and a total length of 7 ... 21 m, with an operating pressure of 0.07 MPa ... 0.24 are used. Airbag dimensions and specifications can be changed at the request of the consumer.

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4 Basic rules of the bag operation  

Handling, transportation and installation. 4.1 Airbag loading and unloading is to be made one by one on pallet folded, without using of transport rope hooks or any metal objects that can damage the product. 4.2 It is not allowed to drag bags on a hard surface because of the risk of damage.

4.3 After each use, the outer surface of the bags must be cleaned, the air must be removed and the bags must be folded in places of inflection. The transportation of bags must be carried out on a flat horizontal platform, by road or by rail. 4.4 The long distance transportation of the inflated bags is not permitted. The  rolling of the inflated bags on the territory of the enterprise is allowed, if there are no objects on the ground (like broken glass, nails, some other sharp objects) that may damage the shell structure of the bag.

4.5 The installation  of bags is carried out by the specialists briefed on the use of bags. 4.6 When you connect bags to pneumatic system (receivers, compressor), check the correct operation of the gauge, when the air pressure in the bags must be checked by two pressure gauges, if the pressure gauge readings will be different, it is necessary to stop pumping and replace faulty gauges.

5 Slip and bags preparation 

5.1 Surface of the launching track (slip) must slope towards the water and go into the water at a certain depth. The slope of tracks depends on the launching weight of the vessel. The slope is determined by ratio of the height of full raise to the length of the slip. The value of the slope for a variety of slips depends on the size of vessels to be launched:

the slope for small vessels is from 1 : 8 to 1:12

the slope for middle vessels is from 1 : 14 to 1:16

the slope for big vessels is from 1 : 18 to 1:24 

Before the operation it is necessary to clean the slip surface removing foreign objects (like metal, broken glass, nails and some other sharp objects) that may damage the bag shell structure and to level the surface with sand (removing the pits and hills). 

5.2 During the operation is not allowed:

• exceedance of the working pressure in the bag shell;

• lifting of loads which  exceed the weight carrying capacity bags;

• moving or dragging bags on surfaces, which can damage the bag;

• rolling bags when the lifting height is less than 400 mm;

• storing bags inflated for a long time.

5.3 When using the bags the perpendicularity of the axis of the vessel to the axis of the bag must be strictly observed.  

5.4 The physical impact on the outer surface of the bag is prohibited because of the risk of the destruction of the layers and the break.

5.5 By launching, upgrading and transporting of the vessels the parallelism and at most 6 meters intervals between the airbag axes is to be adhered, if the operations are carried out without the development of special methods of launching, upgrading and transporting of the vessels.

5.6 When transporting the vessel on bags the bags should be placed in strict compliance with the schemes specified in the project documentation.

5.7 Use of rubber pneumatic bags for other purposes is prohibited.

5.8 Deflated pneumatic bags are slid under the ship and inflated with compressed air, carrying out the transfer of the vessel from the construction area to the launching device. The launching is made on the air bags used as the rollers. This launch can be both uncontrolled and controlled. In the latter case the launching speed is regulated by the traction mechanism which is located at the head of the slip.

Table 1 - The dependence of the working pressure on the bag ply rating and diameter. 

AB-diameter, m

0,8

1,0

1,2

1,4

1,6

1,8

2,0

Number of cord plies

Working pressure, MPa

4

0,16

0,14

0,12

0,09

0,08

0,07

0,06

5

0,2

0,18

0,16

0,12

0,11

0,10

0,08

6

0,24

0,22

0,2

0,16

0,14

0,12

0,1

7

0,27

0,25

0,23

0,2

0,17

0,14

0,12

8

0,3

0,28

0,26

0,22

0,2

0,17

0,14

9

0,32

0,3

0,28

0,24

0,22

0,19

0,16

 

When selecting bags Table 2 with weight carrying capacity data should be used.

The weight of the bags shown in Table 3 

Table 2 - The weight capacity of the bag 

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Таблица 3 – The weight of pneumatic bag

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Deviations by weight does not exceed 10 %.

