No matter how good the marine fenders unit might be, the whole integrity of a fender system is compromised by poor quality and/or badly designed accessories. This trend has reached dangerous levels with inadequate or weak specifications and pressures to cut prices.
Tip 1. Inadequate paint and corrosion allowances mean high maintenance and early replacement.
No paint lasts forever; 10-15 years being typical. After this, the steel will corrode and weaken unless corrosion allowances are added. If corrosion allowances are not specified, they will invariably be ignored and the life expectancy of the panel will be drastically reduced. For cold water climates, a corrosion allowance of 3mm per exposed face might be suitable, much more where temperatures are higher and corrosion is greater.
Tip 2. Internal construction of a large panel with deep channel section reinforcement (before welding).
Frontal Panels of a fender system need to resist combinations of bending, shear and local buckling. There are many ‘limit state’ design codes (BS5950, etc) and finite element software packages able to determine these loads and stresses, but very often unqualified persons use simplistic methods or even guesswork that lead to dangerously weak and under-designed fabrications.
Tip 3. Cost cutting and ignorance of design codes often leads to serious fender accidents.
Nobody can afford to buy the cheapest. If price becomes the sole purchasing criterion, then it is the end user who ultimately loses. He takes risks with the health and safety of staff, and risks accidents and damage to ships and structures. He also risks the high ongoing costs of maintenance and early replacement of the fenders. The only solution is better specifications and measures to ensure that these are adhered to.
Tip 4. Corrosion of chains and accessories are a principle cause of early fender failure.
Any fender system is only as good as the weakest component. Calculations for loads should be presented, and fixings selected accordingly. Chains are always a maintenance item and this should be considered in the specifications. Galvanising may last around five years, after which loss of diameter quickly weakens the links. Routine maintenance means chains should be easily and inexpensively replaceable, whilst permanently embedded items, like anchors, must last the life of the fender system.
Tip 5. Thin panels cannot resist bending, shear or local buckling.
International Navigation Association (PIANC) recommends 12mm as the absolute minimum when exposed to seawater on both faces, 10mm for exposure to one face and 8mm for internal sections not exposed to corrosion. This means a frontal panel of fender system should be a bare minimum of 160-180mm thick if standard internal steel channels are used to stiffen it. Bigger systems often need panels 250-400mm thick.
Tip 6. Computer modelling can be used to predict fender performance before expensive mistakes are made.
Tip 7. Testing of materials and rubber fenders ensures quality standards are maintained.
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