Views: 325 Author: NANJING TAIDUN Publish Time: 2026-09-22 Origin: Site
Content Menu
● What Are Ship Launching Airbags and How Do They Work?
● Understanding the ISO Standards: What Every Buyer Must Know
>> ISO 14409:2011 – The Product Standard
>> ISO 17682:2013 – The Operational Standard
>> Why Standards Matter for OEM Partners
● How to Calculate the Required Number of Airbags: A Technical Guide
>> The ISO Calculation Formula
>> Practical Rule: Always Prepare Spares
Marine airbags for ship launching are cylindrical, inflatable devices constructed from multiple layers of synthetic rubber reinforced with high-tensile cord fabric. When placed under a vessel's hull and inflated, they function as rolling cushions that support the ship's weight while enabling controlled movement toward the water.
The physics of airbag launching is elegant in its simplicity:
- Load Bearing: Inflated airbags support the entire vessel weight, distributing it evenly along the hull to minimize structural stress
- Rolling Motion: The airbags function as cylindrical rollers, converting what would be sliding friction into rolling friction—dramatically reducing the force required to move the vessel
- Impact Absorption: The pneumatic cushion absorbs dynamic shocks during movement, protecting both hull and equipment
The rolling friction mechanism differs fundamentally from solid-body rolling. Research shows that bending moments in the airbag shell constitute the primary resistance component during rolling—a unique characteristic that makes airbag launching both controllable and predictable.
Per ISO 14409:2011, ship launching airbags consist of three primary components:
| Component | Description |
|---|---|
| Body | Cylindrical main section providing lifting capability when pressurized |
| End Connections | Conical pieces connecting body to fittings |
| Valves | Metal valves at both ends for inflation; one includes pressure gauge |
Materials: Synthetic tyre cord reinforcement layers vulcanized with inner and outer rubber layers. Layer count typically ranges from 3 to 10, depending on required load capacity.
The ship launching airbag industry operates under a well-established international standards framework. Understanding these standards is essential for OEM partners evaluating supplier compliance.
This international standard specifies requirements for designing, manufacturing, testing, and accepting air bags used for vessel launching. Key provisions include:
Classification: Type and model designation based on diameter and construction
Materials and Dimensions: Rubber compound specifications, cord reinforcement, dimensional tolerances
Testing Requirements:
- Gastightness test
- Compression test
- Bearing capacity test
- Bursting test
- Compression-recovery test
Documentation: Marking, packaging, transport, and storage requirements
While ISO 14409 defines what airbags *are*, ISO 17682 defines how they should be *used*. This methodology standard covers:
- Airbag selection and arrangement
- Ship launching procedures
- Safety safeguards and contingency planning
China's GB/T 41888-2022 is the identical adoption (IDT) of ISO 17682:2013, providing a unified national standard for shipyards in the world's largest shipbuilding nation.
When sourcing ship launching airbags for international markets, ISO compliance documentation provides assurance that:
- Product construction meets internationally recognized specifications
- Testing protocols follow standardized methods
- Performance data is comparable across suppliers
One of the most critical aspects of planning an airbag launching operation is determining the correct quantity and spacing of airbags. This calculation directly affects safety, equipment utilization, and operational cost.
According to ISO standards and shipbuilding industry practice, the required number of airbags is calculated using this formula:
N = K₁ × (Q × g) / (Cb × R × Ld)
Where:
- N = Number of airbags required
- K₁ = Safety coefficient (generally ≥ 1.2)
- Q = Vessel weight (tonnes)
- g = Gravitational acceleration (9.8 m/s⊃2;)
- Cb = Block coefficient of the vessel
- R = Allowable bearing capacity per meter of airbag (kN/m)
- Ld = Contact length between vessel bottom and airbag at midship (m)
The center-to-center distance between adjacent airbags must satisfy two constraints:
Maximum spacing: L / (N − 1) ≤ 6k
- Where k = 1.0 for steel vessels, k = 0.8 for wood/aluminum/FRP vessels
Minimum spacing: L / (N − 1) ≥ πDv/2 + 0.3
- Where Dv = nominal airbag diameter (m)
Industry best practice requires 2 to 4 additional airbags prepared as standby for ship movement operations. These spares address:
- Unexpected pressure loss
- Position adjustments during rolling
- Emergency replacement needs
A 330-foot barge with 3,655.2 tonnes light weight, using 1.8m × 12m airbags at 0.11 MPa working pressure (rated 138.22 kN/m bearing capacity), requires 18 airbags with spacing between 6.66 and 11.78 meters.
Not all airbags are suitable for every project. OEM partners and shipyards should evaluate the following factors.
| Vessel Size | Recommended Airbag Diameter | Typical Layer Count |
|---|---|---|
| Under 1,000 DWT | 0.8–1.2 m | 3–4 layers |
| 1,000–5,000 DWT | 1.2–1.5 m | 4–6 layers |
| 5,000–20,000 DWT | 1.5–1.8 m | 6–8 layers |
| Over 20,000 DWT | 1.8–2.5 m | 8–10 layers |
Key selection principle: Airbag height when deflated must exceed keel block height to enable proper positioning.
