Heave-compensating arrangement for a floating device

A floating device such as a drilling platform or ship for overhauling offshore hydrocarbon wells comprises a fixed drill floor 2 provided with an opening 3, a vertically movable working deck 5, riser tensioners 8, and attachment means 6 for connection to a riser 7 from a well. The working deck is suspended in the floating device by the riser tensioners in order to maintain approximately constant tension in the riser during vertical up and down movement of the floating device. The working deck does not move relative to the riser and allows personnel to perform overhaul procedures on the riser end 10 via valves 24. The working deck is laterally secured by guide members 12 connected to the platform 2 and which co-operate with guide rollers 14 which are securely fixed to the working deck