As reported in OSJ on a number of occasions, using fibre rope rather than conventional steel wire can help cranes lift heavier loads and deploy them to greater depths. This is because, unlike conventional steel wire, fibre rope is neutrally buoyant in water. Because it weighs so much, steel wire significantly reduces hook capacity as more and more wire is paid out to reach greater depths. A number of companies have developed hybrid concepts that make use of steel wire and fibre rope, including NOV, which unveiled a fibre rope extension system (FRES) back in 2009. The FRES was a portable, self-contained containerised fibre rope storage system with specially designed hang-ofF sheaves with locks attached to the end of the crane jib. The system inserted fibre rope in sections of about 1,000m into the wire carrying a load. It was an elegant solution, but National Oilwell Varco (NOV) has taken the concept an important step further and developed a completely new type of crane that is designed to use fibre rope alone (although the new crane can also use steel wire if required).
展开▼
