Two Tips for Maximizing the Useful Life of Marine Fenders
Just like energy calculations, no matter how bad some fenders may be, they seem to give adequate enough service for the marketplace. However, the long-term quality of mass-produced fenders looks destined not to improve. Good design can significantly increase the percentage of potential useful life that marine fenders actually achieve.
Tip 1: Proper Rubber Specification
The ultimate useful life potential of any rubber product is controlled by its chemistry. Aging and ozone resistance of the rubber, from which fenders elements are molded, are two of the most important criteria that determine useful life potential. Most fender specifications don’t specify rubber ozone resistance at all, and many specify an acceptable aging resistance that is considerably lower than it could be for maybe one per cent higher cost.
Tip 2: Eliminate or Minimize the Possibility of Fender “Hooking”
Other than proper rubber specification, the most effective strategy to ensure the long life of rubber fender elements is to design fender installations that eliminate or dramatically minimize the possibility of fender ‘hooking’, which the specifying engineer has total control over.
‘Hooking’ of fender panels can be subdivided into failures. Simultaneous with inadequate tending of mooring lines. This can be caused by either large water level variations or, more commonly, by large draft changes (usually in dry or liquid bulk berths). Basically, when a vessel is moored tightly against a plastic-faced panel, with the vessel deck either below or only slightly above the elevation of the mooring bollard, the vessel subsequently moves downward without the mooring lines being adjusted adequately. This results in dragging the vessel hard against the fender panel, eventually locking the panel to the hull. Beyond this point, further downward movement of the vessel results in breakage of chain anchors, chains or brackets and finally the rubber element.
Mooring lines passing under a fender position (under the water’s surface, where they cannot be observed), when first attaching to a cleat or bollard, cause the lines to rise up under the fender when the line is winched in, after the vessel has been berthed against the fender in question and nobody is around to observe. The resultant, severe upward stretching of the fender can result in breakage of chain anchors, chains or brackets and finally the rubber element.