The retractable keel is a device used on megayachts and other high-performance vessels to reduce draft while navigating in shallow waters, without compromising stability and performance on the open sea. One such keel, weighing over 60 tons, was the subject of a maintenance operation on a mega yacht with an aluminum hull and an overall displacement of 500 long tons.

For this task, four lightweight alloy double-stage telescopic cylinders from the COL#D series were used. The operation was meticulously planned well in advance and required dedicated equipment due to limited access beneath the hull. The compact design of the COL#D cylinders, their generous support base, and integrated handling grips allowed for precise and efficient positioning even in extremely tight spaces.

Powered by a hydraulic power unit equipped with flow dividers, the cylinders lifted the keel and enabled the removal of the pivot pin at the joint. The integrated counterbalance valves ensured a controlled descent to the ground, where the guide bushings were replaced and the control hydraulic cylinder underwent maintenance. The subsequent lifting and repositioning of the keel were carried out with the same precision, allowing the pivot pin to be properly reinserted into its housing. At the end of the operations, the megayacht was able to return to the sea in full safety.

The COL#D series telescopic cylinders, traditionally used in the railway sector for the re-railing of rail vehicles represent an extremely effective technical solution in all contexts where a long stroke is required but available space does not permit the usage of single-extension jacks.