Always apply a safety factor of 1.5–2.0 over the calculated vessel weight. This margin accounts for:
- Dynamic loads during rolling
- Uneven weight distribution
- Ground surface irregularities
Wear resistance matters more than maximum pressure capacity according to experienced shipyard operators. Key quality indicators:
- Outer rubber thickness and abrasion resistance
- Cord layer integrity (no bulging after repeated use)
- End fitting durability
| Condition | Recommended Feature |
|---|---|
| Rough/abrasive ground | Enhanced abrasion-resistant outer layer |
| Cold climates | Low-temperature resistant compound |
| Saltwater exposure | Corrosion-resistant valve materials |
| Frequent use | Higher layer count for durability |
A successful airbag launching requires disciplined execution of a well-defined procedure. The following steps reflect ISO 17682 methodology and established industry practice.
Site Preparation:
- Clean the launch path; remove all sharp objects, debris, and rocks
- Verify ground bearing capacity
- Establish safety perimeter
Airbag Inspection (conduct before positioning):
- Check each airbag for surface damage, cracks, or valve issues
- Verify pressure gauge calibration
- Reject any airbag with visible defects
Arrangement Principles:
1. Position airbags perpendicular to vessel centerline
2. Space according to calculation (minimum 0.8m between inflated airbags)
3. Use appropriate layout based on vessel width:
- Single row: Airbag length > vessel beam
- Cross-over: Airbag length > half beam but < full beam
- Two rows: Airbag length < half beam
Practical Note: New airbags should be positioned preferentially near bow and stern sections where loads are highest.
Sequential Inflation Protocol:
| Stage | Target Pressure | Check Point |
|---|---|---|
| 1st | 0.05 MPa | Verify alignment and block clearance |
| 2nd | 0.10 MPa | Check hull movement and airbag compression |
| 3rd | 0.15–0.18 MPa (stern to midship) | Confirm vessel is lifted; remove keel blocks |
| Final | 0.13–0.15 MPa (bow section) | Maintain even support |
Critical Safety Step: Keel blocks can only be removed after the vessel is confirmed fully lifted by airbags.
- Apply controlled pulling force via winch
- Monitor airbag pressure continuously
- Maintain vessel alignment with guide ropes
- If pressure drops, reinflate immediately to prevent stress concentration
Rolling Resistance Note: The coefficient of rolling friction varies with ground conditions—typically 0.01–0.02 for concrete ramps, slightly higher for compacted natural ground.
- Deflate airbags slowly (below 0.03 MPa before removing hoses)
- Inspect each airbag for damage
- Record condition and label any units requiring repair
- Clean, dry, and store properly for future use
Project Background: An Indonesian shipyard needed to launch a 5,800 DWT coastal cargo vessel but lacked permanent dry dock or slipway infrastructure. Building a conventional launching facility would require months of construction and significant capital investment.
Solution: 36 ship launching airbags (1.5m × 18m, working pressure 0.09 MPa) arranged under the 108m vessel hull.
Key Preparation Steps:
- Inspected all 36 airbags before positioning
- Verified inflation pressures and load distribution
- Installed guide ropes and emergency procedures
- Monitored weather conditions continuously
Results:
- Launch completed in under 2 hours
- No worker injuries
- No hull deformation or coating damage
- Cost reduction of approximately 35% compared to building permanent facilities
- Delivery schedule maintained
Client Feedback: *"This was our first project using ship launching airbags, and the launch went exactly as planned. The preparation was straightforward, the operation was smooth, and we were impressed by how stable the vessel remained throughout."*
A shipyard operator with ten years of airbag launching experience shared valuable practical insights that go beyond textbook procedures:
While cost savings drove initial adoption, the real advantage is operational flexibility:
- Adjust airbag quantity for different vessel sizes
- Work with uneven ground conditions
- No need to rebuild yard infrastructure for each project
Key quality indicators emerge quickly:
- Surface wear patterns
- Any bulging indicating weak internal layers
- End fitting stability during inflation
Most airbag failures stem from operational errors, not product defects:
- Uneven pressure during inflation
- Poor ground preparation (small stones cause punctures)
- Incorrect spacing creating concentrated loads
After repeated use, wear resistance proves more important than rated pressure capacity. Airbags that perform well initially may fail by the third use if outer rubber quality is inadequate.
Well-maintained airbags can be used up to 50 times over 10 years. This changes the economics entirely—total life cost, not purchase price, determines value.
