Pipe lay system with tension compensator

A pipe lay vessel with a reel for carrying a length of pipe and first drive part for controlling rotation of the reel. A substantially vertical guide structure includes at its upper end a deflection member for deflecting the pipe from a first trajectory extending between the reel and the guide structure to a second, substantially vertical trajectory. A clamping member carries the vertical pipe section and has second drive for feeding the pipe along the vertical trajectory. A movable tension compensator (7) is provided at the first pipe trajectory for lengthening or shortening the first pipe trajectory to maintain a substantially constant tension of the pipe along the first trajectory during unwinding of the reel. By displacing the tension compensator, the first pipe trajectory can be lengthened or shortened to compensate for variations in speed due to non-uniform winding of the pipe and varying diameter of the spooled pipe and to compensate for sagging of the pipe due to its own weight and length variations upon unspooling in view of occuring plasticity and partial straightening of the pipe.