Fenders - Best practice examples

Once the specific parameters and requirements for your project have been determined, the manufacturer starts with the manufacturing of your customized fenders.

Ensuring compliance with your requirements is done via the so-called 𝗩𝗲𝗿𝗶𝗳𝗶𝗰𝗮𝘁𝗶𝗼𝗻 𝗧𝗲𝘀𝘁𝗶𝗻𝗴 - the most relevant fender testing procedure as it confirms the performance and material quality of the product.

Verification testing consists of:

☑️ material testing
☑️ traceability
☑️ performance testing
☑️ verification of dimensions
☑️ visual checking

The first one is done on the actual rubber compound used for the production of the fender, whereas the other test procedures are performed on the final fender that has been produced for your individual project.

All of them are covered in more depth in our 𝗪𝗵𝗶𝘁𝗲 𝗣𝗮𝗽𝗲𝗿 #𝟰 ‘𝗧𝗲𝘀𝘁𝗶𝗻𝗴 – 𝗔 𝗯𝗲𝘀𝘁-𝗽𝗿𝗮𝗰𝘁𝗶𝗰𝗲 𝗮𝗽𝗽𝗿𝗼𝗮𝗰𝗵’. ⬅️ Download it from our website and Join The Safe Side.

Where the berthing analysis focuses on the kinetic energy of the vessel during berthing, the mooring analysis focuses on forces on the berthed vessel, that are due to wind, current, tension lines and others. A thorough mooring analysis can prevent the fender from damages and failure. Here is how:

The mooring analysis might reveal that load cases need to be considered that include 𝗰𝘆𝗰𝗹𝗶𝗰 𝗮𝗻𝗱 𝗰𝗼𝗻𝘀𝘁𝗮𝗻𝘁 𝗹𝗼𝗮𝗱𝘀. The main difference here is that with cyclic loads, there is an oscillation motion, whereas constant loads deflect the fender permanently until release of the vessel. Both loads could also occur simultaneously, which poses potential design challenges to the fender and its life cycle.

Examples for cyclic and constant load cases are permanent mooring situations, like
➡️ FSRU’s
➡️ floating docks
➡️ stationary vessels, like museum vessels (e.g. the barque ‘Peking’ in Hamburg)

Taking into account cyclic and constant loads during the design process, the designer needs to focus on the 𝗳𝗲𝗻𝗱𝗲𝗿’𝘀 𝗿𝗲𝗮𝗰𝘁𝗶𝗼𝗻 𝗳𝗼𝗿𝗰𝗲, to make sure that wind and other loads do not exceed the load limits of a fender. But most important, the 𝗱𝗲𝗳𝗹𝗲𝗰𝘁𝗶𝗼𝗻 𝗼𝗳 𝘁𝗵𝗲 𝗳𝗲𝗻𝗱𝗲𝗿 under cyclic and constant loads should be limited.

That could be achieved by  
☑️ a correct mooring arrangement, and/or
☑️ an oversized fender where the expected loads correspond to a 5-10% deflection of the fender.

📝 𝘍𝘦𝘯𝘥𝘦𝘳𝘴 𝘰𝘧 𝘢𝘭𝘭 𝘵𝘺𝘱𝘦𝘴, 𝘨𝘳𝘢𝘥𝘦𝘴, 𝘲𝘶𝘢𝘭𝘪𝘵𝘪𝘦𝘴, 𝘱𝘳𝘪𝘤𝘦𝘴 𝘢𝘯𝘥 𝘧𝘳𝘰𝘮 𝘢𝘭𝘭 𝘮𝘢𝘯𝘶𝘧𝘢𝘤𝘵𝘶𝘳𝘦𝘳𝘴 𝘸𝘪𝘭𝘭 𝘧𝘢𝘪𝘭 𝘪𝘧 𝘯𝘰𝘵 𝘥𝘦𝘴𝘪𝘨𝘯𝘦𝘥 𝘧𝘰𝘳 𝘤𝘺𝘤𝘭𝘪𝘤 𝘰𝘳 𝘤𝘰𝘯𝘴𝘵𝘢𝘯𝘵 𝘭𝘰𝘢𝘥𝘴 𝘣𝘶𝘵 𝘣𝘦𝘪𝘯𝘨 𝘦𝘹𝘱𝘰𝘴𝘦𝘥 𝘵𝘰 𝘴𝘶𝘤𝘩.

Fender manufacturers offer a wide range of fender types suitable for different requirements. The purpose of fenders is to 𝗮𝗯𝘀𝗼𝗿𝗯 the kinetic energy of berthing vessels 🚢, and on the other hand, to 𝘁𝗿𝗮𝗻𝘀𝗳𝗲𝗿 the reaction force via different components of the fender system onto the vessel hull and into the berth substructure. High energy absorption while having acceptable reaction forces is key to a good fender system design. However, simply calculating 📐 the berthing energy requirements results in a long list of suitable fender types and sizes.
  

