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Selecting the right ship-to-ship (STS) pneumatic fenders requires evaluating vessel size, berthing energy, fender dimensions, inflation pressure, and operating conditions. The selected fenders must provide sufficient energy absorption while keeping reaction forces within acceptable limits for both vessels.
Pneumatic fenders are widely used in ship-to-ship transfer operations because their floating construction helps accommodate relative vessel movements during berthing and cargo transfer.
This guide explains how to select suitable ship-to-ship fenders, compare net-type and sling-type designs, determine fender size and pressure ratings, and evaluate fender arrangement, inspection, and safety requirements.
Two common types of pneumatic fenders for ship-to-ship (STS) transfer are net-type and sling-type fenders. Both are designed to absorb berthing energy and protect vessel hulls, but their external protection and handling arrangements differ.
Net-type pneumatic fenders feature a protective net, commonly made from chains and tires, surrounding the reinforced rubber body.
The external net helps protect the fender against abrasion and mechanical wear during vessel contact. Net-type fenders are often considered for demanding STS operations where additional external protection is required.
Sling-type pneumatic fenders have no external protective net. Instead, they use designated lifting and suspension arrangements for installation and handling.
Their net-free design avoids direct contact between protective chains or tires and the vessel hull. Sling-type fenders may be preferred where contact surface requirements, handling arrangements, or operational conditions make a protective net unsuitable.
Selection Factor | Net-Type Fender | Sling-Type Fender |
|---|---|---|
External Protection | Chain-and-tire or other specified protective net | No external protective net |
Hull Contact | Protective net and associated rubber components | Rubber fender body |
Handling Requirements | Net weight and lifting arrangements must be considered | Suspension and lifting arrangements must be considered |
Abrasion Protection | Additional protection provided by the external net | Depends primarily on rubber construction and contact conditions |
Maintenance Focus | Net, chains, tires, fittings, and rubber body | Rubber body, slings, and end fittings |
Selection Priority | Applications requiring additional external protection | Applications where net-free contact is preferred |
Which Type Should You Choose?
The choice between net-type and sling-type pneumatic fenders depends on vessel contact conditions, handling requirements, expected abrasion, and project specifications.
Regardless of fender type, the selected size and inflation pressure must provide sufficient energy absorption while maintaining acceptable reaction forces for both vessels.
Berthing energy is the energy that a fender system must absorb when two vessels come into contact during a ship-to-ship (STS) operation. Estimating this energy is a critical step in selecting suitable ship-to-ship pneumatic fenders.
Berthing energy depends on the vessels' displacement, relative approach velocity, contact geometry, and operating conditions.
The basic kinetic energy equation is:
E = 0.5 × m × v²
Where:
E: Kinetic energy (J)
m: Mass (kg)
v: Velocity (m/s)
However, this equation alone does not determine the final design berthing energy for an STS operation.
A complete assessment must consider the relative movement of both vessels, added mass effects, eccentric contact, approach angle, and other applicable correction factors.
Because berthing energy increases with the square of velocity, changes in approach speed can significantly affect the required fender capacity.
The final design energy should be calculated using an appropriate marine engineering method and the specific STS operating conditions.
Guaranteed Energy Absorption (GEA) is a key performance parameter used to evaluate pneumatic fender capacity. It represents the minimum specified energy absorption under defined testing conditions and is typically expressed in kilojoules (kJ) or kilonewton-metres (kNm).
When selecting pneumatic fenders for STS transfer, the available energy absorption capacity should be compared with the calculated design berthing energy, including applicable project safety allowances.
Reaction Force (RF) must also be considered. A suitable fender arrangement should absorb the required energy without exceeding the acceptable structural loads on either vessel.
Manufacturers provide performance data for different fender sizes and initial inflation pressures. For detailed dimensions and performance comparisons, refer to our Pneumatic Fender Size Chart.
The final fender selection should be verified against the actual STS operating conditions and approved engineering requirements.
Selecting the appropriate ship-to-ship pneumatic fender size requires balancing energy absorption, reaction force, vessel separation, and handling conditions.
The fender should have sufficient capacity to absorb the calculated berthing energy without creating excessive contact loads or unnecessary separation between the vessels.
Pneumatic fender dimensions are expressed as diameter × length (D × L). Both dimensions influence fender performance and its suitability for a particular STS operation.
Fender Diameter: Influences the fender's compression behavior, energy absorption capacity, and separation distance between vessels.
Fender Length: Affects the available contact area, load distribution, and positioning along the vessel hull.
