Abstract: A riser tensioner that tensions a riser extending to the seabed from a drilling ship which drills for submarine resources such as oil. The riser tensioner is disposed under a drilling ship to tension a riser used for drilling operation of submarine resources and includes a plurality of cylinders. The riser tensioner further includes: an injection nozzle for injecting water to a surface of a piston rod exposed from each of the cylinders; and a scraper unit which removes salt or seawater from the surface of the piston rod by scrapping the surface of the piston rod to prevent salt from accumulating on the surface of the piston rod.

Abstract: A riser tensioner that includes an oil collecting means and tensions a riser extending to the seabed from a drilling ship which drills for submarine resources. The riser tensioner further includes a piston rod partially inserted into each of the cylinders and reciprocating within the cylinder, a piston seal disposed between a head of the piston rod and a wall of the cylinder to provide fluid sealing, an oil collection passage extending from the head of the piston rod to an outside of the cylinder through the piston rod to allow oil leaking into the cylinder through the piston seal to be discharged from the cylinder to the outside of the cylinder through the oil collection passage, and an oil leakage detection sensor which detects oil leakage positioned on the head of the piston rod.

Abstract: A riser tensioner has an emergency seal and tensions a riser extending to the seabed from a drilling ship which drills for submarine resources such as oil. The riser tensioner is disposed under a drilling ship to tension a riser used for drilling operation of submarine resources and including a plurality of cylinders into which oil is supplied. The riser tensioner further includes a piston rod partially inserted into each of the cylinders and reciprocating within the cylinder, a piston seal disposed between a head of the piston rod and a wall of the cylinder to provide fluid sealing therebetween; an oil leakage detector detecting oil leakage through the piston seal, and an emergency seal disposed in a groove formed at an upper portion of the head of the piston rod to be compressed towards the wall of the cylinder and protrude from the head of the piston rod to prevent oil leakage through the wall of the cylinder when the oil leakage detector detects oil leakage.