6 Air bag selection

Selection of the required number, diameter, and ply rating of the bag is tailor-made. We recommend the following algorithm

The effective length of the bag is not less than the maximum width of the vessel or other object to be moved. If the width of an object exceeds the working length of the bag, for valuation purposes the number of rows of air bags, and accordingly, the total length of all movie-bags are used to calculate. However, it is necessary to ensure the distance  between the bags to access the air hose and couplings with pressure gauges. The total length of the  air bag should be calculated as the effective length in addition to the diameter. In most cases, this approach ensures stability when moving the sail spread or cargo imbalance object.  The diameter of the bag is caused by the height of supporting units. If the height of the unit is 0.5 m, the diameter of the bag at least 0.8 m is to be selected. If the height of the unit is 1 m, the diameter of the bag at least 1.6 m is to be selected. If the height of the unit is 1.5 m, the bags with 2 m diameter are most suitable.To use the air-lift effect, the bag diameter or length is mainly caused by buoyancy. When using bags at a deep depth, the water pressure is to be taken into account. The most suitable bag diameter for float case moving is 0.8 to 1.0 m

When upgrading and launching of ships (weighing less than 2,000 tons) with the reduction of area towards the keel in the middle of the bag the pressure is insufficient. This is achieved by increasing the pressure or using the shorter bags. Typically, the bags with 5-6 ply cord are quite enough for most engineering operations. Only in some special cases, the bags with 7-8 plies are to be used, in order to increase the strength and to guarantee the level rise.

Using bags with a small diameter of 0.8 to 1.0 m is possible only on the slip with the firm prepared ground, for the slip with mixed sand and clay soil the bags with minimum diameter of 1.2 meters are to be used. This brochure concerning selection of bags has a recommendation purpose, a more accurate calculation for dragging or lifting objects is to be made ​​individually by the project experts. 

The tables 4 and 5 and the figure 2 give an example for the bag selection for upgrading and launching vessels with the light-ship 218 tons.

Table 4

Total length
of the vessel, m
Estimated length
of the vessel , m
Width , m
Load factor ,
t / m2
Light-ship,
m
Upgrading height 
of the vessel, m

62,3

62

9,3

0,38

218

0,7

 Table 5

Number of plies

 

The actual distance 
between the
centers

of the AB , m
Evaluated 
AB-pieces
The maximum 
distance

between
the AB-centers, m
AB-diameter, 
m
AB- length, 
m

Quantity of AB,pcs 

4

5,6

5,34

6

1,2

10

11

 

 

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Picture 2 – AB installation diagram.

Launching  operations include the following steps:

 - To bring airbags under the ship; 

- To pump air into the pneumatic bags to achieve the working pressure; 

- To move  the ship from the ship building devices to pneumatic bags.  Launching (uncontrolled) - To cut the lateral lines(pauls) at the same time on both sides of;

 - To cut the bow rope; 

- To launch vessel via the pneumatic bags. Next towing vessel to the outfitting quay and delivering bags to the beach, removing the air, cleaning and storage.

This technology can greatly simplify the launching and reduce the cost of hull repair. 

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Picture 3 –Ship launch.

7 The buoyancy of pneumatic bags

 If necessary, the airbags can be used to transfer the buoyancy to different objects or to reduce the draft of the vessel, when passing shallow depth areas. The air designed for  giving the buoyancy are equipped ​​with additional fixtures ( eyelets ) for fixing to an object. The number of bags and their certain dimensions is evaluated according to the volume of AB. 