❓ How to select the right fender? 

There are many other factors which need to be considered, like: vessel details (e.g. vessel type, hull pressure, beltings), berthing information (e.g. berthing mode, type of substructure, fender spacing, stand-off requirements), project conditions 🌊, preferences of the client 📝, and more. Selecting the right fender for your specific project needs a unique approach and cannot be done by an automated tool. The topic of fender selection again shows why it is beneficial to rely on 𝗽𝗲𝗿𝘀𝗼𝗻𝗮𝗹 𝗲𝘅𝗽𝗲𝗿𝘁𝗶𝘀𝗲 𝗮𝗻𝗱 𝗲𝘅𝗽𝗲𝗿𝗶𝗲𝗻𝗰𝗲.
  

Contact us 📞 📧 for a 𝗳𝗿𝗲𝗲 𝗰𝗼𝗻𝘀𝘂𝗹𝘁𝗮𝘁𝗶𝗼𝗻 – we are available already at the design stage of your project: https://bit.ly/33M08vp 

Or seeing it from another perspective, it is the percentage that a material fails to recover of its original height after being compressed. For example, a compression set for foam fenders of 20% indicates that the foam fender only regained 80% of its uncompressed diameter.
There are several 𝗿𝗲𝗮𝘀𝗼𝗻𝘀 for that:  

▶️ overloading

▶️ insufficient foam density for the application 

▶️ manufacturing method 

Fenders which are laminated with small strips of foam are more prone to that, due to the higher probability of gaps in-between the layers and potential bonding failures between layers. This can be avoided by using wide sheets of 1.5m – 2m, which is the SFT standard. 

𝗖𝗼𝗻𝘀𝗲𝗾𝘂𝗲𝗻𝗰𝗲𝘀 are simple but severe. If a foam fender’s compression set is too high, it’s diameter is smaller than before. This can lead to  

▶️ Clearance issues especially for ship-to-ship operations 

▶️ Reduced energy absorption of the fender 

▶️ Smaller deflection as the fender only recovers to a smaller amount of its original diameter 

▶️ Reduced life time, higher cost of ownership to the early replacements 

▶️ Fender is less sustainable as the foam core is permanently damaged and the fender needs to be replaced

Manufacturing and designing foam fenders requires longstanding expertise and skills – something where you can truly rely on us. We manufacture foam fenders of various sizes at our own production facility in Germany, from Ocean Guard Fenders, to Donut Fenders, to Buoys.  

Learn more about Foam Fenders

This ‘inverted’ cone fender impacts the durability and stability of the fender system and the safety at the berth. The weight of the steel panel and rubber unit of an ‘inverted’ cone fender introduces a large moment into the head section of the fender over the full stand-off distance, leading to irregular compression and more stress (see additional picture in the comment section). Even a slightly different shape of the rubber body compared to ‘standard’ cone fenders does not prevent the rubber unit from potential cracks and deformation.

Inverted fenders might be suitable when deflection and weight of the panel is guided, e.g. with Parallel Motion or Pile/Pivot Fender Systems or where several units are combined in one system, but typically not for conventional fender systems.

Cone Fenders are more stable, durable and robust, when installed with the wider flange to the substructure. ‘Inverted’ cone fender designs should be avoided and challenged, to not compromise the operation and, above all, the safety at the terminal. https://bit.ly/32bohLe

As per PIANC, if steel plates are exposed on two surfaces, the min. steel thickness is 12 mm. That would be applicable to open panel, as all plates are exposed on two surfaces. Even if the plate could structurally be thinner, a 12 mm plate for the entire system is a must.

Looking at closed box panel, here the plates are only exposed on one surface, with the advantage that these plate only need a min. thickness of 9-10 mm and inside members could even be 8 mm, as they would never be exposed. You could argue that an open panel does not need a back-plate and therefore the savings compensate for the thicker steel plates. Often, that is not the case, as the back-plate provides a lot of strength to the fender panel, i.e. you can use less or thinner (min. 8 mm) inside leading to an overall lighter panel design. Even if the closed box is heavier, which can be the case in certain design, clients’ needs to consider the maintenance aspect as well, over the typical life cycle of 15-20 years.

Open panels have a much larger surface for potential corrosion, trapped water, debris getting stuck on or behind the panel – all leading to higher maintenance and service cost. Also the rehab of such a panel is more difficult due to the larger and uneven surface area. Closed panels on the other hand, have only 4 exposed surfaces, which are even, easy to access and easy to clean, sandblast and coat during life extending full scale maintenance works.

If you are unsure which way to go, check with the SFT Group to get a comparison and recommendation of the way forward for your particular project: