Developing efficient marine fender solutions

Introduction

As vessels have grown larger and more diverse, so have the demands on fenders. A century ago, timber (first generation) was cheap and worked adequately for the small vessels of the day. Old tyres (second generation) were abundant and softer but required expensive maintenance and absorbed little energy. Cylindricals (third generation) were the first purpose designed fenders, gaining popularity over 50 years ago, but inefficient use of rubber and low performance by today’s standards makes them costly. Arch and simple buckling fenders (fourth generation) had better performance and integrated the rubber with steel fixing plates. Today, marine fenders have evolved to a fifth generation thanks to improved design, engineering expertise and advanced manufacturing capability. Marine facilities no longer need to ‘make do’ as the development of highly sophisticated computerdesigned fenders is helping ports to make certain that both safety and efficiency are maximised.

Solutions per specification

Bringing a vessel into berth requires the vessel’s kinetic energy to be absorbed or dissipated in order to prevent structural or vessel damage. The design and manufacture of fenders suitable for protecting modern ports and terminals, diverse vessels and high value cargo require a great deal of expertise and design engineering in order to optimise significant investment made, reduce downtime and maintenance needs as well as maximising the fender’s lifecycle.

Fender systems are mission critical equipment and should be designed and engineered according to the functional and operational requirements of the specific project, as well as site conditions, environment and other design criteria such as local standards, desired service life, maintenance cost and frequency. Suppliers should be fully engaged, not only in specification and design, but long after this stage, into the development of maintenance plans and audits for the equipment provided. Indeed, with a growing demand for offshore developments, as well as increasingly complex demands on onshore ports and terminals, it’s becoming increasingly important that developments are considered holistically from the conceptual engineering stage.

Tailored solutions

There’s really no such thing as an ‘off-the-shelf ’ solution. As ports look to upgrade infrastructure to accommodate the demands placed on them, we’re finding that people are increasingly looking for full service solutions, so the need for in-house design, engineering expertise and manufacturing is growing. With projects requiring in-depth engineering and application know-how and total fender solutions, we’re also seeing more of a requirement to get involved in the design of accessory products that are complementary to the core fender system.

As an example, consider the growing market for floating storage and floating storage and regasification units (FSRU) and floating liquefied natural gas (FLNG) projects – it is critical that a short-term attitude, with low-cost procurement in mind and lifecycle maintenance planning of secondary importance, does not take hold. Safety and reliability over a long and arduous working life must be the key drivers. ‘Off-the-shelf ’ solutions are not an option, as a customised maintenance package is required to minimise whole-life project costs. Maintenance is a core element in the achievement of optimised product performance and if maintenance costs are factored in to begin with, this will translate into long-term cost savings. It’s now almost a case of reverse-engineering attitudes to ensure that increasingly complex onshore solutions are considered as holistically as offshore developments.

Compound considerations in rubber fenders

A variety of factors influence the specification of a fender system, such as local marine environment, exposure of harbour basins, class and configuration of vessels expected to berth against them, the speed and direction of vessel approach and the type of berthing structure.

There are a myriad of different types of rubber fenders and whilst it’s relatively straightforward to identify their potential applications, what is more complex is determining the rubber compound and compound mixture required to absorb the kinetic energy the fenders will be required to accommodate. The performance characteristics of the fender very much depend on the manufacturing process: compound formulation, the mixing of these rubber compounds, embedded steel surface preparation and building of the fender itself, through extrusion, wrapping or moulding. Correction factors applied to fenders are also determined, not only by a fender’s geometry, but the rubber grade and compound used. So specifiers must have an understanding of the ways in which rubber type and grade affect performance.

The service life of a fender depends on the mechanical and physical properties of the rubber compound – usually, the higher the properties, the longer the service life. For example, it is accepted and proven that rubber compounds with a higher percentage of recycled rubber have lower mechanical properties than compounds made with virgin rubber.

Considering fender types

Again, all these principles mean that fender solutions must be determined on a project by project basis to optimise performance over the entire product lifecycle. However, broadly speaking, there are certain applications that particular fender types lend themselves to.

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Richard Hepworth, president, Trelleborg Marine Systems
Edition: Edition 57

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