Marine riser tensioner

A push-up tensioner 11 for maintaining a tensile force in a riser 13 having an axis 39 couples to a floating platform and maintains the tensile force while the riser 13 tilts variably from the vertical. The tensioner 11 includes a plurality of cylinders 19 having a lower end pivotally coupled to the deck 17. The cylinders 19 are substantially perpendicular to the deck 17 in the running position and at an angle to the deck 17 in the tensioning position. After running of the riser 13, a placement assembly 51 moves the cylinders 19 from the running position to the tensioning position. A tensioner ring 21 is run on the riser 13 proximate to an upper end of the cylinders 19, and the cylinders 19 are then automatically coupled to the tensioner ring 21. Also claimed is a riser tensioning system having a guide roller 45 assembly adapted to mount on the deck 17 and roll along the riser 13 and a conductor sleeve 25 extending from the tensioner ring 21 parallel to the riser 13 and adapted to interface with rollers of the guide roller 45. When the riser 13 rotates relative to the deck, the conductor sleeve 25 resists rotation of the tensioner through react forces exerted by the guide roller 45 and when the tensioner imparts rotation to the riser the conductor sleeve 25 resists rotation of the riser through react forces exerted by the guide roller assembly 45.