Crane’s structure often persist longer than its parts.
It’s subject to LOAD CYCLES, or phenomenon of structure effort. Each crane, in its planning phase, is designed to resist a maximal number of lifting cycles, after which the capacity isn’t longer ensured. In fact, with the succession of lifting cycles, may arise phenomenon of effort in the structural components. This means that over time will generate small cracks on the material, also not visible to the naked eye, that at each cycle will amplify, eventually leading to breakage of the structural component, with all the damage and dangers that may result.
Beyond the tenth year placing on the market of the device, the manufacturer is no longer responsible of the product (D.Lgs. 206/2005 art. 106). Therefore it’s necessary to appeal at the employablevalutation of the machine and perform to the CALCULATIONS OF RESIDUAL LIFE, defining, according to the class of the project and the real cycles of use, the number of cycles that the device can still perform safely.
Beyond the twentieth year placing on the market of the device, instead isn’t enough perform the calculation of residual life, but you must perform a a further investigation, or a structural inspection purposed at identifying possible defects or anomalies mainly due to phenomena of structural efforts.