Riser tensioner having an emergency seal

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.

1 . A riser tensioner 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 comprising:
 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.   
     
     
         2 . The riser tensioner of  claim 1 , wherein the emergency seal is attached to the upper portion of the head of the piston rod by a fastening member. 
     
     
         3 . The riser tensioner of  claim 1 , wherein the emergency seal is guided by a seal guide attached to the upper portion of the head of the piston by the fastening member. 
     
     
         4 . A riser tensioner 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 comprising:
 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 the head of the piston rod to protrude from the head of the piston rod to provide fluid sealing between the cylinder and the piston rod when oil leakage is detected by the oil leakage detector.   
     
     
         5 . The riser tensioner of  claim 4 , wherein the head of the piston rod has a groove formed on a surface thereof, and the emergency seal is compressed by hydraulic pressure to protrude from the head of the piston rod through the groove. 
     
     
         6 . The riser tensioner of  claim 1 , further comprising: an actuator that compresses the emergency seal. 
     
     
         7 . The riser tensioner of  claim 6 , wherein the actuator comprises a fluid passage extending to the emergency seal through the piston rod, and an oil valve supplying oil into the fluid passage, the oil valve being opened to transfer hydraulic pressure to the emergency seal through the fluid passage when oil leakage is detected by the oil leakage detector. 
     
     
         8 . The riser tensioner of  claim 1 , further comprising:
 a collection tank connected to a collection passage of the piston rod, through which leaked oil passes,   the oil leakage detector determining the oil leakage based on a detection result of an amount of oil collected in the collection tank.