Davits on the Ijsselmeer
Davits are special jib cranes with inclinable cantilever arms mostly used on ships. There they are used to lower lifeboats and heavy anchors. Together with Oostingh Staalbouw and STAHL CraneSystems, the Dutch company CraneSolutions has developed a new davit crane for offshore wind turbines. Mounted just a few metres above the water, it serves to lift tools and spare parts from the ship on to the wind turbine’s platform during maintenance and repair work. Forty-eight of these cranes have been in use in the Westermeerwind wind farm on the Ijsselmeer in the Netherlands since the beginning of this year.
The newly developed davits are versatile and are specially designed for offshore use on the platforms of wind turbines. They are manufactured by CraneSolutions in the Dutch town of Katwijk and are conform to the EN13852-1 standard for offshore cranes and the crane-building standards EN13001-1, EN13001-2 and CEN/TS 13001-3.1.
Their lifting capacity with 1/1 reeving is 650 kg and 1,300 kg with 2/1 reeving. Depending on the reeving, the electrical chain hoist reaches lifting speeds of 20 or 10 m/min respectively. Use of these cranes is possible in up to state 3 seas.
Thanks to a slewing ring with crank handle, the arm of the davit can be rotated 360°, which facilitates work on the confined platform. A hydraulic cylinder under the arm makes it possible to lock the arm of the davit in four positions.
The crane uses a robust special chain hoist based on the ST series from STAHL CraneSystems; it is additionally protected against saline spray by a cover of stainless steel. All controls are housed in a control box made of stainless steel at the foot of the crane pillar.
Fulfilling the EN50308 standard for wind turbines, every davit has a fastening point for lowering of people in emergencies.
The bottom of the base plate is machined and equipped with bore holes for mounting on the steel structure of the wind turbine platform.
The crane is coated in a C5-M compliant coating system, the highest corrosion class, as recommended by ISO 12944 for coastal and offshore applications with high salinity.