Vessel Compatibility: Fender dimensions should be evaluated against hull geometry, freeboard differences, and expected vessel movements.
Handling Requirements: Larger fenders may require additional lifting equipment, deck space, and installation planning.
Choosing the largest available fender is not always the best solution. Excessive fender diameter may create unnecessary vessel separation, while an unsuitable length or arrangement can affect contact conditions.
For detailed dimensions and performance data, refer to our Pneumatic Fender Size Chart.
High-pressure pneumatic fenders are commonly available with 50 kPa and 80 kPa initial inflation pressure ratings.
Selection Factor | 50 kPa Fender | 80 kPa Fender |
|---|---|---|
Initial Inflation Pressure | 50 kPa | 80 kPa |
Energy Absorption | Lower for the same nominal size | Generally higher for the same nominal size |
Reaction Force | Generally lower | Generally higher |
Selection Consideration | Projects where the rated capacity meets energy and hull-loading requirements | Projects requiring greater capacity within a given size, subject to reaction-force limits |
The appropriate inflation pressure should be selected by comparing Guaranteed Energy Absorption (GEA) and Reaction Force (RF) at the specified operating conditions.
A higher inflation pressure does not automatically make a fender more suitable. The final configuration must satisfy the required energy absorption capacity while keeping contact loads acceptable for both vessels.
A suitable ship-to-ship fender system requires more than selecting the correct pneumatic fender size. The number, positioning, and arrangement of fenders are also important for managing contact between two vessels during berthing and cargo transfer operations.
STS fender arrangements typically include primary fenders, with secondary fenders considered where additional protection is required.
Primary Fenders
Primary fenders are the main energy-absorbing units positioned between the vessels. They are selected to accommodate the expected berthing loads while maintaining suitable separation between the hulls.
Secondary Fenders
Secondary fenders provide supplementary protection at locations where vessel contact may occur outside the primary fender arrangement. Their use depends on vessel geometry, relative movements, and the planned transfer operation.
Secondary fenders should not be treated as substitutes for an adequately designed primary fender system.
The required number of STS pneumatic fenders depends on several factors:
Vessel Dimensions: Length, beam, freeboard, and hull geometry of both vessels.
Berthing Energy: Expected impact energy and the rated performance of the primary fenders.
Relative Vessel Movements: Changes in draft, trim, freeboard, and vessel position during transfer.
Contact Areas: Locations where the vessels may come into contact during approach and alongside operations.
Operating Conditions: Sea state, wind, current, and the planned STS operating arrangement.
There is no single fender quantity suitable for every ship-to-ship transfer. The final number and configuration should be determined through a project-specific STS fender assessment.
STS pneumatic fenders should be positioned to protect the expected contact areas between the two vessels.
The arrangement should consider vessel parallel body geometry, relative freeboard differences, cargo manifold access, and anticipated movements during the transfer.
Fender diameter also affects the separation distance between the vessels. Excessive separation can complicate transfer arrangements, while insufficient clearance may increase the risk of unintended hull contact.
Before operations begin, the fender layout, suspension arrangements, and positioning should be checked against the approved STS transfer plan and applicable operating guidance.
The quality of ship-to-ship pneumatic fenders affects their pressure retention, durability, and performance during marine transfer operations. In addition to selecting the correct size and arrangement, buyers should evaluate fender construction, applicable standards, and supporting test documentation.
When evaluating pneumatic fenders for STS operations, consider the following factors:
Outer Rubber: Should provide suitable resistance to abrasion, weathering, and marine environmental exposure.
Synthetic-Tyre-Cord Reinforcement: Helps maintain structural integrity, pressure resistance, and fatigue performance during repeated compression.
Inner Rubber: Provides an airtight barrier to help maintain the specified inflation pressure.
End Fittings and Connections: Flanges, valves, and lifting arrangements should be compatible with the fender design and operational requirements.
Manufacturing Quality: Consistent construction and verified material properties help support reliable fender performance.
Material specifications and manufacturing quality should be assessed using appropriate product documentation and test reports rather than appearance alone.
ISO 17357-1:2014 specifies requirements for high-pressure floating pneumatic rubber fenders, including materials, construction, performance, and testing.
When purchasing STS pneumatic fenders, buyers should request documentation appropriate to the selected product and project requirements.
