Recently, the Ship Repair Operation Department of CSSC Chengxi Shipyard Co., Ltd., a subsidiary of China State Shipbuilding Corporation (CSSC), has successfully won the projects of bulbous bow modification for 2 container ships and special painting and installation of desulphurization towers for a number of chemical tankers.
The main function of the bulbous bow is to change the pressure difference distribution of the fluid by changing the movement direction of the incoming flow from the bow, so as to reduce the wave resistance of the whole ship and achieve energy-saving effect of the ship under the economic speed.
In recent years, shipping enterprises have generally started to reduce the speed of container ships. Under low-speed conditions, changing the bowline shape of the ship by doing “nose surgery” can further adapt and optimize the hydrodynamic performance under the new speed, improve the ship’s propulsion efficiency, reduce fuel consumption, and achieve the purpose of reducing operating costs.
It is understood that there are three main difficulties in the retrofitting of bulbous bow: first, tight cycle.Ships to be repaired often have the problem of not being able to provide integrity information of the original ship, which leads to a large deviation in the accuracy of the old and new structures closing and increases the time of repairing in the dock.
Secondly, easily deformed. In the retrofitting of bulbous bow, the original bow retains a long overhanging section, which is susceptible to sagging and deformation under the influence of gravity.
Thirdly, difficulties in installation. The new bulbous bow is generally installed in two ways, namely, segment by segment and total segment as a whole. The former requires a large number of auxiliary scaffolding platforms and towing equipment, and has to be loaded in a sequential manner. The latter can be installed at one time because the segments have been pre-formed into the total segment, but it cannot be installed by conventional lifting method due to the weight and size limitation.
Previously, CSSC Chengxi Shipyard has accumulated relevant experience in bulbous bow modification. Under the situation of reduced resources in ship repair industry this year, the output value of ship repair orders received by Ship Repair Operation Department in the first quarter increased by nearly 12% year-on-year, exceeding the schedule by more than 7%, injecting strong kinetic energy for realizing the annual target tasks.