Proper care dramatically extends ship launching airbag service life:
1. Clean surface thoroughly; remove dirt and debris
2. Inspect for cracks, deformation, or valve damage
3. Dry completely before storage
4. Apply talcum powder inside and outside
| Requirement | Specification |
|---|---|
| Location | Indoor, cool, dry, ventilated |
| Temperature | Avoid heat sources |
| Contact | No acids, alkalis, oils, solvents |
| Positioning | Lay flat; never stack heavy objects |
- Before each use: Full visual inspection
- Quarterly: Detailed surface examination
- Annually: Pressure testing and documentation review
Ship launching airbags have evolved from a niche solution to a globally accepted methodology underpinned by ISO standards. For shipyards of all sizes—and particularly for OEM partners serving international markets—they offer a combination of flexibility, cost-efficiency, and proven safety that traditional methods cannot match.
The technology has successfully launched vessels exceeding 73,000 DWT, demonstrating capability across the full spectrum of commercial and naval vessel sizes.
As NANJING TAIDUN continues to serve global OEM partners, we see growing demand for ISO-compliant, traceable, and durable ship launching airbags. The key to success lies in selecting quality products, following standardized procedures, and maintaining equipment properly.
Need ship launching airbags for your shipyard or OEM project?
Contact NANJING TAIDUN MARINE EQUIPMENT ENGINEERING CO., LTD:
- Email: service@taidunmarine.com
- Website: www.taidunmarine.com
- OEM Services: Custom specifications, ISO compliance documentation, third-party testing coordination, technical support
1. ISO. "ISO 14409:2011 – Ships and marine technology – Ship launching air bags." [https://www.din.de/en/getting-involved/standards-committees/nsmt/publications/wdc-beuth:din21:145624764/toc-1821461/download]
2. ISO. "ISO 17682:2013 – Ships and marine technology – Methodology for ship launching utilizing air bags." [https://www.din.de/en/getting-involved/standards-committees/nsmt/publications/wdc-beuth:din21:188073560/toc-2024912/download]
3. SORTA 2018 Conference Proceedings. "Determination of Airbag Number (ISO 14409)." [https://bib.irb.hr/datoteka/1011176.SORTA_2018_-_Book_of_Proceedings.pdf]
4. ISO. "ISO 14409:2011 – Overview." [https://inen.isolutions.iso.org/ru/standard/54715.html]
5. US Patent 9469957. "SLAB Air Pad Characteristics." [http://patentimages.storage.googleapis.com/4a/7a/5a/d0491b1fe22c21/US9469957.pdf]
6. Brazilian Navy Maritime Magazine. "Airbags for Ship Launching and Recovery." [https://www.marinha.mil.br/rmb/sites/www.marinha.mil.br.rmb/files/RMB%204T-2022%20completa.pdf]
7. Politeknik Batam Repository. "Analisa Perhitungan Jumlah dan Jarak Airbag." [https://repository.polibatam.ac.id/server/api/core/bitstreams/74659e3b-7a52-4e7d-b2d7-af986c7b128a/content]
8. International Shipbuilding Progress. "Rolling resistance of marine airbags at the longitudinal inclined slipway during ship launching." [https://sage.cnpereading.com/doi/10.3233/ISP-130105]
Marine airbags have been successfully used to launch vessels exceeding 73,000 DWT. However, practical limits depend on airbag specifications, ground conditions, and operational planning. For vessels above 20,000 DWT, larger diameter airbags (1.8–2.5m) with higher layer counts (8–10) are typically required.
With proper maintenance, high-quality airbags can be used up to 50 times over a 10-year period. Key factors affecting lifespan include:
- Ground surface conditions (abrasive surfaces accelerate wear)
- Operating pressure (exceeding rated pressure reduces life)
- Storage conditions (UV exposure, temperature extremes)
- Inspection and maintenance frequency
ISO 14409 defines product requirements—materials, construction, testing, marking, and documentation for ship launching airbags.
ISO 17682 defines operational methodology—how to plan and execute ship launching operations using airbags, including arrangement, procedures, and safety requirements.
Both standards work together: ISO 14409 ensures you have a compliant product; ISO 17682 ensures you use it correctly.
Use the ISO-based formula: N = K₁ × (Q × g) / (Cb × R × Ld)
You need: vessel weight (Q), block coefficient (Cb), airbag bearing capacity per meter (R), and contact length (Ld). Always add 2–4 spare airbags. For complex projects, consult with airbag manufacturers who can perform detailed calculations based on your specific vessel parameters.
Critical safety measures include:
- Never exceed rated airbag pressure
- Remove all sharp objects from launch path
- Inflate sequentially, not all at once
- Remove keel blocks only after vessel is fully lifted
- Maintain pressure monitoring throughout operation
- Keep personnel clear of airbag ends during deflation
- Have emergency deflation procedures ready
Yes. The same airbag systems used for launching can also be used for ship recovery and dry-docking operations. This dual functionality makes airbags particularly valuable for shipyards with limited infrastructure. The process is essentially reversed: airbags are positioned under the vessel, inflated to lift it, and used to roll it onto shore.
