Si tratta di un tubo verticale, montato sulle piattaforme

The tube 4 will be referred to below as an I tube, the conventional name for a vertical, platform-mounted tube for receiving the riser. Its lower end carries a fixed flange 6 used to couple to the bend stiffener assembly 2 . There are other types of tube used to receive risers. In particular where the riser is not vertical where it enters the tube, a so-called “J” tube can be used to accommodate the riser inclination. The I tube of this embodiment is a substantial metal component. As hereinbefore explained it may be mounted at large sub-sea depth and may in practice be subject to marine fouling, as well as significant manufacturing tolerances in its dimensions.