Table 3 - Volume of air bags

AB- Length , m
Design volume of air - bag, m3
Diameter of the bags, m

0,8

1,0

1,2

1,4

1,6

1,8

2,0

5

2,8

4,6

6,6

9,5

12,7

15,7

19,4

6

3,3

5,4

7,8

11,0

14,7

18,3

22,5

7

3,8

6,2

8,9

12,6

16,7

20,8

25,7

8

4,3

7,0

10,0

14,1

18,7

23,4

28,8

9

4,8

7,8

11,2

15,7

20,7

25,9

31,9

10

5,3

8,5

12,3

17,2

22,8

28,5

35,1

11

5,8

9,3

13,4

18,8

24,8

31,0

38,1

12

6,3

10,1

14,6

20,3

26,8

33,5

41,4

13

6,8

10,9

15,7

21,9

28,8

36,1

44,6

14

7,3

11,7

16,8

22,4

30,8

38,6

47,7

15

7,8

12,5

17,9

24,0

32,8

41,2

50,8

16

8,3

13,2

19,1

25,5

34,8

43,7

53,9

17

8,9

14,0

20,2

27,1

36,8

46,3

57,1

18

9,4

14,8

21,3

28,6

38,8

48,8

60,2

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Picture 4 – Air bags used for giving the buoyancy

If the air bags are used to lift objects from great depths, the water pressure is to be taken into account.

 8 Repair of airbag 

During the air bag operation small mechanical damages can be occurred. Hot curing is one of the most effective ways to repair pneumatic bag. Hot curing must be as close as possible to producing process, the strength of the joint is ≈ 95 % of the strength of the bag.

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Picture 5 – AB-repair.

 

Repair process:

8.1 Thoroughly clean the inside and outside of the bag of dirt and oils.

8.2 Mark the repair. The patch must have multiple layers depending on the number of bag plies and lesion size (2-6 layers). For example, the repair of damage to a length of 50 mm and 100x50 mm perimeter, number of layers 4-6. 

8.3 . Sand abrasive wheel or sandpaper place where there will be a patch, then blow compressed air, so as not to leave any abrasive particles.

8.4. Apply special adhesive patches on each layer (Fig .5) . 

8.5 . At the time of bonding layers of the patch should be laid in accordance with Figure5.

8.6 . Vulcanization process: Arrangement of elements should be as shown in Figure 6 while using a special clamp. Vulcanizing process occurs by local heating to 135 ± 15 ° C and the pressure in load 0,8 - 1,2 kg / cm2 , in place of air leakage, for 40-50 minutes.

8.7. After repair control of the product:

After the vulcanization the product must wait 1 hour. Then the visual inspection, which should confirm the quality vulcanization patch, must be carried out. After these procedures, you must inflate the bag up to the maximum operating pressure and check the repaired place.

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Picture 6 - Vulcanization.

9 Transportation and Storage 

10.1 The bags can be transported by all means of transport in accordance with transportation rules of goods, obtained on this mean of transport. Air bags should not be subjected to mechanical damage. 

10.2 The Bags must be stored in a closed dark room with an ambient temperature from minus 50 to plus 50 ° C and humidity less than 80% at a distance of not less than 2 meters from the heat sources. Storage of bags in several tiers is prohibited.

10.3 Air bags in storage must be protected from direct sunlight and from contamination of fuels and lubricants, acids, alkalis and other chemicals, which can damage the rubber.  

10.4 The pressure to the air bags is prohibited. The possibility of contact of sharp objects that may cause leakage is not allowed.

10.5 Storage of rubber bag under pressure is not allowed.

10.6 In winter it is not allowed to park the bags on the water. 10 Operation guidelines Operation of air bags is carried out according to the set of operational documents for air bags.

11 Manufacturer's warranty 

The manufacturer guarantees the air bag AB requirements of technical documentation in compliance with the consumer operating conditions, transportation and storage . 

The warranty period of 12 months, subject to the requirements of the user instruction manual for pneumatic bag.

Expected useful life, subject to consumer usage and storage is 5 years.

Warranty period of pneumatic bag for 3 years from the date of purchase. 

On the use and purchase of products call

Phone/Fax: (3812) 55-00-18, 51-40-50, 51-41-11, 27-23-23,

Phone. mob.: 8-913-9614554 or refer to address:

644036, Russia, Omsk, 1-Kazakhstanskaya Str., 30,

LLC “NPP “Sibrezinotekhnika”, Omsk

 

Websites in internet

www.srti.ru

www.sibrt.com

e-mail:

sibrezina@mail.ru