Document / Information | Purpose |
|---|---|
Product Technical Datasheet | Confirms fender dimensions, type, and inflation pressure |
GEA and RF Performance Data | Supports berthing energy and reaction force evaluation |
Material Test Reports | Provides evidence of specified rubber and reinforcement properties |
Prototype Test Documentation | Supports verification of fender design performance |
Production Inspection Reports | Records applicable dimensional, airtightness, and other acceptance tests |
Third-Party Inspection Reports (if required) | Provides independent verification within an agreed inspection scope |
Third-party inspection may be arranged through recognized organizations such as CCS, BV, ABS, or DNV, depending on the project requirements.
However, compliance with ISO 17357 should not be confused with third-party certification or classification society type approval. The scope and validity of each document should be verified before procurement.
For detailed material requirements and testing procedures, read our ISO 17357 Pneumatic Fender Standard Guide.
Proper installation and inspection are essential for ship-to-ship pneumatic fenders to perform as intended during berthing and cargo transfer operations. Fender positioning, inflation pressure, attachment hardware, and surface condition should be checked before use.
Before starting an STS operation, the fender arrangement should be verified against the approved transfer plan and the operating conditions of both vessels.
Inspection Item | What to Check |
|---|---|
Fender Positioning | Confirm that primary and secondary fenders are positioned according to the approved STS arrangement. |
Inflation Pressure | Verify the specified initial inflation pressure using suitable measuring equipment. |
Rubber Surface | Inspect for cuts, cracks, excessive abrasion, deformation, or visible damage. |
Protective Net or Slings | Check for wear, broken components, and damage to the protective or lifting arrangements. |
Chains and Shackles | Inspect connection hardware for corrosion, deformation, wear, and secure attachment. |
Valves and Air Leakage | Check valve condition and investigate any signs of pressure loss or leakage. |
Vessel Clearance | Verify fender contact areas, vessel separation, and potential interference with transfer equipment. |
Any fender showing significant damage, abnormal pressure loss, or defective attachment components should be assessed before use.
Pneumatic fenders should be inspected and maintained according to the manufacturer's instructions and the vessel operator's maintenance procedures.
Routine maintenance includes:
Pressure Monitoring: Check internal inflation pressure and investigate unexpected pressure loss.
Surface Inspection: Examine rubber surfaces for abrasion, cracking, cuts, and abnormal deformation.
Connection Inspection: Check nets, chains, slings, shackles, and other fittings for deterioration.
Valve Maintenance: Inspect inflation valves and seals for leakage or damage.
Maintenance Records: Record inspection findings, repairs, pressure checks, and component replacements.
Inspection frequency should reflect the fender's operating conditions, transfer frequency, storage environment, and manufacturer's recommendations.
Damaged or deteriorated components should be repaired or replaced using compatible parts and approved maintenance procedures before the fender is returned to service.
Ship-to-ship (STS) fenders are used to absorb contact energy and help protect vessel hulls during berthing and cargo transfer operations between two vessels. Pneumatic fenders are commonly used because their floating design can accommodate relative vessel movements.
Start by evaluating vessel displacement, relative approach velocity, berthing energy, and operating conditions. Compare the required energy absorption with manufacturer GEA and reaction force data, then assess fender dimensions, pressure ratings, and vessel separation requirements.
The number of pneumatic fenders depends on vessel dimensions, expected contact areas, relative movements, berthing conditions, and the approved fender arrangement.
Primary fenders provide the main energy absorption, while secondary fenders may be included for additional protection. The final quantity should be determined through a project-specific STS assessment.
A pneumatic fender rated at 80 kPa generally provides higher energy absorption and reaction force than a corresponding 50 kPa fender of the same nominal size.
The appropriate rating depends on the required berthing energy, allowable hull loads, and operating conditions. Higher pressure is not automatically the better choice.
Before an STS operation, inspect fender positioning, inflation pressure, rubber surface condition, protective nets or slings, valves, chains, shackles, and suspension arrangements.
Any damage, abnormal pressure loss, or defective connection should be evaluated before use according to the approved STS operating procedures.
Selecting the right ship-to-ship pneumatic fenders requires careful evaluation of berthing energy, vessel dimensions, fender size, inflation pressure, and arrangement. A suitable fender system should provide adequate energy absorption while maintaining acceptable reaction forces and vessel separation.
In addition to performance specifications, buyers should consider material quality, ISO 17357 requirements, inspection documentation, and installation conditions before finalizing their selection.
Hongruntong Marine offers pneumatic fender solutions for STS transfer operations, with size and configuration options based on project requirements.
Explore our Pneumatic Fender Products or contact our team with your vessel details, berthing conditions, and technical specifications to request a suitable solution and quotation.
